# Answer to email about tubes ---Wild Bill



## Wild Bill (May 3, 2006)

Got another question that I thought I should answer here, so that everyone might benefit!

*"Hi Bill, I had a (hopefully) quick question for you. For the 5 preamp tubes in the Traynor YGL-3, do you know which tube (v1, v2, etc) does what?

Also, are the 5 different tube positions in a preamp circuit uniform across all amps? Like would a Fender amp with 5 12ax7s in the preamp have the same functions for v1, v2, v3 etc.?

Finally, when it comes to 12au7, 12at7, 12ay7, etc. what benefit or tonal differences can I expect when it comes to substituting a 12ax7 for one of these guys? Are there certain positions that it makes more sense to substitute one or another tube?"*

Normally, V1 is the 1st preamplfier in the chain. After that it can vary from amp to amp. If you want to know which is what in a specific amp you might check out the schematic. 

A good link is http://www.schematicheaven.com You'll find Traynors under "Bargain Bin" amps.

The reason things vary is that preamp tubes can also be used for reverb, tremolo or other things than just pre-amping.

As far as using other tubes in the 12AX7 family that have the same pinout and similar characteristics, those other types have less gain per stage than a 12AX7. Normally you have far more gain than you actually need for full output so using one with less gain will change the tone, usually giving more headroom and more of a vintage bluesy flavour.

99% of the tone difference comes from changing the tube in the 1st position, V1. After that it makes little or no difference except for overall volume.

12AT7's and the like have only a bit less gain than a 12AX7 so you may not notice much difference. The 12AY7 is really the only one in current manufacture that has enough of a difference to be worth it, IMHO.

Watch out with the 12AU7! Although it fits in the same socket with the same pinout it really requires changes to the resistors and things in its circuit to operate properly. So you'll get the effect of less gain but you will also get a lot of asymmetrical distortion if you don't change the resistors. If you're a shredder you might like it!:smile:

Hope that helps!

:food-smiley-004:


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## hollowbody (Jan 15, 2008)

Thanks for answering my question Bill!


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## mrmatt1972 (Apr 3, 2008)

Bill - or anyone else for that matter- is it true that changing the wrong tube for a lower gain tube can make you eq less effective?


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## guitarman2 (Aug 25, 2006)

Wild Bill said:


> The 12AY7 is really the only one in current manufacture that has enough of a difference to be worth it, IMHO.


I find the 5751 can make somewhat of a difference to be worth it. The 12AX7 has an amplification factor of 100. The 5751 is 70. The 12AT7 - 60. The 12AY7 is 45. Although there is a greater difference between 12AY7 then the 5751 I think going with the 12AY7 for less gain and more overhead is too much. The 5751 is usually the more popular choice.


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## guitarman2 (Aug 25, 2006)

mrmatt1972 said:


> Bill - or anyone else for that matter- is it true that changing the wrong tube for a lower gain tube can make you eq less effective?


Not sure of that one. The only tube swap I did was a 12AX7 in place of the stock 5751 in V1 of a Dr Z Carmen Ghia. Definitely added more noticeable gain. The amp is so responsive and only has the tone and vol knob so it was hard for me to tell if eq was more effective. The eq is just basically turning up the tone knob.
I will be experimenting with replacing the 12AX7 in V1 of my Victorilux with a 5751. So maybe on that amp I'll be able to tell.

http://www.unclespot.com/tubegain.html


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## Wild Bill (May 3, 2006)

guitarman2 said:


> I find the 5751 can make somewhat of a difference to be worth it. The 12AX7 has an amplification factor of 100. The 5751 is 70. The 12AT7 - 60. The 12AY7 is 45. Although there is a greater difference between 12AY7 then the 5751 I think going with the 12AY7 for less gain and more overhead is too much. The 5751 is usually the more popular choice.


Well, if you like it then you like it, Terry! Who am I or anyone else to argue?:smile:

Still, as I've said before, the preamp string in the typical amp has bags of excess gain anyway. We can compare amp factors but we have to keep in mind that the gain of each stage is multiplied, not added!

This means that each 12AX7 tube, having two triodes inside, has a total amp factor of 100 x 100 = 10,000! Most amps have a number of these tubes. The total amplification becomes a ridiculous number that is so far beyond what is needed to drive the output tubes that it really becomes meaningless. Dropping one tube to an amp factor of 70 doesn't add up to much at the end.

I really think that with a true blindfold test someone would be very hard put to be able to tell a 5751 from a 12AX7.

Incidently, the 12AY7 was the original tube of choice for Leo Fender's early amps. That's what gives them such a vintage, bluesy sound.

