1 post / 0 new

Svetlana tubes


Larryl Natalini
Posted on Friday, June 07, 2002 - 04:10 am:   

I really like Svetlana's, but they seem to go micro-
phonic a little sooner than they should. I've heard
they last a few hundred hours. Disappointing! I'm
going to try JJ's or just buy Svets more often.
Are Sylvania's really being made? Thought I would
have heard about that by now! Anybody know of a
supplier? Also looking for MM values of Sprague
electrolytics- small order suppliers.
Steve Kennedy
Posted on Friday, June 07, 2002 - 10:28 am:   

JJs are well thought of in most circles as are the Svetlanas.

You can "stretch" tube life by running your amp in low power unless it is absolutely necessary to switch it to high power.

You can try these places for the caps:


Michael Kaus
Posted on Sunday, June 09, 2002 - 08:15 am:   

I have been using JJ's in my 2-10 65 for about six months now and we pretty much work every weekend Fri and Sat. They have been great sounding tubes, so much so that I have all but retired my JBL Twin(too stinking heavy-AND it's in a flight case!), so I am really happy with hem. Check them out at www.eurotubes.com. Bob is real cool and helpful. Tell him you are using them in a MM and he will tell you to use the EL34L's as they are suppose to handle the higher voltages better. Sound great and they are REAL reasonable. Mike Kaus.
carl from AUS
Posted on Thursday, January 16, 2003 - 04:10 am:   

i have svets, and used over 2 years now, my amp sounds great but the valves rattle. is this the "filiment" (dont know tech name) inside vibrating against the glass? my previous valves did not do this. is this bad?
thankyou in advance.
carl from AUS again.
Posted on Thursday, January 16, 2003 - 04:11 am:   

what are JJ's?
Posted on Friday, March 21, 2003 - 07:44 am:   

JJ's are a brand of tube that come from
the Tesla Co.

Nicola Tesla and J.J. Thompson were contemporaries.
Posted on Friday, September 12, 2003 - 02:49 pm:   

The Svetlana information provided in the first post of this thread;

"...they seem to go micro-phonic a little sooner than they should. I've heard they last a few hundred hours..."

is COMPLETELY bogus. The Svetlana 6L6GC is second to none.

Buy a matched quad and you've done the best job you can.

Also as S. Kennedy has stated innumerable times,
on your 2__ HD combos leave the back ohm switch set for 4 and the front power switch on low.
Posted on Friday, October 22, 2004 - 08:57 pm:   

Hey, I have a 210-HD130 that needs tube replacement.
Do I have to re-bias if I buy a matched quartet?
Steve Kennedy (admin)
Posted on Sunday, October 24, 2004 - 09:35 pm:   

It is ALWAYS a good idea to check the bias on a new set of tubes. Buying a matched set ensures that the four tubes will be matched to each other but this has no bearing to how they will perform as a set in YOUR amp.


Posted on Wednesday, October 27, 2004 - 12:58 am:   

Hey thanks a lot for the info Steve! This website is an amazing resource. I just had a couple of questions about biasing tubes.

#1 I noticed this posting on another thread here

Electro-Harmonix has released a Russian-made copy of the Philips/Sylvania "big-bottle" 6CA7 output tube! These are physical copies of the original Sylvania 6CA7 tubes that most pre-1980 Music Man amplifiers shipped with from the factory.

These look like the best bet for use in Music Man amplifiers... and should be able to withstand shock and high voltage better than most (if not all) EL34 types.

Since this is an exact physical copy of the original tubes would I have to bias them anyway? My guess is probably yes but I thought I'd ask anyway. Maybe save some money....

#2 Also....what happens if you don't re-bias the amp with the current tube set. Does it cause damage to the amplifier or the tubes?

#3 And finally.....do you know any reputable technicians who work on music man amps in the San Francisco Bay Area?

Once again, I thank everyone on this site for such a vast, helpful amount of info.

Steve Kennedy (admin)
Posted on Thursday, October 28, 2004 - 02:02 pm:   

The Electro-Harmonix 6CA7 tube DOES look like a close copy of the original Sylvania tube as far as the internal construction goes. It is a bit different in physical shape and probably in the vacuum and "formula" used in creating the emissive materials.

Since it is not being manufactured on the same machinery or tooling as the original it will probably not be an exact copy but definitely better for high-voltage use than an EL34 because of the increased element spacing.

