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.

Telefunken and Mazda (silver plates) 12ax7 are great if you want to amp up detail. The smooth plate Teles are warmer; ribbed plates are a bit more dynamic but also touch brighter. Mazda silver are the best omg - but a tad bright and expensive! The Trumpet MC is warm overall so it’s very accepting of these tubes, more than most.

I don’t have much for 12au7 in my collection but I do have British Mullard CV4003 in there now (warm) and the result with brighter more detailed 12ax7 is quite nice.

Modern Russian production tubes are really quite good too. The Mullards are quite warm. The Tung-Sols give you a bit more detail and energy up top and I like them in the Trumpet MC. The overall tonality/balance of Russian Mullards and Tung-Sols actually tracks pretty well with their vintage counterparts.

Teles are expensive from “trusted” sources but they’re really quite common. So many of these were imported to USA, e.g. in Fisher gear. No need to overpay for Teles. Find a few “used tests strong” pairs and keep the best. Of course this works much better if you or a friend have a tube tester.

I’m not really a fan of RCA tubes but they’re OK, sometimes. GE triple mica black plate 5751 are much better than RCA 5751 but I haven’t tried a 5751 in the Trumpet MC yet. It’ll certainly work, but not sure how the sound will be.

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 :)

Well I actually tried a pair of 5751 in the 1st 12AX7 slots. It sounds great - this is an improvement over the Russian Tung-Sol gold pin 12AX7 I had in there, for sure. Sweeter midrange, a little more 3D - as is often the case going from Russian to good vintage tubes. Excellent clarity. It did NOT shift the tonal balance to darker. It’s just nicer, overall. It did lose a dB or 2 - that’s noticeable and easy to adjust for.

These are just RCA TM BP 5751, since I have very limited tubes available here where my "B" system is located. Also the "B" system is something I just recently put together, haha. So at some point I’ll bring over a bag of vintage 12AX7, 5751, and 12AU7 and go to town as I continue to familiarize myself with the B system and refine it (basically it needs a better turntable). We'll see if 5751 hangs with the better vintage 12AX7. 

But 5751 in that first slot is good! No worries if you want to try it there. I guess I should also try the 2nd slot next.

The B system:

• Tannoy Glenair 10 speakers
• VAC Signature 200 iQ stereo tube amp
• Rogue Athena tube preamp
• Hagerman Trumpet MC
• Fluance RT85 w/ Ortofon 2M Blue - this will be replaced with Clearaudio Innovation Compact in a week - but it’s kinda neat how good it sounds through a downstream which far outclasses it.

Sure I get the concerns about 5751 subs affecting the RIAA EQ. That’s why I’ve shied away from using 5751 in phono stages in the past. But sometimes you just have to try things. There can be a lot of variance in measurements between 12AX7 tubes, too.