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

[wegman]

Hi Marty.

That is the picture of the place that has them for sale.

I sent them an e-mail asking if they are NOS and tested like you recommended.

 

[RiverRatt]

Wow. I like the Tele! I think it edges out the Mullard for the V1 spot. It's great clean, it gets good 'n' crunchy, and with the gain cranked it's a monster. I've heard people describe tubes as having a "3D" sound, and I think this is what they mean. The highs on this thing are so smooth - I actually turned UP the treble on a DSL! Pinch harmonics are nice, too. With the RFT EL34s and the Raytheon BP and these last two tubes (the Mullard and the Tele), my amp sounds like a different beast altogether. It's as dramatic a change as any mods I've heard, and better in some ways.

Congrats, Wegman, those look like some nice RCAs. I don't think we've met yet. What kind of amp are you playing?

 

[MartyStrat54]

Wow. I like the Tele! I think it edges out the Mullard for the V1 spot. It's great clean, it gets good 'n' crunchy, and with the gain cranked it's a monster. I've heard people describe tubes as having a "3D" sound, and I think this is what they mean. The highs on this thing are so smooth - I actually turned UP the treble on a DSL! Pinch harmonics are nice, too. With the RFT EL34s and the Raytheon BP and these last two tubes (the Mullard and the Tele), my amp sounds like a different beast altogether. It's as dramatic a change as any mods I've heard, and better in some ways.

Congrats, Wegman, those look like some nice RCAs. I don't think we've met yet. What kind of amp are you playing?

Gee, Alan...when I read stories like this I just want to cry. I really loved that one line about, "It's as dramatic a change as any mods I've heard and better in some ways." God that sounds nice. See what a little tube rolling can do. Oh, it helps to have some good tubes. I knew you would like the Tele.

 

[solarburn]

Just check'n in real quick! Looks like guys are having fun roll'n!

I have to let the daughter's use the computer for homework so I will catch up to you bruther's later then.

 

[wegman]

Wow. I like the Tele! I think it edges out the Mullard for the V1 spot. It's great clean, it gets good 'n' crunchy, and with the gain cranked it's a monster. I've heard people describe tubes as having a "3D" sound, and I think this is what they mean. The highs on this thing are so smooth - I actually turned UP the treble on a DSL! Pinch harmonics are nice, too. With the RFT EL34s and the Raytheon BP and these last two tubes (the Mullard and the Tele), my amp sounds like a different beast altogether. It's as dramatic a change as any mods I've heard, and better in some ways.

Congrats, Wegman, those look like some nice RCAs. I don't think we've met yet. What kind of amp are you playing?

Hi RiverRatt nice to meet you.

I am struggling with a JCM 800 2210 from 1989. Since having it re-tubed it sounds awful. I have learned a mountain of information from this site and this thread. From everything I have read it looks like I am going to have to start playing with the pre-amp tubes to find "my tone" again.

I saw those RCA's for sale and I was considering picking them up after the really knowledgable people said they look decent.

 

[MartyStrat54]

Yeah, unlike the 800 I used to own, you have the hot rod model. The 2210 uses four preamp tubes. The most important for tone are V1 and V2. For V3 and V4, I still recommend NOS or ANOS (Almost New Old Stock) for these slots. You can get by with current production (CP) tubes, but V3 can be hard on CP tubes. However, many people are running their amps with CP in V3 and V4.

The main thing is V1 and V2. On the 800's I've sold tubes for, it is imperative that you have a nice, high gainer in V2 to get that amp to perform as it should. It would be nice if one of those RCA's tested higher than the other. This would be your V2. The main point is you can't guess at what you are putting in. If you don't get a high gainer in V2, your 800 is not going to sound as good as it can.

 

[racko7566]

Did you say BONG? I saw nothing, I think, damn cant rememb........

 

[wegman]

Yeah, unlike the 800 I used to own, you have the hot rod model. The 2210 uses four preamp tubes. The most important for tone are V1 and V2. For V3 and V4, I still recommend NOS or ANOS (Almost New Old Stock) for these slots. You can get by with current production (CP) tubes, but V3 can be hard on CP tubes. However, many people are running their amps with CP in V3 and V4.

