Improving BFPR Tremolo

I finished my 6L6 BFPR build and everything sounds AWESOME.

Only trouble is the Trem is not very deep. I have to have the Intensity on 10 for it to be very prominent at all.

I did mod the bias section to run 35 - 60 mA for 6L6's (transformer swapout as well), so perhaps the bias based Trem is effected by this... IDK... I'm no expert, so:

Anybody have any tips on making the Intensity control a bit "more?" I aint expecting the tube driven Trem sounds from say a Deluxe, but any improvement is good.

My only guess would have been to lower the value of the cathode resistor on the trem but it's already running "hot" with the 3.3k since the plate is 260v. Don't have an unused triode available do you?

I had weak trem for some time on an amp that uses the same trem type. Turned out that one of the el-84 JJs was going bad and microphonic.

My only guess would have been to lower the value of the cathode resistor on the trem but it's already running "hot" with the 3.3k since the plate is 260v. Don't have an unused triode available do you?

I had weak trem for some time on an amp that uses the same trem type. Turned out that one of the el-84 JJs was going bad and microphonic.


The only reason I went with a Princeton for this build was because I knew I'd be using 6L6's and could only fit so much in a Champ chassis!

Yeah - a Champ chassis! Who else has a 40 watt 6L6 amp with reverb and trem in, of all things, a Champ sized package?

Too bad... I always heard PR trem was pretty weak, but IDK if this is the same kind of "weak" or not since I've got it fixed adjustable with bigger iron and 6L6's instead of 6V6's... there's gonna be some surprised folks who think "is that guy playing a converted SF/BF Champ head?" and then I turn the volume up to 10...

JC - It's fundamentally because your 6L6 is cathode biased. Bias vary trems just don't work that well with cathode bias. The reason is because the lower 3dB bandpass of that R/C is higher than the frequency of the trem oscillator.


EDIT - Had I been paying attention, I might have realized that this amp *is* fixed bias (?).

Eman, I'm confused here - why would a PR be cathode biased?

Oops - I edited that post...for some reason, I thought this amp was a Heinz 57.

I think I'll post a thread asking PR owners what their trem sounds like. I'm not sure if this is how weak it is on a normal PR or if my modding it for 6L6's + adjustable bias is partially to blame.

If it wasn't all crammed into a Champ chassis, I woulda given it another tube for a proper trem, the PR trem was all I could do.

I have a 68 non reverb Princeton amp!! when I had the 6v6 tubes running the Trem sounded great then I put el-84's with THD Yellow Jakets and lost the trem almost completely!! My buddy at bonepickerguitaramps.com told me it was due to the amp being a push/pull and the EL-84's changed all that.
This problem your having sounds about the same as I had, Had to dime the Trem to get it to make sound.

my Princeton Reverb has plenty of trem. I don't like it or use it because it's just too mechanical sounding - thump-thump-thump. I guess it works as an effect, but not for every-day use. Maybe that's why Fender dropped tremelo after a while, and why no other amp manufacturers ever really picked up on the idea.

I haocaisiove heard of mods for slowing it down, or making it stronger. I guess slowing the trem way down might be useful. Making it stronger - no way!

If I was you, Johnny Crash, I would dump the trem and save the space. How often do you actually hear a good tremelo? How often do you really want to use that effect? There are effects devices that can do a better job on those rare occaisions that you need a tremelo.

Just imagine, you're playing the stars out of the sky with your beautiful little PR 6L6 amp behind you going "whump - whump - whump"....

Johnny!!
Send some photos of the new power-Runt!!

Coupla things, now that I'm with the program here.

JC, if you can, do me a favor and with the wiper of the Depth pot dis-connected, measure the P-P amplitude of the oscillator signal on each side of the 250K pot. REMOVE the output tubes.

What components did you chage to re-center the DC grid bias?

If you run the Plate current too high, the trem effect diminishes.

jjmantele, this tube is running right ~180mW on the Plate..not too hot.

I have a '62 Princeton, and the trem on this is the way trem ought to sound.

Lower the value of the 1M resister coming off of pin 1 of the last preamp tube (where the 220K and 1M resisters meet). I usually lower it to half that value...470K. Some folks go lower than that. You'll get a deeper and richer tremolo. If you don't do this, the hotter biasing of the power tubes will likely wipe out most of your usable tremolo.

Lower the value of the 1M resister coming off of pin 1 of the last preamp tube (where the 220K and 1M resisters meet). I usually lower it to half that value...470K. Some folks go lower than that. You'll get a deeper and richer tremolo. If you don't do this, the hotter biasing of the power tubes will likely wipe out most of your usable tremolo.


Cool.

I can't believe how much I learn here on TDPRI... I also can't believe how patient and nice everyone is... sometimes the big brainers are mean to newbies on other forums :)

Thanks EMan and PhatTele!!!!

I may actually try a 330k and inch up from there.

THANKS AGAIN GUYS, this amp kicks ass so far!!!

The Brown Princeton I heard had one of the sweetest trems ever. I had heard too, that biasing them fairly hot would wipe out most of the tremolo.

Good trem is a great thing IMO.

Damn.

I had it sounding great with a 330k... decided to try a 270k... I think I had it on without the rectifier tube in (a lot of distractions at my house today) - next thing I know - no more sound.

I put the 330k back in and looked at a few other possiblities... (a few accidental short locations - its cramped in this little chassis).

All voltages look around normal, except the 12AX7's plates are very low.

I hope I didn't fry the OT or something... damn.

