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Re: [funwithtransistors] Ongoing Amplifier Project - More Pictures


Jan 16, 2012

 


----------------------------

#546 Jan 16, 2012

Hi all.

Attached are three schematics that pertain to my amplifier project. The number one is representative of the amplifier as I had it this morning. Number two is the modifications I made today and number three is what I would like to do to it in the near future.

If you don't know what you're looking out, it's a dual compound-pair output stage driven by a class-A driver and biased by a "rubber zener" or bias servo. In the final build the servo transistor will go between the output transistors and sit right next to the heatsink, stuck to it with thermal paste. The heat from the power transistors will cause the bias transistors to slow down the current and keep them from going into thermal run-away.

The changes I made to it this evening were relocating the 1-ohm output resistors. I decided to move them to the emitters rather than the collector circuit. This is because the emitter circuit is much more sensitive to voltage changes than the collector, and should provide a hint more of stability. Being that the output transistors need to be able to push at least two watts, this resistor will drop a fair bit of current at full power. I also changed the driver load resistor to 680 instead of 2200. I think the lower resistance will make more current available to the output transistor sets so they can conduct the high current needed during the peaks.

The next thing I want to do to it is shown in the Stereo3 picture. Basically I will add an NFB loop around the whole stereo to 1) reduce gain and 2) increase the bandwidth and clear up distortion. I want the amplifier to deliver 2.5 watts into 4 ohms when driven by 1vrms. I may have to tweak it a bit before I wrap it up. I've already started on the cabinet/case for the amplifier; it's going to sit under a 1/8" sheet of aluminum that is 9"x12".

I was originally going to use two transformers I found that have capacities of 24 VAC / 40 VA. Since the capacitors I have are rated 4700 uF at 35v, I decided instead to go with a pair that are 18 VAC at 1A, allowing for lesser maximum voltage. Each channel will have its own power supply with two 4700 uF reservoir capacitors, a 1-ohm series resistor, and 4 4700uF filter caps. I need the DC voltage to be as pure as I can get it. At such a low standby current (about 75 mA) the ripple will be low indeed, but during heavy sine tests the output will be modulated by 120 Hz hum. If anyone has any comments or advice I'm more than willing to hear it.

When this project is done we will all feel like fighter jets made of biceps.Ed



----------------------------

#547 Jan 16, 2012

A suggestion, my $0.02. Since you are using two power transformers anyway

have you thought about making a symmetrical power supply and doing away with

the 2200 uf cap?



Regards.



Max. K 4 O D S.



Email: max@...



Transistor site www.funwithtransistors.net

Vacuum tube site: www.funwithtubes.net

Music site: www.maxsmusicplace.com



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----- Original Message -----

From: "J Ed" jedwardsat1@...>

To: funwithtransistors@yahoogroups.com>

Sent: Monday, January 16, 2012 12:17 AM

Subject: [funwithtransistors] Ongoing Amplifier Project





> Hi all.

>

> Attached are three schematics that pertain to my amplifier project. The

> number one is representative of the amplifier as I had it this morning.

> Number two is the modifications I made today and number three is what I

> would like to do to it in the near future.

>

> If you don't know what you're looking out, it's a dual compound-pair

> output

> stage driven by a class-A driver and biased by a "rubber zener" or bias

> servo. In the final build the servo transistor will go between the output

> transistors and sit right next to the heatsink, stuck to it with thermal

> paste. The heat from the power transistors will cause the bias transistors

> to slow down the current and keep them from going into thermal run-away.

>

> The changes I made to it this evening were relocating the 1-ohm output

> resistors. I decided to move them to the emitters rather than the

> collector

> circuit. This is because the emitter circuit is much more sensitive to

> voltage changes than the collector, and should provide a hint more of

> stability. Being that the output transistors need to be able to push at

> least two watts, this resistor will drop a fair bit of current at full

> power. I also changed the driver load resistor to 680 instead of 2200. I

> think the lower resistance will make more current available to the output

> transistor sets so they can conduct the high current needed during the

> peaks.

>

> The next thing I want to do to it is shown in the Stereo3 picture.

> Basically I will add an NFB loop around the whole stereo to 1) reduce gain

> and 2) increase the bandwidth and clear up distortion. I want the

> amplifier

> to deliver 2.5 watts into 4 ohms when driven by 1vrms. I may have to tweak

> it a bit before I wrap it up. I've already started on the cabinet/case for

> the amplifier; it's going to sit under a 1/8" sheet of aluminum that is

> 9"x12".

