Sound differences between same model amps...

[singlehum]

I've got I've got two JCM 800 2205's, and it is amazing how different they sound. One has WAY more gain than the other, but is much tighter in the bottom end. Both have Drake trannys. We swapped tubes between the two to see how much of a factor that was. It made a difference, but not enough to say that was the main factor. I realize that it is impossible for two things to be identical, especially in the context of electronics, guess maybe I was a bit naive to think that the same model amps would be more consistent than they are. Anyone else notice this with other manufacturers?

[Rupe]

Re: Sound differences between same model amps...

When you swapped tubes, did you rebias the amp for them? This will make a huge difference if the tubes had different performance charactaristics which most likely would be the case.
That said, I have frequently noticed tonal differences between like model amps...more so with older amps and handwired ones than with PCB amps, although I've seen it with these as well. Not infrequently, there are certain anomolies in an amps parts, wiring, etc. that give it a little "mojo" that sets it apart from its brothers.

[Cleveland Metal]

Re: Sound differences between same model amps...

Older Marshall are very well known for that.

The main thing they used lower grade parts throughout the construction. Everyone did that then as the technology for higher tolerance parts either wasn't there or prohibitively expensive for use in "guitar amps".

The lesser grade parts have MUCH more differences in tolerances. Like +/- 15% or probably something even WORSE. The effect is, over all the differences in tolerances of all the parts throughout the amp, the amps all sound different. Some great ones, some not so great.

Funny thing is, nowadays, if you built a corresponding unit with high grade +/- 5% stuff using the OEM schematic and values, it may not sound great either. It was the indivual mix of slightly mismatched parts that would create the magic. You'd literally have to find an old great sounding amp, rip it apart into pieces and rate the values of each and every part, and then match each part with a corresponding value new high tolerance part. Then you'd have the close to the mojo and be able to reproduce the sound closer in the newly produced ones.

Now THAT would be a boutique, haha...

[siggy14]

Re: Sound differences between same model amps...

You might also have two different years on the 2205, if i remember right the originals did not have as much gain and had the bleed through problem from the clean to dirty, then they did some mod's on the later versions and gave it more gain. I could be reversed on the bleed through thing, i just remember some have the bleed through.

[singlehum]

Re: Sound differences between same model amps...

Yes, the 2205's are a year apart. The later one has less gain. And yes, we did re-bias when swapping power tubes, er, valves. Very important! I agree about the differences in parts and tolerances. And on some of the older stuff, I'm told they would make substitutions during mfg. based on what was available and what they ran out of. I've got a brown Fender Pro that sounds simply amazing. The thing is without a doubt 100% original, but it has slightly larger transformers than the schematics called for. Mojo indeed.

[horns666]

Re: Sound differences between same model amps...

what John said..

+ 1

Me


I concure


yes.. we were there together.. [img]/images/graemlins/laugh.gif[/img]

I had five 5150...and ONE sweet one...all the stock tubes and shit..i dunno. [img]/images/graemlins/laugh.gif[/img]