Newer Fender Amp Tip

[myles_rose]

Just a quick tip for owners of the newer Fender Pro Tube amps (Pro Reverb, Pro Twin, and Concert).

 

In V4 I believe, the Phase Inverter, Fender uses a 12AX7. In past Fender designs, a 12AT7 was used. The 12AT7 has a bit less gain but a lot more current drive ability.

 

Try sticking a 12AT7 in the PI position of these amps .... you may like it very much. It will give the amp more clean headroom, which may not be needed on the clean setting, but really helps when switched to the distortion setting, as it makes the distortion more usefull with a wider range of usable settings on the Volume and Gain controls.

 

The second "improvement" is to use a GOOD 12AX7 in V1 .... a 12AX7R3 (Electro Harmonix type) is fine here, and they can be found all over the place. The stock tube in V1 (which also feeds V2), can be improved upon in a few minutes cheaply enough.

 

The "third" improvement, is to replace the Sovtek 6L6WXT's with different output tubes, if you want a different sort of feel and tone. The stock tubes in these amps work very nicely actually, but I heard a few of these now with other output tubes, and I think its worth a listen. The KT-66's sound great in these amps ... don't worry, it looks like a tight fit between the top of the speaker magnet and the bottom of the tube (the tube's top actually), but once in the socket, it fits with room to spare by a touch. This is a great blues tube in the clean channel when pushed.

 

The other tube that just SINGS in this amp is the 6L6S from the JJ factory. Its a great rock, hard rock, heavy hard rock, metal, speed, and thrash rock, grunge, and insane tube. These are 30 watt tubes, not the normal 25 watters as a lot of 6L6's, so check your bias. They are very strong, and do really nicely in the lack of microphics department being so close to the speaker. They are also CHEAP, which is a nice side benefit. The more I listen to the 6L6S, the more it sounds like an E34L and 6L6 cross.

 

Myles

[Gabriel E.]

The 12AT7 has a bit less gain but a lot more current drive ability

Please forgive my ignorance, but does this basically translate into more "clean gain"? I.E. It actually makes the signal louder w/o overdriving?

 

I have been using a 12AU7 in the PI of my tweed super. It sounds less "buzzy" than a 12AX7, but also lowers the volume a bit. Would a 12AT7 give me the volume without the buzz?

 

I always assumed the only differences in dual triodes (aside from quality) was gain.

[WDC]

Nice!

[Wickerman]

Myles, I'm not sure if you're very familiar with Carvin amps but the Bel Air/Nomad chassis uses five 12AX7s. Would you're best bet be that V4 would still be the phase inverter and do they could V1-V5 from left to right (looking at the front of the amp) or from right to left? Thank you for any and all help you can give. You're the wind beneith my wings.

[WDC]

What about using the new GT6L6GE in the output stage? Not surprisingly, Groove Tubes said this would sound awesome in my amp.

[myles_rose]

Originally posted by Gabriel E.:

The 12AT7 has a bit less gain but a lot more current drive ability

Please forgive my ignorance, but does this basically translate into more "clean gain"? I.E. It actually makes the signal louder w/o overdriving?

 

I have been using a 12AU7 in the PI of my tweed super. It sounds less "buzzy" than a 12AX7, but also lowers the volume a bit. Would a 12AT7 give me the volume without the buzz?

 

I always assumed the only differences in dual triodes (aside from quality) was gain.

Gabriel E ....

 

The current drive ability of a AT7 is almost ten time greater than an AX7, although a spec AX7 has a gain of 100 vs. 70 of a spec 12AT7.

 

You have more clean headroom with an AT7, as well as tighter control of the output section. Play a Rickenbacker 12 with a barking chord with an AX7 as a PI in a twin reverb, then the AT7 .... big difference in bite and attack.

 

Myles

[myles_rose]

Originally posted by WDC:

What about using the new GT6L6GE in the output stage? Not surprisingly, Groove Tubes said this would sound awesome in my amp.

WDC ....

 

That is the tube that was used a lot back when the Fender amps were made.

 

It is my favorite, but then again, if Groove Tubes says it's their favorite, and since part of my day is spent at GT, then I guess I go along with that also for the same reason.

 

Basically though, the first 6 month run of tubes lasted 3 1/2 weeks .... the second run was gone almost as fast, and we are 80% through the third run.

 

Some of the last sets of this run of quads, that I picked out for a tour, I have on ebay from my own personal stock. .... they are that hard to get at the moment.

 

Myles

[myles_rose]

Originally posted by Wickerman:

Myles, I'm not sure if you're very familiar with Carvin amps but the Bel Air/Nomad chassis uses five 12AX7s. Would you're best bet be that V4 would still be the phase inverter and do they could V1-V5 from left to right (looking at the front of the amp) or from right to left? Thank you for any and all help you can give. You're the wind beneith my wings.

Wickerman ....

