Preamp Tubes? - Who, What, When, Where, Why, and How?

[solarburn]

I got a Penta Labs 12AX7 in place of the JJ803S that died on me in less than 4hrs. Just got it today. Any ways I rolled it in V1 "tube to tube" against the RFT I had in V1.

The RFT kicked its ass across all frequencies as well as response to picking dynamics, guitar roll off, pick up changes from bridge/middle to neck and had a more toneful gain. It cleaned the Chinese tube's clock on the clean channel.

IMO the Penta Lab would be fine for high gain. It did good there. For blues and rock it was mediocre to my ears. Not good, not bad. Usable.

This test was only in V1.

 

[ken361]

I got a Penta Labs 12AX7 in place of the JJ803S that died on me in less than 4hrs. Just got it today. Any ways I rolled it in V1 "tube to tube" against the RFT I had in V1.

The RFT kicked its ass across all frequencies as well as response to picking dynamics, guitar roll off, pick up changes from bridge/middle to neck and had a more toneful gain. It cleaned the Chinese tube's clock on the clean channel.

IMO the Penta Lab would be fine for high gain. It did good there. For blues and rock it was mediocre to my ears. Not good, not bad. Usable.

This test was only in V1.

Hey solar wassup? was it a regular penta? If you bought it from doug he might take it back, I just sent back one of my M tubes. Doug is pretty cool for that!

 

[ken361]

I think most of us here on the thread have at least one RFT. And yes, they are a nice V1.

How do they sound next to a Mullard? since I dont have one yet?

 

[RiverRatt]

My short experience with Mullard and RFT is weird. I thought I had some good RFTs and I sent one to Marty and it tested at just slightly above DEAD. I think I have a good Mullard. It's a classic sounding tube, with a little more grit than most of my others. Unless I get something I like a lot more, it's earned a permanent spot in V1 with the Raytheon BP in V2. Marty talked me into a strong Sylvania in V3 and I've got an RCA in V4. I've got to get a real RFT now and an Amperex. Once I get those I think I'll have tried all the ones I set out to and then some.

 

[RiverRatt]

I solved the mystery of the Sonotone side-getter ECC83. I got the second tube out and it does have a very faint 12AX7A printed in the classic RCA font and inside the rounded corner rectangle. It must have been completely covered up on this tube. I still haven't found a picture of another RCA that looks like this, but that's what it is.

 

[MartyStrat54]

That's odd, because the font is "skinny" an it just fits inside of the flattened octagonal box of an RCA tube. I'm looking at the "12AX7A" on your tubes and it is "thick." Is this from a secondary relabeling on the tube and the RCA logo is not visible to me?

 

[MartyStrat54]

How do they sound next to a Mullard? since I dont have one yet?

That depends on where the tubes are placed. If you stick an RFT in V1 and a Mullard in V2, you are going to hear more of the tones from the RFT as V1 is the dominant gain stage. Switch them around and now the Mullard will be the dominant tone.

In some ways a Mullard is similar in tone to an RFT. Both tubes when driven hard produce some grit.

Amperex and Telefunkens will distort, but they do so softer than a Mullard or an RFT. However, that's the beauty of tubes, is that they have very smooth distortion characteristics compared to solid state. That's why a 100 watt tube amp will sound bigger that a 100 watt solid state amp. Most 100 watt Marshall's dimed will produce over 120 watts at 10 per cent THD.

 

[RiverRatt]

That's odd, because the font is "skinny" an it just fits inside of the flattened octagonal box of an RCA tube. I'm looking at the "12AX7A" on your tubes and it is "thick." Is this from a secondary relabeling on the tube and the RCA logo is not visible to me?

I think the Sonotone paint has rubbed off to the point that you can see the RCA numbering underneath it. I don't know why the numbering is so thick on that tube. It looks like that Tung-Sol branded Raytheon AT7 I sent you. You can see the RCA numbering better on the other tube, but barely. Here's the best shot I could get. It's like trying to photograph a ghost. I can see it fine under the right light, but it won't photograph.

What's all the white stuff on the leads? Did they use silver solder and some sort of flux like borax to solder the connections?

 

[solarburn]

Hey solar wassup? was it a regular penta? If you bought it from doug he might take it back, I just sent back one of my M tubes. Doug is pretty cool for that!

Yeah it was Doug. He replaced the JJ with the Penta. Its a 12AX7B. Pretty much sounds like my other Chinese preamp tubes. Good for high gain average for clean to midgain stuff. It will make a good back up tube though. I just picked it cause it was in the same price range. I already have Tung Sols, Mullards, JJ83S/803S, EH's and Ruby's so I really wasn't wanting anything else CP wise.

