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Vacuum Tubes
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12AX7 COMPARISONS

Telefunken ECC803S (E83CC)
In my opinion these are simply the best. Very hard to find, this tube is Vintage and Extra Rare! The ECC803S is a very low noise, special quality 12AX7, made with the old-style Telefunken German precision. These have the ultra wide bandwidth of the Telefunken ECC83, but also have nice matched internal triodes, gold pins, and have been carefully factory screened for low noise. You will pay dearly for them, but if you want the best, this is the tube!

Telefunken ECC83 / 12AX7
This tube is a main stay in many Guitar and Bass Amplifiers, Microphones and Outboard gear. It is an Excellent tube for Recording Studio Applications due to its extreme low noise. You want quiet recordings? You want this tube! The Telefunken 12AX7 also has a very long life span and will outlive all cheaper 12ax7's by a mile.
Rod ~ World Tube Company

Amperex ( Bugle Boy )
These vacuum tubes are used in high end guitar Amplifiers and audio gear, AC/DC radio equipment and in many diversified applications such a multivibrators or oscillators in industrial control devices. This tube is a main stay in many recording studio Guitar and Bass Amplifiers. They are also widely used in recording studio outboard gear such as Mic preamps and such.
Amperex tubes are some of the best tubes you can get and are getting hard to find.
Rod ~ World Tube Company

Telefunken
The Telefunken ECC83 / 12AX7 was made with both Rib Plates and Smooth Plates. The smooth plate is one hell of a tube. These tubes are some of the best sounding tubes you can get. The Rib plate is also a very good quality tube.
Rod ~ World Tube Company

Mullard
The Mullard 12AX7 / ECC83 is a Very Smooth Sounding tube. It is one of the best sought after European valves made. The NOS tubes are becoming a little rare to find. As far as the New Production tubes go . . . . . . . . . . . . . . . . . . . . . . Buy NOS!
Rod ~ World Tube Company

RCA
The RCA 12AX7 is simply the hottest sounding of the US made tubes. If you get your hands on one. . . it will make you smile. They are as beautiful sounding as they are rare. And they are becoming very rare. Need I say more?
Rod ~ World Tube Company

Ei ECC83 - (Yugoslavian)
This is basically an exact copy of a Telefunken ECC83 smooth plate tube, and for good reason; it was produced on the authentic Telefunken tube manufacturing equipment! Ei bought it all and produced these excellent smooth plate tubes that pretty much nail the Telefunken tone - but for a fraction of the price. These were made at a time when all electrical items used tubes, hence a very high level of quality control.
Rod ~ World Tube Company

JJ ECC83 - (Russian)

Very Good for Marshall Amplifiers and amplifiers that need rugged construction for extended road work and transportation to clubs and Concert hall gigs. Rod ~ World Tube Company

QUESTION: I have an Ampeg Superjet with Sovteks and would like to swap the tubes and see what tonal changes are affected, but I don't want to go out and buy a couple of each different types? Any ideas?

ANSWER: From Ted B. From tabreau
Yes. I have done quite a bit of time consuming, tedious research with different preamp tubes in different amps. In a nutshell, here are some plain and simple guidelines which will get you where you want to go all for about any amp application:

With respect to my NOS Mullards as a basis of comparison...

Chinese 12AX7A - Harsh, not very musical. Avoid.

Groove Tube 12AX7 C - Harsh, not very musical. This is Groove Tubes' Copy of commonly re-branded Chinese tubes. Avoid.

Sovtek 12AX7WA - Brittle, thin, low gain. Avoid.

Sovtek 12AX7WB - Darker than the WA, better gain.
These tubes sound Very Good in Marshall Amplifiers. ~ Rod

Sovtek 12AX7WXT - Better, quieter still, but more $$. Better suited for audio amps.

Tesla ECC83 - Good gain, quiet, best tube for drier sounding high gain amps (i.e. modern Marshalls). Robust internal structure, well balanced sound.

