Preamp tubes - most important, most overlooked, and least expensive ones in your amp

[myles_rose]

The tonal signature of your sound and interchangeable without adjustment or the need of an amp tech.

 

Unlike power/output tubes, which are routinely matched when they are sold (in different ways, some much better than others), preamp tubes are tested at best to: (a) make sure they work (b) they are not microphonic. In testing, we have found that some suppliers dont seem to test their preamp tubes at all, as we have found one side of the triode that is dead at times. Since most warranty preamp tubes for up to 6 months and longer, they possibly figure that is cheaper to just send them out as they get them in, and if there is a problem, it is cheaper to just give the customer another tube. This is of little comfort to somebody that either has to make another trip to their music store, or worse, box up the bad tube and ship it back to the supplier, and then wait for its replacement. This is one reason to consider a proven supplier when you buy preamp tubes.

 

Todays amplifiers, whether modern high gain types or boutique amplifiers, have one thing in common; the preamp tube in the first gain stage (usually V1 and / or V2) sets the tone and initial gain structure of the amplifier.

 

Amp design -

 

Todays modern amps get just about all of their characteristics in the preamp section. How the gain stages are set up, how the EQ is set up, gain structure, and tone stacks, all are the main aspect of the sound character of the amplifier.

 

Amps such as Mesa Boogie, Fender, Marshall, Bogner, Peavey, and others, all use the same Sovtek, Svetlana, JJ/Tesla, Electro Harmonix, and other power tubes from the same factories. In spite of the same output sections, and in many cases the same range of B+ voltages on the plates of the output tubes, these amps sound different. This is all because of different designs, primarily in the front end, or initial gain section of the amplifier.

 

Inconsistencies -

 

Todays newly made preamp tubes are very inconsistent compared to the tubes of the 1940s to 1960s. There is little need in the medical sector or the military sector for tubes. They are primarily used today in audio applications. For the high end audiophiles, their needs are more easily met, as their tubes are not subjected to the same stresses as those on a guitar amplifier, they use less of them, and they last much longer. There are high end audio suppliers that will match tubes and hand select them, at much higher costs (check out a Western Electric 300B matched pair for example). They pop their tubes in, and ten years later, all is still just fine.

 

Tubes for the guitar and bass player for use in the preamp section, are a different story. The tubes today are very inconsistent. You contact your local tube supplier, plunk down your money, and the roulette wheel is now set into motion.

 

To show the inconsistency, we went through a batch of over 100 tubes that were from the Electro Harmonix 12AX7EH, ECC83, 7025, Sovtek 12AX7WA, LP, LPS, Chinese 12AX7C (old tooling and new tooling), and a few others.

 

Basically, the standard 12AX7 spec that applies to 12AX7 / ECC83 / 7025 tubes, has a reference of 1.2 mA at 250 volts with a -2 volt bias.

 

Some people like to use those little references that say if you want less gain than a 12AX7, use a 12AT7, as it has only 70% of the gain of a 12AX7 etc. These little tips are cute, but with the wide range of inconsistency out there, they are not all that useful, as it is still a matter of chance. The 12AT7 has a different current capacity than a 12AX7, so if you are just looking for less gain, then you may, or may not get it with just a different 12AX7, even from the same brand, same date code, and same batch just by swapping tubes around already in your amplifier. With todays inconsistent offerings, the old tables of gain cannot be used with much accuracy.

 

In the tubes we went through, keeping in mind our 1.2 mA / 1600 transconductance industry standard spec, we found our samples ranged from 0.7 mA to 1.6 mA. When you take into account, that the amplification factor of a 12AX7 is 100, there is a dramatic difference in these tubes.

 

Looking at a 1.6 mA tube, we see a factor of increase over the standard of 33%. This is a LARGE number. A 1.0 tube versus a 1.2 tube will turn the gain you loved in your 5150 into something less than what you used to know what you liked there. You sit dumbfounded how can this be? I just put in new tubes, the same as what I had before?

 

You want even MORE GAIN from your Triple Rectifier or Bogner look at those first gain stage preamp tubes, and get some tube vendor to measure them for you. If you have a 1.1 in there, and put in a 1.3, you will hear the difference in gain IMMEDITATELY. This is not a subtle change that only the "experts" can hear. Leave the settings on the guitar and amp the same, swap the tube, and listen again.

 

When we see a transconductance of 1200 versus the 1600, the way the tube reacts is different too, in this case, its rise time is about 25% slower. This might be just the ticket for a blues player, looking for some nice initial compression on the pick attack, but it may not be the sound for a metal or speed player.