Even closer to a "real" 6CA7 may be the new Groove Tubes US made 6CA7GT that uses the original GE Tooling and "recipe" (just as the GE 6L6GT that they also build in the US). These are spendy and I have no personal experience with them but if you can justify the expense they are probably a dynamite tube!

The 6CA7EH is probably the biggest bang for the buck in this comparison. I always keep one eye over my shoulder when running EL34s in a Music Man on high-power and using a real 6CA7 would go a long way towards stopping that habit!

Bias: Tube bias is simply a measurement of the DC current flow through the tube when it is just sitting there (no signal through it). It is sort of a "head-start" for the tube to conduct your guitar audio signal when it makes it to the tube. If the bias is too low, there will be increased cross-over distortion (not a "good" kind of distortion but pretty low level compared to distortion generated on purpose for tone) and the amp will tend to sound more sterile and life-less. It is a bit like running a car too rich... it will actually run cooler but it doesn't run as well or efficiently as it should.

Running a higher bias increases operating temperature and usually improves the sound until you get past a certain point (as you approach Class A operation, which would be a REALLY high bias setting!) where "thermal run-away" can occur. Increasing the bias cause a temperature increase AND temperature increases cause the tube to draw more bias current. Once you turn the bias up to the point that results in the tube not being able to settle to a static operating point, it "runs-away" thermally. Increasing temperature causes more bias current which increases temperature which causes more bias current... this will continue to escalate until the plates of the tubes are glowing red or orange and you either pop a fuse, burn-up tubes or overheat an output transformer (or all three!).

Different tubes will draw different bias currents from the same amp circuit because of differences in internal construction, gain and vacuum/gas quality. This is why you really want to re-bias (or at least check the bias) in a new set of tubes (only replace them as a set, not individually) to ensure that they are operating somewhere near where they ought to be.

A happy amp is neither too cold or too hot on the bias. It is a balancing act to get the most optimum sound quality, operating temperature and tube life. Once you deviate from the optimium area, one or more parameters will suffer while others may improve.

Normally simply changing tubes to a known good set doesn't absolutely require a re-bias, but if you don't know where you are to start with it is a gamble (albeit a small one). It is safer and good insurance to always check the bias before and after tube swapping.

If you don't want to be reliant on a local tech for just checking the bias, this can be done externally with a "bias tool" and a voltmeter. I bought my dual bias tool on eBay for about $35 or you can build your own if you are into electronics.

I can't help on the technician, but any reputable tech that can handle Fender and Marshall should be able to bias a Music Man if you provide the biasing instructions and schematic for your model available on this web site.


kenneth m. warman
Posted on Saturday, December 04, 2004 - 09:01 pm:   

Hey: not being a tech(just an old hippie musician) I purchased one of those dual bias testers for my early 210-65(has the 12ax7 tube) what should the reading be using a digital mm on the dc mv scale
Michael Kaus
Posted on Sunday, December 05, 2004 - 08:02 am:   

It really depends on what your actual plate voltage is. The MM's run close to 700v on the plates so you can't bias them like you would an EL34 in a amp with lower voltage. The EL's are considered to be 30 watt max rated tubes so 70% max disp is considered to be the max, so that's 21 watts @70 percent. If you figure out that you have 700v on the plates, that means that you can technically have up to 30mA's of idle current. Trust me, that will probably eat any new production tube out there. The MM amps had a bad habit of eating tubes back when they were new and were using tubes that were a lot more robust than what we have now. A also don't like their 1/2v at point Y theory fromn back then. We do know a little more now about the subject. I bias my MM's at 21-23mA of idle current with no signal and master on zero. I get great tone and just as importantly. THEY LAST. Also, do not buy cheap tubes. It's not needed to buy NOS but get some good ones. The newest JJ E34L's series is what I use and they seem to hold up well. Mike.
kenneth m. warman
Posted on Monday, December 06, 2004 - 09:03 am:   

Michael: Thanks for this info. I also bought the electro-harmonix version of the big bottle 6ca7 mentioned above, just wanted to check bias to be sure everythings good. I checked with these new tubes and its at 26ma on one tube 27 on the other I should lower this to your recommendations?
michael kaus
Posted on Tuesday, December 07, 2004 - 04:50 am:   

