Why it sounds different.. ?

[R.G.]

You might try it with a different speaker or speakers too. In testing the Workhorse amp prototypes, we found a profound difference in the "voice" of different lines of speakers. This plus the OT differences can easily account for a different voice to an amp. Add capacitor tolerances to this and the problem starts to become how to ever make them sound similar.

[hebaton]

O.K. I installed the parallel resistors as suggested and immediateky found the amp plays cleaner and I feel, not as lou. Both very positive changes.
I will be ordering the Metrospec OT also.

I am not able, to follw the B+ as suggested for now, would ned to lift the board to be sure I see everything.
I do find the amp "stiffer" than what I remember, and would like to change that if it is possible.

THanks all, will return to this after the tranny change !

[hebaton]

if i can guess.. bottom picture amp sounds too dark, and is not cutting in the mix.

It does !

[bepone]

if i can guess.. bottom picture amp sounds too dark, and is not cutting in the mix.

It does !

i had the same problem, related with too much carbon comps... so change PI anode resistors to carbon film, and all others anode, tone stack too, if is not enough proceed also to all others..
bright carbon film are koa speer, perkusive, instant change in tone, but i will chose some generic cf 1-2w cheap , like are in marshalls

[martin manning]

Is this a case of resistors drifting up in value? Still not sure if you removed or lifted one end from the circuit to measure them.

[hebaton]

No, did not lift them.
I was under the impression Resistors could be measured in circuit. I know caps cannot.

[martin manning]

It both cases it depends on what is around them. If there are any other components that make a parallel path, lifting one end is required to get an accurate reading. For example measuring the feedback resistor you have a parallel path made up of the Presence pot and the OT secondary.

[WhopperPlate]

if i can guess.. bottom picture amp sounds too dark, and is not cutting in the mix.

It does !

i had the same problem, related with too much carbon comps... so change PI anode resistors to carbon film, and all others anode, tone stack too, if is not enough proceed also to all others..
bright carbon film are koa speer, perkusive, instant change in tone, but i will chose some generic cf 1-2w cheap , like are in marshalls

Koa are really percussive ime , top end pings nicely and easy to play , but they don’t have anywhere near the midrange of a piher or an iskra, and I find that I usually need to make up for that one Way or another

[R.G.]

Koa are really percussive ime , top end pings nicely and easy to play , but they don’t have anywhere near the midrange of a piher or an iskra,

Is there any way to measure the frequency response of these resistors?

[bepone]

better is spectrum analyse

[R.G.]

better is spectrum analyse

That's fine too. I'm open to nearly any way to measure frequency response differences in resistors.

I'm well aware that there are very, very small amounts of second order distortion in carbon comp resistors due to the voltage coefficient of resistance. It's measurable with good instrumentation and some modestly picky pre-set-up.

The idea of using a spectrum analyzer implies the generation of non-fundamental frequencies by the resistor - which, by definition, is distortion.
This is somewhat different from the idea that a different kind of resistor affects the time-domain response ("percussive") or tonal balance ("midrange", "top end pings").

I'm very open to things affecting sound/tone/etc of amps. I just think that if some effect is real, there ought to be a way to measure it. And I'd love to find me some mid-range-y resistors, or percussive ones.

[WhopperPlate]

better is spectrum analyse

That's fine too. I'm open to nearly any way to measure frequency response differences in resistors.

I'm well aware that there are very, very small amounts of second order distortion in carbon comp resistors due to the voltage coefficient of resistance. It's measurable with good instrumentation and some modestly picky pre-set-up.

The idea of using a spectrum analyzer implies the generation of non-fundamental frequencies by the resistor - which, by definition, is distortion.
This is somewhat different from the idea that a different kind of resistor affects the time-domain response ("percussive") or tonal balance ("midrange", "top end pings").

I'm very open to things affecting sound/tone/etc of amps. I just think that if some effect is real, there ought to be a way to measure it. And I'd love to find me some mid-range-y resistors, or percussive ones.

