Octal tube preamp or OD in Dumble?

[10thTx]

Anyone tried something like a 6SL7 in either the preamp or the overdrive section of a Dumble or Dumblish inspired amp?

If so, how'd you like it and how did it compare to a 12A_7?

with respect, 10thtx

[PaisleyTube]

never tried in a d-esque circuit but in general and to my ears:
- less gain
- more "woody" tone, more 3D and mo' "space"
- can be very microphonic

[bluesfendermanblues]

TwoRock has done an Octal version for Steve Kimock. Read about in a "ToneQuest" article.

[talbany]

Blues..I have tried it in the OD spot once and used a 56k Plate 1K cathode..It was OK..6sl's and 6SC's have a gain factor of 70..You will get the same kind of thing with a 5751..The big plates on the old octals can give you a bit more low end..The deal breaker for me was the noise factor..Those things can HUMMMMMMMM in a high gain spot so you would also need a DC filiment supply..Allot of work for a not so great improvement..For Me!!

Good Luck..If you decide to go there..


Tony

[10thTx]

Tony,

I am always appreciative of your response! Thanks.

IF I try this it would be on the clean channel of a Dumblish inspired amp with a 5879 in the OD section and an active FX. So perhaps in the V1 position and a weaker OD section than a normal Dumble would allow it to work out OK? This would be a cathode biased Tweed BluezMeister 5879 OD with 6V6's. .

http://www.el34world.com/Forum/index.php?topic=16449.0

Will post the results IF I attempt this in a few weeks out after finishing another project. I can always rewire it back to the 12AY7 that I am currently using.

With respect, 10thtx

[talbany]

Tony,

I am always appreciative of your response! Thanks.

IF I try this it would be on the clean channel of a Dumblish inspired amp with a 5879 in the OD section and an active FX. So perhaps in the V1 position and a weaker OD section than a normal Dumble would allow it to work out OK? This would be a cathode biased Tweed BluezMeister 5879 OD with 6V6's. .

http://www.el34world.com/Forum/index.php?topic=16449.0

Will post the results IF I attempt this in a few weeks out after finishing another project. I can always rewire it back to the 12AY7 that I am currently using.

With respect, 10thtx

Your welcome!!
If it matters!..When I think of designing an amp around a certain tube I try to exploit the appealing qualities of that tube.. Some tubes do certain things well, like clean or over driven,(pentodes work great for slightly overdriven clean tones) I designed an amp once around an ECC 88 that had an awesome clean tone but didn't overdrive too well in a Cascade design..IMO some of the more popular octals like 6SL/6sc/Shared cathode's don't really shine when you hit the grids with a ton of signal so these are better used as a clean channel tube.. The big thing you have to be concerned about is how the clean and OD tubes sound (harmonic character) together..This will effect tone and sustain..I generally find when you keep all the gain stages symmetrical and balanced using the same tube and incerase gain more evenly throughout your more likly to have an amp that harmonically sounds musical.. This is just my opinion and really kind of depends on how you set it up..(especially with pentodes)all kinds of variables here so take it with a grain of salt please..We can talk all day about how this or that tube might sound good on paper and in theory but you will never know for sure what your going to get (harmonically speaking) until you build it play around with it (or find the right combination of tubes)..I had a blast designing the ECC88 amp..So have fun with it and Keep us posted on what you find!!

Especially in an Overdrive amp...It's all about harmonics!!...IMO

Good Luck!!

Tony

[10thTx]

The deal breaker for me was the noise factor..Those things can HUMMMMMMMM in a high gain spot so you would also need a DC filiment supply..Allot of work for a not so great improvement

I tried an octal in V1. Same hum problem. I was not happy with the results. Took it out to put a 12A_7 back in place. Just thought I'd pass that on.

With respect, 10thtx

[ampedup]

I built a boost pedal with a 12sj7 and it sounds pretty good in front of my dlite clone It does have a little hum at high gain settings, not sure if elevated heaters or a humdinger would cure that. You can check it out here: http://jonesamps.webs.com/jonesampsschematics.htm