Let's talk about 6SL7 tubes!

[BurningSkies]

I've been figuring that while I want a few nice 6SL7's around, I also wanted to grab a spare rectifier tube for the new preamp just to have as a spare/backup. Found a NOS GE branded Mullard (Blackburn plant) up online for 12 bucks BIN...so that's headed my way too. That's the price of a new production EZ81...not a GE/Mullard.

 

[JimmyM]

Whatcha gonna try first? What are the likely candidates?

Whatever you and chadds say to get

 

[Lo-E]

A little disappointed that the one that went out I just got 4 months ago to replace one that had a little over 3 years on it. If Sylvania were still making tubes, I'd trash them publicly.

Yeah, it's always a little bit of a crap-shoot with NOS tubes. They're SO hyped so much of the time that it's easy to lose your sense of perspective. Sylvania was one of the last companies to continue producing tubes into the 80s. A lot of the JAN stuff is 80s stock. 80s stock is sort of a double-edged sword: By then, the manufacturers really new how to produce great tubes. They had had almost 60 years of practice and they had it down to science so they were capable of producing immaculate quality. On the other hand, they also knew they were getting out of the tube business and started to cut corners toward the end of the run so quality control of 80s tubes was sometimes as bad as some of the Eastern European stuff.

Also, a lot of the really good NOS stuff got snapped up by hoarders years ago and the stuff that's available now... it's impossible - for the buyers and the sellers to know how it was treated. Even very honest, reputable dealers get stuck with a batch of dogs from time to time because there's just no way to predict every failure.

As some of you have pointed out, modern production can be a better choice in some circuits. It really just depends upon the situation. I used to have a pretty low opinion of modern productions stuff, but they've gotten better and better at it in the last 10 years or so. Some modern tubes are every bit as good as some NOS stuff.

 

[Lo-E]

I am starting to dream up a new fantasy preamp. Two channel tube preamp using 3 6SL7's (1 for each 2 stage channel and possibly 1 as a phase inverter feeding a small output transformer) and a proper power supply (toroidal transformer). Footswitch to change channels. Gain, bass, treble and level controls per channel. Very similar to a B15 preamp I guess, but with switchable channels and possibly a little more gain per stage. Sigh... nice to dream.

I've been considering the exact same thing only with three channels for a while! I rescued a nice chassis from the discard pile at work, fan-cooled and everything. Really high-quality stuff. I couldn't let it perish in a dumpster!

My thought was to use two different iterations of the B-15 pre and a B-25 as my three channels. I even went as far as to draw up a layout for the three channels on three separate, stacked boards but by the time I got to start designing a power supply I got too busy with other things.

I'd have a lot more time for this stuff if I wasn't playing that stupid bass all the time....

 

[Passinwind]

I am starting to dream up a new fantasy preamp. Two channel tube preamp using 3 6SL7's (1 for each 2 stage channel and possibly 1 as a phase inverter feeding a small output transformer) and a proper power supply (toroidal transformer). Footswitch to change channels. Gain, bass, treble and level controls per channel. Very similar to a B15 preamp I guess, but with switchable channels and possibly a little more gain per stage. Sigh... nice to dream.

One of my DIY rig configurations is fairly similar to that, but with a solid state second channel. The tube side uses two 6SN7s to drive a 4:1 Jensen output transformer. Haven't bothered to make it switchable, since my intended use would be doubling on EUB and BG, or bass and guitar synth.

 

[BurningSkies]

Whatever you and chadds say to get

I'm really interested in trying these:

If microphonics are an overreaching issue for 6SL7's then having a tube with good 'structure' appeals to me. These are triple mica spacers with additional stiffening rods.

Link Removed

I also have a set of RCA 5751 black plates with very similar structure (extra rods, triple mica) that sound really nice in a few settings, my Kern, my Vibrochamp, and even my Twin. I have a set of Russian Military 1579's that are NOS 1950's on their way...we'll see what they end up doing.

 

[Lo-E]

Those 5691s are bulletproof, but give them extra warm-up time. All the 'ruggedized' military tubes take a long time to warm up because there's so much structural stuff in there that acts like a heat sink. ...like, really A LOT longer than standard tubes.

Give them about three minutes. Not very long, really, but when you're waiting to play your bass it seems like 1,000 years!

If you hit those tubes with a signal before they are fully warmed up it will result in cathode stripping, which can seriously reduce the life of the tube.