Tesla E83CC - High priced, very low noise. Save your $$, as this is only an advantage in phono preamps!

Ei ECC83 - (Yugoslavian) - Great gain, very noticeably warmer sound, and will warm up any amp. Best tube for Vox, Fender, vintage Marshall, and any other vintage amp. Telefunken 'diamond' copy, but not as quiet. Some are a little microphonic.

Ruby 7025STR - An upgraded, premium Chinese made tube. Anodized plates. Reported (by "Lord Valve") to be much better and quieter. Production ceased.

To sum it up, I find that if you are buying Tesla and/or Ei, that you really don't need other brands. Preamp tube selection is very important, and often will significantly change the sound of your amp.

Ted B. From tabreau--(at)--eworleans.com Thu Mar 26 15:31:21 CST 1998 Article: 93367 of alt.guitar.amps From: "Ted Breaux" Newsgroups: alt.guitar.amps Subject: Re: 12AX7 Tube Comparisons? Date: 25 Mar 1998 09:24:57 GMT Organization: AccessCom, THE New Orleans Internet Provider Lines: 43 Message-ID: <01bd5801$40e67aa0$02bdb5c--(at)--efault> References: <3518FA4A.572EEBF--(at)--hellus.com> NNTP-Posting-Host: p302.accesscom.net X-Newsreader: Microsoft Internet News 4.70.1155 Xref: geraldo.cc.utexas.edu alt.guitar.amps:93367

What is the difference between a 12AX7 and a 12AX7A?
ANSWER - Back in the Old Days the "A" was Used to Designate the Tube as LOW NOISE. With Modern 12AX7's it Makes No Difference at All.

What is the difference between a 12AX7A and a Chinese 12AX7B?
ANSWER - The Chinese 12AX7B tube has a higher gain and a little more overdrive than the standard 12AX7A tube. It also is a quieter and Warmer sounding tube. It is a good tube to use for higher gain guitar amplifiers. If you want to upgrade, go with a 7025 tube or a Good Ol' NOS Telefunken, Buble Boy, Valvo or RCA 12AX7.

What is the difference between a 12AX7 and 7025?
ANSWER - The 7025 vacuum tube is basically a 12AX7 with Lower microphonics and Lower Hum. It is a much quieter sounding tube as far as tube noise is concerned.

What tubes can you substitute or replace for a 12AX7?
ANSWER - You can substitute a 12AX7 for a 12AT7, 12AU7, 12AY7 or a 7025. But what are the differences? It depends on which tube you are replacing. Let's assume it is the first preamp tube.

12AT7 * * * * The 12AT7 is a clearer sounding tube than a 12AX7 but with a little less gain.

12AU7 * * * * The 12AU7 sounds like a 12AX7 but produces a lot less gain in the preamp circuit. Arguably the Best sounding American 12AU7's ever made are the RCA Clear Tops and Tung-Sol's.

12AY7 * * * * The 12AY7 sounds warmer with more bottom end to it than a 12AX7.

7025 * * * * The 7025 has a higher gain than a 12AX7 tube. It is also a crisper sounding tube. This is the industrial version of the 12AX7. You can beat the crap out of it and it will still go!

Interesting notes:
I have heard that ECC803S tubes (12AX7's on Steroids) are great for guitar amps because they have a spiral filament for reduced microphonics. I have also heard that because of their long plates, they can have excessive microphonics and are therefore not a good idea to use in high gain stages of combo amps. You will have to make your own call here.
Interesting though. ~ Rod.

More Information on the Differences Written by Other People.

