New Express build; first time post

[WhopperPlate]

Terry say's he's got some Saratov and RCA's that he is recommending.

Charlie

[WhopperPlate]

Tube Tramp is sending me a quad of old "Saratov" EL34's, so I'll let everyone know how things run after some real working tubes are installed.

I was going to get some RCA 12ax7's, but I ran across an old stash of tubes that my friend dropped off for me awhile back. I never really got around to checking them out (alot of rectifiers and various 12AXX type tubes, mostly stuff I don't use but still some 12ax7's to tryout)so I'll try swapping them in as well the the power tubes arrive.

A little off topic but you guys might get a kick out of it; I have a big stash of NOS tubes at my shop. Most of them are also weird values I'd never use, but I did find a NOS pair of Phillips 6l6GC I never saw before the other day!

I don't know whether to sell them or hold on to them and someday build an amp for them.

Anyways, back to work.

Charlie

[Big Jim]

Hey Charlie,
Squirrel them things away my friend. NOS stuff is getting harder to find.
I have a guy here in Fla. where I get some NOS from time to time, but mostly preamp tubes....
Jim

[redshark]

Yes, is always a good idea if you have a "matched" set of NOS tubes to keep it.
I have 2 sets of old matched tubes, a pair of 5881's tungsol and a pair of 6V6's also tungsol.
Actually I used those 6V6's in my express with no problems until I found Siemens EL34's, that was for like 1 month. At that moment I was reading in threads that some people liked the express better with EL34's but to be honest those old 6V6's sounded killer.
In one of the early Gerald Weber books he mentioned that his favorite 6V6 was the tungsol, better than RCA's and I have to agree.
Not sure how I could use those 5881's but maybe making a rocket-bassman hybrid could work....

[WhopperPlate]

You guys are right; money might be in short supply but NOS tubes are much more rare.

I found a Tungsol 5881 as well, but only one

Charlie

[geetarpicker]

For a while now my favorite preamp tubes for my Express have been quite old Slyvania 12AX7s. They don't have to be NOS, just decent used. I actually like them a little better if they aren't as gainy, which in some cases means ones with a little more time on them. The lower gain means I can get the volume up just a tad higher where the bright cap is just a little tamer and in the sweet spot for me. That said these tend to run pretty microphonic, but that is usually not a big problem if you don't stack the amp on the cab.

Lately I've been going between a quite fresh set of original Mullard XF2 EL34s, some vintage NOS National RFT tubes which I think are the same as the Seimens EL34s, and new Groove Tubes EL34Ms. The Groove tubes are suprisingly good sounding and for most things hang quite well with the others. They seem to loose their tone a little quicker than the NOS tubes but are easy to obtain and I've yet to have a dud out of about a dozen of them so far. I've had a couple drift a bit out of balance, but within reason out of balance output tubes can sometimes still sound just fine.

[M Fowler]

I use all new tubes the JJ ECC83S gold pin tube and JJ / Tesla's EL34L as well as the Groove Tube Gold Series GT-EL34-M.

No NOS tubes and sometimes hard to find good preamp tubes.

Mark

[WhopperPlate]

Hey everyone,

I put back in the v1b 1.5k grid stopper and it definitely helps a great deal removing that parasitic oscillation blocking distortion sound. Also changing out all of the 12ax7 to various RCA GE and Mesa also eliminated some of the distortion as well, but the ghost like modulation on the note is still very apparent at almost all volumes. Got a pair of tubes that bias up good as well, but the problem persists.

The saga continues

Charlie

[PlinytheWelder]

The tubes that I currently have in mine are V1 Tung-Sol 12AX7 RI, V2 NOS Tung-Sol 12AX7, V3 NOS Mullard CV4024 (12AT7) and new Svetlana EL34's

Out of all the tubes I currently have, the TS re-issues are the quietest and sound good ,too. The Mullard 12AT7 is my favorite tube for PI use. I just love the way they sound and there's lots of good ones still available on Ebay.

[WhopperPlate]

I love the Tungsol too, but they seem to be exaggerating my problems.

[JamesHealey]

I found that the Tungsol 12AX7 Reissue tubes after a few weeks of heavy gigging start to hum like filament heater noise, and i've had a few sets do this.

the JJ ECC83S never does this, just simply more reliable.

I really like old Mazda Grey Plate ECC83 when I can find them.

[WhopperPlate]

Exactly what I noticed as well.

[WhopperPlate]

Well I've tried a lot of things to get rid of this ghost note and distortion.

Removed the bright switch connections for testing.

First I threw in the shielded cable on v1b, helped some.

Threw in the 36k grid stopper on v1a, that didn't help any.

Completely cleaned and resoldered the pots and buss wire (used a flat tip iron, nice shiny smooth connections), still no difference.

Tied in a 16uf cap across the mains and then the v1 B+ with no help. Maybe I'll try the rest later.

Though the amp feels and sounds great through my new Scumback m7560 (excellent speaker worth anybodies time; Thanks Jim!), the ghost note congests everything and clashes big time on double stops and "dazed and confused" type bends.

I'm going to try fiddling with power section wires the next time I get a chance to tinker.

Charlie

[geetarpicker]

Dang that thing is stuborn!

Are you testing this amp hooked straight to the cab? What kind of speaker wire are you running? Also what kind of guitar cable?

[WhopperPlate]

Hey Glen.

Guitar cable is 18ft horizon and Horizon speaker cables, forget what gauge but thick stuff. I take care of my cables; I have too much experience with bad cables.

I've tried with and without an attenuator, I still get the same symptoms (though the MASS200 high cut does induce oscillation when engaged). Cabinet is a 112 on the floor, amp is on bench.

I have for the most part killed all audible hf oscillation with the mentioned adjustments, but this weird ghost thing still persists. Hashes up the clean highs and totally modulates the distorted tone. Seems like power supply ripple because "A" and "D" take off and really ghost bad.

I moved the mid and bass wires farther away from the front panel to allow more wire to chassis contact, about a 1/2 inch or so so we'll see what that yields tomorrow.

I also keep neglecting and forgetting to scope the thing, so I'll hook that up as soon as I have the chance. Maybe narrow things down a bit.

Charlie