>

> I was originally going to use two transformers I found that have

> capacities

> of 24 VAC / 40 VA. Since the capacitors I have are rated 4700 uF at 35v, I

> decided instead to go with a pair that are 18 VAC at 1A, allowing for

> lesser maximum voltage. Each channel will have its own power supply with

> two 4700 uF reservoir capacitors, a 1-ohm series resistor, and 4 4700uF

> filter caps. I need the DC voltage to be as pure as I can get it. At such

> a

> low standby current (about 75 mA) the ripple will be low indeed, but

> during

> heavy sine tests the output will be modulated by 120 Hz hum. If anyone has

> any comments or advice I'm more than willing to hear it.

>

> When this project is done we will all feel like fighter jets made of

> biceps.

> Ed

>







----------------------------

#548 Jan 16, 2012

I have. It would require twice the amount of capacitors as I already have (although I have to get more anyway). Also, I don't know if the configuration I have is compatible with a DC-coupled output. It would allow me to use the 24vac transformers I originally wanted but it would still be more voltage than I need.

I read somewhere that if you want to have no output capacitor, you need two transistors on the input/driver stage. That is, the driver I have now will respond to ambient temperature changes and the output voltage will change. If I did away with the output cap and set the voltage at 0v, it could be a problem to keep the DC away from the speaker.

With a long-tailed input stage, apparently the second transistor (the one that does not receive the input signal) will balance the changes in the first if temperature changes.

Are you suggesting I change the whole design? I'm open to the idea if it will get me a better amplifier. Keep in mind that this is a "practice" amplifier to get ready to build the 50w amplifier that will sit in my living room. My main desires for this amp are low distortion and good frequency response. The amount of power I've pushed through it as-is is more than ample for my needs.

Thanks for the $0.02. They make excellent tie points (if they're the solid copper or copper alloy pennies). All you have to do is epoxy one to a wooden spacer and drill some holes in it around the edges. They also make good transformer washers.

Ed



----------------------------

#549 Jan 16, 2012

Hi Ed.



Granted, you would have to add one or more transistors to the design to be

able to reference the input to ground so the output DC could be stabilized.

If simplicity is what you are after the circuit is fine. It worked fine in

silicon amplifiers from about 1960 to 1975. I always sort of missed that

turn on thump that was the identifying characteristic of the Heathkit AR-15.



Regards.



Max. K 4 O D S.



Email: max@...



Transistor site www.funwithtransistors.net

Vacuum tube site: www.funwithtubes.net

Music site: www.maxsmusicplace.com



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----- Original Message -----

From: "J Ed" jedwardsat1@...>

To: funwithtransistors@yahoogroups.com>

Sent: Monday, January 16, 2012 1:20 PM

Subject: Re: [funwithtransistors] Ongoing Amplifier Project





>I have. It would require twice the amount of capacitors as I already have

> (although I have to get more anyway). Also, I don't know if the

> configuration I have is compatible with a DC-coupled output. It would

> allow

> me to use the 24vac transformers I originally wanted but it would still be

> more voltage than I need.

>

> I read somewhere that if you want to have no output capacitor, you need

> two

> transistors on the input/driver stage. That is, the driver I have now will

> respond to ambient temperature changes and the output voltage will change.

> If I did away with the output cap and set the voltage at 0v, it could be a

> problem to keep the DC away from the speaker.

>

> With a long-tailed input stage, apparently the second transistor (the one

> that does not receive the input signal) will balance the changes in the

> first if temperature changes.

>

> Are you suggesting I change the whole design? I'm open to the idea if it

> will get me a better amplifier. Keep in mind that this is a "practice"

> amplifier to get ready to build the 50w amplifier that will sit in my

> living room. My main desires for this amp are low distortion and good

> frequency response. The amount of power I've pushed through it as-is is

> more than ample for my needs.

>

> Thanks for the $0.02. They make excellent tie points (if they're the solid

> copper or copper alloy pennies). All you have to do is epoxy one to a

> wooden spacer and drill some holes in it around the edges. They also make

> good transformer washers.

>

> Ed

>



----------------------------

#550 Jan 16, 2012

That's pretty much what I wanted to know. Still, I want to build *this* amplifier like I'm going to build the 50w and make the only necessary change to be the power supply. In the larger PA I may use more protection circuitry.

I do want to try and implement a relay-delay adapter in order to protect the speakers from that thump. Apparently it's a big thing.

Ed

On Mon, Jan 16, 2012 at 11:33 AM, Max Robinson max@...> wrote:

.Hi Ed.



Granted, you would have to add one or more transistors to the design to be

able to reference the input to ground so the output DC could be stabilized.

If simplicity is what you are after the circuit is fine. It worked fine in

silicon amplifiers from about 1960 to 1975. I always sort of missed that

turn on thump that was the identifying characteristic of the Heathkit AR-15.



Regards.