12ax7ís and 7025ís are similar. The 7025 used to be a low-microphonic version of the standard 12ax7. Thatís why itís specíd in all sockets of old Fenders except for the tremolo oscillator (a non- audio section). Now it seems that manufacturers choose a number that pleases them, so I wouldnít count on, say, Groove Tubes to have any relevance to the criteria above. The 12at7 tube is a completely different design. A bit lower Ďmuí, much lower plate resistance, higher transconductance. That makes it suitable for drivers, though many amps (Marshalls for example) use 12ax7ís for their drivers. Some amp books recommend swapping 12ax7ís into Fender driver stages, but donít expect a lot more gain if you try that. In fact, due to the higher plate resistance of the 12ax7, you could end up with a bit less gain in some of the newer Fender circuits. Also, you might expect just a bit more zip on the top end with a 12at7. Or conversely, some think the 12ax7 sounds a bit Ďbeefierí than a 12at7. MGarvin NYC Response: >12ax7ís and 7025ís are similar. The 7025 used to be a low-microphonic >version of the standard 12ax7. Thatís why itís specíd in all >sockets of old Fenders except for the tremolo oscillator (a non- >audio section). Just thought I should clarify: I meant the Ď12ax7-typeí sockets. Of course Fender specíd 12at7ís for phase splitter/driver stages. MG Response: Just my impressions Of course it all depends which tube your replacing. So Iíll just speak of the first preamp tube. 12AT7 sounds a little clearer than a 12AX7 with not as much gain. 12AY7 sounds warmer or bassier than a 12AX7, maybe evan mushy. 12AU7 sounds kinda like a 12AX7 only without as much gain. Response: In the old days the 12AX7 and 7025 were different quality tubes. 12AX7 is the U.S. and 7025 is the industrial name. 7025 is higher in gain and a bit brighter then the 12AX7. Itís also more heavy duty so it can take a beating. Nowadays tubes are not made this specific so the name mean almost nothing except on old tubes. A Russian 12AX7 is the same as a Russian 7025. The 12AT7 is a diffrent tube. It has a gain of about 60 in the average circuit while the 12AX7 has a gain of about 100. Old black faced amps use the 12AT7 in the phase inverter. If you put in a 12AT7 it will not drive your power tubes as hard so youíll get a cleaner sound with alittle less volume. If you like output tube distortion then you should go with the 12AX7 tube or if you like more bite. Iíve switch the 12AX7 in my amp with a 12AT7 for a comparason and in the above paragraph I gave you my opinion. I ended up sticking to my 12AX7 tube but thatís just my taste. Your amp friend, Andrew Okincha

