A couple of MusicMan 65 questions

radioegg · Post by **radioegg** » 29 Jun 2012, 22:26

I tried this over at TGP with no luck, got a couple of links to other forums, but honestly, I am a bit tired of signing up for yet another forum, and then yet another... So I ask here. Besides: TGP folks are probably too snobby to answer questions about a MusicMan amp, as it has only a 12ax7 phase inverter and 2 6ca7/EL34 power tubes. Besides that it Solid State. AND: The only places I really got any help was here, and over at the BYOC forum.

So here we go:

I can get hold of a MusicMan 65 reverb head on a long term loan, but it has a couple of issues: The tremolo doesn't work right (noisy somehow), and also the tremolo channel sounds very thin and with less output compared to the normal channel. Impossible to get a good sound out of it, but normal channel sounds GREAT! The guy who owns it thinks it might be the the 12ax7 phase inverter that causes this. Is this likely, wouldn't this affect the normal channel too? What else could be the problem?

Also there are EL34 power tubes in it. The original tubes are 6ca7. What's the difference here? I want to use the MM for Fenderish clean sounds, it's good with the EL34, but could I get more of the Fender-sounds out of it with 6ca7's? And could I even use 6L6's in it?

Thanks for any information and advice!

Tor

lead2203 · Post by **lead2203** » 30 Jun 2012, 02:11

radioegg wrote:I tried this over at TGP with no luck, got a couple of links to other forums, but honestly, I am a bit tired of signing up for yet another forum, and then yet another... So I ask here. Besides: TGP folks are probably too snobby to answer questions about a MusicMan amp, as it has only a 12ax7 phase inverter and 2 6ca7/EL34 power tubes. Besides that it Solid State. AND: The only places I really got any help was here, and over at the BYOC forum.

So here we go:

I can get hold of a MusicMan 65 reverb head on a long term loan, but it has a couple of issues: The tremolo doesn't work right (noisy somehow), and also the tremolo channel sounds very thin and with less output compared to the normal channel. Impossible to get a good sound out of it, but normal channel sounds GREAT! The guy who owns it thinks it might be the the 12ax7 phase inverter that causes this. Is this likely, wouldn't this affect the normal channel too? What else could be the problem?

Also there are EL34 power tubes in it. The original tubes are 6ca7. What's the difference here? I want to use the MM for Fenderish clean sounds, it's good with the EL34, but could I get more of the Fender-sounds out of it with 6ca7's? And could I even use 6L6's in it?

Thanks for any information and advice!

Tor

See if this helps..... http://www.music-in.de/pics/hd130b.gif
Check the trim pot?

GuitarlCarl · Post by **GuitarlCarl** » 30 Jun 2012, 04:13

I inherited a Musicman 65 combo and it is an awesome amp. Mine has no tremolo, so I can't help you there. but, I believe the El34's and the 6CA7's are a direct replacement, I have the original RCA's in mine and they have both numbers printed on them. I do want to put some new tubes in mine but she sounds so good now it's not on my priority list. Fenderish tones??? It's gonna depend on the cabinet you use. Maybe a 2 x 12 open back will get you there. In addition to the MM 12" in my combo I push a 15" in an old Teisco open back cabinet. sounds real nice with the bass boost on.

stonefreed · Post by **stonefreed** » 30 Jun 2012, 09:25

When you buy a Musicman amp it's always important to bear in mind that those old RCA 6CA7's could take 700 volts on the plates. The tubes were a much higher quality than present day production.This the voltage which is used in the poweramp section.
Tubes that are built nowadays aren't that rugged anymore and if you put a present El 34 in it the tubes are very likely to fail very fast.

So if you have to swap tubes , try to get hold of original powertubes or choose a tube which can hold the 700 volt plate voltage.

deltafred · Post by **deltafred** » 30 Jun 2012, 17:36

radioegg wrote:... The guy who owns it thinks it might be the the 12ax7 phase inverter that causes this. Is this likely, wouldn't this affect the normal channel too? What else could be the problem?

You are quite correct, if it were the phase inverter it would affect both channels the same.

All sorts of things could cause the problem.

Try swapping tubes out of the normal channel into the tremolo channel if they are the same type.
It could be a capacitor gone leaky, or an electrolytic dried out.

As always, fault diagnosis over the net is a tricky business.