Tube selection

[Bill SAS 513]

Never had a good tube amp...Just picked up a used Dr Z Mini Z...has a 12 AX7 and EL 84 ...if I replace the AX7 with an AU7 , will it take more volume before it overdrives??

 

[LJD]

I've tried that with a 5751 and just had to turn up the volume knob to get to the same place, only less beef/body to the sound. No headroom improvement, but it can tame a harsh top end depending on the tube/amp.

 

[DHW]

a 12ay7 might be a better choice. The au7 will probably be too far in the other direction.

 

[helmi]

I've owned 3 dr.z's. there's a few 12 ish tubes you can try. there's also a 12bh7 tube you can try that some people use in DR.Z carmen ghia's to get more headroom. you have to remember, your dealing with a 5-watt amp. you only going to get some much headroom no matter what you try. I actually only live about 15 minutes away from the dr.z factory, and have been there several times. great people. you can go to the dr.z forum page and go under the mini-z heading and read about the amp and ask ?'s there. great group of very helpful, nice guys over at that forum.. believe it or not, you can still call dr.z and someone will actually ANSWER the phone in person and answer your ?'s.

 

[Bill SAS 513]

Awesome...Thanks for the responses, all. I will pick up an AY, It is a pretty cheap fix, and there's a ton of options. and I've been stalking the Dr Z forum since I got it.

 

[gball]

I would just get several types and try them to find what you like the best. 12AX7/12AT7/122AU7/12AY7/5751 are all different amplification factors and just as importantly have different transconductance values, so you won't know for sure until you try them. Luckily they are inexpensive enough to experiment a bit with.

I really like 5751 in Fender amps but hate them in high-gain applications, where I prefer a good-quality 12AX7. The Mini is not an amp I associate with "high gain" in the modern sense, but it seems the Dr. has designed the circuit to break up early and often so a different preamp tube might give you a small amount of additional headroom but I wouldn't expect very much.

 

[Brad737]

Bill,

When I need to swap out an AX7 for a lower-gain option, I'm a HUGE fan of the GE 5751. I've yet to find an AT, AU, or AY that sounds as toneful. None of those are very pricey. I'd suggest getting one of each and seeing which you prefer. Now when you start playing with AX7s, it gets expensive quickly.

I've only played a Mini Z once, but it had the stock tubes loaded. Zaite is a lying douchenozzle of the highest order, but he makes nice amps. I've owned 7 of them, and they were all extremely tube sensitive. By that, I mean each amp's tone changed a LOT based upon the tube complement. I think you should start scouring ebay. There are still lots of deals to be had.

BTW, if that were my amp, I think I'd be looking at vintage Mullard 12AX7 and JJ EL84, and blasting through an Alnico Blue.

Good luck!

 

[Brad737]

I really like 5751 in Fender amps but hate them in high-gain applications, where I prefer a good-quality 12AX7.

I get what you're saying. But if you were local, I'd love to have you check out my 1st-year Peavey 5150. Those amps are notorious for having a pretty "gainy" clean channel. With the 6L6s biased to 38mA and a pair of GE JAN 5751s in V1 and V2, that amp has a lovely clean tone now. And with the cascaded preamp, it still has wayyyyy more gain on tap on the lead channel than I'd ever need. I never go above 7 on the preamp gain, even with the 5751s loaded. FWIW, I think the key is replacing V1 AND V2. With just a single 5751, it didn't really affect the tone that much.

Good luck!

 

[gush]

I get what you're saying. But if you were local, I'd love to have you check out my 1st-year Peavey 5150. Those amps are notorious for having a pretty "gainy" clean channel. With the 6L6s biased to 38mA and a pair of GE JAN 5751s in V1 and V2, that amp has a lovely clean tone now. And with the cascaded preamp, it still has wayyyyy more gain on tap on the lead channel than I'd ever need. I never go above 7 on the preamp gain, even with the 5751s loaded. FWIW, I think the key is replacing V1 AND V2. With just a single 5751, it didn't really affect the tone that much.

Good luck!

You are right on the money about the 5150 gain thing. I run my gain between 4 & 6 depending on what I'm going after. I always use the lower gain input too.

 

[Bill SAS 513]

Update...started messing with a 12 AU 7 and it definitely cleaned up the grind, but, as DHW said, too much so...been enjoying the tone, which is still full and juicy, but definitely gonna mess with an AY next...btw...JJ EL 84 in power section...still cheap experimentation is fun.

...or the GE 575 ...

 

[yakbass]

Bill,

When I need to swap out an AX7 for a lower-gain option, I'm a HUGE fan of the GE 5751. I've yet to find an AT, AU, or AY that sounds as toneful. None of those are very pricey. I'd suggest getting one of each and seeing which you prefer. Now when you start playing with AX7s, it gets expensive quickly.

I've only played a Mini Z once, but it had the stock tubes loaded. Zaite is a lying douchenozzle of the highest order, but he makes nice amps. I've owned 7 of them, and they were all extremely tube sensitive. By that, I mean each amp's tone changed a LOT based upon the tube complement. I think you should start scouring ebay. There are still lots of deals to be had.

BTW, if that were my amp, I think I'd be looking at vintage Mullard 12AX7 and JJ EL84, and blasting through an Alnico Blue.

Good luck!

+1 for the tube recommendations. A Celestion G10 Gold is also a very nice speaker for a low wattage amp.
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