Hagerman Trumpet MC (12AX7 Tube Suggestions)

@djohn

Awesome! So glad you’re enjoying it :)

Just this past week I’ve been playing the Trumpet MC with Plantinum grade gold pin Tung-Sol (Russia) 12AX7 from Upscale Audio - no noise problems there. Maybe Viva just doesn’t like selecting them for this role ;)

But certainly, a good set of Teles will be amazing. I need to dig them up again from my stash. I ’ve been playing with lot of gear the past few years; now trying to settle things down a bit - the ARC Ref 3SE is sold to a friend, the VAC Renaissance SE reigns again in the now all-VAC main rig with Tannoy Canterbury GR, and the new fun 2nd system at my girlfriend’s home is anchored by a really nice set of Tannoy Glenair 10 and this Trumpet MC.

I just went through my photos and see that a couple years ago, when I was really enjoying the Trumpet MC in the main rig (it holds up extremely well and is still probably the best I’ve heard my Benz LPS), I had it stocked with a quad of Tele ribbed plates. So it can use the extra detail and dynamics of this variant (versus smooth plates) without getting too bright - but I also had those warm Mullard CV4003 (12AU7) to balance them out a bit. Shame that Upscale finally ran out of those :(

As @lewm points out, 5751 has a lower mu than 12AX7 - 70 versus 100. But most tube circuits are quite flexible for this. By math 20 * log (0.7) - this is a 3dB difference. However, this assumes an infinite load and in practice it is usually less than this (~ 2dB?). Subjectively, 5751 have a different "kind" of sound. I find them to have tighter, sharper, smaller imaging. They sound very clean and precise. Whereas 12AX7 have a bigger, bolder, more dynamic sound - but with a potentially more "grungy" cast to the sound. But again, haven’t tried 5751 here yet. The GE TM BP are a good go-to for a classic 5751 sound. The "holy grail" 5751 are supposedly Raytheon windmill getters or Sylvania triple mica black plates (TM BP) and I haven’t been lucky enough to snag either. The later 1960’s Sylvania gray plates are awfully bright and lean. Sadly that has been my experience with later make Sylvanias across types - you really want to stick to the 1950s and earlier.

One more note on the 5751 tubes tangent - the absolute sweetest sounding of the GE 5751 TM BP are a specific variant only produced between 1953 and 1954. This variant has unusual silver colored metal "clips" crimped over the plate "ears" that normally poke through the top & bottom mica spacers. These "ears" are normally left bare (not just 5751 - all tube types). For some reason GE saw fit to clamp them down extra tight in this case. And for whatever reasons, this version sounds sweetest :)

From Jim Hagerman the Designer;

Yes you can use a 5751, but the tonality (EQ) will change.  Probably a bit darker.

I will be sticking with the 12AX7.
 

Picked up my second Trumpet over the years a few months ago. Brent Jessee over at Brent Jessee Tubes recommended NOS Amperex BB's. I can't quite remember what tubes I rolled in my previous Trumpet iteration, but it sounded wonderful no matter what. Great thread, btw!

The quote from Mr Hagerman about the 5751 may indicate that the 12AX7 it would replace is involved in the RIAA correction filter, as well as adding gain. Since the 5751 might change slightly the output impedance of the stage, it might also affect RIAA, resulting in a sonic coloration that has nothing to do with the brand or vintage of the 5751 chosen.