• 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.

EL84 Amp - Baby Huey

Can one infer the continuous current capacity of the chokes from their core size?
If so, I'd guess the 6H choke is rated for about 150mA continuous, and so is just marginal for use in this circuit. Or am I wrong about that?
i wouldn't worry much, either choke will do and the dc resistances are typical of chokes used in that range,
remember that when we dimension our parts we took the maximum/worst case scenario, but in actual listening with music, those values of calculated currents will never pass/exceeded, not in an el84 pp amp...
 
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Is the orientation of the power transformer OK in relation to the output tubes?
Does that 6H choke look capable of handling two channels of push-pull EL84s?
looks ok to me, 90 degree coil orientation is followed vis PTX and OPT, that is a check...

re: chokes, at 150mA current draw, 92 ohms is just a 14vdc drop and lower for the other at 6.43v., compared to your b+ of 350+dc, peanuts...
 
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100uF cap driven by the rectifier?
Solid state rectifier there is one thing, but that and 100uF first cap might make for a very warm secondary, depends on the secondary current rating for a capacitor input filter.
Many tube rectifiers will not drive a 100uF capacitor input filter, unless there is Lots of series resistance to each plate from the secondary
(or lots of series resistance from the filament/cathode to the first capacitor).

Your blue power transformer appears to have an air-gap. Did you use a single ended Edcor output transformer to "Model" the power transformer you will use?
Maybe it is just the picture that did not give enough detail for my eyes.

Is your chassis aluminum, or at least non-magnetic steel?

You are proceeding well for a nice sounding amplifier.
 
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Your blue power transformer appears to have an air-gap. Did you use a single ended Edcor output transformer to "Model" the power transformer you will use?
Maybe it is just the picture that did not give enough detail for my eyes.
camera angle...but of course it is always possible to make ptx with all E's and I's on one side, take the MOT's for example..
 
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Hi Tony,
The peak charging currents are far higher when using a high input capacitance. You get higher IR losses and a lot more hash from rectifiers. Remember, at higher capacitance the same energy must be transferred over a much shorter time period (conduction angle). That means your peak current goes through the roof very quickly. You will suffer more IR losses with that higher peak current. You're going to excite any stray capacitance and inductance as well. I'd rather not, thanks.

100 or 120 Hz is a lot easier to reject than the higher harmonics are. The old engineers knew precisely what they were doing, we don't seem to! lol!
 
- I will be using solid-state rectifier diodes, not a vacuum tube. I understand that tube rectifiers typically cannot stand up to the current pulses caused by using a large value reservoir capacitor (>47uF).

- I could use 10uF, 22uF, 33uF, 47uF, 100uF or 180uF. I am concerned about excessive current pulses charging/discharging the reservoir capacitor. I was thinking 100uF would be a good compromise between max ripple reduction and tolerable current pulses in the transformer-rectifier-reservoir cap loop. I could put 180uF there also (I have some nice 180uF 500V radial electrolytics).

I was thinking of a CLC filter with 100uF - 6H - 800uF.
Yes, the 800uF cap is excessive, but I think I can get away with it after the choke (but not before). It's rated for 330V DC.
I also have a 470uF 450V capacitor I could use there.

I have a fairly well-stocked junk box, and I want to use up some parts.

- That is not an audio output transformer being used as a power transformer. As stated several times above, the blue transformer is an Edcor XPWR065-120 with 120VAC primary to 500VCT 250mA + 6.3V 4A secondaries. EI core. Standard stuff.

- The chassis is aluminum (aluminium).
 
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Hi Tony,
They did have higher values than they used. They didn't for a reason.

In fact they came up with a rule of thumb for filter capacitance, 1,000uF / ampere. I have found it is valid for solid state and tube product.

It's up to you of course, but I have found they made excellent decisions back then, and they actually understood their circuits a lot better than current engineers do on average.
 
Hi Tony,
They did have higher values than they used. They didn't for a reason.

In fact they came up with a rule of thumb for filter capacitance, 1,000uF / ampere. I have found it is valid for solid state and tube product.

It's up to you of course, but I have found they made excellent decisions back then, and they actually understood their circuits a lot better than current engineers do on average.
i did made a caveat, that it is just me and that folks need not try this at home with their own amps, as i am not the type who tells people what to think or how to think...i just share my post, i never imposed on people...
 
- That is not an audio output transformer being used as a power transformer. As stated several times above, the blue transformer is an Edcor XPWR065-120 with 120VAC primary to 500VCT 250mA + 6.3V 4A secondaries. EI core. Standard stuff.
Edcor made fine traffos.....can you confirm unloaded ht winding voltages? my understanding is that the 500vct@250mA meant that 500vct is the terminal voltage when 250mA dc is developed across a load resistor...this is also how i design ang build my power traffos....
 
I also like the idea that this simplified version has fewer active parts, so should be easier to troubleshoot should problems arise.
For the Baby Huey PCBs, I'd like to start from scratch, punching the holes in the right places the first time.
I also went the simplified route, but went for a slight variation on Yves original, I think it was the first draft from Marc ...
Baby Huey ECL86/Dissident Audio
The OPTs are nothing special, but the sound is amazing, crystal clear highs. On that one I have a little PCB mounted transformer with a doubler for the negative bias supply. I can switch between ECL86 and PCL86, but even PCL86 are starting to get a bit pricey now.

I got bogged down with the PCB/Gingertube BH84 since I had the wrong power transformer (saw 275AC on the PCB which was wrong), and it got sidelined.
 
@rongon
Being a different project, I'd suggest you to start another thread.

I've seen you added source followers ac coupled to the output tubes.
Being a simplification of the BH, I would avoid them, going towards Yves Monmagnon original design (where everything started: http://www.dissident-audio.com/PP_ECL86/Page.html ).

You can get the needed negative rail for the CCS from the bias as he did.