I was experimenting with the JJ803S in both my amps. I really liked it in V1 of my DSL but hated it in my NT. Too bad it only lasted about 4hrs. I liked it way better than the higher gain ECC83S by JJ.

 

[MartyStrat54]

I think the Sonotone paint has rubbed off to the point that you can see the RCA numbering underneath it. I don't know why the numbering is so thick on that tube. It looks like that Tung-Sol branded Raytheon AT7 I sent you. You can see the RCA numbering better on the other tube, but barely. Here's the best shot I could get. It's like trying to photograph a ghost. I can see it fine under the right light, but it won't photograph.

What's all the white stuff on the leads? Did they use silver solder and some sort of flux like borax to solder the connections?

I can see the logo much better now. The only problem is that I am thinking these tubes were made before 1960 and that could either be a Tung-Sol logo or and RCA. In this case, I tend to think that they are RCA. To be blunt, I've never seen any side getter 12AX7's until I tested your Sonotones. These could have been spec tubes or SRT's. (Special Request Tubes.) Maybe you have seen more of these from other manufacturers, but I haven't. It was quite common for GE to use side getter and sometimes one side and one top getter in some of their power tubes. Most of the line of thought back then was in favor of top getters. I would have to say that those tubes are probably somewhat rare.

Was the white stuff always there? I'm hoping that a crack didn't occur around a pin and the tube is getting gassey. They used boric acid and boron. The way the tubes were made was they put the bottoms on first and melted the glass around the pins. Then they took the guts and soldered it to the proper pins. I'm assuming that they used silver solder. That was the norm. Do both tubes show white in the bottoms? If so, then as long as it has already been there, I would say it is just from some sort of process.

 

[solarburn]

How do they sound next to a Mullard? since I dont have one yet?

So far my NOS Mullard has sounded good with a few of my other tubes now.

In V1 or vice versa.

 

[solarburn]

Does anyone else roll preamp tubes like me?

When I'm roll'n preamp tubes I'll keep the amp in stand by and warmed up between tube rolls so I put the least amount of listening time in between tube to tube. I don't want to lose my frame of reference by waiting for tubes to cool off, pull them and then put new cold ones in and wait another couple of minutes for it to warm up. That 2 minutes to warm up is all I want to wait between playing again.

Going back and forth is much quicker and my frame of reference judging each tube is fresher and I think more accurate than waiting longer.

If I ever screw a tube up by doing this though, I'll quit and let them cool down first. Until then these NOS are hardy tubes and I find they handle this just fine. So do the CP tubes. I am a very gentle tube roller...

Power tubes of course are much hotter and need biasing between rolling so obviously I can't do this with them.

Anyways I was just curious. I know most don't want to handle them while they are heated for fear of damaging them. They may be more fragile in a heated state. Course I found this out after rolling them my way for some time although I had seen vids of others doing it. I haven't had any problems so far. I mean they all keep working...

I'm not advocating this. "Better be safe then sorry." Just wondering if anyone else does it like this.

 

[RiverRatt]

I can see the logo much better now. The only problem is that I am thinking these tubes were made before 1960 and that could either be a Tung-Sol logo or and RCA. In this case, I tend to think that they are RCA. To be blunt, I've never seen any side getter 12AX7's until I tested your Sonotones. These could have been spec tubes or SRT's. (Special Request Tubes.) Maybe you have seen more of these from other manufacturers, but I haven't. It was quite common for GE to use side getter and sometimes one side and one top getter in some of their power tubes. Most of the line of thought back then was in favor of top getters. I would have to say that those tubes are probably somewhat rare.

Was the white stuff always there? I'm hoping that a crack didn't occur around a pin and the tube is getting gassey. They used boric acid and boron. The way the tubes were made was they put the bottoms on first and melted the glass around the pins. Then they took the guts and soldered it to the proper pins. I'm assuming that they used silver solder. That was the norm. Do both tubes show white in the bottoms? If so, then as long as it has already been there, I would say it is just from some sort of process.

No, the only tube I've seen that looked anything like these was a Japanese made tube labeled ITT I think. These tubes came from a hi-fi stereo set. I can't even remember the make now, but I think the carcass may still be around somewhere. I believe the date on the tube chart was 1960 or 61, so the tubes very well could be pre-1960. That thick logo on the other tube is strange, as the tubes are clearly identical in construction. The one with the thick writing has no RCA-style logo.

The white stuff is clumped up at the solder points, so I'm thinking it is boric acid or borax paste that wasn't cleaned off. I've just never seen it left on.

Compared to my RCA cleartop 12AU7As, they only bear a passing resemblance. The getter is similar and the plates are similar, but not exact. The AU7 uses mica spacers with flat sides, and the Sonotones are round.

