What tweak are you carrying today?

[microstrip]

Replacing the SoundLab A1 PX crossover power resistors with Vishay thick film ones. Bias expectation is high - it is a lot of work!

 

[JackD201]

That looks like more than just tweaking to me micro.

 

[LL21]

+1! Let us know how it goes!

 

[Douger33]

Last week an audio friend alerted me to the charcoal tweak from Audio Direction in Honolulu... I put three charcoal bricquets on top of each of my Tannoy Canterbury's, on top of paper towels and toward the front. It is an organic thing, and totally reversible. I received good results...

 

[garylkoh]

Why are you using thick film resistors? Thick film resistors are oxide paste film. They have the most self-noise, worst tolerances, and high temperature coefficients.

Even thin film resistors have better temp coefficients and lower noise. They are made of a sputtered metallic nichrome film and in general sound a lot better.

In a loudspeaker, I would use wirewound with non-inductive Ayrton-Perry windings. The very best would be the Vishay metal film, but those are supremely expensive and difficult to get in the right values.

In some cases, I would use a carbon resistor for a different sonic characteristic.

 

[microstrip]

Why are you using thick film resistors? Thick film resistors are oxide paste film. They have the most self-noise, worst tolerances, and high temperature coefficients.

Even thin film resistors have better temp coefficients and lower noise. They are made of a sputtered metallic nichrome film and in general sound a lot better.

In a loudspeaker, I would use wirewound with non-inductive Ayrton-Perry windings. The very best would be the Vishay metal film, but those are supremely expensive and difficult to get in the right values.

In some cases, I would use a carbon resistor for a different sonic characteristic.

Gary,

Thanks for the wise advice. I have used them because I saw SoundLab used them in their "HotRod" package. I have to say they were not my choice after the listening tests - the current winners are the Mundorf M-Resist Supreme (high power large wire ceramic resistor). As I use a lot of them in series/parallel I connect them minimizing the inductance reversing the sense of the currents along inline resistors. BTW , they are not used in serial - just in the bottom of a CR network.

Great to have the collaboration of experienced experts in WBF!

 

[garylkoh]

Try these: http://www.vishay.com/docs/31801/mra.pdf

Using a lot in series/parallel is not recommended. The reason is that you are then subject to a lot of different signal paths depending on the tolerance of each resistor.

 

[microstrip]

Try these: http://www.vishay.com/docs/31801/mra.pdf

Using a lot in series/parallel is not recommended. The reason is that you are then subject to a lot of different signal paths depending on the tolerance of each resistor.

Unfortunately they are rated at 10W - SoundLab uses resistors totalizing 100W in this position. Some users reported increase in sound quality using 200W.
Do you think that associating resistors in series should be better than in parallel? I checked the values and they match to .5%.

 

[garylkoh]

If they are not in series, and at the bottom of a CR shunt, then they would never be dissipating anywhere close to 100W. If they were, your amplifier would be driven to clipping at all times.

The reason that you would have huge power dissipation is due to the fact that thick film have bad temperature coefficients. In particular, thick film are prone to transient noise due to slow heat dissipation. Wirewound are a factor of 10 or more better for this job. I prefer associating them in series to parallel. However, as a shunt resistor below a capacitor, the phase effects of the capacitor swamps the resistor, so that should not matter as much. However, because it is in series with a capacitor, the lower the inductance (parallel) the better.