Profklamen10-24-2007, 10:44 AM I've just started playing with switching around preamp tubes - I'm aware that they have different amounts of gain, and that each tube has different tonal qualities. I've read a lot about people using lower gain preamp tubes to get more clean headroom, etc. However, in my limited experience I didn't get more clean headroom, just less volume. For example, my victoria bassman with a 12ax7 breaks up at about 5 on the volume knob - which is at a considerable volume. When I substituted a 12au7 - with the volume on 5 - the tone is clean, but the volume is much lower. If I turn it up to a volume commensurate with the 12ax7 on 5, which is about 9 with the 12au7, the amp begins to break up. so, here is my question. Is a 12ax7 on 5 essentially a 12au7 on 9? Maybe the sound of a cranked 12au7 is the same as a 12ax7 with the volume turned down a bit? Are people really gaining clean headroom at the same volumes? Thanks -------------------------------------------------------------------------------- harryjmic10-24-2007, 12:35 PM A 12au7 is extreme, most of the time it's 5751 or a 12ay7. There is a volume drop with these also but not as much, who knows maybe they are going buy the numbers then the actual perceived volume output. I think what happens is if the amp is softer then you have to turn it up more to adjust, when you get to a certain point the power tubes start distorting and this what people claim they want to hear. Funny thing is everytime you use a preamp booster (overdrive pedal) you basically clip the preamp which creates the distortion in the circuit not the power tubes. -------------------------------------------------------------------------------- Blue Strat10-24-2007, 01:23 PM I've just started playing with switching around preamp tubes - I'm aware that they have different amounts of gain, and that each tube has different tonal qualities. I've read a lot about people using lower gain preamp tubes to get more clean headroom, etc. However, in my limited experience I didn't get more clean headroom, just less volume. For example, my victoria bassman with a 12ax7 breaks up at about 5 on the volume knob - which is at a considerable volume. When I substituted a 12au7 - with the volume on 5 - the tone is clean, but the volume is much lower. If I turn it up to a volume commensurate with the 12ax7 on 5, which is about 9 with the 12au7, the amp begins to break up. so, here is my question. Is a 12ax7 on 5 essentially a 12au7 on 9? Maybe the sound of a cranked 12au7 is the same as a 12ax7 with the volume turned down a bit? Are people really gaining clean headroom at the same volumes? Thanks The only time you'll get more clean headroom from a swap like this is in an amp where your preamp circuit is breaking up (clipping) when you use a 12AX7, especially with hot pickups. Even then, the improvement will be slight at best. -------------------------------------------------------------------------------- billyguitar10-24-2007, 01:36 PM Tweed Bassmans were designed to use a 12AY7. 12AX7s are too harsh in the first position for me. Same with most of the other tweed amps too. -------------------------------------------------------------------------------- strumminsix10-24-2007, 01:41 PM Gotta agree with Mike here.. I swapped out the first valve in my DSR for an AT7. This allowed me to have my guitar volume on 10 without overdriving the preamp which is exactly what I wanted. Also it gave me a tiny bit more headroom in a situation where I am just barely breaking up early. Nothing earth shattering at all. This is the closest thing I have gotten as for as "more clean headroom" with a tube swap. -------------------------------------------------------------------------------- Blue Strat10-24-2007, 02:08 PM Gotta agree with Mike here.. I swapped out the first valve in my DSR for an AT7. This allowed me to have my guitar volume on 10 without overdriving the preamp which is exactly what I wanted. Also it gave me a tiny bit more headroom in a situation where I am just barely breaking up early. Nothing earth shattering at all. This is the closest thing I have gotten as for as "more clean headroom" with a tube swap. Part of what you're getting with a 12AT7 in a 12AX7 socket is more highs, less mids, which leads to less distortion and an illusion of clarity. This swap works great in muddy overdrive circuits. -------------------------------------------------------------------------------- mcdyas10-24-2007, 03:06 PM my vox heritage ac15 has a pentode/triode switch for the ef86. there is a tremendous clean you can get out of the ef86 channel in ef86 triode mode. i cannot get the same clean out of that channel in pentode mode with the volume just turned down. -------------------------------------------------------------------------------- Profklamen10-24-2007, 03:23 PM I may be wrong about this, but I think ef86's are a different animal and may create different results. Billyguitar mentioned that 12ax7's seem too harsh for him in a tweed bassman circuit. What I'm wondering is - let's say he likes his amp with the volume on 7. Set like this the 12axy is too harsh and the 12ay7 is just right. Could it be (with the exception of the tonal qualites of each particular tube) that the 12ax7 would sound the same as the 12ay7 if he turned the volume down to 6? By "same" I mean the same volume and the same amount of gain. -------------------------------------------------------------------------------- Fxrs10-24-2007, 06:02 PM Part of what you're getting with a 12AT7 in a 12AX7 socket is more highs, less mids, which leads to less distortion and an illusion of clarity. This swap works great in muddy overdrive circuits. Oooh...maybe I should try this in my Mesa in V2 