2A3 monoblock power supply

[tenderland]

Well IM ready to build but before I spend $500.00 for a pair of plitrin output xformers I have one more question. The desiagn attached is the stereo version I assume If i leave the choke and capacitors the same the b + will be higher in a mono design. Is this a concern?

Thanks Jeff

[arnoldc]

You can leave the caps and choke as they are but you need a lower HV secondary from your power transformer as you'll have only half the current draw now.

[SHiFTY]

It might be a little higher, so maybe a slightly lower voltage transformer would be a good idea. You can always use a 5U4 or 5Y3 rectifier instead, they have a higher voltage drop than a GZ37 or GZ34.

Otherwise, increase the cathode resistors on the output tubes a little, or get sovteks and run them HOT!

[arnoldc]

Originally posted by SHiFTY
Otherwise, increase the cathode resistors on the output tubes a little, or get sovteks and run them HOT!

Here goes I was expecting somebody would say that

[tenderland]

Well I gues the question is how do you know what voltage xformer to use , is there a way to estimate the correct value , and thank you for the replys

[arnoldc]

Hi tenderland,

For a single channel (mono) we want ~300V at 65mA. Hammond make a 275-0-275 transformer - 270EX (but you'll need a filament transformer for your 2A3, I used 166L2 on mine). Using that transformer, and 5U4-G rectifier (GZ37 is a bit hard to find), 10uF Solen -> 100mA Hammond choke -> 100uF Nichicon Muse, we will get the 300V we want.

You can download PSUD from Duncan Amplification website to verify.

Cheers!

[tenderland]

Thanks Arnoldc , very helpfull , was looking at the Plitron powerxformers and couldnt even come close I do like the plitron chookes though

plitron chokes

I will download PSUD and check it out , thanks again , big help

[tenderland]

I am trying to model the attached scheme only in a mono configuration. I am using PSU and for some reason it seems the output voltage is not correct.

power xformer = Hammond 270 ex 275 volt ct @ 125 ma
Im not sure what to use for source resistance i tried 2.2k ohm

im using a Full wave bridge using a 5u4-g

L1 = 10 H @ 50 ohms

C1 = 1000uf wkz Black gate ESR = 1/10 ohms

R1 i used 5 k ohm

I attached the origainal print "stereo version"

Help

[arnoldc]

Hi Jeff,

Do not use a resistive load. Change it to constant current and put in 65mA (the 2A3 in the diagram already draws around 62mA).

Also when modelling for tube rectifiers, make sure that you don't exceed the maximum value for capacior input design. THe limit is on the tube rectifier manual.

Cheers!

ps.

What I suggested will include CLC

10uF -> 100H -> 100uF

[tenderland]

Well looks like there is no CLC option for filter , The sorce resistence you can use the source calculator but need the primary and secondary dc resistence of the trany , I emailed Hammond 2.2k doesnt provide good results

Thanks
J