Max. K 4 O D S.



Email: max@...



Transistor site www.funwithtransistors.net

Vacuum tube site: www.funwithtubes.net

Music site: www.maxsmusicplace.com



To subscribe to the fun with transistors group send an email to.

funwithtransistors-subscribe@yahoogroups.com



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----- Original Message -----

From: "J Ed" jedwardsat1@...>

To: funwithtransistors@yahoogroups.com>

Sent: Monday, January 16, 2012 1:20 PM

Subject: Re: [funwithtransistors] Ongoing Amplifier Project



>I have. It would require twice the amount of capacitors as I already have

> (although I have to get more anyway). Also, I don't know if the

> configuration I have is compatible with a DC-coupled output. It would

> allow

> me to use the 24vac transformers I originally wanted but it would still be

> more voltage than I need.

>

> I read somewhere that if you want to have no output capacitor, you need

> two

> transistors on the input/driver stage. That is, the driver I have now will

> respond to ambient temperature changes and the output voltage will change.

> If I did away with the output cap and set the voltage at 0v, it could be a

> problem to keep the DC away from the speaker.

>

> With a long-tailed input stage, apparently the second transistor (the one

> that does not receive the input signal) will balance the changes in the

> first if temperature changes.

>

> Are you suggesting I change the whole design? I'm open to the idea if it

> will get me a better amplifier. Keep in mind that this is a "practice"

> amplifier to get ready to build the 50w amplifier that will sit in my

> living room. My main desires for this amp are low distortion and good

> frequency response. The amount of power I've pushed through it as-is is

> more than ample for my needs.

>

> Thanks for the $0.02. They make excellent tie points (if they're the solid

> copper or copper alloy pennies). All you have to do is epoxy one to a

> wooden spacer and drill some holes in it around the edges. They also make

> good transformer washers.

>

> Ed

>







----------------------------

#561 Jan 19, 2012

I applied the other feedback loop today. The first implementation massacred the sound. Then I found out what I was doing wrong: I took the NFB resistor directly from the output to the base of the input transistor. What this did was put the DC from the base into the speaker and pretty much murdering the sound.



I used a 100uF cap and a 3900 ohm resistor and took it back to the base. I bypassed the 3900 ohm resistor with a 68pF cap to kill RF oscillation. For the source resistor (the one in series with the input) I used a 1K.



The objective is to keep the gain of the power amp low and derive all my gain from a preamp section. Maybe I will build a separate preamplifier (or several preamps using tubes, JFETs, or something stranger still. Maybe I'll make a transformer-based magnetic preamp).



Also, my 1% metal film resistors came in the other day. I think I'll be using them from now on.



So...I think I am done with this design. All that remains is to build two identical amplifier cards and then start working on power supplies. I want to overdo it on the power supply capacitance to serve a dual purpose of eliminating hum and providing extra reserve for the peaks.



If anyone has any more advice it's welcome. Although it's a single-ended amplifier with an output capacitor, my next one will have no capacitor and will have a bipolar power supply. Sooner or later I will return to tube designs and make something I really want.



Ed



----------------------------

#563 Jan 23, 2012

Hi all,

I did some wood working today. Although I cut the side pieces of the amplifier a bit short, I have enough wood to cut new ones. I cut them to 7" and I needed them to be 10". I suppose I can use those pieces for one of the pre-amplifiers. Attached are pictures of the new back panel. The back panel will include all connections except for the pilot lights and will be able to accommodate a 1/8" plug as well as RCA plugs. I will have to get a large metal plate to put on the outside edge of the wood for mounting of the various jacks.

The lighter wooden blocks are to support the top and bottom plates. Screw holes will be drilled in them and I will sink some pan-head screws into the blocks themselves. The screws will go through holes in the top plate but will not be threaded in any way. Right now, the white blocks are just attached with cyanoacrylate now but I may put some wooden pegs into them for additional support. Somehow I don't want to trust glue by itself. Does anyone have comments on this?

The IEC filter is inserted between the first set of blocks. The fuse and power switch will likely be between the second set. The output posts are undecided as of yet but may be between the third set, right next to the switch and fuse holder. The input terminals are all to be panel-mount and will be on the far-right in a vertical line.

The front panel will be laid out in a similar fashion except that it will be much less busy. I intend to just put the LEDs on the front panel. I could be extra-classy and go with #47 lamps instead. I think the lamps would consume more current than the amplifiers at zero-signal (I have them biased to 50 mA). Since the transformers are rated only at 1 amp, I think I'll shy away from that and use lower-current LEDs. If I really wanted to be mindful of my energy I'd put a 120v pilot lamp in parallel with each transformer primary, but that would give me no indication that the DC power supplies were working.