to "clear up" the lead channel. I've only used AT7's in V4-V6(rhythm,reverb and PI). Or do you think I should try V1? -------------------------------------------------------------------------------- billyguitar10-31-2007, 02:58 PM The AX7 is too harsh in the tweed circuits, to my ears, all thru the volume range. Might be why Leo spec'd the AY7, cuz he could've used an AX7 if he wanted. -------------------------------------------------------------------------------- rockon110-31-2007, 03:02 PM Oooh...maybe I should try this in my Mesa in V2 to "clear up" the lead channel. I've only used AT7's in V4-V6(rhythm,reverb and PI). Or do you think I should try V1? Try it in each position or even both if you want to reduce gain too. Ive found it affects the overall tone the most in the V1 even though your trying to "clean up" the OD. Bob -------------------------------------------------------------------------------- pacomc7910-31-2007, 03:06 PM Part of what you're getting with a 12AT7 in a 12AX7 socket is more highs, less mids, which leads to less distortion and an illusion of clarity. This swap works great in muddy overdrive circuits. So what does the 5751 for 12AX7 swap do for the character of the tone? more clarity as well? -------------------------------------------------------------------------------- CocoTone10-31-2007, 03:35 PM So what does the 5751 for 12AX7 swap do for the character of the tone? more clarity as well? Don't know, but I'll tell you just as soon as I get the one I ordered for my Super Reverb. Common swap for Fender amps when looking for just what your after. Bit more headroom, and little bit less gain. Should get you this tone. http://youtube.com/watch?v=Yfi9fKpm3yU CT. -------------------------------------------------------------------------------- edward10-31-2007, 03:38 PM ... so, here is my question. Is a 12ax7 on 5 essentially a 12au7 on 9? Maybe the sound of a cranked 12au7 is the same as a 12ax7 with the volume turned down a bit? Are people really gaining clean headroom at the same volumes? Thanks General "rule" as I've read it: If a 12ax7 has an assigned value of 100, then a 5751 is about 70% of that, 12at7 about 60%, and a 12au7 about 50% What swapping tubes does (oversimplified) is twofold: - changes the gain structure of the amp such that clipping will occur earlier or later ...but which is "better" sound is still up to the user - alters the voice and dynamics of the amp (since the gain structure has been altered) ...again, which is better is up to you. What Mike said about tubes affecting lows/mids/highs is right on, and remember that this is on top of the fact the gain has changed so your picking/playing will also sound different because of these changes in dynamics. And each amp, as well as each individual tube slot, will respond differently with each tube choice. So a 5751 in V2 yielding an "improvement" in tone will not necessarily be an "improvement" in v3, v4, or in v2 of a different amp. Maybe an AT7 will sound better, maybe the AX7... As if these variables were enough, each tube of the same family, while sharing similar characteristics, are still markedly different. Of course, there's current stock vs NOS, and of NOS brand A vs NOS brand B. Just one example, FWIW, in one of my boogies, going to a Mullard ax7 in V1 made no discernable difference than sticking with the cheap Mesa ax7. BUT, replaing any ax7 in that slot with an at7 (any old one I had laying around) just sounded sweeter and more pleasant. Then, swapping from a good NOS RCA at7 to a NOS Mullard cv4024 (also an 12AT7) sounded much better ...(and to be fair, the NOS RCA sounded better than the Mesa AT7 before it). This is why experimenting with tubes can be so frustrating, yet rewarding when you finally find the right recipe. I only have 3 amps, myself ...nothing terribly fancy or esoteric, but they sound wonderful for me. Yet each has gone through a slow, laborious tube trial/error regimen to find what I liked best in each. It took a while, but I found it (and I don't even have that many tubes left over unused ;) ). It's scary, but I will say that I am very satisfied with the results, and have no desire to swap or acquire another amp (gasp, please don't ban me). And if tube swaps don't get you what you want, dump it and keep looking. :) Edward -------------------------------------------------------------------------------- edward10-31-2007, 03:42 PM So what does the 5751 for 12AX7 swap do for the character of the tone? more clarity as well? Yes and no (see above post ;) ). FWIW, I went with a 5751 in one spot in one amp, but hated it in another slot and found the ax7 better suited there. Let you ears decide. And if I may add, be patient and live with the tone for a while. "Ear fatigue" can set in fairly quickly, and you arrive at a tone you like today (after you've been pluggin away at volume for an hour), only to hate it tomorrow when you play with fresh ears. Edward -------------------------------------------------------------------------------- rockon110-31-2007, 04:12 PM So what does the 5751 for 12AX7 swap do for the character of the tone? more clarity as well? A 5751's specs (aside from the lower gain) are much closer to that of a 12AX7. Hence they dont have the same thinning(more highs/less mids) affect like a 12AT7. A better choice for just gain reduction.The "clarity' you might achieve from using a 12AT7 is due to its other specs than arent as close as that of a 12AX7 when subbing it for the 12AX7. Of coarse if you have one -try it! Its hard to predict how things will sound given the variables. Bob -------------------------------------------------------------------------------- vBulletinģ v3.8.5, Copyright ©2000-2010, Jelsoft Enterprises Ltd.

