Tube Experiment Help and Brands

[afu]

Hey, I'd like to do an experiment with those of you who roll tubes in the power section or have different brands to try. I'd like to first explain the problem and solution, my initial conclusions, and then the experiment.

Issue

I had to swap my set of barely used Mesa tubes back into my amp. When I did this, the channel settings I was using sounded really bad. It was disappointing, because it was grainy and had less bass response.

The old, Ruby tubes were marked for 38ma plate current. From what I've read, a higher natural plate current actually causes the amp to run cooler in Mesas "fixed" bias circuit. By comparison, the Rubys had an emphasis on the lower mids, full bass, and tapered highs when compared to the Mesa tubes.

Later, I followed my own instructions for using the Send to get a better tone with the loop on. It mitigated the differences between the tubes. My channel volumes came down a little and the Send went up. A channel volume would cut some highs when it comes down, because it doesn't have a bright cap.

It won't sound exactly the same, but it should make a person's normal settings sound good from brand to brand.

My conclusions were:

• Differences between tubes can be largely mitigated by Channel Volume and Send controls.
  
  The higher the upper-mid level the 6L6GC is peaking at, the lower the Channel Volume will need to be to dial out grain/fuzz/fizz.
  
  To put #2 a different way: if a person hears an abundance of grainy fizz, turn down the Channel Volume and turn up the FX Send with the Output at Noon (or the desired “moderate” level a person wishes to be their gig volume). Use the Send to push the preamp sound down the line, rather than pushing the loop with the Channel Volume and creating unwanted overtones.
  
  If the tubes work in the amp, a person can dial in a great sound; Don’t spend more money than you have to. Spend 3 to 5 minutes with the level controls and move on.

Experiment

I'd like to see if some of you would swap out for different sets of 6L6GC tubes, make adjustments, and see if you find the same conclusions, any of the conclusions, or different conclusion. We all hear things a little differently and I want to be sure this works. The only Rectos that can't be included are the miniature version, because there's no Output/MV on it.

The order of operations for the adjustments after a tube swap are:

• 1) Bypass the loop and dial in a great tone, beginning with the Channel Volume.
  2) Engage the loop.
  3) Turn Output to Noon.
  4) Increase Send until the sound is about as loud as bypass and/or sounds good enough/loud enough to use.
  
  Try not to increase the channel volume much after the loop is on.

I just want to make sure this works. If I'm wrong, I'm wrong. That's better than passing along bad information.

Thanks in advance.

 

[afu]

I plan to thank people who help when I do an article on the blog. I'll link to whatever thing you'd like to share (music/web page) if you have something that needs exposure.

 

[afu]

Aw, c'mon guys.

I'll tell you what: if you have several sets of tubes and just want to see if your regular settings with channel volume adjustments makes a difference, that'll work for me. You don't have to do the Send control thing. I was asking for that to keep it as tight with control against other influences as possible, but the effect has to do with the volume entering the power stage interacting with the frequency levels the tubes naturally produce from brand to brand.

 

[thunda1216]

mesa's get their distortion from the preamp. I can not play my heartbreaker at the volume levels necessary to get power tube distortion. it sounds great with the old shuguang str 420 (6L6GCR), the sovtek str 430 (6L6WXT+) the shuguang STR 440 (Ruby 6L6GCMSTR) and some old Sylvania 6L6GC STR387 tubes. I get better but still subtle tone differences with preamp tube changes. The most noticeable tone changes come from speaker changes. YMMV.

 

[afu]

It isn't about power stage distortion. I think my worn out Ruby tubes ran out of spec in the amp. I think they were slightly cooler, a little less loud, and produced less high end. I now know that Ruby supplies Mesa, but there was something a little different from a set of Ruby and my white label Mesa tubes from the beginning. The Mesas are practically new. The Rubys have 3 years on them and just started to change for the worse last week.

What I found was: adjusting the channel volume down a couple of hairs compensated for the difference between them in volume and highs. I wanted to make sure I wasn't just hearing things. It's the overall sound, not just distortion.

 

[totosik]

Hi Afu, i have a matched quad of Ruby 6L6GCMSTR with PC 52 and TC 3500. Are they ok to use in Recto?

 

[afu]

I am not sure. I've e-mailed Magic Parts to ask if they would provide test conditions. If they do, I can scale the voltages and identify the range.

It seems that higher current equates to a colder tube in a fixed bias. 52ma wouldn't fry your amp, but it might run too cold and not amplify correctly. I'll be able to tell you wattage if they respond.

 

[3124+]

My favorite power tubes are STR-425 and STR-430. Green or Grey bias color.

 

[totosik]

Thanks for the info, afu. I will try those set in my triple, with 4 tubes installed only. Mesa grade their 6L6 s with color code, just wondering if those higher pc of Ruby closer to green in Mesa grade .. (if they will run colder).

 

[totosik]

Currently i run matched 6 of Sovtek 5881WGC in my triple and they perform superb in that amp. The distortion sound more aggressive and brutal, punchy and depth. They have been there for more than 7 months and i never willing to re install the Mesa 6L6 back.

 

[3124+]

Currently i run matched 6 of Sovtek 5881WGC in my triple and they perform superb in that amp. The distortion sound more aggressive and brutal, punchy and depth. They have been there for more than 7 months and i never willing to re install the Mesa 6L6 back.

Yes, the Sovtek 5881WGC is the Mesa STR-425. Great sounding tubes and super durable construction.

 

[afu]

Ruby didn't reply. Trying a vendor.

 

[afu]

Mesa's pick of Ruby tubes fall between 33ma and 52ma using Ruby's test. I don't know if they do a frequency sweep to select after that, but tubes in that range should be fine.