Tube roll in Custom 50

[Deleted member 5962]

Well, I tried my first tube swap in the 2 Channel Custom 50 last night. V1 was replaced with a Tung Sol. I like to replace one at a time initially.

This is only a first reaction, as I want more time with it and to try a few other guitars. My initial response is very positive though. I think there is more clarity in both channels. I am going to cautiously check to make sure I didn't lose some fatness on the clean channel. Or, if I did if a simple slight bump of the mids will add it back. But the OD channel was a nice little improvement. I plugged into the 2x12 PRS cab with V30s (the one that I've had some objections to the ice pick with) and it seems to have taken a bit of the roughness off the gain channel, making the ice pic a bit less objectionable.

This is preliminary. And switching back and forth on V1 is not easy. I had to pull both power tubes to get up my hand in there to get V1 in and out. A current production Tung Sol is a very popular V1 with owners of many kinds of amps these days so I thought I'd try it first. I have a balanced Ruby for the PI, and another tube that is supposed to be pretty good in the cathode follower position and I'll try those next... after a few days with this one to form a more solid opinion.

If the right new tubes make this amp even better, I'll start hunting down some old stuff. I see I can still buy NOS Mullard EL34s for it for $199 a piece... (yikes! LOL)

 

[László]

Sounds like a good swap!

I had the new Tung Sols in my last Two-Rock, and I thought they sounded pretty sweet.

 

[andy474x]

If you want to tame rough edges, I've found the JJ 5751 to be great for V1, if you don't mind losing some gain. Took the grainy sound out of my amp, the breakup is less fizzy.

What does the balanced PI do for you? I've also noticed that my amp is very sensitive to different phase inverters, 12at7's of different brands and even different 12at7's of the same brand make a noticeable change. I've been wanting to try a balanced PI, despite the fact that lots of people claim they don't make a difference. Worst case scenario I have another extra PI lying around.

 

[Deleted member 5962]

Andy, thanks for the tip. Not sure I want to try lower gain tubes yet, but I do have a nice NOS 5751...

I think the differences you hear in different PI tubes are a couple things, but one big one is the balance between the two sides... see below.

oh boy... this is a big can of worms, but since I know Les is a fan of balanced PI tubes, I'll dive in but jump back out before I get in too deep. Prefaced with the fact that, while I have some electronic knowledge, it's only enough to be dangerous and not enough to be an amp designer.

Some (or many) people believe that it is important or very important to have a balanced PI tube. Some believe it's not important at all. Here is why I fall into the group that thinks it is "normally" important. It's said that most amp designers design in a bit if assymmetry in the power stage, because that is more pleasing to the ear. The simplest explanation I can give for balanced PI is that the ONLY way you get exactly what the builder designed, is with balanced PI tubes.

Now I could write 3 pages about the other factors and other opinions. And, you should ALWAYS go with what "sounds" best. But (IMHO) when you hear someone say "I tried balanced PI tube and the tube I had in there before sounds better" it's not that they're wrong, it's that they prefer the shift in balance that a particular tube applies to the circuit. So, maybe the amp builder builds in a little bit of assymmetry (I think I'm making up a word here, LOL) in the power stage, and a balanced tube gives exactly that, but a particular guy likes his unbalanced tube better because perhaps the unbalance provides just a bit more assymmetry and he likes that better. I've also read that if the amp designer does not build in some assymmetry that an unbalanced tube will sound better to most because it provides it.

Back to amps with that designed in: What if your designer builds in his perfect idea of how much unbalance there is, but your tube adds to the strong side wave, making it more assymmetrical? Might be appealing, might not. But what if your PI tube actually is stronger on the side of the wave that the amp designer made to be lower? Now it's pushing the designers "Ideal" assymmetrical wave form back to maybe being symmetrical, defeating something he carefully designed in.

So, without getting any deeper, you might find an unbalanced tube you like better, but what about when that tube goes bad? Can you find another with that same balance? If not, you'll never get that sound again. But with a balanced tube, you can always replicate what the designer intended, and when that one goes bad buy another balanced tube, and get the same thing you had.

DISCLAIMER: All the above is IMHO. Consult your physician for erections lasting over 4 hours.

 

[Boogie]

It would be interesting to hear Doug's take on this subject. I truly believe that certain designs are more sensitive to PI tube selection. Randall Smith's Mark series does not benefit from a specifically balanced phase inverter tube, but then again, who's to say M/B's 12ax7s aren't all sorted for balance and standing current? They do make it easy to replace tubes and get consistent results. I'm also of the opinion that PRS uses JJ's in the same respect, except they tend to customize the tube cocktail in CAD amps. But in my MkIII, the only tube I've never changed is the PI...it's 26 years old and still going strong and sounding better than if I used a newer M/B sorted tube.

 

[andy474x]

Andy, thanks for the tip. Not sure I want to try lower gain tubes yet, but I do have a nice NOS 5751...