Notice the 12AT7 driver tube, it can be substituted with a 12AX7 "DRIVER" for greater tonal choices. The 12AT7 has a very strong tendancy to be microphonic, and tonally is very brittle sounding, harsh. You can listen to it in the "GAIN" position if you are interested. It wont hurt your amp, but bring the volume up slowly as it almost certainly will squeal. Putting in a 12AX7 will add more gain - at higher volumes you will be able to hear the gain, at lower volumes you will be able the tonal improvement.

Harmony Central Forums > General Forums > DIY (Do It Yourself) > 12ax7 vs 12AT7 vs 7025 etc. -------------------------------------------------------------------------------- PDAView Full Version : 12ax7 vs 12AT7 vs 7025 etc. -------------------------------------------------------------------------------- mrbrown4911-28-2006, 02:39 PM I play out of an ampeg superocket 100 watt combo. I am interested in swapping preamp tubes to try and get a sweeter sound with a litte more sparkle. Right now it is stock with 12ax7 pres and 6L6 power tubes. Suggestions? -------------------------------------------------------------------------------- molsen11-28-2006, 02:42 PM these 12ax7 tubes get great reviews: http://www.tubedepot.com/ts-12ax7.html or http://www.musiciansfriend.com/product/Tungsol-12AX7-Tube?sku=212231 -------------------------------------------------------------------------------- mrbrown4911-28-2006, 09:57 PM Groovy. Thanks guys. i will give a couple a try. How do the ECC83 compare to 12ax7 in terms of gain? -------------------------------------------------------------------------------- molsen11-28-2006, 10:06 PM ecc83 is the same as 12ax7, just the european designation -------------------------------------------------------------------------------- guitarcapo11-30-2006, 08:04 PM lower gain preamp tube have less sparkle to me -------------------------------------------------------------------------------- TimmyP12-02-2006, 12:43 AM The Tung-Sol was highly recommended to be by a vendor who's known for his testing and sonic evaluations of tubes. (He wasn't trying to sell me anything, as we buy from the same supplier that he does.) -------------------------------------------------------------------------------- synthetronic12-04-2006, 09:12 AM Can anyone tell me what difference substituting a 12AX7 with a 12AT7 makes? We just got a semibroken Fender Showman with the 12AT7 inverter tube (the one that splits the signal for push-pull use) replaced with a 12AX7. Seems to work but distorts a bit early, which would go with the increased gain on a 12AX7. Has anyone tried both? -------------------------------------------------------------------------------- mrbrown4912-05-2006, 01:07 PM Originally posted by synthetronic Can anyone tell me what difference substituting a 12AX7 with a 12AT7 makes? We just got a semibroken Fender Showman with the 12AT7 inverter tube (the one that splits the signal for push-pull use) replaced with a 12AX7. Seems to work but distorts a bit early, which would go with the increased gain on a 12AX7. Has anyone tried both? I have only tried both in the first preamp slot of my ampeg superocket. The 12AT7 was a bit smoother, cleaner, and sweeter sounding. I loved that sound but I couldn't push the amp as hard for OD. The 12AX7 had a more bite and grit with a punchier overdrive. The tonal characteristics were a bit different too but not sure if that is a direct result of the tubes or the tubes interaction with the other circuitry. How does it sound with the 12AX7 in the inverter slot? Is it beneficial to you have it break up early. I read alot on here about people really having push their fenders to get them to breakup. -------------------------------------------------------------------------------- synthetronic12-06-2006, 07:14 AM Originally posted by mrbrown49 I have only tried both in the first preamp slot of my ampeg superocket. The 12AT7 was a bit smoother, cleaner, and sweeter