transconductance amp

[HemiSam]

Interesting development.  

I was looking into the Bakoon headphone amp several months ago out of curiosity and again this week to power Fostex TH900's which are easy to drive (i.e. overkill) and HD650's, both currently powered by a Woo WA7.  The difference though, if I've read the prior posts correctly, is that I was not looking into the Korean version that's battery powered.  The Japanese HDA-5210 MK3 SATRI-IC-EX is the one I found much more interesting and would be more practical for my needs.  

Are you putting the Japanese 5210 Bakoon in the same boat with the Korean HPA-21 Bakoon?

Thanks.

HS

[kevin gilmore]

tyll tested the korean version i think.

[HemiSam]

Thank you, Kevin.  I don't get the battery powered approach they took, but hey...what do I know.

Will be following the latest here with interest.

Cheers,

HS

[MLA]

Have the transconductance amp up and running at 25V currently. Brilliant sound, really like it! In addition to being good for planars, also does wonders for my older AKGs.

While waiting for a few more resistors to arrive so I can set the GRLV at 30V (simply didn't have any useful combo at hand), is it possible to estimate the current draw at 30V? Thinking of running a balanced version off a single GRLV.

[congo5]

with 30v rails I measured

2.27v across the 50R  .054ma

2.34v across the 562R .004ma

so standing current is very low, just add what current you want going to your phones.

[MLA]

Definitely no problem then. Thanks for the measurements!!!

[G600]

Any reason not to build a balanced version of this ?

[kevin gilmore]

its not like a voltage amp, so a balanced version is still the same output current.

other than the cast output circuit i'm unaware of any balanced transconductance amps.

[G600]

Okay, a small saving then !

[wink]

Surely this wouldn't stop anyine from building one anyway..    Think of the bragging rights.

"My amp transconducts four times as much as yours - and it's balanced.........."   

[HemiSam]

I hope more of these get built and we get to read impressions/comparisons.  It's looks like a nifty amp.  

The only commercially available amp that's piqued my interest for use with my TH900's is the Japanese made Bakoon (not the Korean made battery powered one).  There are a few versions / options available and this is the plain vanilla one.  

http://www.amazon.com/Bakoon-Headphone-amplifier-HDA-5210MK3-SATRI-IC-EX/dp/B00MWMJ5HI/ref=sr_1_4?ie=UTF8&qid=1454339536&sr=8-4&keywords=bakoon+amplifier

HS

[kevin gilmore]

http://gilmore.chem.northwestern.edu/currentamps.jpg

 

[MLA]

So, how to think about volume pot values in front of these? 10K?

Edited February 13, 2016 by MLA

[kevin gilmore]

I use 10k pots for everything. makes it simpler

[gepardcv]

Not 10k for stat amps, though, right?

[kevin gilmore]

Sure.  Lower noise

[luvdunhill]

Yeah, folks need to just get "real" sources, cuts all those wimpy fly-by-night operations out of the mix.

[FallenAngel]

On 1/26/2016 at 10:40 AM, congo5 said:

with 30v rails I measured

2.27v across the 50R  .054ma

2.34v across the 562R .004ma

so standing current is very low, just add what current you want going to your phones.

 

Silly question, but what do you mean by "want going to your phones"?

How would you calculate that for, lets say 35 ohm HE1000? Applying ohm's law, that's almost 2A with 30V rails (60v) and that can't be right...

Edited February 29, 2016 by FallenAngel

[wink]

Quote

Silly question, but what do you mean by "want going to your phones"?

How would you calculate that for, lets say 35 ohm HE1000? Applying ohm's law, that's almost 2A with 30V rails (60v) and that can't be right...

This is about the current flow through the headphones when there is no input.

If you were getting rail voltages, the amp would be seriously broken.

You calculate the curent flow through the impedance/resistor ( the headphones) by the voltage across the impedance/resistance divided by the impedance/resistance.   i.e. I=E/R

2.27/50=0.0454A = 45.4mA.

2.34/562=0.0042A = 4.2mA

 

If you had 30V into 35 Ohms = 30/35=0.857A = 857mA

More realistically 2.27/35 = 0.0649A = 64.9mA.

 

Edited February 29, 2016 by wink
more info

[FallenAngel]

Thanks!

So basically that would mean a GRLV psu would barely need heatsinks to power one of these amps.

How large should the heatsinks be on the amp though?

[congo5]

Use heatsinks like in Kevin's picture above, I used these

532-529802B25G

for the power supply mount the two pass transistors to the case or find a sink, examples are in pictures on this site,

As for current for phones, with my phones (Sensitivity : 96 dB/mW) 50R ortho's I measure 2vrms when they are Loud..   2v / 50R = .04A

so allowing for peaks  I might need  300ma?

[Malvin]

Looks like I missed this GB.. Interested to build transconductance amp and GRLV. Any chance someone will have a spare set? Thanks

 

apology, wrong thread

[FallenAngel]

Any thoughts on running this amp off +/- 20V?

Also, how sensitive is this amp to power supply quality? As in, is there much difference for this amp to use a simple LM317/LM337 vs Sigma22 or GRLV?

Edited March 13, 2016 by FallenAngel

[congo5]

I found a large difference when using the golden reference power supply    versus a bench Supply

 

[FallenAngel]

11 hours ago, congo5 said:

I found a large difference when using the golden reference power supply    versus a bench Supply

Cool