The main thing is V1 and V2. On the 800's I've sold tubes for, it is imperative that you have a nice, high gainer in V2 to get that amp to perform as it should. It would be nice if one of those RCA's tested higher than the other. This would be your V2. The main point is you can't guess at what you are putting in. If you don't get a high gainer in V2, your 800 is not going to sound as good as it can.

Thank you for the info. It lays out where I need to begin my search.

My amp has 5 pre-amp tubes.

 

[MartyStrat54]

Thank you for the info. It lays out where I need to begin my search.

My amp has 5 pre-amp tubes.

I'm not real familiar with the 2210. I forgot that the PI tube is listed with the power section. I'm always fascinated with Marshall amps that have a lot of preamp tubes (like the 6100). If the 5th tube is the phase inverter, do you know what the other tubes do? I mean I would assume that V1 and V2 are your gain stage tubes, but then what does V3 do? I'm assuming again that V4 is the tone stack/cathode follower tube. That leaves V3 as "another gain tube?" Who says an 800 doesn't have any gain?

Let me know about those tube positions if you know what they are.

 

[RiverRatt]

Marty, I found some info on Google about the 2210 - it only has 3 preamp tubes. V4 and V5 are the reverb driver and the PI.

 

[ProfChaos]

Hey All! I'm still a bit new to the Marshall Forum, but already I have seen quite a bit of discussion regarding the selection and operation of power amp tubes. But... I would really like to get some feed back regarding the selection of preamp tubes.

I rarely play out, and quite frankly seldom have opportunity to turn my TSL122 up past 1 or 2. I am aware of the fact that because of this, I will be getting most of my tone from my preamp section, and not from the power amp. That being the case I would like to know more about how preamp tubes effect my sound.

I play mainly classic rock ranging from AC/DC to Def Leppard. Clearly I love distorted guitar tone, but I also love the way my TSL122 sounds on the clean channel. So...

What I am hoping for is feedback from you more experienced members of the forum regarding such topics as: How will different tubes change my sound to better suit my style of playing? What tonal qualities do different preamp tubes have? What is a good starting point for finding the right tubes for me? Can I "mix-and-match" preamp tubes? How long do preamp tubes last? How often should I replace them?

Please, do share your thoughts on this subject. I am eager to know what your experiences have been. Thanks in advance for your responses!

I play a Model 6100 30th Anniversary head--the EL34 version. In that amp, I prefer to spend the extra dough and go with Mullard 12AX7 pre-amp tubes. The new Mullard 12AX7 (re-issue) tubes are very friendly to overdriven tone--as in the pentode (Mesa Boogie-like) 100-watt setting of the 30th Anniversary head.

Even so, I would caution against merely replacing all your 12AX7 tubes willy-nilly; be sensitive to and aware of which tube came from which tube socket: The last 12AX7 (V4?) in the pre-amp of your Marshall is what is known as a "Matched Phase Inverter" (MPI); it is a "Special Application" tube. The MPI-tube drives the first stage of the power amp. More specifically, it is critical in the "push-pull" Class AB Marshall power amp that the MPI that drives the power amp be balanced for equal sine wave output on both negative and positive voltage cycles of the tube. (The specially balanced MPI tube averts a really weird, wobbly effect that would occur if the tube were not tuned to provide equal output at both negative and positive voltage cycles.)

Lastly, I might be wrong, but it seems to me that, in characterizing your sound as "distorted guitar tone," you might be confusing the terms "distortion" and "overdrive." Unless you use a "stomp box" pedal like a Pro-Co "Ratt" or an ElectroHarmonix "Big Muff Pie," you likely mean "overdrive," and not "distortion." (The yellow and red LED channel indicators represent different levels of overdrive--as in yellow = "Crunch," as in moderately overdriven, and red = [soaring] "Lead," as in heavily overdriven.)
As a flexible--yet general--rule, distortion = stinky-bad; overdrive = oh-so-good. The overdrive effect is what gives the Marshall its crunch and the Boogie its bite.


cheers,
--Professor Chaos

 

[Madaxeman]

I know a tech who swears that you're better off with an unbalanced valve as a phase inverter. He reckons certain guitar amps sound worse with a balanced PI.


With preamp valves in general, I swap em around until I find a combination that works.
Right now in my Jubilee 2554 I'm running Siemens EL34's and Shuguang 7th/8th Gen in V3, Mullard ECC83 in V2 and a Pope/Amperex ECC83 in V1.

