My question is about the tubes. It has 4 6L6's. There are alot of different tubes out there that apparently have different sounds to them. Does anyone have any recomendations for the cleanest sounding ones? Before I sold it I put Peavey 6L6's in it and was happy. I just want to see what the options are. Also, about biasing? I didn't have it re-biased when I changed them before. Is it really necessary if you use matched tubes?

Order on Monday, tell him what you are putting them in and he'll select an appropriate quad and they will be in your mailbox Wednesday.

The rep on these tubes is that besides sounding good (maybe not spectacular but definitely good) they are robust and can take some abuse.
This means that they will probably survive a mis-biased amp. But to get the best sound and life-span out of a tube they should be biased for optimum performance.
I repeat---my experience is minimal but I am running these tubes in a couple of different amps. I also use the JJ 12AX7 and AT7's in the preamps. Is this MM the hybrid solid state/tube model or is it tube preamp?

-----
BTW--nothing sweeter than netting that fish that got off the hook.

[This message was edited by Jon Light on 19 October 2003 at 08:31 AM.]

Other than that I have no real preference, as long as the set is matched.
Heres two reviews by two great Amp Techs.

(I only use tubes for standard guitar so maybe this is not a valid comment for this forum).

BTW,
Mike Sweeney told me some great things about you. I look forward to meeting you in CT. I'll only be there Saturday afternoon.

-j0ey-

[This message was edited by Joey Ace on 19 October 2003 at 08:46 AM.]

This amp has a solid state pre-amp and a tube power amp. Very warm mid-range and brilliant highs that blend together rather than cut you. It has good bass but it could be better. I found to compensate for this, the secret is in the treble control. The treble overrides the bass control. So if I run the treble between 3 and 4, it is still nice and bright but the bass control works better. Something could probably be done internally to voice the amp differently.

you will find a load of information on the old MusicMan amps here, including schematics, parts list, info on biasing and replacement tubes. There is also a message board where you could ask your questions.

Hope to have helped,
Rainer

Larry beat me by 2 minutes!
------------------
Remington D-10 8+7, Sierra Crown D-10 gearless 8+8, Sierra Session S-14 gearless 8+5, '76 Emmons D-10 8+4, Peavey Session 400 LTD

[This message was edited by Rainer Hackstaette on 19 October 2003 at 09:18 AM.]

Larry and Rainer, thanks for the Music Man Forum site info. Alot of information there.

[This message was edited by Randy Beavers on 19 October 2003 at 11:45 AM.]

I didn't think there was an adjustment pot on the 150 watt amps. I was going by what someone said on the M-M Forum. If there's not a bias pot, I'm good to just plug in new tubes and play right? I mentioned that the tubes never get real hot. Is this by design, or should they be running hotter? It never had a power problem. It would get real loud and stay clean. When I changed the original tubes the amp was starting to lose its deffinition in string separation. Not really distortion though. Also the bass wasn't punchy. The amp really sounds good now but I know the tubes have in there for about 12 to 13 years. However, I'm sure they don't have more than 100 hours on them. The guy that had the amp hardly ever played it, and when he did it was at his house at low volume.

I have fixed a bunch of Fender amps but no MM stuff. In as much as tubes are concerned there are only a few manuf. plants on the earth that are making tubes. Basically you got your Chinese and you got your Sovietish stuff. The more you pay for the tube you are paying for packaging, hype, advertising, hype and hype.
Best thing you could find would be a quad of NOS matched USA tubes no matter what they were. They will be expensive.

Next best thing in my opinion--worthless to everyone except me---would be to buy a simple matched set of Sovtek whatevers that are advertised as 6l6 copies. Get them online or at a music store and pay as little as you have to. I used to buy dozens and dozens of these to repair Fender amps and never had a problem with any of them. They are reasonably priced. If you knew the bias setting on your amp, if it is a fixed bias, you can buy tubes rated according to output when testing that you could just plug in and be assured of getting close to your best sound.

You say you biased the amp by "ear" by listening to the hiss. There is a better way that will assure the best results.

Take a dig meter that reads in DC MA. Put the red probe on your output center tap and the black probe on pin three of the second and then the third power tube of a quad or the left tube of a set of two. The reading for a quad of outputs should be around 60ma. per side, 30ma for a set of two.

You do not need matching tubes or adjusting the bias..that has been designed for those tubes to not need to be matched or the bias
adjusted. Tom Walker Leo's partner designed those MM amps that way.

I am happy that you like your HD 150..I have two of them and in my opinion they are the best that I have played through.

I use 6L6 tubes. the 6550 were too hot and caused filamemt rattle and excessive heat.

Question,,look at the back of your amp where
the power tubes are located, is there a metal
plate shield behind the power tubes?? let me
know. This was an in field modification to reduce the heat from the tubes.

5881 Tubes will work. 6550's as well..but a good set (if there are any) 6L6's will be best. No Bias adjustment is necessary.

The Tubestore was always good to me. They take returns no problem when the tube was bad.

This guy looks good if you are into the NOS thing:
http://www.tubemonger.com/

I have had good dealings with this guy:
http://www.nebsnow.com/LordValve

Bob

I also had a Music Man 115-HD which I bought from Autry Rutledge in Tulsa in 1981. I sold it and have been sorry every since. I looked everywhere for one with no luck. I found that there were several 212HD's showing up on ebay with the 150 watt chassis.

I bought one, removed the baffle with the two 12's, made a new baffle and installed an old EV 15" that I had removed from the original amp.

I now have a 115HD which is about 2" shorter than the original but still has that same sweet sound.

As to the tubes running cool, the output stage is designed to shut down when there is no signal incoming. The tubes only draw filament current until a new signal shows up. That's why they stay reasonably cool.

Only sosmeone who has owned one of these great amps can appreciate them. They are very heavy to carry around but that is a small price to pay for the sound you get.

------------------
Mike Brewer

I have thought about replacing the caps but this amp is so clean and clear I have put that off for the time being. They are relatively easy to change and are not really very expensive. I think that if they were starting to deteriorate, a significant hum would develop.

I have some problems with my hearing, particularly on the high end. However, I like a big full tone and I rarely set the treble above 4. I set the base on 10 and then play around with the middle until I get a sound that fits the room.

By the way, Autry lives about a hundred miles North of me in a little town called Noxapater, Miss. I see him from time to time at one of our association meetings here on the Gulf Coast.

------------------
Mike Brewer