This is true of all tubes, actually. Make sure they're fully warmed up to get the longest possible life out of them!

 

[BurningSkies]

Those 5691s are bulletproof, but give them extra warm-up time. All the 'ruggedized' military tubes take a long time to warm up because there's so much structural stuff in there that acts like a heat sink. ...like, really A LOT longer than standard tubes.

Give them about three minutes. Not very long, really, but when you're waiting to play your bass it seems like 1,000 years!

If you hit those tubes with a signal before they are fully warmed up it will result in cathode stripping, which can seriously reduce the life of the tube.

This is true of all tubes, actually. Make sure they're fully warmed up to get the longest possible life out of them!

I usually have my preamp up and running well before I turn on my amp and plug in my bass. That way any errant start up noise doesn't hit my power amp or my speakers...which could be an issue, with several thousand watts on tap.

 

[BassmanPaul]

I do it for fun, mostly. Only about 25% of my tube restoration work is for pay, and it's almost always for friends, so I end up working pretty cheap!

Much the same story here. I'll help out a friend but I no longer need the stress of dealing with unappreciative folk who think I should work for $10 an hour! :scowl:

 

[Lo-E]

...but I no longer need the stress of dealing with unappreciative folk who think I should work for $10 an hour! :scowl:

Oh, I see you've met my friends!

 

[BurningSkies]

I'd be appreciative if either of you would work on my tube amps for 10$ an hour.

 

[Lo-E]

If you had to drag yourself all the way down here from Syracuse for amp work, I'd say you'd deserve the discount! The gas would cost 3x the repairs.

 

[BurningSkies]

If you had to drag yourself all the way down here from Syracuse for amp work, I'd say you'd deserve the discount! The gas would cost 3x the repairs.

Eh. I've done worse. I have a keyboardist friend who has his Moogs serviced down state...and I've pondered having my Space Echo serviced by a specialist down around there.

I also drove 6 hours each direction to pick up my Mesa 400+ when I bought it rather than shipping it, then when I sold it I ended up driving it to Boston (luckily I happened to be going anyway).

 

[beans-on-toast]

I'm really interested in trying these:

Despite being pricey, they are great tubes. With a 10,000 hour life, you can play about 10 hours a week for 20 years!

The one drawback of this tube is that the nominal heater current is 0.6A as compared to 0.3A for a regular 6SL7GT. So your power supply will have to be capable of providing the necessary heater current.

 

[BassmanPaul]

The one drawback of this tube is that the nominal heater current is 0.6A as compared to 0.3A for a regular 6SL7GT. So your power supply will have to be capable of providing the necessary heater current.

That's the drawback to a lot of output tube rolling as wall. Folk tend to disregard the increased heater draw of some tubes.

 

[BurningSkies]

Despite being pricey, they are great tubes. With a 10,000 hour life, you can play about 10 hours a week for 20 years!

The one drawback of this tube is that the nominal heater current is 0.6A as compared to 0.3A for a regular 6SL7GT. So your power supply will have to be capable of providing the necessary heater current.

That's the drawback to a lot of output tube rolling as wall. Folk tend to disregard the increased heater draw of some tubes.

I'll have to ask Jule if it would be a good fit. Luckily, he's pretty approachable.

 

[juledude]

A simple trick gathered from the HI FI crazies (good folk) is to mount tubes in rubber mountings. The idea has little to do with road life, but all to do with keeping rumbles out of tubes.

The usual rumbling culprit is the power supply transformer humming away at some octave of 60 (or 50) cycles. All those laminated metal plates, unless they are incredibly well manufactured, get to moving pretty aggressively. Ends up as low end rumble. Not something bass players always appreciate. The rubber mounts can reduce it.

Mounting on top of a speaker cabinet potentially is going to introduce some of this rumble. The question of, "how much" has much to do with how the amp/preamp is mechanically assembled. Some will transfer more than others. I've even caught solid state gear picking up mechanical noise.

I'm not surprised that there are widely varied responses to the same tubes. They, each of them, have a personality that comes from their mechanical analog design and construction.

We all know people who can not hear any difference. Thank goodness we can. To our sensitive ears, there is going to be a lot of variation in tone and playing characteristics.

These octal tubes were designed as car radio tubes originally. The idea behind the blunt, stubby package was that they could be installed upside down in a car police radio and they would not fall out. There is a very interesting museum at Motorola (first US police car radio) in Shaumurg IL. that shows these tubes in their heyday.

