Trem observations and the 5751

[cloudhopper]

I recently finished my 18 Watt and have been playing around with my trem some. I originally had JJ tubes in it and when I swapped them out for some vintage sylvania tubes, I made the mistake of putting a 12AU7 in the trem. I played it this way for a couple days before realizing it wasn't a 12AX7 when I pulled it to try another tube. My amp has the boodle mod and one thing I did notice with the 12AU7 was if I had the trem turned on and up, I would hear a slight squeal when I was playing lower notes through the normal channel. When I replaced the tube, I made another mistake, or at least I put in another tube I thought was a 12AX7 and it wasn't. I had purchased some RCA blackplates on fleabay and they were sold as 12AX7's, I didn't bother checking before I popped them in and after playing for a while and liking what I heard, I pulled them back out to save them for later and I realized that the two RCA blackplates are actually 5751's and not 12ax7's. After hearing about so many problems with the trem, I was surprised to find my trem worked well with the JJ 12AX7, Vintage 12AX7's, the RCA blackplate 5751 and a sylvania 12AU7. The 12AU7 was the only one that had some squeal issues. The plate resistance of the 5751 is enough lower than a 12AX7 that the actual gain in hardly reduced, what I did notice was the 5751 in the trem position reduces the speed just a bit and it reduces the intensity some, which is exactly what I was wanting anyway. Makes me glad I haven't tried any actual circuit mods yet. The switching out of the various tubes really is a mod in itself.

[sgtoverdrive]

an amazing tube to be sure soldier.ive been trying to get these noncoms in for the big win on these and a few smart guys picked up on the lingo and scuttlebutt.my complaint with the rcas is the usual one too noisy in most cases i think this is why the 5751 was invented basically a cleaner quieter close cousin to the ax7 it works in pedal and preamps and compressers like nothing ive tried.i have 1970s bell nos for about 35 for two.which is the goin rate for one.and they are flowin out.im anxious to hear the results form the 18 watt division on these. they spike the dst marwatt to new overdrive they clean up and add a little headroom to v1 somethin we can all use with 18 watts and work wonders in reverb trem and phase inverter applications .the bell is superb like the mullard in its cool operration you can pull em out after half an hour with your bare fingers .anytime you see a four number designation your lookin at a tube built to mil spec for the military and other high level organizations.when they sound good you got a winner all the way ....5881 ring a bell? used on bombay doors in b52s back before norman numnutts invented the transistor and diode> when the world was young and unspoilt! my advice to anyone looking for a quick change in there amps short of a mod is try one and see.in v1 as ive said before you get bluesbreaker all the way just enough to turn the average 18 into one of the best low wattage blues platforms i ever heard.sgt tell no lie

[kinmike]

Any thoughts about using a 12DW7? This tube has two different triodes in one envelope, one triode is like a 12ax7 and one like a 12au7. Anybody try this? Could be a best of both worlds situation.

Then again, I must admit I don't really know much about it...

Mike

[cloudhopper]

Hey Mike,
The 12DW7 might be fun in an amp like a bassman, where the two triodes are used for the two different channels. You would want to bias the two triodes independently though. It sure wouldn't work well for a PI, and for a trem circuit, you would need to know which triode went to the trem and which went to the preamp.

I have sure come to prefer the 5751 in the trem position. I'm savin' my pennies so I can try one of sgtoverdrive's bel labs 5751, I have been told they are even better than my rca blackplates. Thing is, sarge already talked me into a pair of amprex EL84's and then a pair of EL84 roznov's. Not that I'm complaining, He has the best tubes and shares them at very honest prices. I also got a pair of his russian mil 7189's and currently have them in my 18 watt. They were pretty harsh to start with, but are sweetening up quickly with use. I have some Tronal EL84's that are nearly identical in design to the 7189, and they don't sound too bad, but they don't have the quality of build as the 7189. Only 2 of the 6 tronals I got tested up where a new tube should test and the plates have a very thin coating on them like they were trying to save money by not using as much coating material as they should, I will be surprised if the tronals last very long.

Well, getting back to the subject of the trem, I guess I'm surprised that my trem with the boodle mod seems to work no matter what tube I stick in it. Maybe I just got lucky.