Let's talk about 6SL7 tubes!

[BurningSkies]

It's a fun little gimmick that allows folks with little electrical skill the ability to subtly change tone without causing any damage - but with most tube amps you're likely to see more change in going from a venue with 110VAC to one with 130VAC than in general tube rolling (assuming we aren't talking about two different tubes, like swapping a 12AU7 for a 12AX7).

I'm personally more likely to go after things which have bigger effect - like actual component value changes or tube type changes, like swapping a 5AR4 for a 5Y3.

Maybe its time for you to start a 5AR4 swap for 5Y3 thread then.

The rest of us here can discuss our 'gimmick' tube amps and the tubes that go in them.

 

[Lo-E]

From a design standpoint, I have to agree with aborgman (I have an EE degree, which I never really used professionally, and I've owned and restored dozens of vintage tube amps). Part of an engineer's job is to provide a stable design; something that will provide consistent results when influences from the outside world are less than consistent, and I agree that the best circuit designs are those that can do that.

HOWEVER, this is a thread about tube rolling and the results achieved by doing so, significant or otherwise. To question the merits of tube rolling in the midst of a tube rolling thread (which I did myself), well, it's sort of looking for trouble, isn't it?

Let's all try to play nice. Some circuits - perhaps good, perhaps not - are more sensitive to swapping tubes and some people have a good time finding out what those differences are. Let's just leave it at that, mmm?

 

[BurningSkies]

From a design standpoint, I have to agree with aborgman (I have an EE degree, which I never really used professionally, and I've owned and restored dozens of vintage tube amps). Part of an engineer's job is to provide a stable design; something that will provide consistent results when influences from the outside world are less than consistent, and I agree that the best circuit designs are those that can do that.

HOWEVER, this is a thread about tube rolling and the results achieved by doing so, significant or otherwise. To question the merits of tube rolling in the midst of a tube rolling thread (which I did myself), well, it's sort of looking for trouble, isn't it?

Let's all try to play nice. Some circuits - perhaps good, perhaps not - are more sensitive to swapping tubes and some people have a good time finding out what those differences are. Let's just leave it at that, mmm?

I agree.

Some times that little <5% change in how your amp sounds because of a tube change can be a wonderful thing. Not everyone might hear it, but if you can and you like it, there's absolutely no harm in pleasing yourself. Now that my Monique is working up to spec, I'm interested to hear some of the different tubes and how they change the tone.

For the score:

-2 green label Sylvanias (untested), that were a wedding gift from TB'er wcriley. The logo looks to be 50's at the latest.

-1 Tung Sol tall bottle, black base tube, also a gift from wcriley. When I originally tried this in V1 It appeared to have a lot more gain than the others (Shuguang), but was hard to tell with a 'throttled' output at the time. When I ran the line out to the front end of my LMII to test, the Tung Sol was huge...but showed signs of microphonics.

-1 NOS/JAN Western Electric/RCA blackplate from the 1940's.

-1 NOS/JAN Western Electric/Sylvania blackplate from the 1940's

-1 GE branded NOS Mullard (Blackburn plant) 6CA4 rectifier tube.

-2 1950's Russian military 6SL7's. These haven't arrived yet...interested to see what's up with them too.

Stock tubes in the unit I have:
2xShuguang 6SL7 metal based tubes, JJ 5CA4 rectifier, and 1 ??? 12AU7. The AU7 will probably become a nice GE grey plate, or an RCA black plate.

-

 

[chadds]

I wouldn't.

The more tolerant a design is to component variation, the better the design is.

If you can circuit design your way around component variation, you do. No good engineer chooses to use .1% tolerance components when they could use 10% tolerance components and get the same results.

Most show VERY minimal changes among tubes that test well. Big changes are likely the result of:

1) Other components drifting
2) The tube being replaced being of marginal quality

Most of the favored designs of the past 60 years, if up to original specs (not 40 year old electrolytics in the supply, etc.) will show minimal sound change due to swapping of two tubes which are both in good operational order.

I'm an Electrical Engineer.

BS Computer Engineering, University of Michigan.

6 years as a Design Engineer at Intel working on the Pentium 4 and variants.

6 years as head Electrical Engineer at a company that made sub-millionth of an inch precision quality control systems for measuring manufactured parts (Surface finish, out of roundness, concentricity, squareness, etc. See ASME B46)

2 years as Electrical Engineer for the Aerospace Engineering Dept. at a major research university.

...and if we want to ignore all the amplifiers I've built and maintained as part of my job, we can just start looking at the dozens I've worked on/designed for fun and entertainment.

I've designed and built tube amps ranging from 2.5W single ended toys all the way up to 300W SVT types. I've repaired tube amps ranging from early Dukane PA amps all the way up to modern PCB based tube units. I've designed/built/repaired hundreds of solid state amps - ranging up to about 5KW.