 

Transconductance in the testing, ranged from 1060 to 1790. 1600 is the industry standard.

 

There is one other aspect of preamp tubes. Unlike power tubes, where one tube is one tube a preamp tube is two tubes in one bottle. There is an A side and a B side. The are independent units sharing only the heater. In a Fender blackface amp as an example, input 1 uses one side of the tube, and input 2 (lower gain input) the other side. In the NORMAL channel, V1 is used, and in VIBRATO CHANNEL V2 is your first gain stage. Since these are two different circuits, it is not as much of a concern if the A and B side of the tube are close to the same performance, or "matched". BUT, anytime we use that tube in the phase inverter position or driver position of the amp (which is the driver for the power tubes), then having the two sides matched is important. This matching subject has been covered before, so I wont elaborate on this again here.

 

New versus Vintage amp needs -

 

NOS tubes are sought after by folks that have original amps like Fender Tweeds and the like. If you want the original sound, feel, and character of these amps, then NOS is about the only way to go. Getting NOS tubes for your amp to be correct is much easier in some ways than getting decent new tubes for an amp. There are folks that deal with NOS tubes. Some of them are on my website, but I will say here, that I can recommend KCA and Tube World very highly. Please DO NOT confuse Tube World with TheTubeStore they are NOT even close. Either of these folks have the tubes and the equipment that will let you know that when you purchase a Mullard or RCA 12AX7 or whatever, its characteristics will be noted for your information. If you are in Europe, check with Watford Valves, as they also have NOS offerings. Eurotubes in the USA, a JJ importer, also may have some NOS offerings.

 

When it comes to new tubes for you modern or class amp, or new boutique amp, there is the problem. Preamp tube suppliers guarantee the tubes to work, and not be microphonic. That is about all they can do. Going though tubes that retail for less than $20 in most cases, one at a time to measure them, is beyond reason economically. Watford Valves will do this for folks. Other folks offer these services, and in most cases, they are an additional cost. In my mind, the money is well spent. When you want a nice high gain tube for your Rivera or Demeter, putting in a tube that is 30% down from spec., is not the ticket! At that point, what can you do with that tube? Take it back? Why? It works. The store or vendor never stated it would do anything more than "work". Perhaps they will exchange it, and now you start the process over? And over. And over.

 

Recently I was working with a fellow named Tom Dunn. He plays a 5150 II. We performed a blueprinting session of his amp, and it was found after going through maybe 2 dozen of his own tube stock, that he had picked out his tubes by ear, and placed them in the most advantageous position in his amp. You can do this by ear, if you have the ears of this guy, and also the time (he did this over many months), and the tube stock.

 

Conclusion -

 

Your first gain stage in your amp is its soul, sound, and character. We talked here about gain, and a little about rise time, which is a subject in itself. We did not get much into "sound", such as the articulation and definition that comes from NOS tubes like the Mullards and Telefunkens. If you have an older amp with a more moderate gain structure, and want it to sound closer to magic, than this is the way to go. In a modern amp, a lot of the articulation from the output section is not the target of these designs. Todays designs look for two or three or more stages of gain, channel switching which we did not have on the older amps of yesterday, and flexibility. The only flexibility we had when I was the age of most of you, was a high gain input and low gain input or tuning the reverb on or off J

 

All I can suggest, is try to find a tube vendor that can supply you with the tubes you need with some degree of classification. This way, if you have a 1.3/1670 tube in there now, and you want to tone it down a bit, then maybe go for a 1.1 it will make a difference. If you want tonal changes in color, rather than gain and compression, then you want to go with a little stash of tubes, depending on your use for the day or evening. Most of my clients keep the following:

 

JAN 12AX7A - Most often general use.

12AX7C - Chinese 12AX7 - take off some amp edge or brightness

12AX7EH - Electro Harmonix - general use

ECC83 - for the Marshall sort of sound

7025 - for the Fender 60s and 70s sound

5751 - for blues and less aggressive attack (and perhaps less gain as compared to an in spec 12AX7.

 

Regards,

[TurboDog]

I've mixed the preamps in my amp a few times, and always notice a difference. Some day soon , I'm gonna get a few different tubes and spend a few hours toying around til I find a good mix.

 

I'm just not looking forward to the burning flesh that will result.

 

Signature soon to come.

[myles_rose]

Originally posted by TurboDog:

I've mixed the preamps in my amp a few times, and always notice a difference. Some day soon , I'm gonna get a few different tubes and spend a few hours toying around til I find a good mix.