I think the differences you hear in different PI tubes are a couple things, but one big one is the balance between the two sides... see below.

oh boy... this is a big can of worms, but since I know Les is a fan of balanced PI tubes, I'll dive in but jump back out before I get in too deep. Prefaced with the fact that, while I have some electronic knowledge, it's only enough to be dangerous and not enough to be an amp designer.

Some (or many) people believe that it is important or very important to have a balanced PI tube. Some believe it's not important at all. Here is why I fall into the group that thinks it is "normally" important. It's said that most amp designers design in a bit if assymmetry in the power stage, because that is more pleasing to the ear. The simplest explanation I can give for balanced PI is that the ONLY way you get exactly what the builder designed, is with balanced PI tubes.

Now I could write 3 pages about the other factors and other opinions. And, you should ALWAYS go with what "sounds" best. But (IMHO) when you hear someone say "I tried balanced PI tube and the tube I had in there before sounds better" it's not that they're wrong, it's that they prefer the shift in balance that a particular tube applies to the circuit. So, maybe the amp builder builds in a little bit of assymmetry (I think I'm making up a word here, LOL) in the power stage, and a balanced tube gives exactly that, but a particular guy likes his unbalanced tube better because perhaps the unbalance provides just a bit more assymmetry and he likes that better. I've also read that if the amp designer does not build in some assymmetry that an unbalanced tube will sound better to most because it provides it.

Back to amps with that designed in: What if your designer builds in his perfect idea of how much unbalance there is, but your tube adds to the strong side wave, making it more assymmetrical? Might be appealing, might not. But what if your PI tube actually is stronger on the side of the wave that the amp designer made to be lower? Now it's pushing the designers "Ideal" assymmetrical wave form back to maybe being symmetrical, defeating something he carefully designed in.

So, without getting any deeper, you might find an unbalanced tube you like better, but what about when that tube goes bad? Can you find another with that same balance? If not, you'll never get that sound again. But with a balanced tube, you can always replicate what the designer intended, and when that one goes bad buy another balanced tube, and get the same thing you had.

DISCLAIMER: All the above is IMHO. Consult your physician for erections lasting over 4 hours.

Ah, well said. So the balanced PI ensures the intended asymmetrical output, yet reproducible if you ever need to switch the PI. That would make sense for why PI tubes even of the exact same brand and type sound different in my amp, each tube has differently contrasting triode "halves." Well I will definitely try one, any brand recommendations? I believe I have a Tung Sol in right now, sounded better than a few JJ's I tried but that could have just been the result of a better balancing match to my amp.

And regarding the erection, I don't think I'll call my doctor. Nice enough guy, but he's older and not really my type.

 

[László]

Not that I'm an expert on phase inverters - but I've heard it said many times that the phase inverter's twin triodes should ideally be balanced.

I do know that the object of the phase inverter is to have a mirror image on each side of the tube, that is, each triode. Granted, achieving that is rare, but within a small range of variation it's OK. But the point is that each triode on a phase inverter feeds a power tube (or a bank of tubes). Ideally you do want that symmetry, but of course we guitar players are all about nonlinearities, so on that end I can't help ya. I like mine as balanced as possible on both triodes.

Having fiddled with swapping a few PI tubes on my DG30 only recently, I can say that the PI makes a significant difference to the tone of the amp (and in my case, I swapped only 12AX7s and didn't try a lower gain tube). As an example, the stock JJ ECC83s, which is a pretty gainy tube, gave the amp that sound that we've heard on the latest Grissom record. It's more snarly, and the amp broke up in a very predictable way. Trying an NOS BRIMAR in the same position didn't turn me on at all. The amp lost a lot of the overdrive tone, and broke up too early on the high end. Interestingly, the amp sounded WONDERFUL with the same BRIMAR in the V1 and V3 positions (this is actually the stock setup for the "first 20" DG30 models). After a few more experiments, I decided to stick with the stock setup, it really did sound best to my ear, though I did replace the JJ with one I found that I thought sounded best after trying a few.

 

[andy474x]

Good to know Les, I think I'll go with moderately priced tubes for the PI. Gonna stick with 12at7's for mine, as that was stock, Soon a balanced JJ and Tung Sol are coming my way. Also going to try some 7581A's for my output and the new JJ mid gain 12ax7, for kicks.

 

[Deleted member 5962]

Believe it or not, the humble Sovtek 12AX7LPS is highly regarded in the PI position by many people. I have a couple, and after a few more days of soaking in the new V1, I"m going to test current vs. LPS vs. a nice balanced Ruby (JJ) that I got from Dougs Tubes

Boogie, yes I'd love to hear Dougs take on this. Some of what I mentioned above is taken from a couple highly respected amp designers posts at TGP about this subject.

 

[Iceman63]

I'd like to hear Doug's take as well. Been swapping my PI a little. Right now I have a Sovtek 5751in mine...low noise but not balanced (triode 1 95, 2 is 98). Have tried a Gold lion 12ax7 in there as well, that I had in the pre amp of another amp. It's not balanced either, just high gain. Stock in the Custom 50 was a JJ ECC81. I can't hear drastic differences between them.
Have an old RCA 7025 in V1, everything else stock.