Today, we are using these same tubes to make gorgeous, precise recordings, a use never any part of the thinking of the original designers. But the things sound and play so very sweetly compared to what else is available.

I started using these octal tubes about 8 years ago. Back then, none were being manufactured. The task then was to scour the NOS world. When the gathering net went as far as Belgium, I figured it was all over and they were going to disappear. I'm glad they are being made again.

 

[BurningSkies]

A simple trick gathered from the HI FI crazies (good folk) is to mount tubes in rubber mountings. The idea has little to do with road life, but all to do with keeping rumbles out of tubes.

The usual rumbling culprit is the power supply transformer humming away at some octave of 60 (or 50) cycles. All those laminated metal plates, unless they are incredibly well manufactured, get to moving pretty aggressively. Ends up as low end rumble. Not something bass players always appreciate. The rubber mounts can reduce it.

Mounting on top of a speaker cabinet potentially is going to introduce some of this rumble. The question of, "how much" has much to do with how the amp/preamp is mechanically assembled. Some will transfer more than others. I've even caught solid state gear picking up mechanical noise.

I'm not surprised that there are widely varied responses to the same tubes. They, each of them, have a personality that comes from their mechanical analog design and construction.

We all know people who can not hear any difference. Thank goodness we can. To our sensitive ears, there is going to be a lot of variation in tone and playing characteristics.

These octal tubes were designed as car radio tubes originally. The idea behind the blunt, stubby package was that they could be installed upside down in a car police radio and they would not fall out. There is a very interesting museum at Motorola (first US police car radio) in Shaumurg IL. that shows these tubes in their heyday.

Today, we are using these same tubes to make gorgeous, precise recordings, a use never any part of the thinking of the original designers. But the things sound and play so very sweetly compared to what else is available.

I started using these octal tubes about 8 years ago. Back then, none were being manufactured. The task then was to scour the NOS world. When the gathering net went as far as Belgium, I figured it was all over and they were going to disappear. I'm glad they are being made again.

Interesting history, Jule. I'm not one in believing ALL of the tube propaganda, but depending upon the circuit, I can certainly hear a difference. My ears aren't all that good these days (only partially due to music) but it still is noticeable to me. I've found that I don't always like the same tubes that I'm told are so fabulous, its really hit or miss...which is why I tend to like to gather up a bunch at reasonable cost then earball them all to pick my favorite. Depending upon the setting, sometimes modern production tubes sound best.

I have a couple Ei tubes (AX7's) that were still in production when I bought them, and found I liked what they did better than older well loved tubes like a couple Sylvanias and Mullards I had! Weirdly, I bought two of them and they're completely different looking tubes, one with shiny silver smooth plates, the other with flat grey ridged plates...

 

[Lo-E]

I have a couple Ei tubes (AX7's) that were still in production when I bought them, and found I liked what they did better than older well loved tubes like a couple Sylvanias and Mullards I had! Weirdly, I bought two of them and they're completely different looking tubes, one with shiny silver smooth plates, the other with flat grey ridged plates...

The shiny plates are later production. By the time they went into production of the shiny plate AX7s, the quality control was starting to slide. Some were fine, some were sketchy.
There was a war on while those tubes were being made and that factory was bombed more than once during various production runs.

To my ear, the sound of the shiny plates is the same as, or very similar to the grey plates, but some people will argue that.

Ei made great tubes. I believe they had some original Mullard tooling in use. I was very sorry to see them go.

JJ is my AX7 of choice now, but I still have stock piles of Ei, as well as other NOS goodies.

 

[BurningSkies]

The shiny plates are later production. By the time they went into production of the shiny plate AX7s, the quality control was starting to slide. Some were fine, some were sketchy.
There was a war on while those tubes were being made and that factory was bombed more than once during various production runs.

To my ear, the sound of the shiny plates is the same as, or very similar to the grey plates, but some people will argue that.

Ei made great tubes. I believe they had some original Mullard tooling in use. I was very sorry to see them go.

JJ is my AX7 of choice now, but I still have stock piles of Ei, as well as other NOS goodies.

Yeah, when I originally purchased the Ei's I have, I got them from a reputable dealer, and they were a few bucks more than other tubes due to the cull rate. At the same time, people didn't seem to think they were anything all that special...until they went out of production.

The ones I have I liked because they had some nice top end that many vintage tubes didn't but had more beef than a lot of the newer tubes.