Too tired to work on it now, but it sounded so much better with a 330k in there (a 270k might get me where I want to be though).

I hate my own stupidity sometimes!!

Howdy,

JohnnyCrash: FWIW, my '64 Princeton (non 'verb) had a disappointing tremolo as well. Don't know if that helps any. Good luck with your interesting amp project.
Did you say 6L6 Princeton Reverb..into a CHAMP chasis? Wow! I'm assuming you managed to shoe-horn a good 10-inch speaker into that rascal, right?

Eggman

PS: How does she sound semi-cranked with a mahogany bodied P-90 equipped guitar? :)

JC - that 1 meg is part of the plate load that determines the gain of the trem stage....at some point, reducing that value may stall the oscillator.

Not sure what that value is, and I'm kinda surprised that it still oscillates with the 330K. However, if it works, it works!

JC - that 1 meg is part of the plate load that determines the gain of the trem stage....at some point, reducing that value may stall the oscillator.

Not sure what that value is, and I'm kinda surprised that it still oscillates with the 330K. However, if it works, it works!

Well, it did...

Then I messed something else up. It makes NO sound now.

A few things may be the problem:

1. I accidentally fired up the amp WITHOUT A RECTIFIER TUBE.
2. Something may have grounding/shorted underboard.
3. Something may have come loose.
4. Due to the tiny space, one of the filter cap's leads may have shorted on the bias pot's sweep resistor (a 22k one).

Or perhaps something else happened.

ANY THOUGHTS ON HOW UNRECTIFIED AC WOULD EFFECT AN AMP? Dead OT? Fried Tube? Etc?

I think that if you had no rectifier tube there would be no B+ voltage at all, and there would be no damage to any component.

I think I'll post a thread asking PR owners what their trem sounds like. I'm not sure if this is how weak it is on a normal PR or if my modding it for 6L6's + adjustable bias is partially to blame.

If it wasn't all crammed into a Champ chassis, I woulda given it another tube for a proper trem, the PR trem was all I could do.

My '70 PR (same circuit as BF essentially) has pretty lack luster trem... It's because of the bias vary design I think. If you have good tubes and it's biased right it's a bit better, but just doesnt compare to the DR trem. I only use it for a subtle effect, so I live with it. YMMV.

Well, think about it:

The AC goes from the switch to the power transformer where it's bumped up to 300+ volts AC. It then goes to the rectifier which transforms it to volts DC for the B+. If that rectifier isn't there, then the B+ vDC aren't being created and aren't flowing into the amp. So, no problem. The only voltage flowing into the amp from the PT are the bias voltage (in your case, 50v) and the 6.3v used for the heaters. I don't think having the rectifier out caused the problem.

So, if it's not creating sound now, then something else is wrong. check the obvious first: fuse, tubes, speaker connection. If all that looks good, then start tracing the voltages starting at the point the AC enters the amp and then move methodically through the amp (transformer leads at the rectfier, B+ leads, voltage on the filter caps and resisters, etc.) You'll find it. Something that had been showing voltage will be showing some other value or nothing at all when you come across it. Then you'll know where your problem is.

I've been gone all morning... finally can get back at it.

Yeah, I realized like an idiot that the tube rec being not present means nothing HAHA, I got to sleep last night at 6am and woke up at 9:30... needless to say, my already naturally slow brain is even slower.

With only heater voltage and bias voltage flowing, I'm sure all was well. Like I said, building this in a Champ chassis had its own challenges - one of which is wires going EVERYWHERE. Underboard wires are causing me headaches and perhaps I lost pin 1's wire to resoldering in that 330k (which sounded MUCH better by the way!)... time to dig out the needlenose pliers and see if anything fell loose.

Thanks again guys... BRB soon enough :)

OK,

I've got the proper voltages to the 6L6's and OT. I have nothing going to the 12AX7's plates... looks like a wire may have slipped out with the help of gravity and some resoldering...

I'm hunting for that lost voltage - hopefully I'll be back online with this amp soon... its dirty twin, the 6V6 18w sounds too killer to play by itself... be back soon...

Finished. It was my the wire that fed all my triodes' voltage that came loose.

Got everything up and running, the Trem actually sounds like trem (instead of a slight "whoob whoob" of a ceiling fan's oscillations through my pickups HAHA).

Thanks for the tip PhatTele!! Thanks for the help EMan!!

Cool, glad you got it worked out. You've just about built my dream amp there... the power I like, the tubes I like, with the reverb I like and a trem close to what I like.

I'd love to hear it ripping though 2 10's.

A Vibrochamp Reverb through a 12" would also be about my dream amp. Just saying... :wink:

Cool, glad you got it worked out. You've just about built my dream amp there... the power I like, the tubes I like, with the reverb I like and a trem close to what I like.

I'd love to hear it ripping though 2 10's.



I'll have some clips soon... and photos.

I have to put these two amps in head cabs before I do anything, they're so vulnerable and exposed and I'd hate to break a tube or something.

I can't wait to get this into my studio room and run them through my other cabs - so far the PR sounds AWESOME dimed through either the 1x12" Jensen Neo 12-100 or my 1x12" Eminence Tonkerlite. Breaks up very nicely - good big cleans... piles of reverb, and a very very cool trem (the PR trem doesn't seem so bad) thanks to PhatTele.

I can't believe how good these things sound! The 6V6 18w Marshall/Deluxe is a perfect dirty amp to this PR's clean... I can't wait to start using them now!