Either way, they sound good. You tested them at 24-23 and 23-28.

 

[MartyStrat54]

Joe, I test mine like that most of the time. I just try to minimize the jiggling around. The heater filaments are pretty rugged. Your right about keeping the time span to a minimum. Some tubes can sound pretty close. I wish that I could afford that rig you posted a while back, but I would like mine to be able to hold four tubes. That would be cool to flick a switch and go from tube to tube, because the heaters would all be on.

 

[RiverRatt]

I've always been afraid to test like that, especially as much as these tubes cost. I used to swap tubes in my old Laney head on standby and I noticed a couple of them seemed more noisy later. Probably just paranoia, or they may have been a little microphonic to begin with.

 

[LosAngelesAceFace]

Welcome to the thread. If you are happy using current production (CP) tubes, I say go for it. As Ratt said, I will agree that the Tung-Sol is my favorite CP tube. The only problem is that "some" of the Tung-Sol's have been failing in V3. If you got one in there and it is working, great. Just keep in mind that it may fail due to the high voltages on the tube in that particular circuit. You can use a Mullard RI in there as it is not a gain stage and therefore less likely to hear any microphonics. "Or" you could get a NOS tube and stick it in V3 and not have to worry about it. You can pick up a single tube pretty cheap. However, if it was me, I would get two NOS tubes and put one in V1 and the other in V3. I would leave the Tung-Sol in V2. If you like that, then you could step up to a high gain NOS tube in V2. Here again, it could be a Sylvania tube. These are great tubes, they sound better than CP and they are affordable.

I actually have a JJ in V3. Unfortunately, I've already given my Mullard to my brother who just bought a Marshall head. I figured he has more use for it now. Interesting point you make though. I've actually been having an issue where on the clean channel, with full gain with no pedals, will sometime get cleaner for like a few minutes, then go back to full gain. Could it be the Tung Sol?

 

[MartyStrat54]

I actually have a JJ in V3. Unfortunately, I've already given my Mullard to my brother who just bought a Marshall head. I figured he has more use for it now. Interesting point you make though. I've actually been having an issue where on the clean channel, with full gain with no pedals, will sometime get cleaner for like a few minutes, then go back to full gain. Could it be the Tung Sol?

Don't know if the Tung-Sol is in V3, but whatever tube is in there if it is CP it is suspect. V3 is actually operating two separate circuits. One is the tone stack and the other is the cathode follower. If the "half" of the tube running the tone stack is going, you could have the symptoms like you have described.

 

[LosAngelesAceFace]

I was just trying the amp right now. Have it at low master volume (about 3). Doesn't seem to be doing what i said it does. Then again, I haven't fired it up in months. It's a JJ in V3 right now, by the way. Maybe this problem only persists when at high volume. I usually have it at about 6.

 

[ken361]

Does anyone else roll preamp tubes like me?

When I'm roll'n preamp tubes I'll keep the amp in stand by and warmed up between tube rolls so I put the least amount of listening time in between tube to tube. I don't want to lose my frame of reference by waiting for tubes to cool off, pull them and then put new cold ones in and wait another couple of minutes for it to warm up. That 2 minutes to warm up is all I want to wait between playing again.

Going back and forth is much quicker and my frame of reference judging each tube is fresher and I think more accurate than waiting longer.

If I ever screw a tube up by doing this though, I'll quit and let them cool down first. Until then these NOS are hardy tubes and I find they handle this just fine. So do the CP tubes. I am a very gentle tube roller...

Power tubes of course are much hotter and need biasing between rolling so obviously I can't do this with them.

Anyways I was just curious. I know most don't want to handle them while they are heated for fear of damaging them. They may be more fragile in a heated state. Course I found this out after rolling them my way for some time although I had seen vids of others doing it. I haven't had any problems so far. I mean they all keep working...

I'm not advocating this. "Better be safe then sorry." Just wondering if anyone else does it like this.

yeah i roll like you do, I go back and forth to see what pans out the best. Mines jvm sounds great with the RFT v1 and the penta M tube v2, that balances the rft. getting a thick awsome metal tone on my paul guitar.

 

[solarburn]

yeah i roll like you do, I go back and forth to see what pans out the best. Mines jvm sounds great with the RFT v1 and the penta M tube v2, that balances the rft. getting a thick awsome metal tone on my paul guitar.

Right on man. Love a nice thick gain.

I find my JP 12AX7WA in V2 pairs up real well with the RFT in V1. Also putting the JP in V1 and pairing it with a Mullard, BP and RFT all in V2 is good as well. It mixes nicely with other tubes.