Hi all. I posted a few months back about some 'custom' work on my mid 70's HD 210. See pics. Spoiler alert: There are 'pre-amp in' and 'pre-amp out' 1/4in jacks on the back panel, obviously something was modded at some stage. I finally got the tranny out yesterday and saw they'd been completely disconnected from anything on the circuit board. No wonder turning the vol up on my pedal didn’t do anything! I thought it might be an fx loop or something.
Anyway – now for the current issue(s): Tubes. I’ve been reading through the forums (new and old) for the past couple weeks and have learned a great deal. My question is should I replace the 12ax7? I have no idea of its history having purchased from a pawn shop, ordinarily a no-no for me but this one looked like it was in pretty decent shape.
Also what about the power tubes? I’ve read through the ‘tube recommendation’ threads and am leaning toward E34L’s due to a slightly darker tone and durability/longevity. I’ve attached a bunch of pics, the first few show the ones that came with it. The writing on the side is *barely* discernible but seems the say ‘Tesla’. A quick scan of tubes available today on ebay, amazon and eurotube doesn’t show anything similar. I’m wondering if this is just the way the older JJ’s were labeled?
Overall the amp works well and sounds very good. A bit shrill on certain settings, but that seems normal enough. I’ve also got a 65w (also with a 12ax7) and the amps sound basically identical, despite the HD130 having been retrofitted with Eminence speakers around 1998 (that’s the manufacture date on the speakers anyway).
I was initially intrigued by the HD’s 130w potential but am starting to think I might only ever run it on low power due to the potential of the 12ax7 failing and taking the output transformer with it *Please note I’m not a techie by a long shot. If I use wrong terms I probably have misunderstood something*. Who needs 130 watts anyway? I’m wondering if anyone out there has run there HD consistently on Hi power setting while gigging and if they ever had problems? I love the MM clean tones, they are indeed ‘chimey’ as people have said, and to my ears preferable to Twins which would have been my other choice.
Also I notice something strange when I took her apart yesterday: It’s wired in series. My working hypothesis is that this has to do with the eminence speakers. Maybe the previous owner got them from someone else because they were available and wiring in series was the way to match the ohms? Anyone have any ideas? If I want to attach a speaker cab (probably 2 instead of 4), I’ll need to have it rewired to parallel, no?
I’ve asked a lot of questions.
Better quit while I’m ahead.
(PS. Chassis is no 2275-130 so it may have 6CA7's in it currently. I can't tell, as per pic. Any favorite tube suggestions for rock/hard rock would be great.)
Can't Comment on the Speaker Wiring but...
...those power tubes definitely look like EL34s, 6L6s are bigger around (diameter) and sometimes shorter in length.
A local guitarist was using an HD-130 Reverb head on High power before I cleaned and recapped it, now Low power more than meets his needs. He may trade "down" to a 65 Reverb head I am working on. Truthfully, even the Low power setting on that should be more than sufficient for his clean headroom needs.
Also, I would be nervous playing your 130 without a grounded power plug...
Thanks Inertian, I appreciate
Thanks Inertian, I appreciate the input. I'm not sure I understand the idea behind a 130w amp, despite being intrigued by it. As far as that goes, at large venue shows the amps going to be mic'd anyway. I can only conclude, as others have, it was felt at the time that there was a need or niche for amps that could get hugely loud without breaking up. I personally love the sound of MM for what it is, the 'loud' is a bonus I guess. If I needed to turn up that much I'd be wearing hearing protection!
Do you have a preferred 12ax7 manufacturer? I'm looking for longevity, durability, etc. I don't mind paying for quality.
I think Leo was always
I think Leo was always striving for a clean sound from his amps, the MM amps don't break up until you push them almost al lthe way up, as you say the huge volume is a bonus...
If you can find old US tubes, they tend to hold up better. But NOS they get pricey in a hurry. For modern production tubes I like theJJ brand, they perform well, are reliable and durable, and aren't too expensive.
To someone like me who
To someone like me who cherishes both clean and rock tones it's not the easiest thing to achieve breakup without ruining your ears. Going to start a thread on breakup perhaps - there doesn't seem to be a lot about this aspect of MM on the forum.
Anyway, looks like I'll be ordering a new set of JJ's soon.