Charlie Wilson wrote: ↑Thu Apr 07, 2022 7:18 am
He must be measuring the resistance across the chassis. zero ohms. Tony, I'm going to say this real quiet, so Martin doesn't hear me, we did talk about how some chassis (grade of steel?) make for a bad sounding amplifier.
Yes, and there is mention of experiments with chromate conversion coatings by Mike Zaite (for better conductivity) there. It wouldn't surprise me if HAD knew about that. It's easy to do, but it involves dangerous chemicals (Cr6+). I think CW is correct. I can imagine him checking ground path resistance through mechanical connections and across the chassis, and that could be what he was demonstrating. I recall reading another account where the observer was struck by HAD's meticulous checking of the resistance of his solder connections.
talbany wrote: ↑Thu Apr 07, 2022 9:24 amI am not doubting Dumbles expertise it's the vague comments made by guitar players (with no technical background) with very little to no context that raises my B.S meter.
As far as what i think I find it hard to believe Dumble would ask such a thing and then respond? For cosmetic reasons only ( inside the amp) So I am calling B.S on this one :roll
I agree with you on the first point. Combine that with a sense of humor, and you can understand how these anecdotes about cheap parts, chassis charge, etc. come about. On the second, I'll say again Birkmaier's account is believable. He admits to having little technical knowledge of that subject, but remembers it clearly because in spite of that he was asked for his preference.
Charlie Wilson wrote: ↑Thu Apr 07, 2022 7:18 am
He must be measuring the resistance across the chassis. zero ohms. Tony, I'm going to say this real quiet, so Martin doesn't hear me, we did talk about how some chassis (grade of steel?) make for a bad sounding amplifier.
CW
If the silcon content of the steel in the chassis is too damn high, then too much crystal lattice in your ground path will destroy the fragile harmonics.
martin manning wrote: ↑Thu Apr 07, 2022 11:16 am
I agree with you on the first point. Combine that with a sense of humor, and you can understand how these anecdotes about cheap parts, chassis charge, etc. come about. On the second, I'll say again Birkmaier's account is believable. He admits to having little technical knowledge of that subject, but remembers it clearly because in spite of that he was asked for his preference.
Anecdotes don't so easily fall apart for me if they involve EJ. I've heard RF say about his 102 amp, known to have that 68pF bright cap on the master, that it has the best master volume ever because it sounds the same from 1 through 10 -- I'm sure there is a video about this on YT. RF is a tone monster, a great guitarist, etc. However, that statement is simply inaccurate and it's not like RF doesn't have a great set of ears. Not sure why he would say something like that. Does anyone here believe Robben is right his description of the 1-2 master volume? Even without the bright cap, that statement would not hold water. While I appreciate that some people here -- and I think you may be in this camp, Martin -- have stated that they don't hear a difference between part types, it seems to me that EJ would be someone who definitely would be able to hear it.
Last edited by ayan on Fri Apr 08, 2022 1:04 am, edited 1 time in total.
I don't have to listen to RF talk about amps very long to realize that he does not have much knowledge of electronics, and he doesn't really care. It's all about what he hears.
I hear differences between parts, like caps made with different dielectrics, and resistors made from different materials. Those differences are measurable as frequency response, harmonic distortion, and noise, so I'm confident that there is something there, not just a construction of the human psycho-acoustic system. When it gets to different brands of the same resistor type, that's where I don't hear any difference, nor have I seen any measurement data to the contrary.
Charlie Wilson wrote: ↑Thu Apr 07, 2022 7:18 am
He must be measuring the resistance across the chassis. zero ohms. Tony, I'm going to say this real quiet, so Martin doesn't hear me, we did talk about how some chassis (grade of steel?) make for a bad sounding amplifier.
CW
If the silcon content of the steel in the chassis is too damn high, then too much crystal lattice in your ground path will destroy the fragile harmonics.
Dumble may have pulled a few legs here and there, we may never know for sure though.
I don't think Dumble was making a joke here at all, I think what he's saying is the construction of a transistor and how they work (esp when overdriven) prevented him from eeking out the harmonic content he wants from an amplifier. Some might say well what about the FET input? That stage is very early in the amplifier and isn't really responsible for most of the harmonic content generated by the tubes being overdriven in the later stages of the amp. If you consider how much harmonic complexity these amps seem to have you can see why he found it very important to preseve them. Then again who knows..
On the topic of steel, it's an poor conductor compared to aluminum. From my research, aluminum is 4th in a list of metals regarded as good electrical conductors, Silver, Copper, Gold being above it. Steel is much further down the list (still an okay electrical conductor but not anywhere as good as aluminum). Of course this all depends on the alloy of aluminum and steel each having different properties. There are many out there and you can look up their electrical conductivity/resistance if you're curious (as I was )
martin manning wrote: ↑Thu Apr 07, 2022 11:16 am
I recall reading another account where the observer was struck by HAD's meticulous checking of the resistance of his solder connections.
This has come up a few times, can someone explain how one could measure a solder connection? I never understood this one nor have I read it in any past manuals as needing to be performed. It's not in the NASA guide that I grew up with.
martin manning wrote: ↑Wed Apr 06, 2022 1:21 pm Resistor noise is both measurable and audible, so I accept that as real. I have wondered if that isn't what people are hearing, and describing with more flowery language? Or, perhaps if the presence of more or less noise affects the psycho-acoustic perception of the sound.
