transconductance amp

[kevin gilmore]

so tyll has been going crazy over the bakoon for planars.

well there are a lot of things i don't like about that amp, especially the battery power and distortion.

so here is something much better, tested last night at .06%thd, no feedback, output impedance 100k which is solely due to the servo...

http://gilmore.chem.northwestern.edu/currentsourceamp2.pdf

http://gilmore.chem.northwestern.edu/currentsourceamp2.zip

also testing curved traces

[Kerry]

Nice! This is really interesting. I'm going to have to add it to the list.

[spritzer]

It needs MOAR transistors... 

[PretentiousFood]

That's really cool! Kind of looks like an AD844.

Would the cascode (Q1/Q2) be happier with more voltage drop than D1? The BC546/556 have some weird curves and don't saturate as quickly as something like the BC337/327.

[kevin gilmore]

don't see any difference with an extra diode in the synthesis.

 

[Tyll Hertsens]

4 hours ago, kevin gilmore said:

so tyll has been going crazy over the bakoon for planars.

Well, not really crazy about the Bakoon as much as I am intrigued by current source amps and how they might provide benefits over voltage amps. 

Glad to see you working on it, Kevin.  I'll get you those measurements you want within a day or two.

[kevin gilmore]

change the high gain resistor to 75 ohms and the low gain resistor to 450 ohms to atch the gain of the bakoon

this is a bit higher than i thought

Edited December 11, 2015 by kevin gilmore

[wink]

This is what I used to calibrate

 

Pity the AC only goes to 10kHz.

http://www.adler-instrumentos.es/imagenes_web/productos/52120A%20Transductance%20Amplifier.pdf

Edited December 12, 2015 by wink
SHHHHppelllinkkk..

[kevin gilmore]

Congo5 has a working board now.

[UFN]

Pics or it didn't happen!

 

//UFN

[MLA]

I built the CFA2 a while back and am very happy with it, its great for the HE-500 I have, and works really well with the loaner planars I've managed to test it with (PM2, LCD-X).

Guess I have to build this one as well and compare   Any major differences to be expected in performance?

 

 

Edited December 21, 2015 by MLA

[kevin gilmore]

for planar ortho's with an impedance of 50 ohms,this amp really shines. with 30V supplies, does 2 watts pure class A into 50 ohms with a thd of about .03% which is much better than the bakoon does.

for hd800, all it does is accentuate the frequency response issues.

 

[MLA]

Sounds exactly like what I need!

If powering this from GRLV, what components other than the opamps need higher voltage rating to stay intact at 30V?

[kevin gilmore]

no parts changes up to 35V

 

[MLA]

Great, thanks!!!

[joehpj]

Is this amp able to drive desktop speakers?

[kevin gilmore]

2 Watts RMS into 50 ohms and you expect it to drive desktop speakers... NO

klipsch corner horns, probably ok.  not really desktop speakers

much more powerful amp coming at some point

Edited December 21, 2015 by kevin gilmore

[spritzer]

What's up with people thinking that any headphone amp will work at driving speakers?  Some will output sound but that's about it. 

[congo5]

14 hours ago, UFN said:

Pics or it didn't happen!

 

//UFN

https://mightytext.net/zPRzoM

I have no privileges here to store Images and Google drive doesn't seem to work. so trying that  link...

Also on other site... under my profile are pictures, also not much to see as they are not pretty, but they do work.

I use an homemade CNC to route boards.

12 hours ago, MLA said:

I built the CFA2 a while back and am very happy with it, its great for the HE-500 I have,

 

 

I completely agree, Its a Great amp.

 

2 hours ago, spritzer said:

What's up with people thinking that any headphone amp will work at driving speakers?  Some will output sound but that's about it. 

Isn't it about output impedance / the dampening ratio? as well as wattage.....

My Firstwatt F5 headphone amp drives smaller speakers just fine.

[kevin gilmore]

a F5 is a much bigger amplifier, 20 watts into 8 ohms.

also, not a transconductance amp, and has feedback

If you want a transconductance amp, F1 or F1J both of which really like very low impedances and have significantly higher thd.

Edited December 22, 2015 by kevin gilmore

[congo5]

Listening now,

[GrindingThud]

Ooo, looks like a great winer project.

[congo5]

On 12/24/2015 at 0:10 PM, GrindingThud said:

Ooo, looks like a great winTer project.

small size, very low parts count, very low heat output, very large sound....

looking forward to hearing what you think of it!

Its different than the CFP2, I like both a lot..

Edited January 3, 2016 by congo5
missing T

[kevin gilmore]

Winer project?

drinking 1994 BV George's de latour now.

left over from last night. Yumm 

[GrindingThud]

14 hours ago, kevin gilmore said:

Winer project?

drinking 1994 BV George's de latour now.

left over from last night. Yumm 

Now that sounds like a much better project!