So, I'm throwing myself upon the mercy of the court.Ed



----------------------------

#564 Jan 23, 2012

To all,

Here are some more pictures.

1: I set the front and back panels down so I could set the amplifier "chassis plate" on them. So far it holds without falling apart. You may have noticed the pencil markings on the outer wood: those are to mark drill holes for wooden pegs. As mentioned before I don't trust the strength of glue alone to hold my amplifier up. To that end, I have some 1/8" hard wood dowels that I will sink into each little block to increase their holding strength. A pity super glue tubes don't last very long at all. I'm beginning to prefer it to other adhesives.

2: I placed the transformers under the plate so I could see how much clearance I would get. Not much, maybe a quarter-inch. I want to drill some vent holes around the transformers atop the amplifier so some of the warm air around the transformers can push through and create some air current. The holes in the bottom panel (wood) will be substantial but the top holes will be smaller. The Bernoulli Principle *may* take effect here and actively push the hot amp air out of the top plate in the amplifier.

As for heat sinking, I was thinking of mounting the TO-220 transistors directly to the aluminum plate. Maybe I'll install some fins that go under the plate, but the objective is to have nothing sticking up from the top of the enclosure. This will allow me to place another accessory (preamp) or a lamp on top of the amplifier. I want to make the enclosure strong enough for me to stand on but that seems like a pipe dream.

Ed



----------------------------

#565 Jan 23, 2012

Hi Ed. You are using the wrong kind of glue for wood. You should be using

yellow carpenter's glue. A brand example is Titebond II. When properly

clamped while setting up the glue joint is stronger than the wood.



OK, I should have looked at the pictures before shooting off my fingers. I

guess you are gluing up the mitered corners. Because that involves gluing

end grain to end grain there is no glue in the world that will give a strong

joint. Dowels are a viable alternative. There are other fastening tricks

but they need a router or table saw to implement.



Regards.



Max. K 4 O D S.



Email: max@...



Transistor site www.funwithtransistors.net

Vacuum tube site: www.funwithtubes.net

Music site: www.maxsmusicplace.com



To subscribe to the fun with transistors group send an email to.

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----- Original Message -----

From: "J Ed" jedwardsat1@...>

To: funwithtransistors@yahoogroups.com>

Sent: Sunday, January 22, 2012 11:30 PM

Subject: [funwithtransistors] Ongoing Amplifier Project - More Pictures





> To all,

>

> Here are some more pictures.

>

> 1: I set the front and back panels down so I could set the amplifier

> "chassis plate" on them. So far it holds without falling apart. You may

> have noticed the pencil markings on the outer wood: those are to mark

> drill

> holes for wooden pegs. As mentioned before I don't trust the strength of

> glue alone to hold my amplifier up. To that end, I have some 1/8" hard

> wood

> dowels that I will sink into each little block to increase their holding

> strength. A pity super glue tubes don't last very long at all. I'm

> beginning to prefer it to other adhesives.

>

> 2: I placed the transformers under the plate so I could see how much

> clearance I would get. Not much, maybe a quarter-inch. I want to drill

> some

> vent holes around the transformers atop the amplifier so some of the warm

> air around the transformers can push through and create some air current.

> The holes in the bottom panel (wood) will be substantial but the top holes

> will be smaller. The Bernoulli Principle *may* take effect here and

> actively push the hot amp air out of the top plate in the amplifier.

>

> As for heat sinking, I was thinking of mounting the TO-220 transistors

> directly to the aluminum plate. Maybe I'll install some fins that go under

> the plate, but the objective is to have nothing sticking up from the top

> of

> the enclosure. This will allow me to place another accessory (preamp) or a

> lamp on top of the amplifier. I want to make the enclosure strong enough

> for me to stand on but that seems like a pipe dream.

>

> Ed

>







----------------------------

#566 Jan 23, 2012

Max, I will not be gluing the mitered joints just yet. I will attach

the main plate to the panels via screws into those white pine blocks.

Each block will get a dowel for strength. When the four side panels

fit the plate then i am going to attach the corners. After that i will

put a wooden panel on the bottom. The last step will be the corner

blocks. Although i have one and a half carved out of oak, i want to

toss them and make new ones from pine. I have used yellow glue

extensively but wanted to try CA for a change. It seems to work okay

for now but i won't trust it for structural strength. Ed.

On 1/23/12, Max Robinson max@...> wrote:

> Hi Ed. You are using the wrong kind of glue for wood. You should be using

> yellow carpenter's glue. A brand example is Titebond II. When properly

> clamped while setting up the glue joint is stronger than the wood.

