Anyone ever do away with DR rectifier?

[JerryPro]

Has anyone ever done away with the rectifier tube on a SFDR and installed diodes across the contacts. It seems to really add some spank to the amp. It seems some of the 5U4s don't do a good enough job and the amp wants to fall on it's face a bit.

Just an experiment. Wondering if anyones tried it.

[JohnnyAtomic]

the best sounding deluxe reverb i ever heard had a old jensen C12N, a pair of sovtek 5881's, and a plug in solid state rectifier (never use a normal solid state rectifier with 6V6's the voltage will go too high).

johnny atomic

[Marky D.]

That's how I currently have my 65 DR set up (kind of) but I'm running Svetlana 6L6's. You probably shouldn't run 6V6's w/ any SS rectifier - I think it can stress the PT.

I did a few other things to the amp: took out the bright cap, changed the phase inverter cap value, put a switched pot to remove the vibrato circuit, pulled the normal channel tube. And aput in a Celestion V30 speaker. In this config, the amp can get really loud and keep up w/ "bigger" amps and a drummer!

I first ran this same amp w/a 5AR4 recto tube and EH 6V6s until I cranked it up and blew one of the EH's. My plans are to try some JJ 6V6s and a warmer speaker, maybe a Weber F150.

[JerryPro]

The thing sounds incredible right now. I notice the power tubes aren't really glowing at all though. Near the base there is a tiny hint of blue. No cherry or bright orange.

How will 6l6s change the sounds?

[Rick S]

Don't rely on a visual inspection to tell you anything. I think the bottom line is, if you don't know about checking voltages and current and the operating points of tubes, you shouldn't be experimenting like this.

On a SFDR with the 5U4 spec power transformer, I can guarantee that the plate voltage is far too high with a SS rectifier to be within a healthy envelope for a 6V6. I wouldn't be at all surprised to see the B+ in excess of 460vdc.

I think my best advice would be to turn back now, and learn about safe normal operation before getting into any mods.
Rick S

[maxvintage]

I use a weber copper cap in mine--it's a solid state rectifier that plugs into the normal rectifier tube slot. I could not tell a difference between the copper cap and the recto tube. Weber will make a copper cap to exactly the amount of "sag" you want, so if your goal is tigheter response, you can get there. check it out at webervst.com

[JerryPro]

Originally Posted by Rick S

On a SFDR with the 5U4 spec power transformer, I can guarantee that the plate voltage is far too high with a SS rectifier to be within a healthy envelope for a 6V6. I wouldn't be at all surprised to see the B+ in excess of 460vdc.

Rick S

I should have been clearer on this but I'm still finding out things as I go. I'm not going about this as blindly as it might seem. I have an amp tech actually doing the work and calling the shots. He said that amp circuit is BF and the PT is for a GZ34. He said that the 5U4 should not have been in there to start with. He says alot of people use 6l6s when doing this but that mine would be fine with the 6v6. You guys are starting to worry me about this PT issue. I don't care if the tubes go out sooner but the PT is a diiferent story.

[JohnnyAtomic]

if you were to read a manual or old catalog from the glory days of tubes it would tell you the manufacturer specs on those tubes, most 6V6's are rated for around 375 to 400 volts. that's how many volts they can take without shorting out destroying the tube, not how much current that wears them out (lifespan of tube). whereas most deluxe reverbs are slightly higher than this around 400 to 425. this is one reason deluxes sound so good, they are pushing the tubes to the limit. whereas if you put a regular (non-copper cap) solid state rectifier in one it pushes the voltage even higher. maybe as much as 450 or 460. then you are playing on borrowed time. what will happen? i don't know what exactly will happen, no one does. it depends on how the tube shorts out, maybe it'll go open, maybe dead short of one piece in there against another cause the amp to simply quit working, or simply blow a fuse, or take out a transformer, or ?????????.

it's your amp do what you want, i personally wouldn't run a dlx rvb w/ 6V6's and a SSR, 6L6's yes, 6V6's no.

i used to work on amps and i've heard LOTS of times, it sounded incredible then it just quit (talking about all kinds of amps not just deluxe reverbs). i hope that's not what your hearing/experiencing.

[EMan]

...anything over about 425V on a standard 6V6 is asking for trouble. If a output tube arcs from over voltage..it could possibly short and melt the OT. The operative word is "could".

My '72 DR (5U4) running at todays line voltage..is slapping 437V on my 6V6's (biased at 23mA)

It's got a set of the new JJ's in it now...and the manufacturer claims that they will live in extreme plate voltage environments. (which makes me feel better)

To the original question...I did the SS plug in/6L6 deal on this amp, and found it to be kind of Twin like in tone. A little stiffer, and somewhat sterile...but really CLEAN. Not a bad tone for a jazzer...but I tended to like the 5U4/6V6 tones better. BTW, this amp uses a V30 in it.

[Silverface]

He says alot of people use 6l6s when doing this but that mine would be fine with the 6v6

If so, have him tell you exactly what the plate voltage is with the SS/6V6 combination, and use the guidance in the other posts here to make a decision. FWIW that voltage will likely be inordinately high.

And that decision of yours would be to find a new tech.

[Teleologist]

Lots of good advice already. But why solder-in the diodes - that just limits your options. The plug-in SS rectifiers aren't expensive and you have the option of going back to a tube.

I occasionally run Sylvania 5881s in my BF DR both with a GZ34 or a SS plug-in(no sag). With the SS rectifier it sounds like a baby Twin Reverb. You get tighter punchier lows and clearer highs but loose some sweetness and that 6V6 growl. I don't like the higher power NOS 6L6GCs or 7581As in these amps as you can't run 'em hot enough to sound good(I run the 5881s @ 30-32ma. each, 6V6GTs with a GZ34 @ 23-24ma. each).

I also agree about not running 6V6's with a SS rectifier. One other variable is todays AC line voltages. The ANSI standard allows a plus or minus 5% variance from 120VAC, but a lot of power companies 'invent' their own standard and some are running a lot higher(or lower when the weather turns hot). In many areas the voltage varies from location to location, changes based on the time of day, and even the day of the week. The power transformer in a tube amp multiplies these changes(the bias voltage too), so leaving some margin is a good idea IMO.

[JerryPro]

I mean is it safer to run a Weber plug in? I know it does away with the 5v load and it allows the PT to run cooler but is there something about it that makes it safer?

BTW, I found out my plate voltages are right at to slightly over 400. I know some of this was acheived by heating up the bias. That's about all I know though.

Additionally, this was a test to see if we liked it and we didn't have a plug in to use. If it all works out and the amp holds together I will get a Weber unit.

I played last night and the amp sounded really good. I'm even thinking about NOT replacing the speaker now. I agree it does spank like a Twin now. I have two DRs and one is left alone for Blues gigs .

One more question............

If I get a Weber plug in will I have to get the bias reset each time I change from a GZ34 to the plug in? Or do I get the Weber unit that is the replacment for the GZ34 and change nothing?

As always, thanks guys.

[Wally]

One thing not mentioned in this thread vis-a-vis plate voltage is that if you use a variac to set the 'source' voltage at 110, the voltages in the amp come down to voltages that are specified in the schematics. Generally, line voltages are in the 120VAC range. That is about 9% above 110V. An AB763 schematic calls for 410 at the plates. Add 9% to that, and you will see about 446V on the plates. Try it, you may find it interesting sonically and your tubes may last longer.

Edit: My apologies to you, Teleologist. I did not read that paragraph in concerning the line voltage in your post. My error.

[Red Planet]

So what do you have to do to put 6L6's in one. Just Rebias or change some resistors and rebias?