Jump to content

and now for something completely different part 3

kevin gilmore

Recommended Posts

if you want a fully balanced amp, then you need 2 amp boards per channel plus one input board

plus 2 goldenreference boards one set for 40v and the other set for 30v

plus a very large transformer, a pair of 25 amp diode bridges and some really honking large power caps and mass quantities of heatsinks.

if you ever saw the original levinson monoblock class A amps, those were 18 watts (really about 30) This is 100.

you can also build the unbalanced version which is still pretty silly and less parts. And still stable into 1 ohm.


Link to comment
Share on other sites

Thanks, Kevin. This is kinda sick and tempting at the same time. :)

I'm not good at estimating heatsink size for the power dissipation requirements, but could the balanced version be built in one large (4U or 5U) chassis, assuming heatsinks with 50-75mm fins (I'm sure Fischer sells something useable), or would it require monoblocks?

Link to comment
Share on other sites

Very excited for this project.



Sounding off [For the love of Quad]! Busted a diaphragm recently. Going to have to repair mine. : / 
Should note the other (working) segmented driver electrodes in mine are misaligned veritcally by ~2.7 or 3mm.... Perfectly
explains why this one sound lesser than the other.. 

Photos' are old, notice the lack of an amp.
Recently have been using an Aaragon 8008ST. 

Can't wait to hear about what Kerry's thinking on. 

Link to comment
Share on other sites

On 2016-01-20 at 3:00 PM, kevin gilmore said:

the opamp blows up at +/-40V would have to check the other parts, but +/-30V should absolutely work

speaking of power...

unbalanced/balanced/cast to balanced input block for all sorts of things, but mainly the uberamp, just need to find a way to get it into the box will probably involve splitting off the driver section.  Uses GR power supply +/-30V for the front end and another GR power supply +/-40V to run the regulated output voltages to the output amp.  If i add zeners to the servo amp, can easily go to +/-50V  and as shown, its 100 watts of pure class A, and something north of 225 watts A/B

front end NO feedback of any kind, .0025% thd at 20khz, 2nd harmonic.   3rd harmonic not measurable. output amps are current feedback.

i think i have created a monster :lol:



What size of capcitor would be suitable, 47000uF or more?

~1000VA transformer ok?

Also where can I find the pdf or gerber for this?

Link to comment
Share on other sites

  • 3 weeks later...

Question regarding the Uber amp..

to make Stereo Balanced Amp you would need 2 input boards, 4 driver and output boards.

one GRLV @ 30v for the input spliters and a 30v-0-30v 50va transformer

4) GRLV for the driver/output boards and  4) 40v-0-40v 600va transformers

Is this right?

Link to comment
Share on other sites

2 input boards, 4 driver boards, 4 output boards

one grlv @ 30v or 2 if you really want to do dual mono

one grlv @ 40v or 2 if you really want to do dual mono

one or 2 bigass transformers, stack of unregulated caps and 25 amp diode bridges mounted to the bottom.

current version looks a bit different. for the driver board, can stuff parts either top or bottom (other than opamp)

and all the holes line up to stack all 3 boards on top of each other.


Edited by kevin gilmore
  • Like 1
Link to comment
Share on other sites

HI All,apolgize for my english first

I'm planning to build a CFA3, but when reading gerber layout , 


I see silkscreen prints 

GAIN=10K SS,1.5K ZF 
Input=5K SS,100 ZF

and also noticed SS,ZF marked on silkscreen.I assumed ZF is for Zero Feedback and SS for Super Symmetry but not so sure whay they actually mean.so asking what are they mean and how to adjust them if needed to.

Another question is about bias.it seems to be measured by 1Ohm and adjusted by 5K pot,but how much bias is appropriate?


Edited by ang728
Link to comment
Share on other sites

True, and my dac is actually quite well behaved, so no real reason :)

However, I was going to expand my CFA2 to balanced anyway. A friend is building a Dynahi and I'm interested in comparing those two, and putting the input board in front will help test  some single ended sources others have recommended.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...

Important Information

By using this site, you agree to our Terms of Use.