Dr Z Low Frequency Transients...

[EETStudent]

Im not too sure how to explain this issue, but Ill do my best and hopefully somebody can recognize it.

I acquired a Dr Z Carmen Ghia combo a few weeks, but it came with a few issues. At first, it was just fizzing in and out and losing volume, which I thought to be a clear sign that a tube was bad. So I did a complete retube, with a matched pair of JJ EL84s, a reissue Tung Sol 12AX7, NOS GE 5V4 rectifier, and NOS Sylvania 5751. Immediately I noticed a signficant improvement in tone and much better performance.

Still, Im getting a low frequency, edgy, intermittent, rumbling transient tone underneath my base tone. Its not overly noticeable, but it does sound funky. I feel that it doesnt affect my base tone, just sits underneath it. I dont really hear it when the amp is set clean, but when I coax some ovedrive it becomes more pronounced. It also becomes more pronounced when I play higher frequency notes. Its more of a short burst that rises and fades out.

My suspicion would be either the rectifier tube, or weak electrolytics in the power supply. Maybe the speaker(Warehouse Guitar Speaker ET-65), but that being the least likely considering the symptons. Any ideas?

[soundguruman]

Fizzing in and out can be dirty controls and jacks. It can also be bad soldering connections. Clean and test again.
the low frequency rumble can just be "crossover distortion."
It's probably better to post an audio recording, pictures and a schematic.
I mean, right off the bat, I could see that the output tubes may not be biased correctly, if you put new ones in...
and that can cause distortion that sounds weird. The amp needs to be biased hot enough to minimize distortion.
Other than that it would just be guessing, without hearing and seeing.
I don't recommend random parts replacement. I mean it "could" be this or that, but don't replace parts until you narrow it down more.