Battle of the 6L6's ! - Page 3

MAMMOTHvolume · #41 11-25-2012, 04:32 PM

Quote:

Originally Posted by nashvillebill

Caution, don't try to sub EL34's or 6CA7's in the amp if it was designed for the 6L6's, different pinouts. And higher heater current draw than the 6L6.

They have the same pinout. You just have to make sure someone hasn't used pin one in an el34 design to put a component on, which they shouldn't be doing anyway.

nashvillebill · #42 11-25-2012, 04:48 PM

I think you're thinking backwards, Pin 1 is used on the EL34 for g3. Pin 1 is not connected to anything on a 6L6 and I have indeed seen some amps use the idle Pin 1 terminal as a connection point.

Yes, all the other pins are the same, but to me, having Pin 1 used on the EL34 and not used on the 6L6...is different pinouts.

Randyt · #43 11-25-2012, 04:52 PM

Quote:

Originally Posted by jnewmark

$490 for a quad ! That's more than I paid for the amp !

LMAO!!!

jnewmark · #44 11-26-2012, 07:09 AM

Quote:

Originally Posted by nashvillebill

Well, it might be working--sound might come out--but is it really working properly?

Before dumping hundreds of dollars of tubes into it, it would be prudent IMO to have it recapped and have that bias circuit checked. There's several electrolytics in the driver/bias circuit that--again IMHO--it would be wise to change out. 30 year old electrolytics are living on borrowed time.

GlennW's post is only partly written in jest.

I'll keep it in mind, although the seller told me it had visited a tech in the last year, for what that is worth. Really, I've been playing through it the last few days, and it sounds great and the most quiet amp I've ever heard.

jnewmark · #45 11-26-2012, 07:11 AM

Quote:

Originally Posted by GlennW

Alternative: sell that thing and let someone else enjoy pouring time and $$$ into it.

Ime for 6L6GC's the old Sylvania STR-387s sound better than =C='s and RCA BP's, but that's for guitar in the amps I tested them in.

It appears your new jewel is going to be a major PITA; so I'd move it along and get something else.

It's ok, you have tube fever right now, but in a few days you'll be able to think straight again.

Not a major PITA at all, and I have other amps in case this one goes down, but thanks for your input.

Crater · #46 11-26-2012, 08:55 AM

I'm using JJ 6L6GCs in mine and haven't had any issues. You don't need to buy NOS tubes for this amp.

I had Sovtek 5881's in there for many years, and I had to re-adjust the auto-bias circuit to compensate for what I presume is the higher gain of the 5881s compared to the 6L6s. When I first put in the 5881s, the tubes' plates glowed red.

There's a trimmer pot inside the amp chassis, you (or an amp tech.) have to measure the voltage drop across a power resistor to figure out the bias current and set the trimmer appropriately.

Replacing the electrolytic caps is no big deal for a tech.

hdracer · #47 11-26-2012, 09:15 AM

Quote:

Originally Posted by nashvillebill

It's hard to go wrong with the Sovtek tubes, maybe not the most glamorous of tubes but they have always worked well for me. I've also got a pair of new EH 6L6's and they sound great too.

I was not impressed with JJ's, they rattled too much.

Overall, I guess I've been unimpressed with any of the Chinese tubes. And I'm pretty sure spacebassed is correct, Ruby tubes are relabelled Chinese tubes.

Similarly, Groove Tubes as well as Tube Amp Doctors also do not make their own tubes, they relabel tubes made by other manufacturers.

For a regular gigging amp, I'm not sure if I'd pay for NOS tubes. The prices are too high, and some of the current production sound just as good to my ears for a lot less money.

Only some of TAD's tubes are rebranded.
They do have quite a few exclusive tubes like the short bottle EL84 and the 6L6WGC. Being a smaller company their rebranded tubes do go through a in house testing unlike Ruby or GT.

GlennW · #48 11-26-2012, 09:43 AM

Quote:

Originally Posted by jnewmark

Not a major PITA at all, and I have other amps in case this one goes down, but thanks for your input.

Cool, good luck with it.

GBassNorth · #49 11-26-2012, 10:19 AM

I have the same amp MM HD150 (combined guitar and bass amp) and love it, it's a keeper and in mint condition. But considering it's age I am concerned as nashvillebill noted that I'm on borrowed time with the caps and maybe other components and possibly tubes as well. I was planning on having someone look it over and freshen it up as needed, so I'm following this tube discussion closely - hopefully the OP will get back after he's done his swap out to let us know what he ended up using and how well it worked or what he'd do different next time.
In the meantime does anyone have a lead on a reliable amp tech that is familar with the MM amps, they are quite a different beast from any other tube amp I've used (very high voltage, ss pre, tube power, seperate channels for guitar and bass, etc.)

jnewmark · #50 11-26-2012, 10:30 AM

Quote:

Originally Posted by GBassNorth

I have the same amp MM HD150 (combined guitar and bass amp) and love it, it's a keeper and in mint condition. But considering it's age I am concerned as nashvillebill noted that I'm on borrowed time with the caps and maybe other components and possibly tubes as well. I was planning on having someone look it over and freshen it up as needed, so I'm following this tube discussion closely - hopefully the OP will get back after he's done his swap out to let us know what he ended up using and how well it worked or what he'd do different next time.
In the meantime does anyone have a lead on a reliable amp tech that is familar with the MM amps, they are quite a different beast from any other tube amp I've used (very high voltage, ss pre, tube power, seperate channels for guitar and bass, etc.)

yes, I will keep adding to this thread as I go along. I'm making my way through the pertinent posts on the Music Man Amps site, although most of the input seems to be for the guitar amp combos. I'm trying to find out from the seller what, if any, his tech did to the amp, but I'm kinda leaning toward getting a quad of SED Winged C 6l6's, and just taking the amp in to my tech. There is alot of tech info at www.musicmanamps.com. Takes awhile to wade though everything, and most of the posts are years old, but it seems like a good source. But, I left this amp on all day yesterday, and started playing it last night and not a thing seems to be wrong with it, but I did used the low power switch. It is the quietest amp I've ever played though ! I even tried just the bridge pickup on my Jazz and no buzz at all. Don't know if it's the pups on the bass, but I have got that bridge pup noise before with this bass on other amps.