That's not too bad. It's a little high but probably safe. I would probably lower it if it were mine since my amps gets worked pretty hard for 10-15 hrs per week. If you are a strictly home player with a scattered schedule of playing, it should be all right. I just push mine pretty hard for what they are so I have to bias on the conservative side. Try 23ma-you will probably see no change in tone to speak of and you get to play with your new bias gadget thingy that way. The more you do, the more you learn. JUST BE CAREFUL-these are wild animals and they DOOOOOO bite! Mike.
michael kaus
Posted on Tuesday, December 07, 2004 - 04:57 am:   

For KDOG's question about biasing, if you purchase tubes from a dealer that grades their tubes, you can bias your amp once and then buy the same grade of tubes that pull the same idle current as the one's you have. That way, you can bias once and just order the same tube numbers that you have. The only problem with this is in that you have to get your tubes from THAT DEALER. Anyone else's grading system won't mean squat. Just food for thought. I check/adjust bias on amps even if they are SUPPOSED to be the same number as before. You never know and I would hate to smoke somebody's amp that I was working on because I was lazy! Mike.
Posted on Saturday, December 24, 2005 - 10:00 pm:   

Hi all,
I have been using the Winged C brand EL-34's. In my humble opinion, they sound incredible and richer than the jj'S.
mike kaus
Posted on Sunday, December 25, 2005 - 05:28 am:   

Winged c tubes are very good tubes for new production. I have used them and they sounded great too. They did seam to start rattling awful early for me(in the 4 sets I used) so I went with JJ's and have had long life and great tone. Mike.
Peter Maziar (mosfet)
Username: mosfet

Registered: 11-2006
Posted on Tuesday, March 18, 2008 - 02:08 pm:   

My Svetlana winged Cs rattle too, and they starting doing that at very low hours of usage. I attributed it to the heavy vibration due to the HD150s power, and the 4 built-in 10" speakers. Comments?

Re: Biasing an HD150 amp
How would I measure the current through the tubes? The bulletin I read stated that you measure voltage across the 3.9ohm resistors in the phase inverter, and set the lower of the two to 25mV, and the higher of the two to not more than 55mA.

Re: amp impedance
I am running mine on low power, and 8 ohms. The speakers read around 6ohms each on a digital multimeter, and 6 ohms total for all 4, the way they are hooked up from the factory. Is 8 ohms on low power appropriate?
Steve Kennedy (admin)
Username: admin

Registered: 03-2002
Posted on Tuesday, March 25, 2008 - 03:51 pm:   

It sounds as though your speakers are wired properly and 8-ohms is the proper setting for this configuration.

If all you have is a multimeter and an adjustment tool, you have to take the amp chassis out of the cabinet and get into the guts where the the high voltage also lives (potentially deadly I might add).

It is MUCH safer to buy a Bias Adapter tool (a "dual" tool is best) that has sockets that can be inserted between a tube (or a pair) and the amp, then you insert your multimeter all set up for current mode. Then all you need to do is pull the chassis back far enough to gain access to the bias trimpot adjustment and adjust the control for an average "at rest" current (no signal) to 15-23mA (using a plastic adjuster tool, not a metal screwdriver!).

The lower the current, the lower the tube temperature and the longer the tube life, but the tubes tend to sound better towards the higher end of this range.

Checking the tube current in this matter (after a a period of warm-up and stabilization) for ALL the tubes will let you know what kind of shape your amp's output components are in AND how well matched your "matched set" of output tubes actually is.

BTW... if you follow the Factory Service Bulletin's biasing instruction you wind up with a 6mA bias current! They did this to ensure long tube life and survival through the warranty period! The need 3 times this amount to start sounding good with modern tubes.

Peter Maziar (mosfet)
Username: mosfet

Registered: 11-2006
Posted on Friday, March 28, 2008 - 07:33 am:   

Thank you for your response, Steve. I am not afraid of the amps guts, I just am not sure how to check current because of the way Music Man wired these output tubes. Biasing does seem low with these new tubes - they start to distort on very low volume, and my 'old school' tubes never distorted until at least 6 on the pre-amp dial. These tubes are supposedly matched to run at 42mA. I am going to try biasing them by using a scope, and turning up the bias until crossover distortion disappears. I suppose I could measure resistance of the output transformer primary windings, measure voltage drop across them, and calculate current, then I suppose I would have to divide current by two because there are two power tubes on each tap. Would that be right? Please let me know if that makes sense. I will be posting my findings here in any event.
Peter Maziar (mosfet)
Username: mosfet

