| Author | Message | ||
     Matt60 |
Hi there, i´ve a 210/65 with EL34 tubes, but i´d prefer using it with 6L6 tubes. The chassis is a 2275-65 w/o 12AX7 PI tube. I´d never thought that MM built these amps with 6L6, but just read in the Model Chart of this great site that these amps actually exist with 6L6!!! So, could i just swap in some good 6L6 (e.g. Svetlana) or better go with EL34???? Any opinion appreciated..... Matt | ||
| Terry |
Matt, Leave the EL34's in! It can be converted to 6L6's, but you have to change some resistors. It will not make that much difference. You cannot just change tubes and have it sound good. Musicman went to the 6L6's because they could not get enough 6Ca7/EL34 high quality tubes. They are just for power to the transitors. This is a hybrid amp., transistor, tube-powered. Good Luck. | ||
| brenno |
what the original tubes of mm amps.....? philips?? | ||
| Michael Kaus |
Most of the original MM amps(with PI tube) came with either Sylvania or Amperex tubes. I sold them with both in the same year, so it was luck of the draw. I had one with Amperex and with Sylvania. I agree with above, it's not worth changing to 6l6's. Try the JJ EL34L's- I think you'll like them. Mike | ||
| brenno |
you could inform a good regulation to blues in mine mm rd 112 with valves 6l6 svletana? i have a guitar with pickups single, in the case I would leave the button bright in off position to eliminate noises? | ||
| Jeff LaGrange |
I have a 65 reverb (12AX7 PI) head with 6L6s in it. I went to retube with EL34's and whoa, wrong tubes. It has Sovtek 5881 with a plate voltage of 700 (seems past the rating to me). Should I just retube with 6L6 or try to go back to EL34? The inside of my head shows EL34/6CA7 in those locations, but now I am learning that MM put 6L6s in after all. What to do?! | ||
| Jeff LaGrange |
I have posted this info recently, but I wanted to give a little more detail. I have a Sixty Five Reverb head (chassis #2275-65, serial number not handy) with a 12AX7 phase inverter. From what I gather, this seems to put it from the early to mid seventies. It has been working great since I bought it used 5-6 years ago, and I thought it was well past time to re-tube. I have been doing some tube amp research, and I felt comfortable with this task. I got the schematic (from this site) for my chassis, saw the 6CA7 bias trim pot note, read the schematic, and understood what I was supposed to be doing. I bought some 6CA7/EL34 tubes and started at it. I measured the bias setting (at the cathode) with my existing tubes, and it was about .38V instead of the expected .5V. No big deal. I then put in my new tubes, measured the cathode voltage, and it was 5V, not 1/2V. So I quick turned it off, and that is when I found out that my amp had Sovtek 5881WXT tubes, not the spec’d out 6CA7. The tube chart on the inside of my head says it is supposed to have 6CA7. But it has the 6L6 type tubes, with a plate voltage of 700V. I put the old tubes back in and set the bias to what it had been, then left, scratching my head. I have seen on this site that MM actually did put 6L6s in some of their amps, and maybe this wasn’t a previous owner that modded my amp. Here are my questions: 1) what are the pros & cons between the two types of tubes in this amp? 2) Is this truly the configuration my amp was shipped with? 3) What are the circuit changes that would have to be made to go between the two types? 4) does the .5v bias point still apply to the 6L6 type tubes? 5) is the 700V plate voltage standard in these amps? That is my story. I would appreciate any input that might be helpful in my predicament. Thanks, Jeff | ||
| Steve Kennedy |
Your amp originally shipped with 6CA7 output tubes. Depending on tube socket wiring, a 5881/6L6 type can be plugged into the same circuit but I am not sure off the top of my head what other bias-related changes might be required. I would do two things... check your amp against the schematic part by part in the output tube area to see if any wiring or component changes have been made. The amp may indeed have been modified to accept 6L6 tubes. The other thing is to compare the schematics of the 6L6 version of the Music Man circuit and the 6CA7 version to see if any changes were made that you might look for. You typically cannot put 6CA7/EL34 in an amp designed for 6L6/5881 types because the EL34 types draw twice the heater current and may burn-up the heater winding of the power transformer. Going the other way isn't usally a problem if attention is paid to proper tube bias. That said, it is always a good idea to stick with the original circuit and output tubes to ensure things work as designed. Steve | ||
| ph |
Hi folks, I've had two 210-65 combos in the eighties, one with 6L6's, one with EL-34's. I really couldn't tell a lot of difference at the time, so I traded the 6l6 off (groan). While we're on the subject I want to retube the one I kept. Is it true that I don't need to have it biased? | ||
| Michael Kaus |
