Tightest sounding EL34?

gnugear · Post by **gnugear** » Fri Jun 03, 2005 11:11 am

I'm playing around with my '67 circuit which includes a 330uf on V2. As expected, I'm getting a lot of boomy bass. I'm thinking that I can remedy part of the problem with a different set of power tubes. Which are the tightest? I'm guessing the 6CA7s, but what other brands? I've already got the EH 6CA7s and the JJ EL34Ls. What about The EH EL34s, I remember them sounding really good in my 1987x ... actually liked them better than the Svets. Haven't had the opportunity to test much with my 100 watters.

Dai H. · Post by **Dai H.** » Fri Jun 03, 2005 3:29 pm

split cathodes? .68uF cathode R bypass, 2200pF instead of 22nF, 22nF out of the phase inverter should all help reduce bass. 6CA7s or 6550s probably for tighter bottom. EL34s seem a bit mushier or rounder, and sort of not as much bottom.

gnugear · Post by **gnugear** » Fri Jun 03, 2005 7:01 pm

I'm trying to see if I can live with this straight up '67 circuit. If the tubes don't cut it I'm going back to .022 for the phase inverter.

Post by **VelvetGeorge** » Fri Jun 03, 2005 7:37 pm

Hey Gnu, have you tried using a 250uf in V1? It's not a huge difference, but sometimes just enough.

Also, what OT do you have?

George

Flames1950 · Post by **Flames1950** » Fri Jun 03, 2005 8:01 pm

VelvetGeorge wrote:Hey Gnu, have you tried using a 250uf in V1? It's not a huge difference, but sometimes just enough.

Also, what OT do you have?

George

I dropped my V1 cathode bypass cap to 10uF and still barely notice a difference in the bass content.

Billy Batz · Post by **Billy Batz** » Fri Jun 03, 2005 8:37 pm

Maybe its just me but sometimes I think I can hear a real difference and other times I cant. I think it has to do with how much drive Im playing with.

Flames1950 · Post by **Flames1950** » Fri Jun 03, 2005 11:54 pm

But as far as the tightest EL34, for new production I still like the GT E34L's (30 watts plate dissipation, so bias 'em accordingly.) Although some have claimed that the newest ones aren't as reliable; mine were bought as a quad about eight years ago, but I only was using two in a 50 watter. Bigger and cleaner than many EL34's while still haveing a lot of the characteristics of EL34's that we love.

Dai H. · Post by **Dai H.** » Sat Jun 04, 2005 7:42 am

also, reducing the filter cap value at the preamp will cut bass (not just the pramp amp one--the other ones too--but I would start there), and towards the other end, lowering the two 220ks on the power tube grids should also. If you try lowering the 220ks, be careful and make sure you do a good job since you definitely do not want to lose bias on the output tubes!

gnugear · Post by **gnugear** » Sat Jun 04, 2005 9:53 pm

Hey George, this is my original '74 OT which has a lot more bass than my Merc.

I just figured out that I THOUGHT I had a .0022 in V2 but it was really a .022 mustard (those dang pf markings through me off). That .0022 was JUST enough to make the amp sound perfect!