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Old 29th January 2004, 01:10 AM   #1
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Default Resistors and Capacitors

At the risk of opening a can of worms here ! In which parts of a Valve Power Amp is the quality of Capacitors and Resistors important.

Are the heater supplies important?

Is it just the main power supply?

Do the high power bypass resistors in the PS need to be good quality?

Why are so many capacitors dual contructed ie 200u+200u ?

Your thoughts


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Old 29th January 2004, 01:30 AM   #2
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Presumably, the parts that carry signal, but as far as I'm concerned, resistor and capacitor sound is (attached).

Tim
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Old 29th January 2004, 01:45 AM   #3
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So tell me what you really think, go on don't be shy.
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Old 29th January 2004, 04:30 AM   #4
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Hi,

Quote:
So tell me what you really think, go on don't be shy.
Asking the chef for his recipe?

Cheers,
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Old 29th January 2004, 05:45 AM   #5
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Use a large power transformer and low resistance choke, preferably rated for double the current that you plan to draw. Many people buy a 200mA transformer for a 200mA design, and then when the *instantaneous* current goes to 250mA in a loud part, the voltage sags, the tube bias points change and the result is distortion and lower power. A bigger tranny has better regulation and avoids these problems more.

I would go for silicon diodes in a PP amp, with a moderate input capacitor, a low resistance choke and a large cap (~400uF) With a SE amp the jury is still out, a tube rectifier

As far as components go, your output transformers are the most important contributor to the sound of the amp IMHO.

After that, use decent parts that are hopefully rated for long life and decent specifications. Angela.com is a good place to get bits and pieces in small quantities, I am sure people can recommend other suppliers.
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Old 29th January 2004, 06:10 AM   #6
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Quote:
Use a large power transformer and low resistance choke, preferably rated for double the current that you plan to draw. Many people buy a 200mA transformer for a 200mA design, and then when the *instantaneous* current goes to 250mA in a loud part, the voltage sags,
Yes. Keep in mind that for a choke input filter the peak currents are many times the average current so the choke needs serious overrating or a small cap to precede it.

What is audible? Everything. A popular opinion is that indirectly heated tubes are impervious to heater supply quality but that in not my experience. I can clearly hear the diodes and caps in the heaters, presumably due to the heater/cathode capacitance.
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Old 29th January 2004, 07:08 AM   #7
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All good info, many thanks.

Anyone able to explain the dual cap thing. Do you just parallel them to double the capacity or what? Do you need them in series to achieve the voltage rating?

Keep up the great input.

Ralf
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Old 29th January 2004, 07:23 AM   #8
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Anyone able to explain the dual cap thing.

They are meant to be used with resistors/chokes between the cap sections. It just saves space.
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Old 29th January 2004, 07:44 AM   #9
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Be carefull.You can't connect these dual caps in series.Only parallel!!

"Everything is audible",I agree with this.Especially the parts on tha signal path.

The PSU must be as large as you can.I order transformers with three and four times up the needed currents.
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Old 29th January 2004, 07:49 AM   #10
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Thanks guys,

Cool idea with saving space. Noticed caps like Black Gate don't seem to go very high with their capacity so I'd need to use them in parallel to get the capacitance or reduce the design requirements.

Didn't expect every component would need to be good quality ....sigh....

Hoping I could save somewhere.....
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