Stupid Question: How Do Non-bias-matched Tubes Affect Sound

[peterp]

My Lonestar Special was making white noise, so I took it to a shop that builds amps to have it fixed. When I talked to them on the phone, it sounded like they knew all about Mesa and he mentioned installing a bias adjust pot so that the amp could be matched to any tube. During the service, however, they didn't install a bias pot and I think they just put in new "JJ" tubes (but not specifically matched for Mesa).

When I listen to the amp, it sounds very harsh now on both clean and with overdrive. I know non-matched tubes are hard on the power supply, but will they make it sound bad also? Sorry, I know this is a stupid question, but I'm just shocked that a amp-building tech would deliver something sounding so bad. I'm trying to determine if it's just my imagination or if t really sounds bad. The service was not cheap (at all) and they only replaced 6 tubes (4 power and 2 preamp).

I'm trying to figure out what to do next. I think what I will do is just ask them to take the tubes back (I will eat the labor costs) and then order a Rock & Blues tube set from Doug's Tubes. I'm open to any advice since I am a newbie at tube replacements.

 

[peterp]

The short version of my question is: Is it normal for stock JJ tubes to sound bad?

I know JJ's are good tubes in general, but I mean off-the-shelf JJ's without being specifically matched to Mesa LSS.

 

[plan-x]

IDK, I would venture a guess....yes. If one tube is testing hot and another cool, and they are matched together, well then boom! Outer tubes are the pair and inner are the other. Take the amp back and complain that it sounds like a##. Tell him to fix it since his work was not satisfactory. Refuse to pay any more money. You got nothing to lose and maybe something to gain. Squeaky wheel gets the grease. I ordered my set of tubes from Eurotubes and have been totally satisfied. You can actually get them from mesa also. Doug's ought to be fine.

 

[peterp]

IDK, I would venture a guess....yes. If one tube is testing hot and another cool, and they are matched together, well then boom! Outer tubes are the pair and inner are the other. Take the amp back and complain that it sounds like a##. Tell him to fix it since his work was not satisfactory. Refuse to pay any more money. You got nothing to lose and maybe something to gain. Squeaky wheel gets the grease. I ordered my set of tubes from Eurotubes and have been totally satisfied. You can actually get them from mesa also. Doug's ought to be fine.

Thanks for the feedback. I'm a neophyte on tubes, so wanted to get some feedback before I go back to the tech. I was very (very) adamant about having tubes correct for Mesa when I brought it in and they still didn't do that (they did match the tubes to each other, but apparently not to the Mesa fixed bias). I just don't think this shop has the ability to do it right and they also only replaced 6 tubes (though the service cost a lot more than a full tube set), so my guess is the others will fail soon. At this point, I just want to gracefully return whatever I can from this service, lick my wounds, and then replace all the tubes myself.

Thanks for the tube recommendations. I've read here that Euro Tubes or Doug's Tubes sound better than the stock Mesa tubes, so I'm inclined to use those. I was attracted to Doug's Tubes because they seem to use a cocktail of tube types which seems like it might be better tailored to optimize sounds. Are the Euro Tubes a cocktail also or they all JJ's? Basically I'm deciding between EuroTubes Gold Pin kit for LSS or Doug's Tubes Rock & Blues for LSS.

 

[plan-x]

Eurotubes are all JJ"s. I did the upgrade to JJ's when I was disappointed with a set of Mesa's from the Factory. It left my amp flat with no bounce. The difference was fairly impressive considering that the Mesa were factory spec'd. They were Chinese tubes. I hear they use JJ's now. That is not the issue, it's the spec'd rating, Mesa is conservative with there fixed bias amp tube values. Thus leaving the amp lifeless. A 6 tube change is minimally acceptable assuming it entails V1, V2, and the quad. These are directly related to the sound while the others are not as important since they are just powering the reverb, loop, and phase inverter. EHX tubes has a color coded system that you can choose the desired value to match the spec's for one's amp. The red or orange color (I forget) is the one Mesa recommends for the LSS/LSC. So one can pick up tubes without a middle man. And supposedly Mesa honors warranty with the EHX tubes within spec. Having a middle man allows for some designed performance. In my case I asked for a High headroom set. So they spec'd it accordingly ie; lower performance value on V1/V2 to minimize headroom breakup along with higher performance power tubes to put that decreased breakup out there with output volume.

 

[peterp]

Eurotubes are all JJ"s. I did the upgrade to JJ's when I was disappointed with a set of Mesa's from the Factory. It left my amp flat with no bounce. The difference was fairly impressive considering that the Mesa were factory spec'd. They were Chinese tubes. I hear they use JJ's now. That is not the issue, it's the spec'd rating, Mesa is conservative with there fixed bias amp tube values. Thus leaving the amp lifeless. A 6 tube change is minimally acceptable assuming it entails V1, V2, and the quad. These are directly related to the sound while the others are not as important since they are just powering the reverb, loop, and phase inverter. EHX tubes has a color coded system that you can choose the desired value to match the spec's for one's amp. The red or orange color (I forget) is the one Mesa recommends for the LSS/LSC. So one can pick up tubes without a middle man. And supposedly Mesa honors warranty with the EHX tubes within spec. Having a middle man allows for some designed performance. In my case I asked for a High headroom set. So they spec'd it accordingly ie; lower performance value on V1/V2 to minimize headroom breakup along with higher performance power tubes to put that decreased breakup out there with output volume.

Thanks, this is very helpful. I called Eurotubes and spoke to Eddie for a while. Based on that conversation and your comments, I went with their standard LSS kit and requested the cooler side of the range. I was very happy with the sound with the original tubes until they went South, so I will be pretty thrilled if it sounds better with the Eurotubes JJ's.

I called the tech, he is fine with taking back the tubes he sold me and will install the new Eurotube tubes for free. I'm happy enough with that solution.

 

[rfrakes]

I would caution not using the non MB matched tubes. The amp can go into runaway,

stress the transformers, blow the fuse and a Rectifier tube. I went to one of my local music shops.

I needed what I thought was 1 tube since I was using it in 5 watt Class A mode. Well their version of

Class A uses a pair of tubes, and they runaway. Luckily the transformers are robust as well as the hookup wire.

It had to be shipped to Mesa Boogie. The Class A design is proprietary and most non MB service center have trouble fixing.

I would take it back to your tech and get a refund on the power tubes, get 2 matched sets of EL84s from MB. My guess is it will sound awesome again.

 

[ifailedshapes]

My Lonestar Special was making white noise, so I took it to a shop that builds amps to have it fixed. When I talked to them on the phone, it sounded like they knew all about Mesa and he mentioned installing a bias adjust pot so that the amp could be matched to any tube. During the service, however, they didn't install a bias pot and I think they just put in new "JJ" tubes (but not specifically matched for Mesa).

The Lone Star Special is cathode biased. In other words, as long as the power tubes are a matched pair, it doesn't really matter which rating they are, since the amp will adjust itself to the tubes. Some people call cathode biased amps "self biasing" because of this.

Also, FWIW, I've never had a problem with JJ's.