Hiss on 1 channel ideas

[baudouin0]

Glad its sorted. South Coast.

 

[tonescout]

maybe not that far then. I am just North of Worthing near Storrington

 

[tonescout]

I have had to take out/replace a couple of resistors in the process of repairing the pre-amp. I know this is a contentious subject....but the original 300k anode resistors are wire-wound, non inductive 0.5w military spec. The original spec are not available unless you order a min of $250 from the US manufacturer.......so what would you put in place?

How influential on sound are anode, cathode and grid resistors...as in my simplistic logic I would have thought grid were the most important?

 

[6A3sUMMER]

If they are actually Non-Inductive, then metal film and carbon film should work, even if they have spiral cuts in the resistive element to adjust the resistance (the spiral cut makes them "inductive" at several MHz).
This is an Audio Amp, not a Short Wave Transmitter.

 

[baudouin0]

Not contentious, just modern .5W metal film 300k. Modern resistors don't usually add any sound of their own unless they go pop.

 

[tonescout]

I used Takman metal film for the 510ohms I replaced getting the optocouplers out of circuit, so maybe they are a good bet. Not that expensive either. I have a few friends who are into the Audio Note world and think Tantalum is the only way to....but it's big $$

 

[6A3sUMMER]

Speaking of Tantalum . . .
(not resistors)

There are Tantalum Capacitors.
There have been lots of PCBs that are destroyed when a Tantalum Capacitor goes south.
Either a blow out, or a burned PCB, or Both.

Just my experience in a major T&M Company.
(Test and Measurement).

 

[tonescout]

There is a cult following of the old Shinkoh resistors ....no longer made

 

[tonescout]

I am just not inclined to join the cult to find out they make no difference apart from the price/wallet detriment difference

 

[baudouin0]

I would just stick to the science.

 

[kodabmx]

Some interesting info on Tan caps

https://nepp.nasa.gov/workshops/etw..._2013/1600_Teverovsky_Tantalum Capacitors.pdf

 

[wg_ski]

I used Takman metal film for the 510ohms I replaced getting the optocouplers out of circuit, so maybe they are a good bet. Not that expensive either. I have a few friends who are into the Audio Note world and think Tantalum is the only way to....but it's big $$

Those would be tantalum nitride, which does make a very good thin film resistor. Better would be aluminum nitride, which you can overload the hell out of before failure. Used a lot for high power RF terminations where it needs to look resistive from DC to daylight and handle very high peak power. The only resistors of these types I’m aware of are surface mount, which does limit their use in typical tube amps. Not usually used for audio at all. But I suppose you could if you wanted to badly enough, and would be very attractive for a cult because you could make up a lot of pseudo-science. I’ve never needed anything other than run of the mill metal film, oxide film, or nichrome for an audio amp. Any audio amp, even the lowest noise mic preamp. But I also don’t buy any vacuum tube more expensive than a Russian KT88 or a transformer more expensive than a Hammond so take any of my resistor choices with that particular cheapskate grain of salt.

With tantalum Capacitors if you use them you deserve your fate. Aluminum electrolytics have gotten so much better in terms of impedance at high frequency, leakage, and lifetime that there is no need to resort to them anymore.