 

[Deleted member 5962]

So I'm really starting to dig the OD channel as I've experimented more now with the Resonance and pull mid shift. I'm finding that I can use one or the other of these, adjust the bass and mid knobs, and end up closer to the sound I was looking for. At this point, I'm really liking the OD channel more than ever. So...

While I intend to do more rolling (just got started) to find the right mix for the pre-tubes, I'm really wanting to know what to expect if I switch to EL34s in the power section. How much tonal difference will it make? And, I have to turn it up loud for the power tubes to make much difference? I'm getting ready to order some more tubes, and would like to order some EL34s along with the pre- tubes I want. I think I'm going to try something new and affordable first, so I'm really looking for suggestions.

Then, if I really love it, I might down the road spring for some NOS Mullards or =C= or something. But those are about $400 per pair, so I'd rather try the tube type first and see if that's the last piece of the puzzle. I am just trying to push the amp a little more towards the other side of the pond. I have some Mesa stuff so I'm trying to just give the Custom OD channel a little nudge towards the Brit side.

So, how much difference will just the power tubes make? And, what should I try first? Mullard? Tung Sol? Other?

Oh, and so far, the Tung Sol in V1 is NICE!!!

 

[László]

So I'm really starting to dig the OD channel as I've experimented more now with the Resonance and pull mid shift. I'm finding that I can use one or the other of these, adjust the bass and mid knobs, and end up closer to the sound I was looking for. At this point, I'm really liking the OD channel more than ever. So...

While I intend to do more rolling (just got started) to find the right mix for the pre-tubes, I'm really wanting to know what to expect if I switch to EL34s in the power section. How much tonal difference will it make? And, I have to turn it up loud for the power tubes to make much difference? I'm getting ready to order some more tubes, and would like to order some EL34s along with the pre- tubes I want. I think I'm going to try something new and affordable first, so I'm really looking for suggestions.

Then, if I really love it, I might down the road spring for some NOS Mullards or =C= or something. But those are about $400 per pair, so I'd rather try the tube type first and see if that's the last piece of the puzzle. I am just trying to push the amp a little more towards the other side of the pond. I have some Mesa stuff so I'm trying to just give the Custom OD channel a little nudge towards the Brit side.

So, how much difference will just the power tubes make? And, what should I try first? Mullard? Tung Sol? Other?

Oh, and so far, the Tung Sol in V1 is NICE!!!

A lot will depend on things other than power tubes, so take this with a grain of "you'll have to try it and see," but with the EL34s, the bottom should tighten up a little, and EL34s will often break up a little earlier in the upper midrange and midrange than a 6L6. So will a 5881 (6L6 WGB), but in a different way.

I've switched from 6L6 to EL34 in several Mesas that allowed that swap, and it made a difference -- though not a huge one, i.e., it didn't turn, say, my old Tremoverb into a Marshall. It still sounded like a Tremoverb, only with a bit more grit in the mids, and tighter lows, as you'd expect. Same with another Mesa I had.

Switching from 6L6 to 5881s in my old Two-Rock made a cool difference that I think I liked better.

But as with all things amplifier, everything depends on the entire circuit from preamp to output transformer and tubes, and you really need to try it and see. You might like it!

I'd do the swap with something inexpensive until you see how much it does for you. I wound up deciding in the case of my Mesas that Mesa picked the 6L6s with their circuits for a reason, and went back to them.

 

[vchizzle]

Power tube swaps making a big difference depends a lot on the amp itself. It's always been pretty noticeable in the amps I've tried it in. Like Les said, not like it's so big that your Mesa turns Marshall, but still noticeable enough. I really need to swap to the EL34's in my Archon to see how it changes it. I used to swap quite a few in my Bad Cat hot cats. I hated EH 6CA7's in that amp. Loved JJ KT77. Loved New Sensor Mullard reissue EL34. Liked Ruby EL34BSTR ok, though they were a little bright and lacking mids. So if I were to recommend a EL34 with budget in mind, I'd try Mullard reissues first, Ruby EL34BSTR last as they seem to have more 6L6 qualities. I've not been a huge JJ fan in my amps prior to the Archon. Especially pre's. I've always found JJ pre's grainy sounding. I like them a lot in the Archon though, So that goes to show ya, it depends on the amp a lot too. Everyone's got different ideas of what sounds "good" as well. Tube threads are always heavy on the YMMV.

 

[Boogie]

I agree with Les' assessment, too. My only $.02 is that the prices for premium power tubes are unreasonable if you burn through them routinely. Not knowing how long a particular tube would last, I grabbed some run-of-the-mill JJ's EL-34s...the cheapest quality option I could find. The results, after a year in service, are excellent and not different enough to split hairs and pay big dollars. For gigging, the JJ's were excellent.

With th all that said, I swapped my stock =C= EL34s because of microphonics. With the amp sitting on the cab, there were all sorts of audible artifacts. Since then, the amp sits on the floor in front of the cab on a stand. It would be a good experiment to plug the =C='s back in and see/hear any difference after a song the JJ's for so long.