3 W Ge Transistors Power Amp

SPeter · Post by **SPeter** » 23 May 2009, 21:41

Hi everyone, this is very simple design but can be improved with good input buffer / preamp and tone stack! 3 W power is good enough for bedroom practice and as the author states the sound is very tube like !So, enjoy:
http://topopiccione.atspace.com/PJ21TPCTengoNa.html

RnFR · Post by **RnFR** » 24 May 2009, 09:02

hey! i've always wanted to build a Ge power amp! did you build this, or is this your design? i get mixed up with all of the forums and nicknames, etc. looks cool though, and much more mojo than a chip amp! not to mention, it probably sounds a heap better as well

. i was about to order some more russkie germs from that Evita site, now i'll be sure to throw in a few power trannies. thanks for the tip!

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upon looking at the schem further- are the ac188K/187K's power trannies? or is it just 2 low/med power xistors in push/pull?
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i see, they are the big square ones with the heatsinks. i guess they would be considered medium power.

soulsonic · Post by **soulsonic** » 25 May 2009, 04:57

hey RnFR, those GT403 you have (or is it GT404? anyway, it's that big chunky one you put in that weird fuzz built by the crazy hippie) is the sort of transistor intended for this. I remember reading the datasheet awhile ago. It has a complimentary NPN version (like the AC187/188 pair), so if you can find those it should work for this circuit. I have one or two floating around as well, but I still haven't tracked down its complimentary partner (but I admit I haven't tried very hard...)

Cool project! Yes, I want to try this too with those big chunky Russian ones.

RnFR · Post by **RnFR** » 25 May 2009, 05:20

that's right! and that gordelux guy has the comp for the 404's. it's the 403. he might even sell matched pairs. we should totally build up a little amp like that. i've got some 10 in speakers that would be perfect, too.

UZILSD · Post by **UZILSD** » 25 May 2009, 11:45

TPC Tengo Na Minchia Tanta.... LOL WTF
"Tengo Na Minchia Tanta" for the ones out there who aren't from Italy is a dialectal southern idiom that sounds like "I have a big dick".

ac188k/187k are not power trannies but they can stand 1,5w each with a dissipator. They have already a dissipator mounted on (the k suffix indicates that), but I think that who designed this meant an additional heat sink to be mounted.
By the way, you can also use them in place of the ac128/127... unless you have genuine NOS, modern ac18x tends to sound much better than modern ac12x. Modern production ac12x sounds harsh and trebly.

3W, if the amp needs to be cranked to the bone like tube amps in order to get the tone, is still loud anyway!!!
For acceptable bedroom practice, you should go under 1W... the loved-hated ZVEX nano head runs at 0.1w in dist mode for example. But I'm assuming tube like responce, maybe transistors are more quiet.

RnFR · Post by **RnFR** » 26 May 2009, 11:34

i found these which are ac187/188 equivalents in factory matched pairs. they would probably work great for this project.
https://cgi.ebay.com/GC511-GC521-AC188- ... .m20.l1116

then i also found matched 404/402 pairs(not 403's) but only in lots of ten. then i also found a lot of just 402's to go with the 404's i already have. of course then i will have to do the matching myself.
https://cgi.ebay.com/GT402-B-GT404-B-GE ... .m20.l1116
https://cgi.ebay.com/GT402-B-GERMANIUM- ... .m20.l1116

whichever i decide on will probably be dependent on which seller has other cool stuff to order as the shipping is a bit pricey, so i would prefer to make it worth my while. i guess i could always use the other matched pairs in some sort of op amp style gain stage and make something out of that. we'll see. i haven't really decided yet.

RnFR · Post by **RnFR** » 28 May 2009, 10:42

i picked up a couple pairs of the 187/188 equivalents, so we'll see how this goes!

vanessa · Post by **vanessa** » 06 Jun 2009, 18:49

You could sub those 187/188's with BD139/138's. I don't think you would notice much of a difference in tone subbing those on the output. Most likely just better performance.

They also have the heat sink drilled holes that would allow you to fasten to the surface of an enclosure. They might need those mica thermal strips to prevent grounding.