:food-smiley-004:


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## Rugburn (Jan 14, 2009)

Wild Bill I was wondering about your thoughts regarding 7025s. They were used in the V1 socket in most of the Blackface Fenders followed by 12AX7s/12AT7s in the other preamp positions. I swapped out the 12AX7 in the V1 of my PR with an ANOS 7025, and I have to say it was quieter at idle and cleaner to my ears. I've been told I've got "dog ears", but others complimented the amp's sound afterwards not knowing what was different. My thinking has been that these tubes offered more of the "hi-fi" sound Fender seemed to be after with the Blackface line. 


Thanks Shawn :smile:


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## guitarman2 (Aug 25, 2006)

Wild Bill said:


> Well, if you like it then you like it, Terry! Who am I or anyone else to argue?:smile:
> 
> Still, as I've said before, the preamp string in the typical amp has bags of excess gain anyway. We can compare amp factors but we have to keep in mind that the gain of each stage is multiplied, not added!
> 
> ...



Blind test, your probably right. you wouldn't be able to tell the difference. But most people who tweak their amps, know there amps and could tell a difference. And of course it depends on the amp. One of the amps that I experimented with was a Carmen Ghia. It only had 2 preamp tubes a 5751 and a 12Ax7. So changing out one might make more of a difference then an amp with 4 or 5 preamp tubes. The Ghia is very responsive to tube changes and players touch. I will be experimenting with the Victorilux which has 4 preamp tubes. So maybe the change won't be quite as noticeable in that amp.


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## Wild Bill (May 3, 2006)

Rugburn said:


> Wild Bill I was wondering about your thoughts regarding 7025s. They were used in the V1 socket in most of the Blackface Fenders followed by 12AX7s/12AT7s in the other preamp positions. I swapped out the 12AX7 in the V1 of my PR with an ANOS 7025, and I have to say it was quieter at idle and cleaner to my ears. I've been told I've got "dog ears", but others complimented the amp's sound afterwards not knowing what was different. My thinking has been that these tubes offered more of the "hi-fi" sound Fender seemed to be after with the Blackface line.
> 
> 
> Thanks Shawn :smile:


Well, the 7025 was deliberately designed as a "hifi" 12AX7! Most of the elements were the same but the filament/heater was done a bit differently to reduce hum and special attention was paid to reducing noise. So with a genuine 7025 it's not surprising you noticed things cleaned up somewhat.

Nowadays few if any manufacturers pay any attention to the difference and will just mark their 12AX7 as a 7025. They likely aren't trying to hose anyone. They just don't know the difference themselves! Both tubes are identical as far as just plugging them in and having them work.

The only manufacturer I know of that approaches the hum and noise reduction of a 7025 is TungSol. That's their claim to fame and it's well deserved! However, don't use a TungSol in those amps like Carvin, Peavey and many Mesas that try to squeeze too much gain out of the poor 1st position 12AX7. The TungSol doesn't like to be stressed beyond normal specs and might start to squeal and complain.

Not TungSol's fault! Those designers were trying to cheap out and over-stress one tube to save having to add an extra, with its socket, parts and real estate.

:food-smiley-004:


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## Wild Bill (May 3, 2006)

guitarman2 said:


> Blind test, your probably right. you wouldn't be able to tell the difference. But most people who tweak their amps, know there amps and could tell a difference. And of course it depends on the amp. One of the amps that I experimented with was a Carmen Ghia. It only had 2 preamp tubes a 5751 and a 12Ax7. So changing out one might make more of a difference then an amp with 4 or 5 preamp tubes. The Ghia is very responsive to tube changes and players touch. I will be experimenting with the Victorilux which has 4 preamp tubes. So maybe the change won't be quite as noticeable in that amp.


Good point! Obviously, those smaller amps with only a couple of amplifying stages would show more of a difference.

Incidently, some modern 5751's are just re-branded 12AX7's so you might want to play with only old ones.

You can also try 12AZ7's or even a 5965, if you can find one that's not microphonic. The 5965 has the amp factor of a 12AY7 but for some reason they are really prone to getting vibration sensitive. That's probably why they usually are sold so cheap.

:food-smiley-004:


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## Rugburn (Jan 14, 2009)

Thanks Wild Bill. I scored a pair of CBS/Hytron 7025s last year on Ebay for $39 CAD shipped!! They tested as new, and it's the one and only time I ever bid on Ebay lol. See less and less of these up for biding, but I'm going to try and grab a couple more. That ought to last me a lifetime.

Thanks again 
Shawn :smile:


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## guitarman2 (Aug 25, 2006)

Wild Bill said:


> Incidently, some modern 5751's are just re-branded 12AX7's so you might want to play with only old ones.
> 
> 
> 
> :food-smiley-004:


Yes I have a couple of NOS JAN Phillips that I originally bought for my Carmen Ghia that I'll be trying in the Victorilux.


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