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In Reply to: RE: I would not use wire-wound resistors in grid stopper positions posted by Eli Duttman on March 03, 2017 at 08:48:12
What about good quality carbon film resistor for grid stopper??
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Carbon film resistors are LASER trimmed, with a spiral cut. The spiral's presence makes the part inductive, which is a negative in grid stopper service.
Carbon film resistors are what I recommend for plate stopper service. The current in the plate circuitry is substantial and CC noise is an issue. So, some inductance can't be avoided, but at least the non-metallic nature of the resistance element is retained.
Eli D.
So good quality carbon film resistor should be good for R2, R4, R8 and R11 then, right?
CF will do nicely. Buy KOA/Speer parts from Mouser, of an appropriate wattage rating. Remember, Kiwame "audiophile grade" resistors are, in fact, KOA/Speer.Frankly, the fascination with "boutique" parts eludes me. Yes, there are hyper-critical situations where noise factor, low ESR, non-inductive ... matter and a costly part makes sense. Otherwise, good grade ( not "bargain basement"), industrial parts yield eminently satisfactory results. Every last one of us is highly vulnerable to the "Emperor's New Clothes Virus". :> ((
Eli D.
Edits: 03/05/17 03/05/17
Are you talking about this one??
A Mouser search is linked below. The parts branded Kiwame are of the higher rated wattages. I suggest you use parts of an appropriate wattage in any given position.
Good stuff at a reasonable price is hard to beat.
Eli D.
Can I use Mills MRA-5 and MRA-12 for the power supply circuit?
That would be a complete waste of money . The inductance of "ordinary" WW resistors is of benefit (small) in a PSU filter. For Pete's sake, chokes ( inductors ) are part of many an excellent PSU filter.
Eli D.
Edits: 03/06/17
I have no choice as some of the good sounding and dirt cheap inductive wirewound resistors do not have all value for the PSU.
However, Mills has everything I need for this purpose.
What about a few loops of wire around a ferrite bead (i know they can be lossy at high frequency) or the old-timers trick of a wrapping the leads (or another piece of wire) of a CC resistor around the body to make a little air cored inductor in series with the resistance?
dave
A tiny ferrite bead, just big enough to clear the socket lug, cemented to the socket's insulating base has been used. FWIW, I find that idea appealing on the (ostensibly grounded) grid of a cascode's "top" triode.
JMO, anything that truly suppresses parasitic oscillation is fine. "There's more than 1 way to skin a cat."
Eli D.
As politically incorrect as it is, I agree with the cat skinning and was making just that point when I questioned your insistence of a carbon comp because it was non-inductive.
dave
It's a question of Q. Will those devices exhibit sufficient dampening at the frequencies over which the tube exhibits a tendency toward instability? I've seen transmitting tubes oscillate when the carbon comps in anode suppressors (the second device you mentioned) were replaced with spiral-wound carbon film. Depending on the tube, the circuit and the physical layout, this can be a tricky thing.
--------------------------
Buy Chinese. Bury freedom.
What about non inductance wirewound resistor for R2, 4, 8, 11 and Vishay naked for R15 and 16?
IMHO, use carbon comp.
carbon comp for R3, 9, 10?
mt
What about non inductance wirewound resistor for R2, 4, 8, 11 and Vishay naked for R15 and 16?
You are really set on using wire-wound, precision resistors. I suppose you should try "A-B" test and see what you think, between WW and carbon comp.
8^)
Edits: 03/04/17
But the value of carbon comp will drift.
Slight drift really won't matter to a tube that is single-ended, cathode-biased.
But, go with what you want to do. It's DIY. No hard and fast rules. If you run into harsh results, perhaps due to instability... consider trying those "primitive" carbon comp resistors.
There are a ton of vintage equipment running with old school CC resistors. Some sound pretty darn good.
Post your experiences.
8^)
sure, will put CC for grid stopper, and those cathode resistor most likely will be Riken as well as the 82K and 100K.
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