 

I'm just not looking forward to the burning flesh that will result.

 

Signature soon to come.

TurboDog ...

 

Unlike power tubes, preamp tubes don't get nearly as hot. You can even usually try one for a minute or two, switch the amp into standby, and with the power still on, pop out one preamp tube and pop in the next to test. Just make sure the amp is on standby so when you pop preamp tubes you don't get a BIG POP from the output section!

 

Don't try this with POWER TUBES though !!!

 

Regards,

[TurboDog]

Myles,

 

Unfortunately, my Rivera doesn't have a stand-by. 30-12. Nor a presence knob. The only 2 things I dislike about it.

 

If I lived near LA, I'd have you mod it up for me. I don't really know of any good amp techs around here. Then again, I haven't looked real hard.

[myles_rose]

There is a lot of interchage of information on this subject over at Harmony Central. You can see the posts there by following the link:

 

http://acapella.harmony-central.com/Forum17/HTML/032616.html

 

Regards,

[myles_rose]

Originally posted by TurboDog:

Myles,

 

Unfortunately, my Rivera doesn't have a stand-by. 30-12. Nor a presence knob. The only 2 things I dislike about it.

 

If I lived near LA, I'd have you mod it up for me. I don't really know of any good amp techs around here. Then again, I haven't looked real hard.

Turbodog....

 

Your amp is one of my favorite Rivera amps.

 

All you have to do is just turn it off, change the tube, and then back on, waiting 15 seconds or so as the output tubes warm back up.

 

In the search for a tech (although Rivera amps don't need them much), go to the Rivera website, then to the ROG (Rivera Owner's Group), and post a question asking if anybody knows an amp tech in your area.

 

You can also email rivera@rivera.com and ask Paul Sr. or Paul Jr., if they know of somebody in your area.

 

Myles

[Jay]

Unfortunately, my Rivera doesn't have a stand-by. 30-12. Nor a presence knob. The only 2 things I dislike about it.

 

If I lived near LA, I'd have you mod it up for me. I don't really know of any good amp techs around here. Then again, I haven't looked real hard.[/QB]

Contact Paul. The odds are good he will do the mods. If so, simply send him the amp.

 

Later, Jay

[Ian-UK]

Thanks Myles!! you just saved one of my amps!! It was sounding way too toppy and after having read your article I did a bit of research. I changed the V1 tube on the preamp and it sounds like a completely different beast now

 

Cheers!!

 

Ian...........

[myles_rose]

Originally posted by Jay:

Unfortunately, my Rivera doesn't have a stand-by. 30-12. Nor a presence knob. The only 2 things I dislike about it.

 

If I lived near LA, I'd have you mod it up for me. I don't really know of any good amp techs around here. Then again, I haven't looked real hard.

Contact Paul. The odds are good he will do the mods. If so, simply send him the amp.

 

Later, Jay[/QB]

 

Jay -

 

I'd give Paul a call, he may know of an amp tech in your area.

 

Regards,

[baronedo]

Hello Myles,

I enjoyed your article. I have a Marshall Valvestate model 8240 with two 12" speakers, of which I have corresponded with you in the past via email (it had a bad soder joint problem which an amp tech recently fixed). I play Strats and the tone of this Marshall has always sounded too bright and lacking a good warm low and mid end, even with the bass turned fully up and the treble down. I play primarily blues and blues rock.

 

Any ideas on what preamp tube I should change to? Incidentally, do you know how many preamp tubes and the type my amp takes (I believe the tube(s) are hidden in the top chasis which will have to be dropped down after removing the screws on the top of the amp).

 

Lancer

[myles_rose]

Originally posted by Ian-UK:

Thanks Myles!! you just saved one of my amps!! It was sounding way too toppy and after having read your article I did a bit of research. I changed the V1 tube on the preamp and it sounds like a completely different beast now

 

Cheers!!

 

Ian...........

Ian,

 

You are more than welcome.

 

You are in the U.K. I see, and that means you are right in the neighborhood of Watford Valves, who is perhaps the top tube "grader" on the planet.

 

Now, if you want more gain, or more headroom, or more compression, you can just hit them directly, as they are one of the few that can tell you all the differences between a batch of "the same" preamp tubes.

 

If you have not seen their website, its at:

 

www.watfordvalves.com

 

Regards,

[Ian-UK]

Originally posted by myles111:

Originally posted by Ian-UK:

Thanks Myles!! you just saved one of my amps!! It was sounding way too toppy and after having read your article I did a bit of research. I changed the V1 tube on the preamp and it sounds like a completely different beast now

 

Cheers!!