 

[wegman]

I'm not real familiar with the 2210. I forgot that the PI tube is listed with the power section. I'm always fascinated with Marshall amps that have a lot of preamp tubes (like the 6100). If the 5th tube is the phase inverter, do you know what the other tubes do? I mean I would assume that V1 and V2 are your gain stage tubes, but then what does V3 do? I'm assuming again that V4 is the tone stack/cathode follower tube. That leaves V3 as "another gain tube?" Who says an 800 doesn't have any gain?

Let me know about those tube positions if you know what they are.

I found this on line. It has all the positions listed and what they do in many Marshall amps. Don't let the link name fool you. If you scroll down to about a 1/4 of the way they have all the amps listed.

Marshall Amplifiers, Pre-1990

 

[ProfChaos]

I know a tech who swears that you're better off with an unbalanced valve as a phase inverter. He reckons certain guitar amps sound worse with a balanced PI.


With preamp valves in general, I swap em around until I find a combination that works.
Right now in my Jubilee 2554 I'm running Siemens EL34's and Shuguang 7th/8th Gen in V3, Mullard ECC83 in V2 and a Pope/Amperex ECC83 in V1.

When "he reckons certain guitar amps sound worse with a balanced PI," he is almost certainly not talking about the Marshall 6100 30th Anniversary head with EL34's: When I unwittingly replaced the Matched Phase Inverter in my 30th Anniversary head by plugging in a new 12AX7 Groove Tubes Mullard reissue, the amp sounded awful, at both the triode and pentode settings. It might be that your friend is arriving at a balanced phase inverter effect by mixing and matching the 12AX7's (ECC83's) leading up to the matched phase inverter. Whatever the case with your friend, the MPI is the Most Important Tube in Your Amp; this tube immediately precedes the bias circuit, and it drives the push-pull circuit of the four power amp output tubes. Any issues with the matched phase inverter get multiplied through the stages of gain in the power amp.

More specifically, the PDF drawing of the Marshall 6100's power amp shows that V7a and V7b (a matched-phase triode pair) drive all else in the power amp. This is why some audiophile engineers and technicians refer to the matched phase inverter as the "most important tube in your amplifier."

cheers,
--Professor Chaos

 

[solarburn]

I don't buy into putting a matched or balanced tube into the PI slot on a guitar amp. HIFI amps are another story...

Here is a little excerpt from a guy on this subject:

Some simple and more "HIFI" PI's have what's called unity gain, which means no gain at all. Most guitar amps that are based on Fender/Marshall designs use a type of PI called a "long-tailed phase inverter", which has BAGS of gain!

In hifi applications it's common to design a "balanced" PI. This means that each PI output, while out of phase to each other will be exactly balanced so that when the output waves are combined in the output transformer things will be perfectly even on each side of the combined wave. This helps give the lowest distortion and the most "hifi" sound.

Tube stores will sell you 12AX7's that have been matched and balanced, meaning that since this tube consists of two triode amplifiers contained in one glass tube when you use it as a PI each triode will more perfectly provide that same gain, "balanced" output.

Unless you're a purist jazz player, who the heck wants a hifi guitar sound?

Most guitar amps also adjust parts values in the PI stage to provide reasonable balancing but being a bit off actually provides a better tone!

There are a lot of hifi technical ideas that crop up from tube stores wanting to make more money from guitar players that aren't really appropriate. They only make sense in a hifi application. Myself, I would never bother with a balanced PI tube in a guitar amp but in a tube hifi amp it's not a bad idea. Even then, it's easy to get too anal and nitpicky. The human ear is physically incapable of detecting much less than 2-3% distortion. To quibble about .1% vs .2% is frankly ridiculous!

 

[RiverRatt]

I don't buy into putting a matched or balanced tube into the PI slot on a guitar amp.

Me either. I'm finding that I like a higher gain 12AX7 in the PI spot. Quite a change from my old days of nothing but 12AT7s.

 

[MartyStrat54]

Marty, I found some info on Google about the 2210 - it only has 3 preamp tubes. V4 and V5 are the reverb driver and the PI.

That's cool, a tube reverb driver. So is V3 the tone stack and cathode follower?

