Revisiting some "old" ideas from 1970's - IPS, OPS

forgot the evidence...
 

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Hi Evan,

Great job - nice looking boards and good PSU filters!
R44 will not help - it provides adjustment for clipping symmetry.
The right one to change would be R40 - say 1.3K

However, I would recommend to leave it as is. Set 3mV at both channels - in fact, the closer you are to zero axis - the better.

Thimios - these boards allow building both Vertical CFA and VFA (either, or) - some placeholders stay unpopulated.

Cheers,
Valery
 
Both amps started up first try and have been playing for a few hours.

Workshop photos. I'll let these play in the shop for the day tomorrow and they should be in the real system by tomorrow night. I plan on using these to drive the midwoofers.

My only fear is that I will love them and then I'll need two more channels.....

Thanks for the great fun,
Evan
 

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Thanks guys.

I've been liking the monoblock amps.... if these were dual mono in one chassis they would be very heavy.

I have been thinking of rearrange my system. Instead of having all the amps in one rack I want to move the amps to right behind the speakers. Two stacks of four amps seems easier to swallow then the one stack of eight....
 
So I've been listening to the vertical cfa NS ops for a while now. As as I feared...I need/want two more channels.

I used a 7" piece of this for each channel. 12.000" - HeatsinkUSA
They get quite warm after some hours of playing. The new amp will use an 8" piece per channel. Rails will be +-72 Vdc The transformers I have come with an 18 vac output. I assume I can regulate this to the +-15vdc I need for the front end power.

I am attracted to the low distortion of the cfa front end. With the new modular design I can easily compare. What front end do you think would make a good counterpoint to the vertical cfa? Maybe something with a dominant 2nd order distortion. I like how my single ended tube amps sound.
Thanks for the great designs and support,
Evan
 
If you are getting your transformers from Antek, you better verify the aux windings are dual 18VAC. Most are a 12V and a 18v in their AN series. The AS series is supposed to have dual 15VAC. 18VAc is fine, but 12VAC is too low.

My personal preference was the Vertical CFA and the VZ-X4. Both sound very similar. Vertical VFA without nested feedback is almost identical sounding too.