 

usually the 12AX7 that is the last in the preamp chain is the PI .... although in my Fender Pro Reverb (new one) amp, it is V4 out of V8, but then those amps have a "funny" physical layout .... but the PI is still (V4), the closest to the output tubes, in a weird sort of way.

 

I'd think V5 is yours, but give Carvin a call ... they have an 800 number, as I am not near my prints.

 

Usually V1 is the most close tube to the input jack, and count from there.

 

Myles

[myles_rose]

Bumping for new forum folks

[nest18]

Hi Myles,

 

Really love the support you give here .. Ive got a few questions about my new Pro-Reverb .(Which I love by the way)

 

Ive change the ouput tube for Sveltlana 6l6 from the tube store, Its definitely sounding better than the stock 6L6 from GT (Sovtek I think). Ive bias them at 34mv and would like to know if you think this is a good bias point for those amps . Furthermore, Ill like to listen to those JJs 6L6S and, cause the plate volt is 30W, would the bias change ?? (The best place to buy them would it be eurotubes.com ? Ive seen that you are not too keen on tubestore.com )

 

Since Ive change the output tube Ive got a ring in the clean channel with the stock GT ax7, this must be a microphonic tube. I've followed your advise to put a EH in V1 and V2. It sounds great (darker in my opinion).

 

Do you have an experience with JJs from Bob at eurotubes.com in these position (V1, V2)

 

The PI should be match ?!? How can I find matched tube for PI and match with the power tube (6L6). A regular 12at7 should be fine there ? How do I find that match value from my output tube already in place ? Im in the same position as yours, I love the second channel but would like it to be less aggressive or at least be able to dial more then at 4 on the gain

 

I use my effect loop has a second drive channel (more gain) and Im not sure if I change the tube in position V3 and V8 if my sound could be change in this setup ? Ill like to dial an other sound when engaged .

 

Thanks a lot for you support, Sorry for the newbies questions .

 

Cheers

[jsj]

Myles,

 

Its good to hear from you on the new Fender amps. I have really come to enjoy my Pro Reverb since I purchased it in February. I immediately retubed it as follows:

 

V1 - Philips JAN 12AX7WA

V2 - Philips JAN 12AX7WA

V3 - Philips JAN 12AX7WA

V4 - GE JAN 5751

V5 - Philips JAN 12AT7WC

V6 - Philips JAN 12AX7WA

V7 - Philips JAN 12AT7WC

V8 - Philips JAN 12AX7WA

V9 - Svetlana 6L6GC

V11 - Svetlana 6L6GC

Bias = 32 mVDC

 

I biased it a little hot and maybe you have an option on that. My question/comment is I put a 5751 in the PI which is also a lower gain tube. How would you compare it to the 12AT7?

 

I also had to do a lot of experimenting with V5 to reduce a sizable hiss in the reverb circuit. I got best results (lowest hiss) with a 12AT7 and I tried everything I had at the time (12AX7, 5751, 12AT7, etc.) Any suggestions on which is best for the reverb and tremolo systems?

 

Thanks again for addressing these new designs.

 

-John

[jsj]

Double post --- fat fingers --- sorry

[myles_rose]

Originally posted by nest18:

Hi Myles,

 

Really love the support you give here .. Ive got a few questions about my new Pro-Reverb .(Which I love by the way)

 

Ive change the ouput tube for Sveltlana 6l6 from the tube store, Its definitely sounding better than the stock 6L6 from GT (Sovtek I think). Ive bias them at 34mv and would like to know if you think this is a good bias point for those amps . Furthermore, Ill like to listen to those JJs 6L6S and, cause the plate volt is 30W, would the bias change ?? (The best place to buy them would it be eurotubes.com ? Ive seen that you are not too keen on tubestore.com )

 

Since Ive change the output tube Ive got a ring in the clean channel with the stock GT ax7, this must be a microphonic tube. I've followed your advise to put a EH in V1 and V2. It sounds great (darker in my opinion).

 

Do you have an experience with JJs from Bob at eurotubes.com in these position (V1, V2)

 

The PI should be match ?!? How can I find matched tube for PI and match with the power tube (6L6). A regular 12at7 should be fine there ? How do I find that match value from my output tube already in place ? Im in the same position as yours, I love the second channel but would like it to be less aggressive or at least be able to dial more then at 4 on the gain

 

I use my effect loop has a second drive channel (more gain) and Im not sure if I change the tube in position V3 and V8 if my sound could be change in this setup ? Ill like to dial an other sound when engaged .

 

Thanks a lot for you support, Sorry for the newbies questions .

 

Cheers

nest18

 

The Pro Reverb (new one) is a fun amp and very versitile. There are a few tricks though. I mention some of these on my website at:

 

http://www.guitaramplifierblueprinting.com/pastinfo.html

 

The Svets are much better than the Sovtek WXT's that come as stock for most folks. The stock tube is the GT-6L6B or GT Sovtek 5881 WXT. They are a nice sturdy tube, but do leave some sonic issues to be desired.

