GainWire Mk3 CFA pre/phone amp with very low distortion

[didiet78]

Supertex was acquired by Microchip Technology, Inc. DN2540 can be bought directly on their site for 1.30$ and also shipping is not to steep, $12 for Serbia, maybe even less for other destinations. Try ebay also for low or no shipping cost.
I was busy with other things and I couldn't finish mk2 yet so I picked info about mk3 to late for pcb group buy. I hope next GB will not be on so short window of few days, but maybe it's better to have the time to iron things out and test the preamp properly.

Regards, Milan

I stiil can use irf610 and irf9610 with little change on circuit and it work in my MK2. Or I simple use lm317 for ccs to replace dn2540

 

[dadod]

I stiil can use irf610 and irf9610 with little change on circuit and it work in my MK2. Or I simple use lm317 for ccs to replace dn2540

Yes, you can use different CCS, but DN2540 (or other depletion mode mosfets) make simple and excellent CCS.

 

[didiet78]

Agree.

 

[dadod]

All boards shipped except one, erik777 does not respond to my PM.
If somebody else interested for that last board let me know.
Damir

 

[bkdog]

All boards shipped except one, erik777 does not respond to my PM.
If somebody else interested for that last board let me know.
Damir

Hi Damir, I PMd you some time ago - interested...

 

[dadod]

Hi Damir, I PMd you some time ago - interested...

Sorry I forgot, PM your PayPal email address and I will send you Request Payments.
BR Damir

 

[xrk971]

I received my board. Looks very nice.
Thank you Dadod.

 

[31697B]

dadod, I am putting together your CFA power amp. here are a few preliminary distortion resulst.... it will get better as we get the grounding right and best parts and better matching !

1W/8 THD

1W/8 THD+N

300W/4 THD+N

300W/4 THD

300W/4 THD



THx-RNMarsh

 

[mlloyd1]

impressive!
😎
richard, please post some pictures and descriptions of the wiring and grounding changes as you tweak for peak performance.

thanks,
mlloyd1

dadod, I am putting together your CFA power amp. here are a few preliminary distortion resulst.... it will get better as we get the grounding right and best parts and better matching !
...
THx-RNMarsh

 

[platon.rado]

done,tomorow test

 

[dadod]

done,tomorow test

You are fast, but I have one concern, to small(short) shunt regulator heat sinks.
Did you set the shunt regulator voltage?

 

[attalostesla]

An externally hosted image should be here but it was not working when we last tested it.

photo share
6cm-11cm
hi, is this layout ok?
Do you have any suggestions?
Thank you.

 

[dadod]

An externally hosted image should be here but it was not working when we last tested it.

photo share
6cm-11cm
hi, is this layout ok?
Do you have any suggestions?
Thank you.

Sorry I don't see it.

 

[attalostesla]

image attached, sorry
i cannot edit previus message.

 

[dadod]

image attached, sorry
i cannot edit previus message.

I am not going to check your connections, but two things are not so good.
First the grounding, signal ground and power ground should be connected together in some kind of a star ground, not as you did, look my layout of the single channel here: http://www.diyaudio.com/forums/soli...hone-amp-very-low-distortion.html#post4826430
Second, you need a heat sinks for BD139/140.

 

[platon.rado]

You are fast, but I have one concern, to small(short) shunt regulator heat sinks.
Did you set the shunt regulator voltage?

Today I try..

 

[attalostesla]

Thank you, i will try it again,

 

[reaper996]

Damir:

Board arrived Monday, looks good.

Patrick

 

[tdrood]

Samir, do you have any plans to make another set boards? If so, I would be interested in two or three. As an aside, has anyone tried one of the completed units on headphones?

Thanks guys, this is really cool.

 

[Malvin]

I would also be interested in one stereo board