>

> OK, I should have looked at the pictures before shooting off my fingers. I

> guess you are gluing up the mitered corners. Because that involves gluing

> end grain to end grain there is no glue in the world that will give a strong

> joint. Dowels are a viable alternative. There are other fastening tricks

> but they need a router or table saw to implement.

>

> Regards.

>

> Max. K 4 O D S.

>

> Email: max@...

>

> Transistor site www.funwithtransistors.net

> Vacuum tube site: www.funwithtubes.net

> Music site: www.maxsmusicplace.com

>

> To subscribe to the fun with transistors group send an email to.

> funwithtransistors-subscribe@yahoogroups.com

>

> To subscribe to the fun with tubes group send an email to,

> funwithtubes-subscribe@yahoogroups.com

>

> ----- Original Message -----

> From: "J Ed" jedwardsat1@...>

> To: funwithtransistors@yahoogroups.com>

> Sent: Sunday, January 22, 2012 11:30 PM

> Subject: [funwithtransistors] Ongoing Amplifier Project - More Pictures

>

>

>> To all,

>>

>> Here are some more pictures.

>>

>> 1: I set the front and back panels down so I could set the amplifier

>> "chassis plate" on them. So far it holds without falling apart. You may

>> have noticed the pencil markings on the outer wood: those are to mark

>> drill

>> holes for wooden pegs. As mentioned before I don't trust the strength of

>> glue alone to hold my amplifier up. To that end, I have some 1/8" hard

>> wood

>> dowels that I will sink into each little block to increase their holding

>> strength. A pity super glue tubes don't last very long at all. I'm

>> beginning to prefer it to other adhesives.

>>

>> 2: I placed the transformers under the plate so I could see how much

>> clearance I would get. Not much, maybe a quarter-inch. I want to drill

>> some

>> vent holes around the transformers atop the amplifier so some of the warm

>> air around the transformers can push through and create some air current.

>> The holes in the bottom panel (wood) will be substantial but the top holes

>> will be smaller. The Bernoulli Principle *may* take effect here and

>> actively push the hot amp air out of the top plate in the amplifier.

>>

>> As for heat sinking, I was thinking of mounting the TO-220 transistors

>> directly to the aluminum plate. Maybe I'll install some fins that go under

>> the plate, but the objective is to have nothing sticking up from the top

>> of

>> the enclosure. This will allow me to place another accessory (preamp) or a

>> lamp on top of the amplifier. I want to make the enclosure strong enough

>> for me to stand on but that seems like a pipe dream.

>>

>> Ed

>>

>

>



----------------------------

#568 Jan 24, 2012

OK. That will most likely be a face grain to face grain joint. Go ahead

and use the yellow glue. It comes in small containers so you don't have to

buy a gallon of it. When the glue is applied liberally enough but not too

liberal, and clamped, the joint is stronger than the wood. This is not an

old wives tail or an urban legend. Scientific tests have shown that when

such a joint is broken the wood breaks before the joint separates.

Woodworkers make joints like this all the time and they last for decades.



Regards.



Max. K 4 O D S.



Email: max@...



Transistor site www.funwithtransistors.net

Vacuum tube site: www.funwithtubes.net

Music site: www.maxsmusicplace.com



To subscribe to the fun with transistors group send an email to.

funwithtransistors-subscribe@yahoogroups.com



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----- Original Message -----

From: "J Ed" jedwardsat1@...>

To: funwithtransistors@yahoogroups.com>

Sent: Monday, January 23, 2012 12:43 PM

Subject: Re: [funwithtransistors] Ongoing Amplifier Project - More Pictures





> Max, I will not be gluing the mitered joints just yet. I will attach

> the main plate to the panels via screws into those white pine blocks.

> Each block will get a dowel for strength. When the four side panels

> fit the plate then i am going to attach the corners. After that i will

> put a wooden panel on the bottom. The last step will be the corner

> blocks. Although i have one and a half carved out of oak, i want to

> toss them and make new ones from pine. I have used yellow glue

> extensively but wanted to try CA for a change. It seems to work okay

> for now but i won't trust it for structural strength. Ed.

>

> On 1/23/12, Max Robinson max@...> wrote:

>> Hi Ed. You are using the wrong kind of glue for wood. You should be

>> using

>> yellow carpenter's glue. A brand example is Titebond II. When properly

>> clamped while setting up the glue joint is stronger than the wood.

>>

>> OK, I should have looked at the pictures before shooting off my fingers.

>> I

>> guess you are gluing up the mitered corners. Because that involves

>> gluing

>> end grain to end grain there is no glue in the world that will give a

>> strong

>> joint. Dowels are a viable alternative. There are other fastening

>> tricks

>> but they need a router or table saw to implement.

>>

>> Regards.

>>

>> Max. K 4 O D S.