 

Ian...........

Ian,

 

You are more than welcome.

 

You are in the U.K. I see, and that means you are right in the neighborhood of Watford Valves, who is perhaps the top tube "grader" on the planet.

 

Now, if you want more gain, or more headroom, or more compression, you can just hit them directly, as they are one of the few that can tell you all the differences between a batch of "the same" preamp tubes.

 

If you have not seen their website, its at:

 

www.watfordvalves.com

 

Regards,

Yep they are who I get all my valves from. Top people and yeah they really know their stuff. They were the ones who recommended which preamp tube to go for

 

Thanks again.........

[myles_rose]

Originally posted by Lancer:

Hello Myles,

I enjoyed your article. I have a Marshall Valvestate model 8240 with two 12" speakers, of which I have corresponded with you in the past via email (it had a bad soder joint problem which an amp tech recently fixed). I play Strats and the tone of this Marshall has always sounded too bright and lacking a good warm low and mid end, even with the bass turned fully up and the treble down. I play primarily blues and blues rock.

 

Any ideas on what preamp tube I should change to? Incidentally, do you know how many preamp tubes and the type my amp takes (I believe the tube(s) are hidden in the top chasis which will have to be dropped down after removing the screws on the top of the amp).

 

Lancer

Lancer,

 

A pretty common situation you have there...

 

Try replacing V1 (the preamp tube that is the closest to the imput jack), with a 12AX7C (a Chinese 12AX7), but try to make sure it one off the new tooling (with the halo getter), rather than off the old tooling (with the square getter). A decent tube vendor should know what you are talking about if you ask the above of them. If they do not, find a different tube seller.

 

If you want to take the easy route, then just get a 12AX7C from Groove Tubes, as they have the right ones in all their stock now.

 

A nice RCA 12AX7 or a GE 12AX7 NOS tube will also work pretty nice in there, and they are usually less than $25 still. The 12AX7C will be a bit less bright though.

 

Hope that helped....

 

Regards,

[myles_rose]

Originally posted by Ian-UK:

Originally posted by myles111:

Originally posted by Ian-UK:

Thanks Myles!! you just saved one of my amps!! It was sounding way too toppy and after having read your article I did a bit of research. I changed the V1 tube on the preamp and it sounds like a completely different beast now

 

Cheers!!

 

Ian...........

Ian,

 

You are more than welcome.

 

You are in the U.K. I see, and that means you are right in the neighborhood of Watford Valves, who is perhaps the top tube "grader" on the planet.

 

Now, if you want more gain, or more headroom, or more compression, you can just hit them directly, as they are one of the few that can tell you all the differences between a batch of "the same" preamp tubes.

 

If you have not seen their website, its at:

 

www.watfordvalves.com

 

Regards,

Yep they are who I get all my valves from. Top people and yeah they really know their stuff. They were the ones who recommended which preamp tube to go for

 

Thanks again.........

Ian,

 

Talk about luck, having those folks in your own backyard!

 

They are perhaps, the most knowledgable folks around in the tube world from my humble point of view. Their technical details are right on the money, but for some reason I always seem to agree with their subjective points in regard to their listening tests.

 

If you have not looked at some of their .pdf article reprints on their website, I'd really recommend those.

 

Regards,

[myles_rose]

Bumping for the folks that missed this

[daddyelmis]

I've got a Marshall DSL201 1x12 combo and use a Digitech 2101 on the front end. Upgraded both with ECC83/12AX7WA Philips-JAN and man-oh-man what an improvement. I play a wide variety of stuff (Steely Dan through Buffett through U2 through Stones) and consequently need a wide variety of tones. These preamp tubes have great clean tone, but even better is that they break up very nicely when driven. These would not be great tubes for metal, grunge, etc., but absolutely kill for blues, "classic" rock and alternative where you want definition in the chords with just enough break up to add grit.

 

I bought mine at The Tube Store www.thetubestore.com as well as some power tubes. Great prices and great people to deal with.

 

- - - - - - - - - -

"Ignorance ain't what you don't know, it's what you know that ain't so." Mark Twain

[myles_rose]

Originally posted by daddyelmis:

I've got a Marshall DSL201 1x12 combo and use a Digitech 2101 on the front end. Upgraded both with ECC83/12AX7WA Philips-JAN and man-oh-man what an improvement. I play a wide variety of stuff (Steely Dan through Buffett through U2 through Stones) and consequently need a wide variety of tones. These preamp tubes have great clean tone, but even better is that they break up very nicely when driven. These would not be great tubes for metal, grunge, etc., but absolutely kill for blues, "classic" rock and alternative where you want definition in the chords with just enough break up to add grit.

