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RCA Manual Typo?

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I was looking through an old RCA manual trying to find an integrated amplifer to build and found this one shown below. The specs call for a 1200V ct. transformer,but the filter caps would be way below specs,or am I just missing something here?
 

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The power supply uses a choke-input filter.
Eg, first you have the rectifier, wich is immediately followed by a choke and only then comes the first capacitor.
This type of power supply typically has a lower voltage than when the rectifier is immediately followed by a capacitor.
 
Denny -- While I have not constructed that exact amplifier, I have constructed what amounts to the guts of that amplifier: That is, matched 6L6GCs, operated with fixed bias, with regulated 450 volts on the plates, and regulated 400 volts on the screens, set to the quiescent current as specified in the RCA manual for these tubes when producing 55 watts output, driving Acro TO-340 OPTs to provide a 5000 ohm plate to plate load.

Under the above conditions, using 20 db of global NFB, each channel produces 43 watts RMS from 20 Hz to 20 kHz into 4, 8, or 16 ohms, with less than 1% THD, and less than .5% IMD.

In my case, the input circuitry I used was classic Williamson, but the output stage is operating under conditions virtually identical to the ones specified in the RCA design. Therefore, the performance figures I achieved should represent very closely the performance you can expect from this design.

I hope this helps!

Dave
 
Denny -- While I have not constructed that exact amplifier, I have constructed what amounts to the guts of that amplifier: That is, matched 6L6GCs, operated with fixed bias, with regulated 450 volts on the plates, and regulated 400 volts on the screens, set to the quiescent current as specified in the RCA manual for these tubes when producing 55 watts output, driving Acro TO-340 OPTs to provide a 5000 ohm plate to plate load.

Under the above conditions, using 20 db of global NFB, each channel produces 43 watts RMS from 20 Hz to 20 kHz into 4, 8, or 16 ohms, with less than 1% THD, and less than .5% IMD.

In my case, the input circuitry I used was classic Williamson, but the output stage is operating under conditions virtually identical to the ones specified in the RCA design. Therefore, the performance figures I achieved should represent very closely the performance you can expect from this design.

I hope this helps!

Dave

That sounds great! The only problem I have found is sourcing the right OPT,I'm looking at Edcor w/ the 5k p-t-p load,I would have to settle for their 100W trannie. I don't have a problem with that,other than having to pay for the extra iron.
 
Has anyone ever constructed this one,I like the use of a regulated power supply,I have several 6CB6A,and OA2 VR tubes.

Lots of them. For example, my Pyramids look similar, but have better LF stability because of direct connection between anodes and grids with common servo, and sounds (and measures) way better because of nested feedbacks. First Pyramid used VR tube, last versions use solid state Zener diodes (less glow on chassis) and MOSFET followers for voltage stabilizers that don't glow as well... But 6E1P magic eyes do glow instead. :)


amp_concert.gif


Pyramid-VII-M-1.gif
 
Lots of them. For example, my Pyramids look similar, but have better LF stability because of direct connection between anodes and grids with common servo, and sounds (and measures) way better because of nested feedbacks. First Pyramid used VR tube, last versions use solid state Zener diodes (less glow on chassis) and MOSFET followers for voltage stabilizers that don't glow as well... But 6E1P magic eyes do glow instead. :)


amp_concert.gif


Pyramid-VII-M-1.gif

Nice equipment there!!
 
The bottom part of the page seems to be missing missing on your diagram. Usually RCA list the parts there. I checked my copy of RCA R.T.M. but my version only includes the 35Watt version of the amplifier using the 7027, not the 7027A.

Anyway, the 7027A tube working in AB1 PP can run on 600VDC maximum voltage and 35Watt plate dissipation per tube.

So the LC cap value should be ok even with secondary windings of 600-0-600VAC, despite the fact that the excellent 5R4WYB rectifier only have around 60Volt of voltage drop (for a high vacuum tube that is).

Another advantage of this LC power supply is that it has good regulation when compared to more conventional CLC designs. However, it requires a more higher voltage than CLC designs to give the same output tension, as one can see on the 5R4WYB datasheet.
 
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