>>

>> Email: max@...

>>

>> Transistor site www.funwithtransistors.net

>> Vacuum tube site: www.funwithtubes.net

>> Music site: www.maxsmusicplace.com

>>

>> To subscribe to the fun with transistors group send an email to.

>> funwithtransistors-subscribe@yahoogroups.com

>>

>> To subscribe to the fun with tubes group send an email to,

>> funwithtubes-subscribe@yahoogroups.com

>>

>> ----- Original Message -----

>> From: "J Ed" jedwardsat1@...>

>> To: funwithtransistors@yahoogroups.com>

>> Sent: Sunday, January 22, 2012 11:30 PM

>> Subject: [funwithtransistors] Ongoing Amplifier Project - More Pictures

>>

>>

>>> To all,

>>>

>>> Here are some more pictures.

>>>

>>> 1: I set the front and back panels down so I could set the amplifier

>>> "chassis plate" on them. So far it holds without falling apart. You may

>>> have noticed the pencil markings on the outer wood: those are to mark

>>> drill

>>> holes for wooden pegs. As mentioned before I don't trust the strength of

>>> glue alone to hold my amplifier up. To that end, I have some 1/8" hard

>>> wood

>>> dowels that I will sink into each little block to increase their holding

>>> strength. A pity super glue tubes don't last very long at all. I'm

>>> beginning to prefer it to other adhesives.

>>>

>>> 2: I placed the transformers under the plate so I could see how much

>>> clearance I would get. Not much, maybe a quarter-inch. I want to drill

>>> some

>>> vent holes around the transformers atop the amplifier so some of the

>>> warm

>>> air around the transformers can push through and create some air

>>> current.

>>> The holes in the bottom panel (wood) will be substantial but the top

>>> holes

>>> will be smaller. The Bernoulli Principle *may* take effect here and

>>> actively push the hot amp air out of the top plate in the amplifier.

>>>

>>> As for heat sinking, I was thinking of mounting the TO-220 transistors

>>> directly to the aluminum plate. Maybe I'll install some fins that go

>>> under

>>> the plate, but the objective is to have nothing sticking up from the top

>>> of

>>> the enclosure. This will allow me to place another accessory (preamp) or

>>> a

>>> lamp on top of the amplifier. I want to make the enclosure strong enough

>>> for me to stand on but that seems like a pipe dream.

>>>

>>> Ed

>>>

>>

>>

>

>

---------------

>

> Always keep electrons and holes flowing in opposite directions.Yahoo!

> Groups Links

>

>

>

>







----------------------------

#569 Jan 24, 2012

I am aware of this. Normally I use yellow wood glue (I'd say 99% or better). I tried CA glue this time because I wanted to see how it would hold. So far the CA glue has held, but I am wary of making *any* glue the structural support for anything. I'd rather make a wooden joint of some type and supplement it with glue.

Liquid nails sucks and it should only be used as a low-grade cattle feed.

Ed

On Mon, Jan 23, 2012 at 6:49 PM, Max Robinson max@...> wrote:

.OK. That will most likely be a face grain to face grain joint. Go ahead

and use the yellow glue. It comes in small containers so you don't have to

buy a gallon of it. When the glue is applied liberally enough but not too

liberal, and clamped, the joint is stronger than the wood. This is not an

old wives tail or an urban legend. Scientific tests have shown that when

such a joint is broken the wood breaks before the joint separates.

Woodworkers make joints like this all the time and they last for decades.



Regards.



Max. K 4 O D S.



Email: max@...



Transistor site www.funwithtransistors.net

Vacuum tube site: www.funwithtubes.net

Music site: www.maxsmusicplace.com



To subscribe to the fun with transistors group send an email to.

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----- Original Message -----

From: "J Ed" jedwardsat1@...>

To: funwithtransistors@yahoogroups.com>

Sent: Monday, January 23, 2012 12:43 PM

Subject: Re: [funwithtransistors] Ongoing Amplifier Project - More Pictures



> Max, I will not be gluing the mitered joints just yet. I will attach

> the main plate to the panels via screws into those white pine blocks.

> Each block will get a dowel for strength. When the four side panels

> fit the plate then i am going to attach the corners. After that i will

> put a wooden panel on the bottom. The last step will be the corner

> blocks. Although i have one and a half carved out of oak, i want to

> toss them and make new ones from pine. I have used yellow glue

> extensively but wanted to try CA for a change. It seems to work okay

> for now but i won't trust it for structural strength. Ed.

>

> On 1/23/12, Max Robinson max@...> wrote:

>> Hi Ed. You are using the wrong kind of glue for wood. You should be

>> using

>> yellow carpenter's glue. A brand example is Titebond II. When properly

>> clamped while setting up the glue joint is stronger than the wood.

