Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Reduction => Topic started by: jimiclow on June 11, 2013, 04:04:59 PM
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I will be starting to build my Reduction this weekend.
I have a question regarding the 3x0.01uf capacitors in parallel. Can I use a single 0.03 or 0.033uf for this? I saw a 0.03/630 polypropylene at Mouser and a 0.033uf V-cap.
Second, how much current can the 6.3 volt provide? Can I use a 6N1P-EV? I have more than a dozen of these tubes.
Thanks.
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I don't know about the 0.033 but you could use 3 0.01s, 2 0.015s or a single 0.03 -- same difference. The only consideration might be space and small differences in ESr. I'm guessing that since these are the same values as the eros, BH is doing this so they can stock one part for both positions in both phono stages. Which is just smart engineering. Vcap also has 0.015s in tin foil teflon, but 4 of those and two of the 0.01s will add up and be fairly large as compared to stock. If there's room and you have the bucks, it would be an interesting experiment :-).
-- Jim
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If you have the bucks for the V-caps I would go for it. Let us know how it sounds compared to stock. All kinds of stuff you can do. Its like chess. Its unsolved.
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Can I use a single 0.03 or 0.033uf for this? I saw a 0.03/630 polypropylene at Mouser and a 0.033uf V-cap.
Second, how much current can the 6.3 volt provide? Can I use a 6N1P-EV? I have more than a dozen of these tubes.
A single 0.030uF cap will work, but do bear in mind that we provide film and foil capacitors, and the polypropylene caps at Mouser are probably metalized.
The 6.0V supply is fed by a ~11V DC rail, through 11 Ohms of resistance for each tube. If we assume that the voltage drop is 5V for whichever tube we use (which is a relatively safe assuption since the heater current differences aren't that large), then we will see 0.45A of current through the 11 Ohm resistors regardless of which tube is used. That means that a tube drawing 0.45A of current will work theoretically, but with no regulation. A tube that draws less current than this will allow the zener to begin to draw current and regulate the heater voltage. Generall there is a sweet spot in terms of current draw through a zener, but as usual PJ found a part that looks to regulated well with 0.1mA to 1A running through it!
IIRC, PJ mentioned some other change that was a good idea with the 6N1P, but I can't remember it off hand.
-PB
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Thanks for the reply.
Paul, the cap at Mouser is metallized. Is there a disadvantage to using a metallized PP?
The reason I'm asking about the current is because the 6N1p-EV draws twice as much current as a 6922. I don't know much about zener-regulated supplies.
The tube that came with the kit is 6N23P. I have a few of these also. I find them to be very quiet on my Schiit Lyr and I prefer them over 6922/E88CC.
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Crap! I lost my detailed post - didn't check to see that PB posted first.
The heater circuit is designed to still function at -10% power line voltage, where you have only 4v across the 11 ohm resistor. The Zener really wants 100mA to have decent regulation, but it will work down to 40mA. There are other considerations that limit the maximum current at +10% line voltage.
The "other thing" is that the RIAA changes if you mess with those capacitances, or if you change the tube. I'd recommend staying with the design values and looking for higher precision if you want something better. While these values were chosen for availability and convenience, the actual caps were chosen (by Doc B and PB) through listening comparisons with the old Seduction. Oh - and the 6N1P has a much higher output impedance so the output cables must be less than half as long - I'd recommend 0.5 meter maximum.
Final note - the power transformer could power two 6N1Ps heaters if you replace the filament regulators with a different design. But then the upgrade HV regulator doesn't put out enough voltage to reliably run the 6N1Ps. So basically it's a whole new power supply design with a different power transformer.
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Thank you, Paul!
I guess I will stick with the stock RIAA caps for now. I do have a Mundorf silver-gold-oil for the coupling caps.
Paul, if I use the Reduction in amps with low input impedance, is the 0.47uf output cap still optimal for this application? I think I have a pair of 1uf Clarity caps in my box.
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If you have the bucks for the V-caps I would go for it. Let us know how it sounds compared to stock. All kinds of stuff you can do. Its like chess. Its unsolved.
Eric,
You just want him to blow $600 on RIAA caps so you can live vicariously! That is evil, and I want to hear about it too!
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Thank you, Paul!
I guess I will stick with the stock RIAA caps for now. I do have a Mundorf silver-gold-oil for the coupling caps.
Paul, if I use the Reduction in amps with low input impedance, is the 0.47uf output cap still optimal for this application? I think I have a pair of 1uf Clarity caps in my box.
My position is that the Se/Re-duction prefers 50K or greater, and between 15K to 35K a 1uF is better. Below 15K I don't recommend it due to loss of gain, but scaling up the capacitance further would be necessary.
These are based on calculations; listening tests may lead you to larger capacitances. We use 1uF in Eros, which has the same output tube and operating point.
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Thank you very much, Paul!
I'm on page 15 now.
I got some Russian 0.015 this morning.
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My position is that the Se/Re-duction prefers 50K or greater, and between 15K to 35K a 1uF is better.
Hmmm......so if one were going to run s/reduction into Submissive, then you would recommend replacing the output cap with 1uF? Not a problem, but good to know (since I run a seduction and just ordered a submissive).
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Yes I would.
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Thanks, Paul. I think I have a suitable pair of caps sitting around.
And apologies for the tangent, which I just realized this is.