sounding. I loved that sound but I couldn't push the amp as hard for OD. The 12AX7 had a more bite and grit with a punchier overdrive. The tonal characteristics were a bit different too but not sure if that is a direct result of the tubes or the tubes interaction with the other circuitry. How does it sound with the 12AX7 in the inverter slot? Is it beneficial to you have it break up early. I read alot on here about people really having push their fenders to get them to breakup. Thanks, that's really useful to know. Essentially the sound was breaking up at lower volumes than we were expecting, and looking at the spec made me think it could be the 12AX7 doing that; your experience would seem to confirm this suspicion. The amp also seemed a little quieter than we expected though this looks to be down to an intermittent short to ground in the choke (at least, I assume that's what it is--the fault makes the power lamp flicker, but only with the standby switch closed--and furthermore, the choke (we think) makes noises like a kettle boiling--so probably something in there is drawing a lot of current). It might be that we want to keep it that way (distorted, not shorted) but it depends how we use it. Currently we're planning to build a cabinet for a 15" JBL driver using JBL specs and run the Fender through that--we think it might make a sweet bass amp to replace my current Gallien-Krueger, in which case the clean headroom would probably be a good idea. Currently it sounds a little crunchy when played with a bass. -------------------------------------------------------------------------------- isaac4212-06-2006, 02:17 PM Originally posted by mrbrown49 I play out of an ampeg superocket 100 watt combo. I am interested in swapping preamp tubes to try and get a sweeter sound with a litte more sparkle. Right now it is stock with 12ax7 pres and 6L6 power tubes. Suggestions? Preamp tubes aren't expensive. I suggest you buy several, and try them out. See which ones you like in your amp. -------------------------------------------------------------------------------- mrbrown4912-07-2006, 09:46 AM Originally posted by isaac42 Preamp tubes aren't expensive. I suggest you buy several, and try them out. See which ones you like in your amp. I'm going this weekend to my amp guy to get a bunch. Thanks for your suggestions guys. -------------------------------------------------------------------------------- John S. Shinal12-07-2006, 02:32 PM Originally posted by synthetronic Can anyone tell me what difference substituting a 12AX7 with a 12AT7 makes? We just got a semibroken Fender Showman with the 12AT7 inverter tube (the one that splits the signal for push-pull use) replaced with a 12AX7. Seems to work but distorts a bit early, which would go with the increased gain on a 12AX7. Has anyone tried both? Some people use 12AX7s in the phase splitter position like you mention, but sometimes the little bit of distortion it adds there is not really all that pleasant. A 12AT7 has less gain and will preserve the signal (distorted or otherwise) from the preamp, allowing it to be mangled instead by the power stage. :D For the original poster, I happen to like 12AY7s in the first preamp position of lower gain amps. They have less gain than a 12AX7, but tend to distort more readily than a 12AX7 if you hit them with a fat signal, like from a hot pickup or a clean boost pedal. The 12AY7 sounds pretty nice when it breaks up, too - not fizzy, more of a growl. I like the 5751 also, it was a mil-spec 12AX7 that was made to tighter specifications, so true 5751s are "NOS only." -------------------------------------------------------------------------------- synthetronic12-07-2006, 04:04 PM I'll suggest the 12AY7 to Andy, thanks! -------------------------------------------------------------------------------- Powered by vBulletinô Version 4.0.8 Copyright © 2010 vBulletin Solutions, Inc. 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