4Mal · #51 11-26-2012, 11:40 AM

I use the Winged C's in my Rd 100. They sound good and reputed to be the best at handling the high plate voltage. So far so good. Mine came from Tube Depot this go around. Normally I use NBS. I do not ever use EuroTubes.

jnewmark · #52 11-26-2012, 02:35 PM

Quote:

Originally Posted by nashvillebill

This amp is biased by a pair of transistors Q3 and Q4. If this bias circuit is not operating properly, you will promptly cook your tubes. Probably the service manual, if you can find one, will show the voltage that should be present on the resistors R39 and R40 that tie Q3 and Q4 to ground--unfortunately the schematic does not show that voltage.

I'll repeat this for those that are unfamiliar with this design: unlike conventional power amps, the biasing is done by a transistor circuit that delivers a constant current to the bias the tubes. Completely unlike any cathode bias or fixed bias scheme; this design is also found in the Peavey Classic VTX amp and their kin.

According to a tech who works on these amps : " No-the amp is "biased" by q5 and 6. r39 is in the splitter at the reverb circuit." There is no reverb in my head.

nashvillebill · #53 11-26-2012, 04:57 PM

Quote:

Originally Posted by jnewmark

According to a tech who works on these amps : " No-the amp is "biased" by q5 and 6. r39 is in the splitter at the reverb circuit." There is no reverb in my head.

Perhaps we're referring to a different schematic, the one I'm looking at shows Q3 and Q4.

http://www.pacair.com/mmamps//schematics/2100-150.pdf

spacebassed · #54 11-26-2012, 05:07 PM

I'm running SED winged C's in my Ampeg B18n and a friend is running them in a VT40 (585 volts) - they have no problem handling the voltages in either of those amps. The audiophile market has driven up the price of JAN Phillips 7581A's - there's no denying that they are great tubes, but for your purposes I think you'd be just as happy with the winged C's.

jnewmark · #55 11-27-2012, 05:37 AM

Quote:

Originally Posted by nashvillebill

Perhaps we're referring to a different schematic, the one I'm looking at shows Q3 and Q4.

http://www.pacair.com/mmamps//schematics/2100-150.pdf

Got this reply from another tech guy : " Correct, the cathode driver transistors in the 2100-150 schematic are marked Q3 and Q4. The BB-3 is biased the same way as the DB-3 board: Make sure you have just over 25mVDC to ground on the emitters. If you get two different numbers, the lowest should be 25mV. Fine-tuning with a 'scope and a tone generator is of course possible too. " I took a look at it too, and couldn't even find Q5 and 6 !

nashvillebill · #56 11-27-2012, 07:15 PM

Quote:

Originally Posted by jnewmark

Got this reply from another tech guy : " Correct, the cathode driver transistors in the 2100-150 schematic are marked Q3 and Q4. The BB-3 is biased the same way as the DB-3 board: Make sure you have just over 25mVDC to ground on the emitters. If you get two different numbers, the lowest should be 25mV. Fine-tuning with a 'scope and a tone generator is of course possible too. " I took a look at it too, and couldn't even find Q5 and 6 !

Glad this tech guy had the voltage to check on the resistors, wish they had noted that on the schematic!

jnewmark · #57 11-27-2012, 07:54 PM

I decided on the SED Winged C tubes, after checking out alot of reviews. The guys at TCTube will burn them in for me, and also check voltage to be sure they can take the HD150. Then a visit to my tech, who is also a bass player and owned one back in the day. I gotta say though, it sure does sound sweet now, even with the mismatched tubes. Must be a very forgiving amp !

derridiandrift · #58 12-02-2012, 08:14 AM

Quote:

Originally Posted by jnewmark

I decided on the SED Winged C tubes

I think you'll be very pleased, but be sure to post back.

jnewmark · #59 12-02-2012, 08:17 AM

Quote:

Originally Posted by derridiandrift

I think you'll be very pleased, but be sure to post back.

Will do; goes to my tech tomorrow. Of course, with most tech guys who have their own shop, he's up to his eyeballs in work, so it will be awhile.

jnewmark · #60 01-10-2013, 11:48 AM

Quote:

Originally Posted by derridiandrift

I think you'll be very pleased, but be sure to post back.

In a word " WOW ". I don't know if it's the new tubes ( and caps ) but the amp seems to have more oomph, and, I don't know why, but the eq seems to have muscled up also, especially the Bass control, which I can't get past 3 or my windows start rattling. Since I am going for clean power, I max out the Master and get the channel volume up to about 4 or 5 and it's way loud enough for me. I would definitely give the nod to the SED Winged C 6L6 tubes. Not sure a tube amp is really my thing yet, and I have only tried it with my 212 loaded with 3012HO speakers, which are not known for serious bottom. When I get the chance I'm going to try it with my old 215 cab.