If you have one of the cathode biased amps(without the 12ax7 Phase inverter), just plug the EL34's in and go. If you have the 12ax7, the bias has to be set to tolerable levels. These amps shouldn't have more than 15mA of cathode current. This is taking into account the 700 volts on the plates. Yes that is right and normal. I would suggest that you try the JJ EL34L's instead of the regular EL's. They do seem to hold up well and sound very good. Try Eurotubes.com and talk to Bob. Nice guy and helpful. They are also REAL reasonable. So much so that you can get a spare set as backup. I haven't needed them though and I push my 2-10 pretty damned hard at times and it works twice a week with our band with no complaints. Mike. | ||
| ph |
Thanks Michael, I do have the 12AX7's in the combo and a HD130 Reverb head which I just got. I also have been spending most of yesterday at work catching up on all the info in the zipped files....  While I understand the concepts about the amps, I'm not likely to break out a sodering iron on anything more than a cable repair, so I have to rely on others to do my maintenance for me. The problem is that I really don't have a reliable tech to go to in my area (Fayetteville, NC), I would really like to have both amps gone through and recapped. Anyone know of reputable techs in the southeast they recommend? | ||
| Marc |
Svetlana 6L6-GC's slap 4 into an HD-210 _____ . Righteous | ||
| al sansome |
I have 1978 112RP-65 which I bought second-hand way back in 1980.It has always been fitted with 6L6GC tubes but looking at your chart I see that originally it should have had 6CA7. What kind of difference in sound would I expect to notice by fitting the correct tubes? | ||
| infidell |
I've had some experience with both the MM 65 non-reverb head and a 130 reverb head. The 65 is fitted with EL34 tubes and the 130 is fitted with 6L6's. When thinking about which power tubes to use, think EL34 = MARSHALL and 6L6 = FENDER. EL34's have a real aggressive midrange-y tone, able to cut through. 6L6's have less high-end response yielding a sweeter treble, with a bigger bottom. EL34's clip harder and slower than 6l6's. A 6L6 power section will start to distort at lower volumes than an EL34 power section. EL34 amps are better suited for loud rock/metal styles. 6L6 amps are know for blues/jazz tones. Hope this helps! | ||
| john k |
Which tubes? I have a RD-100 head that I bought over 20 years ago and to my surprise, the original Sylvania tubes that were in the amp from the factory, were 1 each of a 6L6 AND an EL34/6CA7! I never saw that. The label inside shows 2 6L6's. I called my friend that has an electronics repair shop, and who now does most of the repairs for Guitar Center here in Chicago, and he checked the wiring and told me it was set for 6L6's. He put in new Sovtek 5881WXTs and the amp sounds great through my 4x12 bottom. Very Fender sounding, which was what I wanted. The person at the MM factory must have grabbed the wrong tube by mistake as they both look exactly the same. A few years ago I put in a set of Groove Tubes but I thought they sounded like garbage so I put the old Sylvanias back in and the sound improved. | ||
| MARVIN |
I HAVE JUST PURCHASED A MM RD112 THAT IS REALLY PRETTY NOISY.......IT SEEMS AS IF THE POWER TUBES HAVE A GLASSY SOUND TO THEM....I WANT TO REPLACE ALL OF THE TUBES, INCLUDING THE PREAMP TUBE, BUT I'M UNSURE IF THE AMP WILL NEED TO BE REBIASED OR NOT......PLEASE HELP!! | ||
| Steve Kennedy |
I assume from your message that this is a 112RD-50 model. All of the "50" watt models (112RD-50 and 110RD-50) are "self-biasing" so as long as the tubes match what should be in there, there should be no problems. If it is a 112RD-65 or 112RD-100 then you should have the bias checked when replacing output tubes, but these models do not have a 12AX7 tube like the 112-50 does. | ||
| T. ROGERS |
hi everyone: I have just restored my 25 year old MM RD112 100 EVL12..My tech has gone completely thur the chassic and everything thing is as should be. my question is; i'm using 6l6 groove tubes and i wish to know are there better tubes to be using in the amp? I have always used grooves since replacing the factory sylvania's .. I play country, rock, and blues thur a gibson lp with p90 pickups with lots of pedels.. I would prefer a bit more edge in the mid range.. hey thanks to everone for all the help in bring my amp back to new again..Steve this site is awesome..ty | ||
| greg |
here we go, sounds like the same issue, but i just want to make sure.. i have an 81 mm HD-150r(2275). when i bought it, it was tubed with el34's, which i have subsequently changed to E34L's. but the sticker on the inside of the amp that shows tube location has 6L6's on the graphic. there is also a 470 ohm 5% resistor across each of the tube sockets that are showing signs of over heating(starting to turn black in the middle) how would i be able to tell what the amp is wired for? | ||
| Roy Simison (froggy) Username: froggy Registered: 09-2006 |
I highly recomend these Phillips 6L6WGB tubes I have been runnibg them for years in my 6L6 amps they are rugged take the high voltage of MM amps and sound better than most http://thetubestore.com/jan6l.html |