 

I bought mine at The Tube Store www.thetubestore.com as well as some power tubes. Great prices and great people to deal with.

 

- - - - - - - - - -

"Ignorance ain't what you don't know, it's what you know that ain't so." Mark Twain

daddyelmis,

 

Its always a big surprise to a lot of folks how much of an improvement can be heard when you stick in some nice tubes over the stock tubes that are used most often today.

 

Happy playing ... you have a nice setup, and I am sure that over time, you will like it even more, as nicer and more articulate tubes in the front end not only give you better tone, but also get rid of some of the components that cause listener fatique.

 

Regards,

[Mr. Dan Licks]

Hi Myles,

I like it around here. More old farts like you and me!

Can you explain to someone who doesn't really know sour owl pucky about amps (but I'm learning....hey, it's interesting!) exactly what the various pre tubes in, say a Boogie 50+ Cal. (just happen to have one lying around the house) do? The power section is clear, but we would like to understand a bit more what the little guys do and how you can shape the overall tone of an amp with different tubes. I have been through your site, and the Watfort site (both excellent!) but I still need some really basic information.

Thanks,

Dan

[myles_rose]

Originally posted by Mr. Dan Licks:

Hi Myles,

I like it around here. More old farts like you and me!

Can you explain to someone who doesn't really know sour owl pucky about amps (but I'm learning....hey, it's interesting!) exactly what the various pre tubes in, say a Boogie 50+ Cal. (just happen to have one lying around the house) do? The power section is clear, but we would like to understand a bit more what the little guys do and how you can shape the overall tone of an amp with different tubes. I have been through your site, and the Watfort site (both excellent!) but I still need some really basic information.

Thanks,

Dan

Dan;

 

All amps are basically the same, but have subtle differences.

 

You might want to get a book on guitar amps, a fellow named Ritchie Flieger (probably spelled that wrong) has done a few really nice ones.

 

Basically, in most modern (after 1960) or so, are common in a few ways.

 

In a basic amp like a Marshall, there are three preamp tubes,

 

The first, V1 is the first gain stage. One side of this tube is used for the normal channel, and the other side of the tube is for the bright channel.

 

The next tube, V2 is something of a second gain stage, and used for the tone driver circuit.

 

The last, V3, is the phase inverter. This is the tube that drives the bigger power tubes. One side of this tube drives one side of a pair, and the other side of this tube drives the other side of the output pair.

 

For most amps, additional preamp tubes are used to drive reverb, vibrato, effects loops, etc. On some amps like the Mesa Mk series, there are two preamp tubes, with one feeding the next, in what is called a cascaded gain configuration. Typically, when you set both of these to drive hard, there is too much gain, and you loose a lot, and end up with a very fuzzy and indistinct overdrive situation. Amps today can have very high gain without cascaded gain circuits, but having this ability can allow you to tailor your front end distortion "just so", which some folks like.

 

The Fender Prosonic uses a cascaded gain structure.

 

Think of it as a volume control followed by another volume control, then followed by the master volume control. One more way to control things ... or one more way to mess it up

 

Regards,

[myles_rose]

bumping for new forum folks

[Mr. Dan Licks]

Hi Myles,

Hey, Man, what you doin' workin' on a Satdy?

Still trying to narrow things down. We find that the lead channel is very hard to adjust. 2 is not enough, 2 1/2 is getting there, and 3 is already too much. Would a different tube break up more evenly so that it doesn't start getting really fuzzy until you get up to say, 6 or 7? (12AX7-A on V1 and 12SPAX7-A on V2).

Thanks, Dan

[myles_rose]

Originally posted by Mr. Dan Licks:

Hi Myles,

Hey, Man, what you doin' workin' on a Satdy?

Still trying to narrow things down. We find that the lead channel is very hard to adjust. 2 is not enough, 2 1/2 is getting there, and 3 is already too much. Would a different tube break up more evenly so that it doesn't start getting really fuzzy until you get up to say, 6 or 7? (12AX7-A on V1 and 12SPAX7-A on V2).

Thanks, Dan

Dan,

 

Just on the computer trying to ignore the kids... its 9:20am here.

 

Your problem is gain, and that is what the amp is known for on that channel.

