7199 substitution in Ampegs

[Zoe_N_Iain]

Yup. Sound pretty much the same. Bit more top end chime, if anything.

The pentode usually has very slightly lower gain than a 7199, given the same B+ and resistance values, and the triode has roughly the gain of a 12AV7 versus ~12AU7/12AY7 for the 7199's (depends on the type how high mu the triode is).

In our experience, the triode is slightly better at rounding the rough edges off the signal, if used as a cathode follower after a gain stage, than the one in a 7199. But that's generally an improvement in tone, rather than a bad thing.

And they're cheap and easy to get, so...

[jrfrond]

The most widely-accepted sub is the 6U8A. I purchased some of these on my last tube order, just to have for whenever we blow through our 7199's. Fortunately, the 7199 has never been a big mover for us. Of course, hindsight is 20/20, and I would have hoarded some 7199's when I had the chance, like I did with 6BK11's.

Unfortunately for us techs, the fine engineers at Magnavox/Ampeg liked to use these oddball TV tubes in their guitar amp designs. I don't recall seeing any other amps other than Ampeg using the 7199, but I could be having a pre-senior moment.

[telemoxy]

Think the Groove Tube Tube Amps Vol 4 has a section describing this change as well as a 6EU7 to 12AX7 rewire.

The 7199 to 6U8A instructions are on page 764. Couldn't find a reference to 6EU7 to 12AX7 but you can still get 6EU7s.

[Albert Kreuzer]

I don't recall seeing any other amps other than Ampeg using the 7199, but I could be having a pre-senior moment.

Sunn?

Cheers,
Albert

[jrfrond]

Thanks! Forgot about that one!

[drewl]

Found this thread while researching a Sunn Solarus I'm fixing.
It's shame the damn 7199 has some hum, otherwise this would be a nice quiet amp.
It seems they also used the 6AN8 in some and the 7199 in others.

[soundmasterg]

Conrad Sundholm has told me in the past that if he knew what he knows today, he would never have used the 7199 or 6AN8 for his designs back then. They aren't very good sounding tubes as compared to some others out there. I'd have at it with swapping to something else. The Stereo 70 mods are all over the map, but I've heard of one using an EF86 and 12AU7 triode stage setup as a cathode follower for each channel that is supposed to perform and sound quite good. YMMV.

Greg

[hasserl]

I don't recall seeing any other amps other than Ampeg using the 7199, but I could be having a pre-senior moment.

Sunn?

Cheers,
Albert

I've got an Alamo Paragon Bass amp here that uses a 7199, a very nice sounding amp for guitar, very nice.

[Enzo]

The SUn amps of that era used the 7199 and the 6AN8. They also used EL34s and KT88 power tubes. The power tubes made the choice of which PI tube was used.

[drewl]

Well that explains it, it seems there's a couple versions of the Solarus, one with 7199 one with 6an8.
Another difference is the trem photocell is on V1a or V1b.

[TD_Madden]

Gibsons.