 

In the case of any tube purchase from "The Tube Store", you may want to check those tubes, as your bias balance is probably at its limit. I used to have those folks on my personal business website, but after they failed matching test after matching tezt, and tried to generate sales by bad mouthing other tube vendors, I dropped them from my website. I recently posted in some area, where a Canoga Park CA music store owner, brought in a set of 6CA7's he purchased from them that had a "rating" of "16" on them. They were not even with 20% of being matched, and were down 40% on output. It was just one more time where I was shown that they offer a suspect product.

 

Long before coming to GT, I had issues in regard to them on my website:

 

http://www.guitaramplifierblueprinting.com/groovetubes.html

 

Your bias on the Svets (assuming they are decent from The Tube Store, would be a bit better at 30mA and this would reduce noise. If there is a fair amount of background noise at lower settings, this can be fixed by tossing those Svets and buying them elsewhere.

 

On the 6L6S, Eueorubes is fantastic. The bias will need to be readjusted.

 

On your EH, it may sound darker for some other reason, as the EH is brighter than the 12AX7C that Fender uses in V1 and V2 of these amps. The other tubes in the amp are Sovtek 12AX7WA's. This should not be the case.

 

In my own Pro Reverb, V1 and V2 are 7025's as was the original Black Face tube a few decades back, and is much more articulate due to a long smooth plate design.

 

Bob's JJ's are ECC83's, and I prefer the 7025's in V1 and V2 in these amps, but that is just personal taste. The ECC83's are more a Brit flavor tube, more suited to amps other than Fender.

 

On the MPI, its not the PI matching the output tubes, it is the two sides of the tube matching each other. I have an article on this at:

 

http://www.guitaramplifierblueprinting.com/pastinfo.html

 

There may also be something at:

http://www.guitaramplifierblueprinting.com/12ax7.html

 

I get rid of the AX7 in the PI slot of these amps and go back to the original AT7 that was in the Black Face design:

 

http://www.groovetubes.com/product.cfm?Product_ID=1722 in V4 (I believe, not looking at my print).

 

On MPI's ... you can do a pretty decent job with folks that will match the two sides for output. You can do a better job if they match for output and rise time.

 

For more usable gain ranges on the gain channel, your V2 needs to be a tube with a rating from 67-92. in NO case should this be above 95.

http://www.groovetubes.com/product.cfm?Product_ID=1735 or http://www.groovetubes.com/product.cfm?Product_ID=1733

 

The tube for the effects loop, reverb driver, and pre out / main in, are current drivers. They have no impact on your tone.

 

Hope this was of some help.

 

Myles

[myles_rose]

Originally posted by jsj@agtechnet.com:

Myles,

 

Its good to hear from you on the new Fender amps. I have really come to enjoy my Pro Reverb since I purchased it in February. I immediately retubed it as follows:

 

V1 - Philips JAN 12AX7WA

V2 - Philips JAN 12AX7WA

V3 - Philips JAN 12AX7WA

V4 - GE JAN 5751

V5 - Philips JAN 12AT7WC

V6 - Philips JAN 12AX7WA

V7 - Philips JAN 12AT7WC

V8 - Philips JAN 12AX7WA

V9 - Svetlana 6L6GC

V11 - Svetlana 6L6GC

Bias = 32 mVDC

 

I biased it a little hot and maybe you have an option on that. My question/comment is I put a 5751 in the PI which is also a lower gain tube. How would you compare it to the 12AT7?

 

I also had to do a lot of experimenting with V5 to reduce a sizable hiss in the reverb circuit. I got best results (lowest hiss) with a 12AT7 and I tried everything I had at the time (12AX7, 5751, 12AT7, etc.) Any suggestions on which is best for the reverb and tremolo systems?

 

Thanks again for addressing these new designs.

 

-John

John

 

V1 - Philips JAN 12AX7WA ... super

V2 - Philips JAN 12AX7WA ... super

 

V3 - Philips JAN 12AX7WA ... nice but not necessary

 

V4 - GE JAN 5751 .... maybe try something else here as an experiment. If you are going for less PI gain, the AT7 is a better choice, as it has much more headroom and current drive ability ... but that is my personal preference.

 

V5 - Philips JAN 12AT7WC

V6 - Philips JAN 12AX7WA

V7 - Philips JAN 12AT7WC

V8 - Philips JAN 12AX7WA

 

These four won't help your tone at all, but will last forever and be great.

 

V9 - Svetlana 6L6GC

V11 - Svetlana 6L6GC

Bias = 32 mVDC

 

Try it at 30mA and see if your low end response is even nicer. You may also hear less background noise. You are fine at 32mA though from a safety and good sound standpoint.

 

The AT7 is also best for a reverb driver or trem driver for me too.

 

Hope this was of some help,

 

Myles