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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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.
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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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..
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!
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).
- 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).
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.
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...
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 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.
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.
I am planning my Baby Huey build and have a question regarding transformer covers. I was thinking of using the Antek 100VA toroid with its accompanying cover.
https://www.antekinc.com/ca-100-steel-cover/
However, I am concerned about how the cover is attached. Here is the description: “There are 2 rubber pads to isolate the transformer to contact with the metal case and lock nut. The center rod is about 0.05” longer so there is not electrical short on this case to the main chassis (assume the chassis is metal).”
The photo shows a rubber washer between the center bolt and the cover top. Would not that allow a short if anything touched the top of the cover and the top of the bolt? Either I am missing something or that design seems to be lacking. Can anyone allay my concerns (or validate them)? Thank you.
https://www.antekinc.com/ca-100-steel-cover/
However, I am concerned about how the cover is attached. Here is the description: “There are 2 rubber pads to isolate the transformer to contact with the metal case and lock nut. The center rod is about 0.05” longer so there is not electrical short on this case to the main chassis (assume the chassis is metal).”
The photo shows a rubber washer between the center bolt and the cover top. Would not that allow a short if anything touched the top of the cover and the top of the bolt? Either I am missing something or that design seems to be lacking. Can anyone allay my concerns (or validate them)? Thank you.
This is a good question. I think you are right to be concerned and get the question resolved. Unfortunately I have not myself seen or used these newish Antek covers. If I understand the description correctly it sounds as if the cover rim is not touching the top plate (if metal) of the amplifier because the “center rod” is 0.05” longer than the cover sides. But if it is slightly lop-sided it will touch. I assume Antek had worked this out, so I suggest you shoot them an email and ask for a explanation of how the cover prevents a short (not completing an electrical path through and around the toroid core). Please share if you hear the answer.
Regarding using a 100VA Antek power transformer; this is fine for monoblocks. But for the price difference of $10 I have used the 200VA transformers to power my stereo Baby Hueys. Yes, it is overkill, but nice.
Regarding using a 100VA Antek power transformer; this is fine for monoblocks. But for the price difference of $10 I have used the 200VA transformers to power my stereo Baby Hueys. Yes, it is overkill, but nice.
Thank you, Francois. I will inquire of Antek and let you know what they say.
With respect to the VA rating, the 100VA version has dual 230v windings, each with 220ma. I would use 1 winding per channel. I think I saw in this thread that each channel needs 100ma. Shouldn’t the 220 be plenty for each channel? (Antek appears to be out of the covers for the 200VA version, which I guess would avoid my problem, but leave me without a cover!)
With respect to the VA rating, the 100VA version has dual 230v windings, each with 220ma. I would use 1 winding per channel. I think I saw in this thread that each channel needs 100ma. Shouldn’t the 220 be plenty for each channel? (Antek appears to be out of the covers for the 200VA version, which I guess would avoid my problem, but leave me without a cover!)
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