P. Millett Engineers Amplifier

[UJF]

Hello Everyone, I am increasing the power output of the designed WPC from 17 to around 40. The power transformer recommended was a "700VCT (350-0-350) to get 450VDC" B+ input. However no current level was ever discussed, so I choose 400 mA and Edcor part number XPWR029-120. Now I find Edcor no longer makes that transformer with that high a current rating. Was I correct in choosing that current level or can I get by with a lesser amount? Can anyone recommend an alternative power transformer. The Edcor was priced right at about $90. Other transformers I looked at with similar specs are quite a bit more.
Thank you for the help.

Millett DCPP
DCPP Amp

 

[tomlang]

The voltage is a little less but the current is good. Double check your filament draw though, depending on tubes used may require an auxiliary filament transformer.

Transformer - Hammond, Power, Replacement for Fender, 120 V | Antique Electronic Supply

Pete full wave rectifies his bias, with this one you'll need to half wave it but should work fine.

 

[TonyTecson]

in my case what i do to get the power capacity of the power transformer required:

1. compute filament power of all tubes used in watts
2. compute plate power requirements, e.g. 40 watts is 80 watts stereo,
160 watts for plate,including those of drivers and preamps,
3. add total for 1 and 2
4. divide that by a factor of say 0.6 to get primary power capacity.

then you can shop around for for suitable power traffo...
getting a bigger power traffo can mean cooler operating temperature...

 

[UJF]

Thank you Tom & AJT for the info. I will look up the data for the tubes and work thru the calculations. I have never done this so it should be interesting. I'll post how it works out. I also have a note into Hammond asking for their recommendations. In the mean time, any other weigh ins will be a learning experience for me. Thanks guys.

 

[harperrc]

there is an entire thread where they discuss increasing the power output from this amp

Posted new P-P power amp design

 

[UJF]

I like the size and mounting configuration of the 290FX Tfxr. Can I assume the 320-320 VDC will result in a lesser wattage output than the 350-350. And Yes, the circuit has a full wave rectifier on the PC board. Can I try that with the Tfxr before I start ripping the rectifier in half?

 

[jackinnj]

Moving to a new home -- the carcase is an AIL Type 81 Noise Generator -- from the era prior to Eaton's acquisition of AIL:

 

[smoking-amp]

There is an upgrade version of the 290FX xfmr with M6 laminations for quieter operation. 291FX Both 10 lb. It costs a little more. $114 at Mouser. Angela Instruments is another good source.

If you want to keep the 700VCT spec at 403 mA, there is the Hammond 373HX, but it is $196. It will be extremely quiet though, 300 series. And heavy, 15 lb.

Or build a universal power supply for all your (future) amplifier projects:

Angela sells the Hammond 378CX 400-0-400V 465 mA for $149. I use two of them (with a 55 VAC isolated Variac to auto xfrm the pri) for 2 universal power supplies for any amplifiers.
It is really big though, 17 lbs. (+ 7 lbs for the Variac and 13.5 lbs each for 193Q inductors, then 2 of them) Dead quiet. Big enough to run most anything (400V or 800V max depending on full/bridge rectifier). Could be used alone with inductor input filtering for 400 VDC.

You can run with less B+ voltage if you lower the OT primary Z some. Don't know what you have planned or with what tubes.

Check out the recent thread on Pete's 50W Monoblock Engineer's Amplifier:

http://www.diyaudio.com/forums/tubes-valves/302586-50w-monoblock-engineers-amp.html

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