>>

>> OK, I should have looked at the pictures before shooting off my fingers.

>> I

>> guess you are gluing up the mitered corners. Because that involves

>> gluing

>> end grain to end grain there is no glue in the world that will give a

>> strong

>> joint. Dowels are a viable alternative. There are other fastening

>> tricks

>> but they need a router or table saw to implement.

>>

>> Regards.

>>

>> Max. K 4 O D S.

>>

>> Email: max@...

>>

>> Transistor site www.funwithtransistors.net

>> Vacuum tube site: www.funwithtubes.net

>> Music site: www.maxsmusicplace.com

>>

>> To subscribe to the fun with transistors group send an email to.

>> funwithtransistors-subscribe@yahoogroups.com

>>

>> To subscribe to the fun with tubes group send an email to,

>> funwithtubes-subscribe@yahoogroups.com

>>

>> ----- Original Message -----

>> From: "J Ed" jedwardsat1@...>

>> To: funwithtransistors@yahoogroups.com>

>> Sent: Sunday, January 22, 2012 11:30 PM

>> Subject: [funwithtransistors] Ongoing Amplifier Project - More Pictures

>>

>>

>>> To all,

>>>

>>> Here are some more pictures.

>>>

>>> 1: I set the front and back panels down so I could set the amplifier

>>> "chassis plate" on them. So far it holds without falling apart. You may

>>> have noticed the pencil markings on the outer wood: those are to mark

>>> drill

>>> holes for wooden pegs. As mentioned before I don't trust the strength of

>>> glue alone to hold my amplifier up. To that end, I have some 1/8" hard

>>> wood

>>> dowels that I will sink into each little block to increase their holding

>>> strength. A pity super glue tubes don't last very long at all. I'm

>>> beginning to prefer it to other adhesives.

>>>

>>> 2: I placed the transformers under the plate so I could see how much

>>> clearance I would get. Not much, maybe a quarter-inch. I want to drill

>>> some

>>> vent holes around the transformers atop the amplifier so some of the

>>> warm

>>> air around the transformers can push through and create some air

>>> current.

>>> The holes in the bottom panel (wood) will be substantial but the top

>>> holes

>>> will be smaller. The Bernoulli Principle *may* take effect here and

>>> actively push the hot amp air out of the top plate in the amplifier.

>>>

>>> As for heat sinking, I was thinking of mounting the TO-220 transistors

>>> directly to the aluminum plate. Maybe I'll install some fins that go

>>> under

>>> the plate, but the objective is to have nothing sticking up from the top

>>> of

>>> the enclosure. This will allow me to place another accessory (preamp) or

>>> a

>>> lamp on top of the amplifier. I want to make the enclosure strong enough

>>> for me to stand on but that seems like a pipe dream.

>>>

>>> Ed

>>>

>>

>>

>

>







----------------------------

#570 Jan 24, 2012

I agree about liquid nails and gorilla glue isn't much better.



Regards.



Max. K 4 O D S.



Email: max@...



Transistor site www.funwithtransistors.net

Vacuum tube site: www.funwithtubes.net

Music site: www.maxsmusicplace.com



To subscribe to the fun with transistors group send an email to.

funwithtransistors-subscribe@yahoogroups.com



To subscribe to the fun with tubes group send an email to,

funwithtubes-subscribe@yahoogroups.com

----- Original Message -----

From: "J Ed" jedwardsat1@...>

To: funwithtransistors@yahoogroups.com>

Sent: Monday, January 23, 2012 9:42 PM

Subject: Re: [funwithtransistors] Ongoing Amplifier Project - More Pictures





I am aware of this. Normally I use yellow wood glue (I'd say 99% or

better). I tried CA glue this time because I wanted to see how it would

hold. So far the CA glue has held, but I am wary of making *any* glue the

structural support for anything. I'd rather make a wooden joint of some

type and supplement it with glue.



Liquid nails sucks and it should only be used as a low-grade cattle feed.



Ed



On Mon, Jan 23, 2012 at 6:49 PM, Max Robinson max@...>wrote:



> **

>

>

> OK. That will most likely be a face grain to face grain joint. Go ahead

> and use the yellow glue. It comes in small containers so you don't have to

> buy a gallon of it. When the glue is applied liberally enough but not too

> liberal, and clamped, the joint is stronger than the wood. This is not an

> old wives tail or an urban legend. Scientific tests have shown that when

> such a joint is broken the wood breaks before the joint separates.

> Woodworkers make joints like this all the time and they last for decades.

>

>

> Regards.

>

> Max. K 4 O D S.

>

> Email: max@...