I like the idea of measuring things , but there ain’t anything quicker than an AB test with alligator clips or switches . Easy test: alligator clip different resistors (or capacitors ) into the front end of an overdriven amplifier with your favorite guitar . The differences between resistors will be more pronounced than comparing them in a clean setting. I like using single coils for referencing. Hours and hours of fun.

[R.G.]

I like the idea of measuring things , but there ain’t anything quicker than an AB test with alligator clips or switches . Easy test: alligator clip different resistors (or capacitors ) into the front end of an overdriven amplifier with your favorite guitar . The differences between resistors will be more pronounced than comparing them in a clean setting. I like using single coils for referencing. Hours and hours of fun.

You're right - there isn't anything quicker than an AB test with alligator switches or clipleads. Unfortunately, there also isn't anything as prone to tester bias.

You are absolutely correct - the differences perceived by the person doing the quickie AB test will be much more pronounced in this kind of test. There is a great deal of formal research into the design of testing and measurement that reinforces this. If the person doing the switching does the evaluation too, they simply cannot filter out their own preconceived notions of how the results ought to turn out.

It is very likely that the differences will disappear entirely if done by measurement or by double blind test. At least that is the history of the perceived differences in audio components back into the hifi mono days.

It's perfectly OK to tell yourself that you like blue (or purple, or Acme instead of SmithCo) resistors that sound more like lasers or UFOs or whatever. You should keep your personal preferences close at hand for your stuff. But it can be very disappointing to submit this to double blind testing to keep any preconceived notions out of the results, or to chase down measuring the results to see if instruments with no preferences at all see the same differences.

I'm not saying that differences can't be perceived. If you hear something special and subtle, it would be really, really good for everyone's knowledge to nail that down, figure out a way to measure it, and then to figure out how we can all use that reliably.

For instance, what if KOA, Piher, or Iskra change their manufacturing process, and in not knowing where the subtle magic sound is hidden, manage to lose the magic entirely? Are all KOA, Piher, and/or Iskra resistors reliably percussive, or midrange-y? Does the magic follow the brand name, or only some of their parts?

Is replacing one resistor in an amp enough to move it toward percussive, or midrange-y, or trebly? Do you have to do all of them? Are there subtle blends of multiple brands that can give you percussive midrange-y and treble-y at the same time? Do KOAs work best with humbuckers, and you need to change out your resistors for Strats?

[WhopperPlate]

For instance, what if KOA, Piher, or Iskra change their manufacturing process, and in not knowing where the subtle magic sound is hidden, manage to lose the magic entirely? Are all KOA, Piher, and/or Iskra resistors reliably percussive, or midrange-y? Does the magic follow the brand name, or only some of their parts?

For one thing inductance with resistors is a significant variable , that’s one thing discussed by Marshall guys like George Metropolous and Dave Friedman concerning piher and iskra . And yes I have heard plenty of people being picky about changes from different manufacturing runs.

Is replacing one resistor in an amp enough to move it toward percussive, or midrange-y, or trebly? Do you have to do all of them? Are there subtle blends of multiple brands that can give you percussive midrange-y and treble-y at the same time? Do KOAs work best with hum buckers, and you need to change out your resistors for Strats?

IME (like I said hours of fun )

1. Yes. Depends where and how much based on composition and brand . In your typical guitar amp try negative feedback , bias feed, PI cathode , v1 plate , ect

2. If you do all of them it will be extreme one way or another , all depends composition and brand .

3. I have to use subtle blends to achieve what I want and others ask of me . I depend on this .

4. Koas do work well for humbuckers, but I find that with a strat you need some other brands to balance the sound as it becomes a bit pingy and too percussive, if that makes sense.

If the person doing the switching does the evaluation too, they simply cannot filter out their own preconceived notions of how the results ought to turn out.

That’s why I ask my wife ! Seriously though, an inexperienced listener can be more easily prone to error , that doesn’t necessarily mean one can’t become experienced enough to remain relatively objective, especially when you build for the demands of others. If can’t hoop it then you won’t make ends meat . And that’s not easy …. most guitarists don’t have the language of knowledge to make that easy.. . That’s my experience.

[R.G.]

OK, but back to the original question. Can it be measured, not just auditioned?