Sorry to bother you guys again. I have been posting in "Help!" recently and got no replies. But now I have a more specific question.
I live in rural France. I recently had my 212 HD-130 serviced in Toulouse. The tech replaced two capacitors in the power section, all the power tubes, and adjusted the reverb unit. He rebiased the amp, which he said had been biased very poorly. He got rid of a loud 50 MHz hum I had.
So now, he recommends that I keep the Master Volume at "10," when I want to play at high volume. The difficulty I am having is that if the preamp volume is set higher than about "2," or maybe even "1.5," the amp starts to distort and chords, in particular, do not sound good. So a typical setting for me now is Master at "10" and preamp volume at "1.5," which is fairly loud and sounds clean. I can get more volume without distortion by going through my Boss multieffects pedal but not directly through the amp. Any increase in preamp volume creates distortion. It seems odd to me that I can get more volume without distortion using the effects pedal than I can get directly through the amp.
So the question is, has this amp been biased correctly? This tech is pretty adamant that this is the proper way to bias the amp, but it seems very odd to me that the preamp volume creates distortion at such low settings. I've talked to two musician friends today, and one thinks this setup makes no sense, the other thinks that some "purists" play their amps this way and that the bias could be correct, or close to correct. I was playing and rehearsing at fairly loud volumes with settings of "5" on Master and "2-3" on the preamp volume before the low frequency hum started.
I have been in email contact with the tech about my concerns, and he seems willing to try to help me or work with me, but at the same time, he is French and has a certain authoritarian quality to his personality.
Thanks very much in advance for your input.
Bias
Hi yep they can give that impression ok!! However try this guy here in Ireland. He loves the MM amps. Sorted an awkward intermittent problem with my MM 212 One Thirty. His site is info@audiotronix.ie
I love playing through my amp. Get a fabulous rich clean tone. Hence my email address mrj335
Good luck.
An HD-130 should be able to
An HD-130 should be able to run at least around 6 - 7 (preamp) with the master on 10 before it really starts breaking up. At that point - the speakers and your ears would be distorting more than the amp would be :)
My concern is that your tech may not understand Musicman amps. They do not bias the same as Fenders, Marshalls, etc... If he set the bias on the Musicman like he would set it for a Fender then your amp is not going to be very happy right now. Actually - it might be screaming in pain.
Print a copy of the first post in the following thread.
http://www.pacair.com/mmamps3/node/1487
Take him a copy and ask if that is how he set the bias. (Note: If your amp has a 12AX7 tube, use procedure #2. If it does not have a 12AX7, use procedure #1). If he refutes the method posted - find a new tech.
Just my 2 cents...
Break up
I will also add to codamedia that MY Musicman pretty much does the same thing only a LITTLE higher. It breaks up awful early but with the way I use it, It works for me. AND the amp IS biased correctly, even a little on the cool side actually. It is a 65 watt with tube inverter and I just have never gotten around to doing anything about it. I might also suggest that if it DOES have a 12ax7a as a PI, try a 12AT7 in that slot and see if it cools down the finals a little. It might be driving the hell out of them Mike.
Bias
Steve ( while trawling through the old forum back in 2002) you noted the following:
"Bias" is basically the current that flows through the amp's output tubes while at rest. It is a "head start" towards passing the signal you are trying to amplify. Too little bias and the tubes run colder, but they sound more "brittle" and lifeless. Too much bias current and the tubes sound wonderful but will burn-up quickly because of excess temperature (the tube's plate will glow red).
Excuse me if I am wasting your time. At Rest: is that when the amp is turned on with no guitar leads attached!! better again no signal going through it? I am trying to get my head around this bias.
You also recommended using a fan. Would this fan just move cool air around the valves?
In the above comment you explained Ohms Law. Thanks.
Bias
Think of the bias voltage as a water faucet. Less control voltage and you allow more water(electrons) to flow. The more control voltage, the more restriction and less flow. I won't get into the fact that control voltage CAN be positive too. We'll leave that one alone for now. But yes, the less voltage applied (in THIS case) to pin 5 of a 6CA7/El34 or 6L6GC the hotter the tubes will run and the less time they will last. They will sound GREAT- RIGHT up to the time they go Chernobyl on you. Fans are good. I use them on all my tube amps (except the vox-it's too little!) Mike.
Get another tech
Let's get realistic here: A properly working MM 130 amp will be unbelievably loud with the master at 10. Depending on how hot the input signal is (humbucker vs. single coil, active vs. passive, any booster pedals etc.) it should not break up at 3 or 4 - but would drive anybody listening away.
What's your location in France? I belong to a group of techs that work on tube amp equipment - there might be a member in your area that could help you out. I do not believe in swapping the phase inverter tube for a different type - the amp was not designed for it. If it doesn't work with a 12AX7/ECC83, something else is wrong and should be addressed. If your amp has the later cathode drive setup, it may be a problem with the driver transistors. Either way, it's something that a competent tech (French or otherwise) should have no problem fixing. Also, if the amp gets so hot that you need a fan to cool it under normal operation in a non-extreme setting, something needs to be fixed. MM amps are built with ample overhead and can get hot but will not get damaged by it (if everything is working within specs).
Sincerely,
Lars Verholt
Get another tech
Lars is your reply above meant for Ledocs!
I ask, as I was the one who mentioned the 3-4 volume.
Thanks.
It was Ledocs
Hi JoJo,
it was meant for Ledocs - if I'm reading your post correctly you are in Ireland, not France.
But yes, I should have written 'volume 1.5' and not '3-4'. Either way, the amp should not distort at this setting.
Sincerely,
Lars Verholt
3-4
Lars you are quite right. With humbuckers there is loads of volume at 3-4. Funny thing when I received your reply I was in France at Lourdes.
A tiny coincidence as the original query came from a guy in France!!!
However I love this amp ( 212-130) so much that I can't wait to turn it on to play through it.
What about a Musicman fest here in Ireland. All you guys could travel for a good time.
For what it's worth when I
For what it's worth when I ran my HD130 head with two 2x12 cabs, with the master on 10. I don't think I ever went past 2 or 3 on the volume setting. It was clean and it was loud, even for outside gigs. I remember folks complaining to me that they couldn't talk/hear each other at their tables. Aww, those were the days..
Most of the time I just ran on the lower power setting. And I didn't know about, or ever used a fan.
That's all I got, but I think your amp should be able to get very,very loud before any distortion kicks in. Good luck.!! Dave.