non-HRM Findings

[ayan]

If you saw my recent post seeking opinions on this subject, you will not be surprised to hear that I changed one of my non-HRM amps to 100K configuration to revisit the subject. I had tried the 100K plate load resistors last century (really) and remember never looking back after leaving them behind. Here is my story this time around:

Background
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Amp was previously configured as 220K/3.3K, 150K/2.2K for both preamp tubes, cathode bypass caps were 4.7uF, 1uF, 4.7uF, 4.7uF for CL1, 2, OD1, 2. Skyliner stack.

Changed to 100K/1.5K across the board, and the new bypass caps are 10uF, 10uF, 4.7uF, 4.7uF for CL1, 2, OD1, 2. Skyliner stack again. So, basically like #124.

Findings
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The 100K amp is a different thing all together and the clean sound is “better” than with the higher plates in every respect. It is definitely chimier and is willing to sing very readily. With the PAB on top of the clean, the amp sounds terrific and feeds back very musically, and, there seems more overdrive available in clean mode from the 100K amp as well. All in all, you can't go wrong with the change as far as the clean channel goes.

The overdrive channel is another story, and I relived the same experience I had encountered back in 1999. The overdrive is way -- and I mean waaaaayyyyy -- more finicky than in the 220K/150K amp. It gets buzzy in the bottom end right away (going to higher bypass caps on the clean definitely does NOT help here) and it gets ice pickey in the top end –- I very much agree with what Dominik had written in my previous thread. I would say, however, that if one likes a very low gain situation, the 100K amp may be the ticket for a guitar with humbuckers.

With the usual pre OD network of 220K + 100K trimmer, I find that with larger than 20K to ground, the OD will just not sound right, and 15K to ground is even better. Of course, dialing that low a gain up front and low gain on the front panel gain control (“Level”) means that one may run out of volume in the overdrive channel, or even if not so, diming the OD master leaves less resistance in series with the output of the OD, which means a brighter and potentially harsher tone. One solution is to go to a higher than 100K master for the overdrive, and I will try that for kicks since it would help by putting a higher series resistance in series with the OD output and by maintaining larger signal level due to lower loading (i.e., more volume on tap). Anyway, with low gain settings as described, the OD can be dialed to be a very natural extension to the clean, but with more hair on tap if so desired. I like that sound a lot, and one can get away with a very fat low-gain OD tone. In contrast, the 200K/150K amp breaks up more quickly (and much more smoothly), so it is harder to dial that type of tone.

While the older configuration got along with my Tele real well and didn’t get along with my 335, the new configuration is just too bright for the Tele, and any high gain settings will sound plain harsh. My 335 sounds great clean and great with very low gain OD settings. I haven’t even bothered to plug in a Strat, since that guitar is the hardest to dial with these types of amps, IMHO.

Conclusions
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I can see why the TR folks had a amp with 100K for the clean channel and something else elsewhere, it could be a way to go. I will try to use this guy as is in some real-life situations, but I don’t believe it is my cup of tea because the lack of flexibility in the OD is a deal breaker IMHO. For very low gain players, and I mean John Mayer type of sound, this could be the right configuration.

Cheers,

Gil

[mlp-mx6]

Gil,

Thank you for performing this test and sharing your results.

Are you going to try the higher plates in the OD tube next?

Michael

[heisthl]

try a .02 in series between the relay and OD entrance, and a bleeder network(330k series with .001 to ground) after the .005 on od2(actually your idea originally?).

[JimiB]

john mayer also bought a dumble

[ayan]

try a .02 in series between the relay and OD entrance, and a bleeder network(330k series with .001 to ground) after the .005 on od2(actually your idea originally?).

I am sure I was not the first one, but yes, I have for many years been putting my own signature in my amps at the pre OD network (not on this one yet), which is a .005uF//4.7Meg resistor (the resistor is to keep the ground referenced to ground so as to prevent it from poppin when switching channels)... and the post OD treble bleed.

But the thing is that the stupid #124, for example, had none of that... and it worked well! You see my frustration? Sure, I can try band-aiding the beast, but putting two of my amps next to each other is all I need to hear: one sounds better in clean more than the other, but the other smokes the first one in the OD department.

Gil

[ayan]

Gil,

Thank you for performing this test and sharing your results.

Are you going to try the higher plates in the OD tube next?

Michael

I probably will as a means to a end, the end state being returning the amp to the way it was before. But, before I do anything else I will take this amp to a real life situation with a band and then assess things again.

Gil

[jelle]

Gil,

I think you need two of those amps for above mentioned reasons!
Please let us know what your real life findings with this CKT are....I know what I prefer with my 64 strat in a band situation.....

Jelle

[Fischerman]

Would going to 180k/120k on CL1/2 and then having the 220k/150k on OD1/2 (all with the 'corresponding' Rk values) be any sort of happy medium?

[heisthl]

maybe an extra 30pf is needed to help simulate the super sheilded cable in #124

[Funkalicousgroove]

Do you think that the extra series resistance on the pre OD network of #124 has anything to do with taming the "Buzz"?

[TimS]

Would going to 180k/120k on CL1/2 and then having the 220k/150k on OD1/2 (all with the 'corresponding' Rk values) be any sort of happy medium?

I was thinking the same thing, only with the 100k on CL1/2 and 220k/150k on OD1/2.

It would also be interesting to see how low values in the clean section and high values in the OD section would compare with "in between" values in both.

[TimS]

Is the OD sound at all similar to Lindley's "Running on Empty" tone? I don't know anything about the circuitry in that particular amp, but based on the time period I would think it would have to be a 100k amp, right?

[bcook]

Gil,
Is it possible that the 500k (345k) trimmer was in parallel with the 220k resistor in #124? I haven't had a chance to try it myself.
-Bob

[ayan]

Do you think that the extra series resistance on the pre OD network of #124 has anything to do with taming the "Buzz"?

More series resistance before the OD means less gain, which would be OK for that amp (since it's sensitive to high gain levels). But obviously it would muddy up the tone some more while, at the same time, helping with the high-end buzz. See, the problem with the 100K resistors and the big (10uF) clean bypass caps is that they make the amp harsh at the top and bottom ends before there is too much overdrive happening, so it's difficult to get your amprs around the whole problem. With the 220K/150K combo, plus lower cathode bypass caps, there is no problem at all per se. However, unless you dial in some gain, the amp sounds a little weak because there isn't a lot of bottom end to begin with.

As I told you over the phone, I believe, #124 is a very brown sounding amp. It sounded great but you can't get a clean tone out of it with humbuckers.

Gil

[ayan]

Gil,
Is it possible that the 500k (345k) trimmer was in parallel with the 220k resistor in #124? I haven't had a chance to try it myself.
-Bob

Not a chance, really. The resistor was 220K and the trimmer measured 345K or so, and they were in series.

Gil