Opinions on 6SL7, 6SN7?

[ampgeek]

I have built a half dozen 5F6A (59' Bassman) with all three holes filled with 5691s. These are the industrial equiv of the 6SL7.

I can attest to the previous statement regarding warmth, roundness, fattness, etc.. They are a very fine sounding tube in that circuit!

Regarding microphonics, I have had at least 4 dozen red based 5691's pass across my bench (most NOS, some strong pulls) in the last 5 years and not a single one was microphonic.

Regretably, I haven't had more than two or three 6SL7s (none of which were microphonic) so I don't have enough data on those to make a comparison.

Good luck!
Dave O.

[LeftyStrat]

Where i work at wienbrock amps we use the 6sn7 as an output tube to great use!

I just checked out the Hobo. Nice to see someone using Guido Landry's design. You wouldn't happen to have any clips would you?

[sparrott]

6SL7's cascade nicely for a decent high gain sound. I built this preamp a couple of years ago for a friend / business partner. He is the one with the guitar playing talent. It was based off of the 4-gain stage similiar architecture of a bogner preamp but with some changes. It has a single-ended 6BL7 output stage good for a couple of watts (maybe?).

http://soundcloud.com/roctal-amps/roctaloctasydemo

It's just my opinion, but I think the 6sl7's overdrive and compress very smoothly a lower plate voltages.

[Phazor]

Thats a very nice sounding 2 watt amp. Very useful for today. Nice job. And your guitar playing friend has great chops.

[sparrott]

Thats a very nice sounding 2 watt amp. Very useful for today. Nice job. And your guitar playing friend has great chops.

I have become a fan of octal tubes giving a "big" sound at lower volumes. After I finished that preamp, the owner of the preamp and myself built a plexi head version with 6b4g push-pull output stage.

http://soundcloud.com/roctal-amps/roctaplexdemo

[gingertube]

My own guitar amp uses 3 off 6SL7 and a pair of 6V6.
2 off 6SL7 as a modified London Power Standard Preamp (Footswitched Clean/Lead).
1 6SL7 as a common cathode stage + split load phase inverter to drive the push pull 6V6 outputs.

The 6SL7 (use Russian 6N8P for modern production) has a little more grid current than the "traditional" 12AX7 and so the "modified" above relates to mods to keep the grid to 0V (signal ground) resistances lower than usual to keep noise down and bias perturbations to a minimum.

A useful "Rule of Thumb" is that the grid to 0V resistance should be no more than 3 times the anode load resistor. Traditional 12AX7 circuits have abused this for many years resulting in preamps with much more noise than they really need to have.

Everone who has used this amp has loved it and I have several requests to build one for these players.

Have a new design ready to prototype, using 6SL7 again, this time 3 tubes in the preamp (6 triodes), extra gain stage common to both clean and lead and one extra gain stage in the lead path. This one will have 3 gain stages in the Clean Channel and 5 in the Lead Channel. That 2nd gain stage which is common to Clean and Lead paths can be bypassed with a switch. When it is in, there is a pot in the interstage attenuator such that at 0 on the pot there is no effective gain bump from the extra triode stage, just a slight "darkening" of tone and with that pot at 10 there is a significant gain boost.

I haven't tried using 6SN7.

Cheers,
Ian

[yankeerob]

I just checked out the Hobo. Nice to see someone using Guido Landry's design. You wouldn't happen to have any clips would you?

Actually... no. But I'm building one out of the very last REV 2.5 transformer set... I'll get some friends to have a blast through it and see what you think...

[stephenl]

The 6SN7 makes a great cascoded input stage - it sounds huge. Self biased, 100k anode, 680R cathode, 680n bypass.

[C Moore]

I use new production tubes and they work quite well. Also chinese tube companies have good sounding non-microphonic tubes I used in the Gibson EH150 build.

Mark

Mark's post goes back aways here but.....
I have built a few amps with octal pre lately.
I have experienced the same thing as Mark and Andy. The NOS tubes are a REAL Crap Shoot.
The Tung-Sol (modern day) SL7 seem to be Much Quieter and sound very nice.
JME
Good Luck

[kgreene]

I like the 6SL7's best out of the three you mentioned. I used to gig with old tweed Fender amps, and some of them were first issued with 6SC7's, then evolved into 6SL7 circuits. They sound very much alike, but the L-type seemed a bit quieter and was, in my experience a little more reliable.

[rp]

I have built three Rockets using the 6sl7 and twin 6L6's on the output. They sell really fast. Very chimey amps.

Is there an old post on this/these builds?

Try a pair (4 triodes) in PP for a 10-15W amp -- it makes a great clean tone.

Whose got a good schematic?