As I understand it, one of the tenets of psychoacoustics is that noise is an integral part of what is called the timbre of a musical instrument.
Here are just two of many statements made by psychoacoustics on this subject:
" ... To study the timbral characteristics of a sound, we often analyze certain characteristics of its spectrum, such as its envelope, centroid, or noisiness. ... " https://mutor-2.github.io/ScienceOfMusi ... index.html
"The Fusion and Layering of Noise and Tone: ... One of the motivations for our study was the realization that the combination of noise and musical elements, traditionally described by ethnomusicologists as "layering", actually takes at least two perceptual forms. Either the sound is truly layered, and listeners hear two or more perceptually distinct sounds concurrently, or the physically superimposed sounds are perceptually fused, so that listeners hear a single sound - a blend of the two sounds - neither of which is identifiable as the primary or the superimposed sound. ... " https://escholarship.mcgill.ca/downloads/47429f376
Thanks for the input and references, Max. I'll have to read through them. In absolute terms, metal film resistor noise is very small, so the difference between brands should be smaller. Still, if the chart here https://eepower.com/resistor-guide/resi ... tor-noise/ represents the range of noise levels from various manufacturers, there is quite a spread, ~30dB (in noise index).
martin manning wrote: ↑Thu Apr 07, 2022 11:16 am
I recall reading another account where the observer was struck by HAD's meticulous checking of the resistance of his solder connections.
This has come up a few times, can someone explain how one could measure a solder connection? I never understood this one nor have I read it in any past manuals as needing to be performed. It's not in the NASA guide that I grew up with.
Basically you try to do a continuity test (which also shows the ohms resistance) from something that is outside the soldered joint, and something on the other end of the soldered connection. Example, say you have a board with a capacitor in an eyelet or turret, that then has a wire going off to a Potentiometer. I'd put my multimeter lead on the leg of the capacitor that goes into the eyelet/turret. You then put the other lead on the bare wire before it goes into the Potentiometer's lug. This gives you the overall resistance of the wire, solder joint and the lead of the capacitor. Then you can move the second lead from the bare wire near the lug to the lug itself past the solder joint. This means you're getting the metal to metal connections and seeing if there's too much resistance in the solder joints. If suddenly one of those reading is more than an ohm or so, the joint is likely problematic.
martin manning wrote: ↑Thu Apr 07, 2022 11:39 pm
When it gets to different brands of the same resistor type, that's where I don't hear any difference, nor have I seen any measurement data to the contrary.
I think there is something else to consider here and this is where I'll admit that I am way out of my league. I had a discussion with Chris Merren a few months back about this very topic and he started explaining that (in the case of plate resistors) they display very different characteristics when under high DC voltage. Even 2 resistors of the same brand and measuring the same value with a DMM (low volage) could have a larger difference when measured under real-world settings (300 VDC). If this is true, I can see how resistors of different brands and constructions would display different characteristics when used in certain positions in an amp.
I'll ask him the next time I speak to him but I'm sure he was specifically talking about MF resistors as I wanted to know why NTE 1/2W MF would sounded different from different years of manufacture. He was also explaining why MF sound brighter as plate resistors over CF and CC. Again, I'm way out of my league and it was a few months back so the memory could be a bit fuzzy
martin manning wrote: ↑Thu Apr 07, 2022 11:16 am
I recall reading another account where the observer was struck by HAD's meticulous checking of the resistance of his solder connections.
This has come up a few times, can someone explain how one could measure a solder connection? I never understood this one nor have I read it in any past manuals as needing to be performed. It's not in the NASA guide that I grew up with.
You can do as Phil described above, but there is also a measurement technique where a known current is passed through the connection and the voltage drop is measured.
I'll ask him the next time I speak to him but I'm sure he was specifically talking about MF resistors as I wanted to know why NTE 1/2W MF would sounded different from different years of manufacture. He was also explaining why MF sound brighter as plate resistors over CF and CC. Again, I'm way out of my league and it was a few months back so the memory could be a bit fuzzy :D
If he can point to some references, I'm interested to read about it.
ayan wrote: ↑Thu Apr 07, 2022 10:58 pm
Does anyone here believe Robben is right his description of the 1-2 master volume? Even without the bright cap, that statement would not hold water.
In some of his recent interviews he talks about moving towards lower wattage amps because the recording spaces are smaller in Nashville and he can't always get the Dumble up to the volume level it needs to be to do it's thing. I think he is probably hearing what exactly what you are talking about, but not quite knowing or expressing the actual reasons why.
I've heard RF say about his 102 amp, known to have that 68pF bright cap on the master, that it has the best master volume ever because it sounds the same from 1 through 10 -- I'm sure there is a video about this on YT. RF is a tone monster, a great guitarist, etc. However, that statement is simply inaccurate and it's not like RF doesn't have a great set of ears. Not sure why he would say something like that. Does anyone here believe Robben is right his description of the 1-2 master volume? Even without the bright cap, that statement would not hold water. While I appreciate that some people here -- and I think you may be in this camp, Martin -- have stated that they don't hear a difference between part types, it seems to me that EJ would be someone who definitely would be able to hear it.
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