using 4 x 6l6 on mesa boogie mark III simul class

[Joi737]

Hi,
could anybody confirm that its defenetely safe to run 4 x 6l6 in a simulclass given the quality on the new 6l6 valve tubes?i was reading that by fitting 2x &L& in the outer they will run hotter. perhaps possible to choose lower or higher bias point from the 2 valves to counteract the hot situation? i have 2 tungsol 6l6sc str in the middle slot bias point 36 and el34 in the outter . the amp sounds great but i want to experiment with 6l6.thanks

 

[bandit2013]

Mesa had a memo or an update on the Mark III manual some time ago. Not recommended to use 6L6GC tubes in the Class A sockets due to short tube life. You could opt for using a 6CA7 or KT77 if you wanted something different.

 

[GJgo]

In Mark II, III and V Simul amps the Class A pair is biased hotter & you want a 6L6 pair that runs a max of around 45 mA. The easiest way to deal with this is just use mesa RED, or maybe YEL.

For the Mark IVs they were biased colder in general and YEL or maybe GRN is good to go for the Class A pair.

I've only had one Mark VII (low sample size) but it was even colder, I bet you could actually use any tube color safely. You know, as they advertise.
Class A
STR445 YEL 28mA
STR440 GRN 33mA
Class A/B
STR445 YEL 19mA
SRT440 GRN 28mA

 

[user 41014]

You know, as they advertise.

lmao

 

[Joi737]

Mesa had a memo or an update on the Mark III manual some time ago. Not recommended to use 6L6GC tubes in the Class A sockets due to short tube life. You could opt for using a 6CA7 or KT77 if you wanted something different.

thanks very much

 

[Joi737]

In Mark II, III and V Simul amps the Class A pair is biased hotter & you want a 6L6 pair that runs a max of around 45 mA. The easiest way to deal with this is just use mesa RED, or maybe YEL.

For the Mark IVs they were biased colder in general and YEL or maybe GRN is good to go for the Class A pair.

I've only had one Mark VII (low sample size) but it was even colder, I bet you could actually use any tube color safely. You know, as they advertise.
Class A
STR445 YEL 28mA
STR440 GRN 33mA
Class A/B
STR445 YEL 19mA
SRT440 GRN 28mA

thanks a lot

In Mark II, III and V Simul amps the Class A pair is biased hotter & you want a 6L6 pair that runs a max of around 45 mA. The easiest way to deal with this is just use mesa RED, or maybe YEL.

For the Mark IVs they were biased colder in general and YEL or maybe GRN is good to go for the Class A pair.

I've only had one Mark VII (low sample size) but it was even colder, I bet you could actually use any tube color safely. You know, as they advertise.
Class A
STR445 YEL 28mA
STR440 GRN 33mA
Class A/B
STR445 YEL 19mA
SRT440 GRN 28mA

i would be buying a matched set of tungsol 6l6 gc str with bias point 36.would this bias point be correct for yellow grn? my inner ones are bias point 36 .i would like to have a matched quad.thanks for your advise

 

[GJgo]

"bias point 36" doesn't really mean anything in Mesa speak since different tube vendors use different test machines. If you're going to buy non-Mesa tubes and you care enough to do it right (eg. get the bias in a safe acceptable range) you'll want to get your own tester to check bias on your amp.

That said, a matched quad is never "correct" for a Simul amp. The Class A pair always runs hotter. It'll work if the tubes are cold enough since Mesas aren't as sensitive to power tube bias as something like a Marshall, but you have to be careful not to have ones that are too hot.

 

[Joi737]

"bias point 36" doesn't really mean anything in Mesa speak since different tube vendors use different test machines. If you're going to buy non-Mesa tubes and you care enough to do it right (eg. get the bias in a safe acceptable range) you'll want to get your own tester to check bias on your amp.