What is your experience and education in this area?

I asked because you could be just a novice. You apparently are not.
I am a musician. Active professionally since 1966. I am a Preschool teacher.

I have played every SS and Tube amp available when they were new and now that they are vintage. I'm not going to name drop here who I've opened for or played with or in what major concert venues. I do get hired because of my sense of time and ear. My gear does what I want it to do. I choose it with that ear.

I associate with ridiculous audiophiles.

This isn't a pissing contest.

I can see why your standards for equipment would be different.

I have to go with 'skies and my Johns Hopkins Applied Physics labs engineers on this though.

We have well designed circuitry that runs adequately on average tubes and excels at showing the differences between a Sovtek and a black plate RCA.

 

[JGR]

I see what both sides are trying to convey.

I've found that my best gear sounds good no matter what I put in it, but at the same time, also does a great job at revealing the subtle differences in various tubes. Win-win IMO. I've found that to be the case with my DB680 as well as my own preamp. I ended up going with stock JJ's in my design because they sounded great, and are (or used to be anyway ) consistent, quiet, and reliable. Some of the folks that bought mine were looking forward to rolling tubes but then changed their mind when they heard it stock - they didn't want to mess with it. It's always nice to have the option, and to know that it can be rewarding if you start rolling, but at the same time know that you don't necessarily have to for stellar results.

Then there are some designs which are overall very nice, but may need a bit of help here an there - maybe a bit muffled or cloudy, and the right tubes can certainly help things. In these instances, the right tubes can compensate for some design shortcomings and also lead to great results, but in the end, it's certainly best to design the issues out in the first place.

Then there are those designs that can't really be helped no matter what you roll in there, and generally mask the subtleties of different tube types. Plenty of crappy all tube designs out there.

The only thing I would caution against when designing is voicing around some specific "golden" tube to the point that tone suffers if you use other types of quality glass. Kind of like in the guitard world where folks design around noisy/drifty carbon comp resistors to get their BS mojo - you can do it (and should) with metal film if you know what you are doing. On those same lines, I always try to test designs using a bunch of basses through a bunch of different cabs, and with other players when possible. I know it's right when it plays well with everything and everyone, and it becomes almost hard to make it sound bad.

Be happy, it's Friday.

 

[aborgman]

The rest of us here can discuss our 'gimmick' tube amps and the tubes that go in them.

Tube amps ain't gimmicks - I play a 1964 B-18, and lust after a 3 channel pre modeled on the B-15...

Tube ROLLING is mostly a gimmick.

 

[aborgman]

HOWEVER, this is a thread about tube rolling and the results achieved by doing so, significant or otherwise. To question the merits of tube rolling in the midst of a tube rolling thread (which I did myself), well, it's sort of looking for trouble, isn't it?

I guess I didn't see it as a tube rolling thread so much as thread ABOUT the 6SL7 and its uses. It seemed more like it turned INTO a tube rolling thread when no one stepped in with technical information.

 

[metron]

Nope, definitely a tube rolling thread from the beginning.

 

[Lo-E]

I play a 1964 B-18, and lust after a 3 channel pre modeled on the B-15...

Which reminds me... I'm going to be spending some time checking out the schematics you drew up for that and comparing notes to the ones I drew up for myself (if I can find them... I used pencil and paper )! I thought I was the only one who wanted to do that but I've recently found that that's pretty far from the truth!

 

[JimmyM]

Ya, definitely all about tube rolling. The technical stuff we can find out easily enough. How they'll work in a circuit like a B-15 or the Monique is what we're after.

As for tube swaps, seems to me that the better circuits would be pushing the tube at a level that brings out the differences. For example, the REDDI comes with a Sovtek 6N1P that sounds great, but I bought a NOS Russian 6N1P that boosted gain by almost 4 db and gave it an overall wider presence that's even more noticeable in a mix than when you hear them by themselves. Can't call that REDDI a poorly made circuit...it's right up there with the B-15 and SVT for best stuff I've ever plugged into. Seems to me that the circuits that makes the least difference with tube swaps are starved plate circuits, which are better than no tube at all, but to us tube snobs they're a joke.

 

[JGR]

So ya think these are any good????

 

[chadds]

Check this out.

Invalid Link Removed

 

[chadds]

So ya think these are any good????

There's something wrong with the one on the left. Wait, there's something wrong with the right one too. I'm PMing my address so I can make sure they are safe for you. Okay?

 

[JGR]

Cool, thanks. They look really old and junky.

 

[chadds]

RCA box is from one already in my Monique.
Mystery Brown base is a GE. Mil spec.
The JAN Phillips.

What are we doing!!!!!!

 

[JimmyM]

You're narrowing down the selection process for me, that's what you're doing.

