Quick question on the PP-C1 amp

[athos56]

Off hand does anybody know what power transformer can drop into the PP-C1 without any schematic changes?

[athos56]

PSU schematic

[athos56]

A Hammond 372X for the 310vac and 6.3vac and a Hammond 266C24 for the 12v?

[gingertube]

NO,
372X doesn't have the High Voltage current capablity you need or the heater supply current capability.

Look up the specs for a pair of triode connected EL34's (at Duncan Amp pages).
High Voltage Current is 130mA at zero signal and 142 mA at max signal.
Allow 8mA per side for the front end ECC88's (16mA total) and that means 148mA at idle and 158mA at full output

For heaters 2 x EL34 + 2 X ECC88 comes to 3.8 Amps

Use a 372FX
The High Voltage is 300-0-300 which means that the rectifier changes to a diode from each side to the output and the centre tap goes to ground instead of the bridge rectifier arrangement. Its rated for 150mA DC BUT because you are not using the 5V winding and not fully loading the 6.3V Heater winding it will handle that 158mA at full power easily. The slight reduction in high voltage resulting from 300 instead of 310 means that your amp will be 16 watts instead of 16.5 Watts - not worth obsessing about.

It has 5 Amp Heater capability so you are only loading that to about 75%.

The -15V supply to where the front end diff amp returns does not have to be exactly -15V. You can get -12V by voltage doubling the unused 5V winding and that would suffice. You could use a second transformer if you wish to generate the -15V (especially since one of those tiny PCB Mount types would do - required VA is less than 1) but its not really necessary.

So all done with one tranny.

Cheers,
Ian

Edit: Thats 1 channel ONLY. You need a 372FX for EACH Channel

[athos56]

Thanks for the response. In the interest of full disclosure my next amp build is between this and the Baby Heuy and maybe the El-Cheapo, basically because I'm weak on tech skill but high in craft skill and thus I base most of my decisions on completeness of schematics, availability of parts, a general consensus by the DIY community of the projects quality, with the addition of a high challenge rating. This will be my second amp, the first went pretty well.

So on with the next question.

The High Voltage is 300-0-300 which means that the rectifier changes to a diode from each side to the output and the centre tap goes to ground instead of the bridge rectifier arrangement.

So instead of 4 of the 1n4008 you would only need 2 and the ground connection would come of the center tap and not where the 2 diodes come together?

You can get -12V by voltage doubling the unused 5V winding and that would suffice.

hmmm I'm interested in this and will have to look up how this is done. If it’s terribly easy an explanation would be appreciated.

Thanks again, I've enjoyed reading about the Baby Heuy, what I've understood at least

Pablo

[athos56]

As an example about the diodes. Is the arrangement you speak of like the arrangment of the b- supply in the el-cheapo schematic below?

[athos56]

Ok I found this on line. It stated that for a neg. polarity reverse the diodes. Would this arrangement work for doubleing the 5V and are the cap values important? Would the 1N4008 and 1000 uf caps in the original schematic be sufficient? Thanks again for the help, maybe this will all sink in someday

[Svein_B]

This is the more common simple voltage doubler :
(reverse diodes for neg. supply)
both this and your suggested one are described here: http://www.play-hookey.com/ac_theory...ltipliers.html

SveinB.

[athos56]

I saw that one but I wasn't sure what to do with the two outputs, so I looked for one with just one output that could be + or -. Hehe if you need the one of the treaties of paris or the Russo-japanese war explained I'm your guy but its the simple things in electronics which stump me. Thanks for responding though, I'll have to figure it out.

[athos56]

On the you posted SveinB, can the bottom output, next to that ground connection just not exist and just use the top one? That was either really dumb or a breakthrough

Second. Quote form the site

"Nevertheless, the output ripple of this circuit is significant, and will normally require either additional filtering or regulation to be usable by most electronic circuits"

Will this be an issue? Does the CCS provide filtering? I assume since it is a Constant Current Source that that the regulation is implied. Again that was either really dumb or a breakthrough

Thanks for the help