JJ 6V6's in a Single Rectifier? Anyone

[theDogger]

Anyone running 6V6 tubes in their Single Rectifier and how do you like as opposed to the 6L6GC?


Also how exactly does the 6V6 drop the wattage down to around 25-30 watts?

theDogger :mrgreen:

 

[94Tremoverb]

I'm not sure I would try this, even with JJs. The voltages are pretty high for any 6V6 - counter-intuitively perhaps, the Single Rec is going to be much more risky than the Dual because you don't have the tube rectifier and the Spongy mode, both of which reduce the voltages substantially. But you could get a Variac and turn down to 100V, which is what the Spongy mode does on the Dual.

6V6s will reduce the power to about half because in simple terms they don't conduct as much current as 6L6s or EL34s. They also have a higher impedance, so if you are going to do this you need to run the speaker from the output for half what the speaker is (ie 4 ohms for an 8-ohm speaker). If you don't, you won't harm the amp but you will shorten the life of the tubes and it will sound really flubby and squashed.

 

[mikey383]

I agree for the most part. You're looking at around 475 plate volts, and most 6V6s are only rated for around 350 volts. Although, if you read the reviews on JJs at thetubestore.com, they claim to have ran a set of JJ 6V6s from 380 to 475 plate volts. Linky: http://thetubestore.com/6v6review.html#jj6v6

 

[theDogger]

Ok I measured my plate voltage and it was 432 volts and the Mesa 6L6's were biased @ 29mA. Pretty cold. I am in the process of researching a BIAS Adjust. (Anyway All the Mesa Rectifiers that I have seen are way cold. My buddies Dual Rec. is running @ 26mA.) I would like to be able to BIAS the tubes around 36mA-40mA (6L6 of course.

I am sure you have heard about EUROTUBES. I have used then before in the past and have been very happy. So after looking at the website and talking to them I bought the High Gain 6V6 option

Mesa Single Rec 6V6 High Gain Option
Price: 90.50
Description: Need more power tube and preamp tube distortion? This kit is for Single Rec's and Solo 50's that are switchable for EL34's. We have a special grade of the JJ 6V6's that will get the bias just right when set to the EL34 mode and lower the power to about 25 watts for earlier breakup. The 6V6's have a very fat sound, a big low end and a great top end sparkle. This kit includes a matched pair of the JJ 6V6's in a special grade, three hand picked high gain ECC83S's for V1, V2 & V3, a standard ECC83S's for V4 and one balanced ECC83S for the phase inverter in V5.

The Single Rec's that are switchable from 6L6 to EL34 mode can also use pairs of 6V6's, KT77's, KT66's and KT88's for a lot a tonal variations. The bias does not have to be modded and made adjustable if the proper grades of tubes are used. So if you order any of these tubes online from Eurotubes then make sure to leave us a note in the comments box on the checkout page to let us know what amp they are for so we can select the proper grade. Of course if you want ultimate control then a bias mod will allow you to dial any grade in.

The front ends of the Rectifier amps are quite happy with the ECC83S's and especially the high gain ECC83S's used in specific locations. The ECC803S and Gold pin versions of these tubes are also a great V1 tube if a fat thick clean is the mission.

6V6s will reduce the power to about half because in simple terms they don't conduct as much current as 6L6s or EL34s. They also have a higher impedance, so if you are going to do this you need to run the speaker from the output for half what the speaker is (ie 4 ohms for an 8-ohm speaker). If you don't, you won't harm the amp but you will shorten the life of the tubes and it will sound really flubby and squashed.

Single Rectifier has 2-4Ohm and 1-8Ohm. I have a 4x12 that is mono 16Ohm and 2-8Ohm in stereo. If the above is correct will I have and issue plugging both 8Ohm into the 2-4Ohms?

theDogger

 

[94Tremoverb]

Connect the cabinet's 16-ohm input to the amp's 8-ohm jack with 6V6s. If you connect both 8-ohm cabinet jacks to the amp's 4-ohm jacks, you will be back with a load of 4 ohms (2x 8 ohms in parallel) on the 4-ohm tap, which is still the wrong match with 6V6s, although correct for any of the larger tube types.

Your Single Rec's plate voltage is unusually low, so you will be safer with 6V6s. I'm still concerned about it, but if Eurotubes think it's safe to sell sets for the purpose, I guess they must know what they're doing unless they want a lot of warranty returns...! And definitely don't try it with any other 6V6s, JJs are quite a lot different from the original design spec and are certainly higher voltage rated. (I just didn't think that much.) The plate voltage will also probably go up slightly with 6V6s too, since they will load the power transformer less.

I fitted my Tremoverb with variable bias for the same reason - the bias is *really* cold in the Spongy and Tube Rectifier modes, much lower than what you're getting. Surprisingly, it doesn't seem to make that big a difference to the tone, much less than I was expecting or have found with other amps. I also have run the 6L6s in EL34 mode to get them even hotter, but you can only get away with this in the Spongy modes, it's too hot really even in Tube Rectifier and Bold. If you are going to try it, make sure you check the current.

 

[theDogger]

OK good to know. I'll check the plate voltage again w/ the MESA 6l6GC's before installing the 6V6's and measure the BIAS again after w/ the JJ6V6's. I'll post those numbers and see if I can't get a decent recording of the JJ6V6's.

Also do you know of any good posts or threads that have info. for a DIY BIAS Adj. for the Single Rectifier? I have found several for the DUAL and Triple. Looking for one with good pics...

theDogger :mrgreen: