Best tube choices for MC225?

[goldear]

Do any of you Mac guys have opinions on the best sounding tube choices for the MC225? I generally try to stick with the better-sounding modern tubes, rather than seeking out vintage unobtanium.

Any opinions on the JJ7591s vs the EH7591s? Jim Mcshane swears that the EH7591s are fantastic. I'm slightly concerned about their size, as well as the fact that the EHs tubes which I have tired tended to be a bit brighter than I prefer.

I'm also concerned about JJs reputation for some of their output tubes shorting. But I don't know if this is just an internet rumor, or if this is truly something to be concerned about.

Also, do you guys have any opinions on how various 12BH7s sound inside of this amp?

 

[62caddy]

After much research, I went with the 7591 from EH for my MAC 1500. They work & sound great.

Only issue is that the cabinet won't fit with the tubes in. That wouldn't apply to the MC 225.

 

[Mike Gibson]

I had EH small signal tubes in my MC-275 for several years and I'm completely happy with the sound. I have Tung-Sol reissues for power tubes and like them fine. If they make some in 7591 I would recommend you try them.

 

[kcin]

The EH 7591 works fine with the the MC225 I have used mine with this tube and it is just about as good as the Westinghouse 7591s. I had just put up my last quad of OS 7591s in Barter town but no takers. I think the EH are just fine.


I cannot tell the difference between various RCA and GE 12BH7s in this amp but I do like the Siemens 12AX7 in the first position.

 

[dewickt]

The JJ reputation is well deserved, at one time the were running a 50% failure rate, the new build JJ 7591 are much better, just make sure you get new ones.. I agree the EH are the way to go, sound and reliability are top notch, they only suffer from size issues.

 

[Phototone]

I have run a set of EH7591's in my MC-225 for over 10 years with no issues what so ever. There is ample room around each tube for ventilation, and my amp sets open in the room air so there is no heat build-up.

 

[LotusFool]

A few years ago I changed my 12BH7A's from Russian electro-harmonix to a matched pair of NOS RCA 1968 ( don't laugh at me because I paid $239.00) and I thought the difference in sound was pretty amazing.

gary

 

[goldear]

I'm assuming that this amp, like many Mac designs, runs the tubes in a very low-stress mode of operation so that they last a very long time. I've never encountered a tube amp which runs so cool. I'm used to tube amps helping to heat my listening room in the winter, but this amp generates less heat than many solid state amps I have owned.

I'm guessing that the unity-coupled design must be operating very close to class B.

 

[goldear]

The JJ reputation is well deserved, at one time the were running a 50% failure rate, the new build JJ 7591 are much better, just make sure you get new ones.. I agree the EH are the way to go, sound and reliability are top notch, they only suffer from size issues.

Wow, that's awful. Was the failure-mode from shorting, or something else? And what kind of time frame was there on these failures?

 

[cduarte]

A few years ago I changed my 12BH7A's from Russian electro-harmonix to a matched pair of NOS RCA 1968 ( don't laugh at me because I paid $239.00) and I thought the difference in sound was pretty amazing.

gary

the signal tubes is where you're going to get your biggest gains on the mc225. I'm running a tele 12ax7, and rca black plate 12au7/12bh7s and the improvement was tremendous.

 

[Mid-Fi]

I use EICO Westies as outputs and can't point to any faults. As for the signal tubes, for the AX7 I use a smooth plate Tele which does no wrong. In the AU7 spot I actually prefer old black plate Hammond units to Teles.

Yes sir the prices asked for old BH7s is getting nuts. I was lucky enough to have a buddy with a stash he let me pick CBS Hytron black plates from. (Thanks Steve)

I hope the egregious glamor shot is acceptable and enjoyed

 

[drknstrmyknight]

+1 on the 12BH7 RCA black plates.
I have Scott labeled Sylvania 7591's in the power section.
The jury is out on the 12AU7's and 12AX7.
I have so many of these and roll them every month or so, but I like the Amperex 12AX7 for most vocal, jazz, etc. I don't notice the 12AU7's much.

 

[Edvar]

The EH 7591 works fine with the the MC225 I have used mine with this tube and it is just about as good as the Westinghouse 7591s. I had just put up my last quad of OS 7591s in Barter town but no takers. I think the EH are just fine.


I cannot tell the difference between various RCA and GE 12BH7s in this amp but I do like the Siemens 12AX7 in the first position.

 

[Snappahead]

When I purchased my 225 I demo'd 3 sets of tubes. The gentleman I bought it from told me that I probably wouldn't hear much or any difference at all because as he explained it: "the power supplies are so good there's hardly any stress on the tube." He was right. That said I left the EH that it came with and never looked back.

 

[twiiii]

Thats why you deal with Audio Classics because they service tube amps all the time and Ryan normally has his ear to the ground and checks out Mac tube amps and usually knows the answers to those types of Questions. Thats why presellected and tested ubes for amps are so expensive now days. There is a pretty high rejection rate no matter who the manufacturer is now days. Its a roll of the dice other wise. You want to buy matched pairs because at least that way you know some testing has been done to the tubes you buy. Back in the 60's it wasn't as critical as it is today. But Davie O'brien did check out the tubes he was using on amps at the factory before placing them in owners units. MC 30's were very demanding about the tubes used. Especially for owners that wanted tubes with the metal envelopes which were always a problem.