>

> Transistor site www.funwithtransistors.net

> Vacuum tube site: www.funwithtubes.net

> Music site: www.maxsmusicplace.com

>

> To subscribe to the fun with transistors group send an email to.

> funwithtransistors-subscribe@yahoogroups.com

>

> To subscribe to the fun with tubes group send an email to,

> funwithtubes-subscribe@yahoogroups.com

>

> ----- Original Message -----

> From: "J Ed" jedwardsat1@...>

> To: funwithtransistors@yahoogroups.com>

> Sent: Monday, January 23, 2012 12:43 PM

> Subject: Re: [funwithtransistors] Ongoing Amplifier Project - More

> Pictures

>

> > Max, I will not be gluing the mitered joints just yet. I will attach

> > the main plate to the panels via screws into those white pine blocks.

> > Each block will get a dowel for strength. When the four side panels

> > fit the plate then i am going to attach the corners. After that i will

> > put a wooden panel on the bottom. The last step will be the corner

> > blocks. Although i have one and a half carved out of oak, i want to

> > toss them and make new ones from pine. I have used yellow glue

> > extensively but wanted to try CA for a change. It seems to work okay

> > for now but i won't trust it for structural strength. Ed.

> >

> > On 1/23/12, Max Robinson max@...> wrote:

> >> Hi Ed. You are using the wrong kind of glue for wood. You should be

> >> using

> >> yellow carpenter's glue. A brand example is Titebond II. When properly

> >> clamped while setting up the glue joint is stronger than the wood.

> >>

> >> OK, I should have looked at the pictures before shooting off my

> fingers.

> >> I

> >> guess you are gluing up the mitered corners. Because that involves

> >> gluing

> >> end grain to end grain there is no glue in the world that will give a

> >> strong

> >> joint. Dowels are a viable alternative. There are other fastening

> >> tricks

> >> but they need a router or table saw to implement.

> >>

> >> Regards.

> >>

> >> Max. K 4 O D S.

> >>

> >> Email: max@...

> >>

> >> Transistor site www.funwithtransistors.net

> >> Vacuum tube site: www.funwithtubes.net

> >> Music site: www.maxsmusicplace.com

> >>

> >> To subscribe to the fun with transistors group send an email to.

> >> funwithtransistors-subscribe@yahoogroups.com

> >>

> >> To subscribe to the fun with tubes group send an email to,

> >> funwithtubes-subscribe@yahoogroups.com

> >>

> >> ----- Original Message -----

> >> From: "J Ed" jedwardsat1@...>

> >> To: funwithtransistors@yahoogroups.com>

> >> Sent: Sunday, January 22, 2012 11:30 PM

> >> Subject: [funwithtransistors] Ongoing Amplifier Project - More Pictures

> >>

> >>

> >>> To all,

> >>>

> >>> Here are some more pictures.

> >>>

> >>> 1: I set the front and back panels down so I could set the amplifier

> >>> "chassis plate" on them. So far it holds without falling apart. You

> >>> may

> >>> have noticed the pencil markings on the outer wood: those are to mark

> >>> drill

> >>> holes for wooden pegs. As mentioned before I don't trust the strength

> of

> >>> glue alone to hold my amplifier up. To that end, I have some 1/8" hard

> >>> wood

> >>> dowels that I will sink into each little block to increase their

> holding

> >>> strength. A pity super glue tubes don't last very long at all. I'm

> >>> beginning to prefer it to other adhesives.

> >>>

> >>> 2: I placed the transformers under the plate so I could see how much

> >>> clearance I would get. Not much, maybe a quarter-inch. I want to drill

> >>> some

> >>> vent holes around the transformers atop the amplifier so some of the

> >>> warm

> >>> air around the transformers can push through and create some air

> >>> current.

> >>> The holes in the bottom panel (wood) will be substantial but the top

> >>> holes

> >>> will be smaller. The Bernoulli Principle *may* take effect here and

> >>> actively push the hot amp air out of the top plate in the amplifier.

> >>>

> >>> As for heat sinking, I was thinking of mounting the TO-220 transistors

> >>> directly to the aluminum plate. Maybe I'll install some fins that go

> >>> under

> >>> the plate, but the objective is to have nothing sticking up from the

> top

> >>> of

> >>> the enclosure. This will allow me to place another accessory (preamp)

> or

> >>> a

> >>> lamp on top of the amplifier. I want to make the enclosure strong

> enough

> >>> for me to stand on but that seems like a pipe dream.

> >>>

> >>> Ed

> >>>

> >>

> >>

> >

> >

---------------

> >

> > Always keep electrons and holes flowing in opposite directions.Yahoo!

> > Groups Links

> >

> >

> >

> >

>

>

>







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