That said, a matched quad is never "correct" for a Simul amp. The Class A pair always runs hotter. It'll work if the tubes are cold enough since Mesas aren't as sensitive to power tube bias as something like a Marshall, but you have to be careful not to have ones that are too hot

perfect.thanks GJgo for this valuable information.i might actually leave the el34 in the outter and 6l6 inner. i just found and bought an m-190 .my plan is to connect my mark III and use the power amp(IIc+ coliseum) from the m-190 with the 6x6l6. i am just reading very good things about the m-190..

 

[user 41014]

perfect.thanks GJgo for this valuable information.i might actually leave the el34 in the outter and 6l6 inner. i just found and bought an m-190 .my plan is to connect my mark III and use the power amp(IIc+ coliseum) from the m-190 with the 6x6l6. i am just reading very good things about the m-190..

Not much info out there about the M-190- nice score! I just picked up one without the covers and rusted tranny's/ tube retainers/etc. I've started cleaning up the tranny's but think I'll pull them to do a better job. If the choke is still available I think I'll just replace that one.

But as you say it has the SD 190555! Or an equivalent.

Does anyone know if there is a manual, owner or service for the M-190? It's a little different from the M-180. My M-180's/M-190/Bass 400/coli's use 3 different sets of trannys and other than the date of manufacture may have been interchangeable.

I think 1st was the P180321/O180322 that adorns all my IIB coli's, then maybe 561180/562180 (which looks like Mesa part numbers so may be the same as another Schumacher part number). Those are on one of my M-'s, and then came then SD 190555 which is on my IIC+ and KOB from '85 and I think the M-190 tho it could have been one of the M-180's.

 

[Joi737]

Not much info out there about the M-190- nice score! I just picked up one without the covers and rusted tranny's/ tube retainers/etc. I've started cleaning up the tranny's but think I'll pull them to do a better job. If the choke is still available I think I'll just replace that one.

But as you say it has the SD 190555! Or an equivalent.

Does anyone know if there is a manual, owner or service for the M-190? It's a little different from the M-180. My M-180's/M-190/Bass 400/coli's use 3 different sets of trannys and other than the date of manufacture may have been interchangeable.

I think 1st was the P180321/O180322 that adorns all my IIB coli's, then maybe 561180/562180 (which looks like Mesa part numbers so may be the same as another Schumacher part number). Those are on one of my M-'s, and then came then SD 190555 which is on my IIC+ and KOB from '85 and I think the M-190 tho it could have been one of the M-180's.

It would be great to find the manuals from the M-190. good call.i can share with you this scaned imaged i managed to find.i will ask in the forum as well if anybody could share the whole manual.

 

[edge59AlnicoIV]

The later Simul-class with 6L6 like in the IVB on started using 150k bias grid resistors, where the early 6CA7/EL-34 amps had 220k on both Class A bias grids, 150k runs cooler for 6L6's I have done that on IIC+ so the owner could run all 6L6's without the risk of burning them out so fast. I have done that on various Mark III's as well with great results, and longer tube life.

 

[Joey1970]

Green/ Gray for the inners, Red/Yellow for the outers.

 

[Joey1970]

The later Simul-class with 6L6 like in the IVB on started using 150k bias grid resistors, where the early 6CA7/EL-34 amps had 220k on both Class A bias grids, 150k runs cooler for 6L6's I have done that on IIC+ so the owner could run all 6L6's without the risk of burning them out so fast. I have done that on various Mark III's as well with great results, and longer tube life.

The Sylvania 6L6's have a magic at mid 40mA in a Simul Mark II/III in the clean channel. You will lose that in the Lead channel with the gain cranked. Go to the Sylvania 6CA7, in that case. If you can find a matched pair.

 

[Joi737]

The Sylvania 6L6's have a magic at mid 40mA in a Simul Mark II/III in the clean channel. You will lose that in the Lead channel with the gain cranked. Go to the Sylvania 6CA7, in that case. If you can find a matched pair.

thanks a lot