 

[juledude]

I wonder if the "micro-phonic" reputation earned by the 6SL7 tubes has to do with the advanced age of the available NOS 6SL7s. As far as I can tell, none of the NOS tubes were made later than the early 1970's.

The current production from China and Russia do not seem micro-phonic at all.

I don't know about tube testers. I've had them around for decades, and seldom use them. In fact, got a vintage one someone can take with them next time they come here - in exchange for a burrito lunch (beer included). Tube testers always seem secondary to putting the tube in and listening.

Chadds, I'm surprised that the GE's weren't that good. I tend to like them better than Sylvanias for other tubes. I won't really know what the ones I have sound like until I have my Monique back, and try one in V1 to see. I did try it briefly but was having such low levels it was hard for me to make any kind of judgement. I can say that the Tung Sol in V1 sounded way bigger, fuller and 'more'. Unfortunately, it also appeared to have some microphonics happening, which won't do.



I wonder this too. The Tung Sol I mentioned above had a recognizably larger envelope and longer plates, of course it seemed to have higher gain and some microphonics. Speaking of which, the reputation of the 6SL7 seems to be one of much greater chance of microphonics...I assume that's because it's a larger tube with longer plates than the standard issue preamp tubes, and microphonics are of a physical/vibrational nature. True?



The JAN RCA's with red bases and black plates interest me (beyond the fact that black plate RCA's tend to sound pretty nice) because they also have triple mica spacers and additional support rods. All of that suggests to me lower chance of physical problems in the tube.

One of these days I'll invest in a tube tester...if Lady Skies will let me have one in the house...

 

[BurningSkies]

I wonder if the "micro-phonic" reputation earned by the 6SL7 tubes has to do with the advanced age of the available NOS 6SL7s. As far as I can tell, none of the NOS tubes were made later than the early 1970's.

The current production from China and Russia do not seem micro-phonic at all.

I don't know about tube testers. I've had them around for decades, and seldom use them. In fact, got a vintage one someone can take with them next time they come here - in exchange for a burrito lunch (beer included). Tube testers always seem secondary to putting the tube in and listening.

I'm more concerned with just making sure a tube is 'good' rather than shorting, or something that might cause catastrophic difficulties.

Ended up with a few extra minutes for load up yesterday and took a moment to get in and do a couple changes...nothing in terms of actually A/Bing or concerted listening, but I did change out my EZ81 to the GE branded Mullard, and have the JAN RCA in V1 with the JAn Sylvania in V2, and just to be difficult, a GE 12AU7. At our rehearsal space, I literally just tested each in the Monique to make sure it was working and not causing trouble, then off to the show...with a backup in case.

Sounded fantastic on stage.

 

[chadds]

I wonder if the "micro-phonic" reputation earned by the 6SL7 tubes has to do with the advanced age of the available NOS 6SL7s. As far as I can tell, none of the NOS tubes were made later than the early 1970's.

The current production from China and Russia do not seem micro-phonic at all.

I don't know about tube testers. I've had them around for decades, and seldom use them. In fact, got a vintage one someone can take with them next time they come here - in exchange for a burrito lunch (beer included). Tube testers always seem secondary to putting the tube in and listening.

Okay basically I'm thinking about said burrito lunch con cervesa!

 

[juledude]

I agree. . . All we need is to sound fantastic.

That EZ81 is a significant tone and playing characteristics contributor. A stiff (brand new) EZ81 sounds and plays less musically than an older (even tired) EZ81.

If you can get hold of an EZ80, that will work nicely as a replacement in Monique. They EZ80 is a lower current version (still plenty for Monique) of the EZ81. The difficulty with the EZ80 is that it is not, to my knowledge, in current production.

The change from hard to soft rectifier is similar to the GZ34(5AR4) to 5Y3 change folks some times make in tube gear. The 5Y3 will give a bit more compression, sag, and touch sensitivity than the GZ34(5AR4) in the right amp. In the wrong amp it will just plain not work.

The JJ EZ81 was my favorite. It appears JJ is working through some manufacturing issues, so the current "best" is the EH EZ81. The EH is a a bit "stiff" compared to the JJ, but seems to be more reliable.

I'm more concerned with just making sure a tube is 'good' rather than shorting, or something that might cause catastrophic difficulties.

Ended up with a few extra minutes for load up yesterday and took a moment to get in and do a couple changes...nothing in terms of actually A/Bing or concerted listening, but I did change out my EZ81 to the GE branded Mullard, and have the JAN RCA in V1 with the JAn Sylvania in V2, and just to be difficult, a GE 12AU7. At our rehearsal space, I literally just tested each in the Monique to make sure it was working and not causing trouble, then off to the show...with a backup in case.

Sounded fantastic on stage.