I looked at Dr. Tube last night and they have a horrible GIF photo for the 2210. However, it does look like V3 may be the TS and CF.

 

[wegman]

Lead models 2205, 2210, 4210, 4211, 4212
V1 is the first preamp. Recommend a low-noise type with a coiled heater, such as NOS 7025s or ECC83s. JJ ECC83s and Sovtek 12AX7LPSs or EHs are suitable. NOS 5751s recommended if lower gain is desired.

V2 is the driver and cathode follower for the tone controls. A low noise tube is not critical, however the heater-cathode insulation must be good quality. NOS JAN 12AX7s are recommended for this position. We understand that some technicians recommend Ei or JJ ECC83s for this duty.

V3 is the mix amplifier after the master volume control. A low noise tube is not needed here. Any 12AX7 of good quality will work, although guitarists picky about their tone may prefer a top-grade NOS version.

V4 is the reverb driver and recovery amplifier. A low noise tube is not critical. This position is very hard on the cathode, due to high current. NOS JAN 12AX7s are recommended for this position.

V5 is the phase inverter. A low noise tube is not critical, however the heater-cathode insulation must be good quality. NOS JAN 12AX7s are recommended for this position. We understand that some technicians recommend Ei or JJ ECC83s for this duty.

Power tubes are 2 x EL34 in 50-watt models, 4 x EL34 in 100-watt models (2210, 4211). These models were designed for 6550s, and can also accept KT88s or EL34s. Bias adjustment is MANDATORY

 

[MartyStrat54]

Continuing on about a balanced PI. This thread is immensely long and over the course of many months we have experimented with unbalanced PI tubes and found them to be highly acceptable in all of our amp. The Marshall amp is built with components that are + or - 20 per cent. With that in mind, we look at the tolerance of the first and second gain stages. These gain stages have a lot of "slack" to them. They are not perfect and they are not "matched." As mentioned by SolarBurn, if you have a Hi Fi amp and it is built to higher tolerances, there is a good chance that it is also a Class A or High Class AB amp. Because it's "stereo," you would want to try to balance the gain out so the left and right speakers were of the same volume. That would be the only reason to "match" the PI tube in a Hi Fi amp. Remember, your ears cannot detect imperfections below a certain dB level or below a certain level of distortion..

I used to fall for the balanced PI and it is just a rip-off by those who push them. Some guitarists actually use a highly mismatched PI tube, because they get "their" sound out of that sort of tube. Harmonica players do this to their amps as well. They get more complicated harmonics from the amp.

Several of us have used all sorts of tubes in V4. High gain, lop-sided, low gain, near matched and they all seem to do the job. Now by doing these tests we realized that a real high gain tube (to high for V1 or V2) will work in the PI and it does affect the overall gain of the amp. Not by much, but there is a difference between running a medium gain tube in the PI and a very high gain tube in the PI. Conclusion? A whole lot of gain makes very little change in this slot.

The other thing is that these are all 12AX7 type tubes. Since we've covered the PI issue, it then allows us to roll the tubes in whatever slot we please. We are experienced rollers. We are mainly interested in V1 and V2. We have carefully selected tubes that we think work best in V3 and V4. This allows us to concentrate on the tonal qualities of Amperex, Telefunken, Mullard and Black Plate tubes.

I appreciate your comments and yes, the 6100 is a unique amp. However, I know how it works and it is still a basic Marshall as far as the power amp goes. It is of the same design as almost every modern Marshall. Your 6100 has a lot of preamp tubes which in a ways can be expensive when it comes time to change them. Marshall figured out how to make multi-channel amps with a smaller amount of tubes...but the amp section is still the same.

 

[MartyStrat54]

V3 is the mix amplifier after the master volume control. A low noise tube is not needed here. Any 12AX7 of good quality will work, although guitarists picky about their tone may prefer a top-grade NOS version.

I looked at the Dr. Tube schematic last night and saw how V3 was being used. Because it says a low noise tube is not needed here, I suspect that mix amplifier could possibly be the same as the tone stack. This would use one half of the tube. I assume that the other half is the cathode follower. The bottom line is that your amp has these circuits and it takes a 12AX7 to drive them.

Other than your tube reverb driver, your amp appears to have the classic four tube arrangement.