SPeter · Post by **SPeter** » 06 Jun 2009, 19:47

To sub Ge for Si transistors? I think there for sure will be tonal difference!

vanessa · Post by **vanessa** » 06 Jun 2009, 20:26

SPeter wrote:To sub Ge for Si transistors? I think there for sure will be tonal difference!

I suspect not much at all in this circuit. Also if you search you'll find these BD139/138's used in a few circuits that are intended to replicate the tone and performance of Ge circuits. And they do a very good job IMO. They have hfe's around 150. Look for the Axis Face project you'll understand what I'm talking about.

SPeter · Post by **SPeter** » 06 Jun 2009, 21:50

vanessa wrote:
SPeter wrote:To sub Ge for Si transistors? I think there for sure will be tonal difference!

I suspect not much at all in this circuit. Also if you search you'll find these BD139/138's used in a few circuits that are intended to replicate the tone and performance of Ge circuits. And they do a very good job IMO. They have hfe's around 150. Look for the Axis Face project you'll understand what I'm talking about.

Yes, this popped first in my mind when I read your post! I agree it will sound good with BD's but I still think a bit different as the FF's with Ge and Si transistors with equal gains will sound a bit different from each other though both will do well!

Fernando · Post by **Fernando** » 19 Nov 2009, 16:26

Interesting amp! Thank you!

- Wich GE diode to sub the OA119? Can't find any. I have 1N276 and 1N60 (1N60 with only 0.22V fwd drop, if that matters)
- Are AC187 and AC188 (no K) good subs for AC127/128? They seem to be equivalents but... the AC128 is overpriced because of fuzzes.

Thinking in a 12U7/12AU7 preamp at 12V to match it... and a 7Ah lead acid battery

thanx again

jessej · Post by **jessej** » 19 Nov 2009, 17:18

Tengo Na Minchia Tanta is also a Zappa song. Devi usare un pollo!

Very interesting project. In my newbie eyes, this looks a lot like a small 60's Ge transistor radio power section... ?

Ben N · Post by **Ben N** » 19 Nov 2009, 19:37

Go to the page--he says this was adapted from an old transistor radio. Also, there is a link at the bottom of the page to a text-pic of Zappa, so there you go. (Althogut for a moment I thought it was Sasha Baron Cohen, LOL.)

Fernando · Post by **Fernando** » 23 Nov 2009, 10:00

You mean the "k" suffix just mean it has a heat dissipator?
I see AC188/187 with and without the dissipator...! So I'd say it means something else...
I thought "k" was a more powerful variety AND with a heat dissipator.
Any knowdledge/comfirmation about this? (AC188 = AC188k)

Also, what about the OA119 diode? Can be substituted with another GE diode in this application?
It seems that the AA119 is an equivalent but not shure...

SPeter · Post by **SPeter** » 23 Nov 2009, 18:37

Here we go!
http://www.datasheetarchive.com/

SPeter · Post by **SPeter** » 23 Nov 2009, 23:19

Sorry, the above link seems to be wrong!

Fernando · Post by **Fernando** » 23 Nov 2009, 23:30

Thank you! This afternoon I found the same datasheet and saw the "k" just indicates the dissipator for AC188/187/k

I also see AC188/187 does not seem to be direct replacements for AC128/127 (although listed as equivalents in some places)

I also found a Tesla datasheet for GC511/521/k, wich are listed as equivalents for AC188/187/k in some places.
They seem pretty similar in specs but I can't say if they are solid equivalents. It would be great if someone can compare their parameters and check (I did compared both datasheets but not all parameters are listed equally so I can't be shure)
http://www.datasheetarchive.com/pdf-dat ... 700258.pdf

OA119 seem to be named AA119 for some time now. No idea about differences in performance andhow old is the nomenclature change.
I mean, I don't kow if one can find "old" AA119 or if they are all modern production (say 80s onwards)

SPeter · Post by **SPeter** » 23 Nov 2009, 23:43

[quote=

I also see AC188/187 does not seem to be direct replacements for AC128/127 (although listed as equivalents in some places)

[/quote]

May be but Mr Jaques makes with them excellent guitar effects so probably they 'll work!
Tesla GC511,511K I hope will work too!

Fernando · Post by **Fernando** » 24 Nov 2009, 00:04

we are getting close then! what do you think about the AA119?