| Author | Message | ||
     Josue Roberto Lopez Lobo (jorololo) Username: jorololo Registered: 01-2008 |
Hello everybody, I just want to ask, if I can use my 210HD-130-12AX7, like 210HD-65, I saw the schematic and I want to know if is possible??? Any info will be appreciate. Thanks!!!  | ||
| Josue Roberto Lopez Lobo (jorololo) Username: jorololo Registered: 01-2008 |
Hello????!!!  | ||
| Bill Traylor (bozzy369) Username: bozzy369 Registered: 02-2008 |
ok,i'm not sure what you are trying to accomplish ,you basically have a 65x2,and being that depending on when a 65 was made it could be solid state preamp ,you are in better shape with that 12ax7 preamp.If its a case of wanting less volume,just turn the amp up half as much ,  ,just kidding,you could try a attenuator,that would let you dial in your perfect volume at the amp running at wide open,THD makes great ones ,and if you can find one the sholtz power soak ,or the Marshall powerbrake. I read on here somewhere were Steve told a guy if he was wanting more push less volume simply remove half the tubes,i do think this will change the amp from a class a/b amp to a class A amp,but that could sound great ,also there are tube adapters called yellowjackets made by THD ,they will make your amp like 1/3 of its original volume ,which would give you a really sweet 30 watt amp,and the best idea,go get on Ebay,the last time i looked there were a few 65's on there without destroying that 130,ok theres my ideas for this adventure,anybody else got any ideas, | ||
| Josue Roberto Lopez Lobo (jorololo) Username: jorololo Registered: 01-2008 |
Thanks Bill, that is exactly to which I talk about, i don't want to change any thing of my amp, i just want to know if is no problem, pulling 2 of the output tubes, the 2 of the sides, just adjust the bias and will work, this is ok??, will work?? sorry for not speak clearly, jorololo | ||
| Bill Traylor (bozzy369) Username: bozzy369 Registered: 02-2008 |
i found this in other posts:# Amps with four power tubes: A bit harder to understand, and quite a source of confusion. (Usually amps in the hundred watt range.) In general, again with some exotic amp exceptions (the Torres Engineering Double Dee Luxe design included) just having four output tubes does not mean the amp had two separate output/power channels, each with a separate pair of tubes. If it did, there would have to be two output transformers, PLUS, the power transformer, and two sets of speaker output jacks powering completely separate speakers. The most common “internet information” is that you can take two of the tubes out and cut the power in half - right, but which tubes? Again, the amp is a push pull amp, with the two tubes on the right being one side of the push pull circuit, and the two tubes on the left as the other side of the push pull circuit. Taking out the wrong tubes will, again, send the amp and the output transformer into crossover distortion - an ugly tone that no one can use. So which tubes do you take out? (Or disconnect.) Take a look at the drawing for clarity. Either the two tubes in the middle, or the two tubes on the outside. Not both right hand or both left hand tubes. Cut the power in half? Again, misunderstandings. This does not drop the volume to half, or anywhere close. All other things being equal, it takes 10 times as much power to make a sound appear to be twice as loud to our ears. So, the opposite is true, it takes 1/10th as much power to sound half as loud. Cutting from 100 to 50 watts is not 1/10th, it is only half. 10 watts would be half as loud (with everything else equal.) But cutting the power will allow the amp to distort or break up earlier, at a more reasonable volume. There are other concerns with removing or disconnecting tubes. The output transformer was made for the four tubes - there is what is called a “primary impedance” - a load that the amp and tubes expect at the input of the output transformer. For example, a 4 x 6L6 transformer primary may expect an impedance of 1,900 ohms from the tubes. Taking two of them out doubles that impedance to 3,800. You did not change the transformer, so now there is a considerable mis match and the transformer has no way to “fix” it other than putting out a different secondary impedance (to the speakers.) Depending on the “winds ratio” of the transformer, now the speaker impedance is wrong, doubled, or close to doubled. The amp will still work, but not as well. Why all this? Simple, a 100 watt amp with two tubes removed doesn’t sound as good as the same model amp really made as a 50 watt amp with the correct transformer. The “10 times” audio factor is also the reason audio taper pots are used in guitars and amps to control powered audio signals. The taper is adjusted so that 1/10th as much power appears across the pot at 5 as at 10, otherwise, we don’t hear very much of a taper at all, most of an “on-off” condition.Also:always run the amp at half power! | ||
| Josue Roberto Lopez Lobo (jorololo) Username: jorololo Registered: 01-2008 |
Thank you Bill, that information its so helpful, Only one question, I understand if I use the amp with only 2 tubes instead of 4, I have to run my amp in low power position, ok??? Thank you again! | ||
| Josue Roberto Lopez Lobo (jorololo) Username: jorololo Registered: 01-2008 |
BTW, all this its only for know what possibility of sound I can get with my amp, Thanks | ||
| Sean Flannery (flannery) Username: flannery Registered: 05-2010 |
Yes! I was wondering the same thing: Can you SAFELY remove one pair of output tubes from the One-thirty - and preserve the tonal character? The hope is that this would effectively shift the power selector from a 130W-65W option to 65W-35W option - and let you push the power tubes into breakup at 25% of full clean power. Logarithmically, that's... what, something like 2/3 maximum clean volume? Other amps can handle removing a tube-pair, as Bozzy mentioned (thanks!), but it probably won't sound "right." My Traynor YBA-3 is the same way; doesn't sound right without all four p-tubes. I'm looking to pick-up my first Music Man, and as a bass-player, I'd love to get 35W-tubey-grit in the bedroom from an amp that also brings 130W of low-end to house shows. For guitar-duty, though, I'm afraid the One-Thirty won't get that roaring-breakup at a reasonable volume, even at low-power. None available for try-outs locally (DC-area). So, Bozzy (or anyone?): why do you have to run the amp at half-power if a pair of tubes are removed? Why is the lower plate-voltage necessary? Thanks! (Post #2!) | ||
| Bill Traylor (bozzy369) Username: bozzy369 Registered: 02-2008 |
that question is answered in the 5th post,you can run a amp with 2 tubes at full power ,but it may not sound as good because of the impeadence mismatch,by taking the tubes out you are in effect making a better 50 watt amp,and there should not be a prob in volume most musicman amps are too loud to begin with . | ||
| Sean Flannery (flannery) Username: flannery Registered: 05-2010 |
Hmm... I guess I don't quite understand how the impedence mis-match would happen - I'd better keep looking at the schematic. I understand that it may sound better, but wanted to make sure it won't damage anything. Thanks! |