 

You can clean it up a little in the lower settings, but Mesa expects you to use the clean channel for that, and then push the clean channel for the middle gain ranges.

 

The Mesa lead channel is something like one of the eras of Marshalls, where the amp was off at 1 and full on it seemed at 2,3,4,,10 etc....

 

You can tone down the lead channel, but you may suffer a bit of gain loss on the clean channel if you change V1. You can drop the value of V2, but without knowing what is in there as far as actual tube characteristics, is all chance.

 

You can contact Watford Valves, and get maybe two 12AX7's from them. I'd try them each in V2 first, even before V1. Keep them identified.

 

I'd ask for one in a 160-175 range, and one in a 225-240 range, and try those first in V2, one at a time, and then try them in V1 if you are not happy, using the stock tube in V2 that came with the amp.

 

Regards,

[Guitarzan]

hi Myles, this may be a dumb question. i have a digitech rp14d . it uses a 12ax7 (sovtek 12ax7wa to be exact) . i know this is by no means an amp, but would i get an improvment if i used a better tube like a 12ax7lps? i am not even sure what the tubes actual function is in this multi effect . but i have read somewhere where another rp14d user changed the 12ax7wa for a 12ax7 philips-JAN and said it was a BIG difference. if this does make an audible difference is there a specific tube i should seek? i have located a local guy who has quite a few NOS tubes and i am hopeful i am going to improve my tone. i plan on using this through a ss power amp and a celestion loaded cab.any info would be great.

thanks

Boyd

[papa]

Myles,

This is tubedude. I have an Gibson GS-15-RVT with 2 6EU7's. I hear this is very similiar to a 12ax7 and easily modified to except this tube with a slight mod to the curcuit. I would like to mod this amp to except 12ax7 in place of the 6EU7 so I can have a wider choice of tubes to experiment with the tone. Do you have any info that will help me make this mod. I can't find any info on the the 6EU7

[myles_rose]

Originally posted by guitarzan:

hi Myles, this may be a dumb question. i have a digitech rp14d . it uses a 12ax7 (sovtek 12ax7wa to be exact) . i know this is by no means an amp, but would i get an improvment if i used a better tube like a 12ax7lps? i am not even sure what the tubes actual function is in this multi effect . but i have read somewhere where another rp14d user changed the 12ax7wa for a 12ax7 philips-JAN and said it was a BIG difference. if this does make an audible difference is there a specific tube i should seek? i have located a local guy who has quite a few NOS tubes and i am hopeful i am going to improve my tone. i plan on using this through a ss power amp and a celestion loaded cab.any info would be great.

thanks

Boyd

Boyd,

 

A better and more articulate 12AX7 will make a nice change is most all devices that use a preamp tube for its initial tone and gain functions.

 

Regards,

[myles_rose]

Originally posted by papa:

Myles,

This is tubedude. I have an Gibson GS-15-RVT with 2 6EU7's. I hear this is very similiar to a 12ax7 and easily modified to except this tube with a slight mod to the curcuit. I would like to mod this amp to except 12ax7 in place of the 6EU7 so I can have a wider choice of tubes to experiment with the tone. Do you have any info that will help me make this mod. I can't find any info on the the 6EU7

Papa,

 

I'd stick with the original tube. They are not all that pricy or hard to find. They are very similar in most ways to a 12AX7, but a bit different.

 

Your full info is at:

 

http://frank.nostalgiaair.org/sheets/093/6/6EU7.pdf

 

Regards,

[Guitarzan]

thanks Myles, you must be very busy man with all these questions. you must do it for the love of music. way to go.

[myles_rose]

Originally posted by guitarzan:

thanks Myles, you must be very busy man with all these questions. you must do it for the love of music. way to go.

guitarzan,

 

I think I do this for a few reasons. One is to help folks that are in a bind. One is so I don't have to listen to amps that don't sound very nice when I go out to a concert. One is also to fill time when I am working on the bench when I want some sort excuse to put something off

 

Regards,

[myles_rose]

bumping for new forum folks

[whosmatt]

myles,

 

what's the relationship between the 12ax7 and the 5751? i have a dr z carmen ghia that sounds a bit shrill with my current line up of cabs and i'm trying to tame it a bit while i save some ducks for a jenkins (or z) cabinet. anyway, i was fooling around with tubes in the z last night and i swapped the 5751 for a 12ax7 from one of my other amps. it didn't seem to make a huge difference. just wondering what the deal is with that tube. also can you specifically recommend preamp tubes that will tame high frequency response a bit?