• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Kofi Annan in: "Pushed and Pulled Back!"

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#61
Kofi Annan said:
4. The B+2 potential divider on the filament supply-- is this to lift the AC supply for the heaters?

5. Also-- are monoblocks or separate PSUs advisable here? This increases the cost but may be the only reasonable way to implement the supply given the current demand.
Click to expand...

4/ yes.

5/ The pp-1c was originally conceived as a retrofit for ST70.

We are currently working on both an EL34 & an EL84 variation of the pp-1c (Allen thinks we shouldn't bother with the EL84, but i've always liked them better than the EL34... besides i have all the iron for a dual mono version (with separate supply for the driver stages)).

dave
 
#62
Thanks for all the responses!

So-- my remaining question about the PPP1c design is about the current consumption. I don't understand why the circuit is not consuming more than 100mA. I know I'm wrong, but when I calculate the current for the EL34s, I'm using the datasheets and coming up with 70mA per EL34 plus 30mA for the total current on the ECC88 side.

Why is that wrong?

Kofi?
 
#63
planet10 said:
We are currently working on both an EL34 & an EL84 variation of the pp-1c (Allen thinks we shouldn't bother with the EL84, but i've always liked them better than the EL34... besides i have all the iron for a dual mono version (with separate supply for the driver stages)).
Click to expand...

The few EL84 amps I have heard do sound nicer than EL34 but the EL34 puts out about twice as much power.

To make power levels equal (say 15W) you'd have to condier EL84 UL vs EL34 triode or (if the user needs about 30W) EL 84 PPP vs EL34 PP right?
 
#64
OK-- after much deliberation and review of the countless posts, blogs and wikis, I believe I'm going with the Baby Huey http://www.diyaudio.com/forums/tubes-valves/72536-el84-amp-baby-huey.html#post826626. I have always been intrigued by it and, based on the feedback from the forum, it is a relatively simple build that sounds fantastic.

I'll probably use Edcors for the power and output transformers since these seem to have a good bacg / buck ratio, but any other suggestions would be welcome. I think Hammond OPTs may not be good enough for this project (actually, gingertube suggested that, I believe) and everything else is too expensive.

I'll be working on a parts list over the next few days and I will post once I'm complete.

Any recommendations on part or design modifications that worked well for you guys would be appreciated.

Thanks!
Kofi
 
#66
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