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Old 24th June 2011, 06:57 PM   #21
Join Date: Nov 2006
Location: Torpoint
I calculated as much.
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Old 27th June 2011, 04:58 AM   #22
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Location: Portland Oregon, USA
I'd use polypropylene, or polystyrene where the values exist, silver mica is real good too for very small values that aren't available in PP or PS. Styrenes are particularly sensitive to heat, so be careful when soldering them in. Tantalums are questionable as are electrolytics, but if you use a Panasonic FM or Elma Cerifine electrolytic (I've heard very good things from a relative expert about these in particular - although these days I'd be surprised if standard ones were a problem), and bypass them with a 0.1uF polyprop, the caps will no longer likely be an issue. Teflon is the best, but a very very tiny difference at a very large dollar cost.

One thing many don't realize is that the power supply is directly in the signal path, and should also have it's electrolytics bypassed with 0.1uF polyprops. Personally, I have a 0.1uF PP cap bypassing the power supply for each section of circuitry, with separate ground returns for each cap, going to the "star-center" grounding arrangement. When the circuit looks at the power supply, it should see zero ohms for all frequencies above about 10HZ. These bypass caps insure that (assuming you've got big electrolytics also in the power supply).

In a feedback amplifier circuit, phase margin and slewing potential needs to be fully understood, or could be a reason for "gritty" or harsh sound. Impedances and loading effects need to be fully understood too.

Grounding is another place people compromise circuit operation without realizing it. All circuit grounds should ideally have a separate return to the "star center", which should have a short wire going to the power supply high surge current junction (the transformer secondary center tap and large electrolytics, or equiv.). The star center is also where the circuit ground should connect to the chassis. I've found that the AC line cord "earth ground" wire (green here in the U.S.) should connect to the chassis in a different place than the "star center". Let me know if any of this doesn't make sense. It's all very important.
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Old 27th June 2011, 12:16 PM   #23
Join Date: Nov 2006
Location: Torpoint
In my Aleph 4 Strikly DIY Project Build thread, Bartha has just suggested that the sibilance could be caused by the mains transformers being connected in anti-phase with each other.

As my two trafos are from different manufacturers I'll have to experiment to find out which way the primaries are wound. A quick bit of DC and a compass should sort that question out.

I would assume (probably incorrectly) that any manufacturer would then continue to wind any subsequent windings in the same direction. The same or similar machine would have been used to wind the primaries and the secondaries ??
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Old 1st February 2013, 11:50 AM   #24
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Join Date: Jan 2012
Is this C11 in the Aleph 30 in the signal-path when you use it single-ended?
In the Owner's Manual is written: "The second connection are the single-ended inputs, which occur through standerd RCA connectors. The input impedance of the amplifier is 47K ohms, and is DC coupled, with no capacitors."
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Old 1st February 2013, 01:42 PM   #25
Zen Mod is offline Zen Mod  Serbia
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Location: ancient Batsch , behind Iron Curtain
it is in signal path all the time - using it SE or Bal

meaning of paragraph in OM is that , in SE mode , (+) input is DC connected

you can toss it out ( bridge it with wire)

Papa probably put it there to increase idiot-proof factor
my Papa is smarter than your Nelson !
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Last edited by Zen Mod; 1st February 2013 at 01:46 PM.
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