Registered: 11-2006
Posted on Friday, March 28, 2008 - 07:57 pm:   

Biased according to the Music Man service bulletin, which is to say 25mV from the emitter to ground across the 3.9 ohm emitter resistors (the higher of the two not to exceed 55mV), my tubes had pronounced crossover distortion (under-biased), as seen on my scope. Turning up the voltage to 50mV on the higher of the two (the lower of the two was around 36mV) eliminated the crossover distortion. I stopped exactly there. I bet that is good bias for these tubes.
Doug Spears (douglasspears)
Username: douglasspears

Registered: 10-2008
Posted on Friday, November 07, 2008 - 04:42 pm:   

I'm getting a lot of tube rattle from some brand new winged "C" tubes....Russian made. Real bad. Any recommendations of a good "non-rattly/low-rattly" tube?

Also,,,,,above it says to run 2__ HD combo's on 4 ohms. Why? Rattle? Tube life?

Lastly, getting a lot of buzz from the amp....ESPECIALLY with the reverb tank wires connected. They seem to act as an antenna. Is that normal? This buzz is coming thru the speakers when nothing is being played....no guitar plugged in,,,nothing. It gets louder the louder I turn the amp. I can kind of even almost hear it thru the music when I'm playing!?!? Normal?

- looking for a good MM tech in ATL

Bill Traylor (bozzy369)
Username: bozzy369

Registered: 02-2008
Posted on Saturday, November 08, 2008 - 07:34 pm:   

Doug ,it does sound like you have some real rf stuff happening here,it could be the tubes,but musicman amps have always been abit rf sensitive,make sure every ground is intact and working ,also this site has updates from musicman reguarding the rf prob and how to fix it .so try that ,maybe new tubes,i've even heard of guys lining thier chasis with aluminum or copper foil ,like sheilding a guitar,if you have a close tv,floresant lights stuff like that your amp will let you know .
Peter Maziar (mosfet)
Username: mosfet

Registered: 11-2006
Posted on Thursday, December 25, 2008 - 08:04 am:   

Doug, my winged Cs rattle too, which is a shame - they sound great once biased to minimize crossover distortion. C'est la vie. Regarding the reverb buzz, my HD150 did the same thing, but I managed to eliminate the noise by cleaning and crimping the RCA reverb connectors. I also cleaned the reverb pot with contact cleaner. If nothing else helps, you may need to replace the wiring and connectors to reverb tank. I hope this helps.
Mike Kaus (mm210)
Username: mm210

Registered: 05-2006
Posted on Friday, December 26, 2008 - 08:07 am:   

You know, it's a shame I keep hearing about "C" tubes rattling. It does seem to be just the EL's though. Great sounding tubes, just not real rugged. I STILL swear it depends on where they're shipped from and how. On a nothe note, the JJ's hold up for me and mine. I nkow peole who swear by Ruby's but I've had NO luck with them. Go figure.
Chuck Bryden (cbryden)
Username: cbryden

Registered: 12-2006
Posted on Sunday, December 28, 2008 - 06:55 am:   

+1 for the JJ tubes. I have had mine in my amp for over two years, biased to about .49 volts at the magic point, just gone through a year of gigging at least once a week, I play loud, early on I used an attenuator to crank the amp and leave the volume low, and they are still kicking and sound great.

One thing though, I got a small $4 ac fan at walmart and always have that blow air over them. I figure it can't hurt and I hope it helps - with everything.
Anthony Hennessy (franzoni)
Username: franzoni

Registered: 01-2008
Posted on Wednesday, December 31, 2008 - 04:16 am:   

i bought a set of JJ KT 77's for my HD130 2x12 when i was changing the caps... i noticed a very,very slight hum if you put your ear up close to the speaker but thats how faint it is....i also got the reverb back working so it could also be something to do with that but it's so faint i'm not too bothered..i,m very happy with the sound out of the amp..i also went with JJ's on the filter caps..i don't know if it's the valves or the new caps but the tone is really sweet with loads of twang and shimmer without the ickpick treble i used to get sometimes...before the amp went kaput i was even considering a speaker change to see if it would help...!!! don't need to do that now.....on a side note i read in a post this forum somewhere that the speaker jack on these amps can be a ticking timebomb for going belly up,so as a precaution i rewired the speaker cable with some good quality speaker cable and a brand new neutrik angled jack plug.....