BF Deluxe Reverb - how to get overdrive smoother?

[johnny99]

Hey guys,
I recently started taking my Deluxe Reverb to practices with a bassist and drummer. To compete with them, I've been putting the amp at around 7 (vibrato channel). The amp starts to break up which is great - no more need for a distortion pedal! But the characteristics of the distortion is pretty "ice picky" and "aggressive", and I was hoping for something smoother.

I already have the bright cap disconnected, but other than that the amp is totally stock AB763 running JJ tubes (biased to 65% I believe?) and into a Jensen Falcon speaker.

Interestingly, the Normal channel has smoother distortion. According to the duncan tonestack calculator, the amp has a pretty large midrange scoop. Would adding more mids smooth the sound of the amp?
Or would changing the tonestack caps to Marshall values help?

Searching a bit on the internet, it seems like I'm not the first to think that the DR distortion is a bit shrill. Someone posted "the negative feedback in the power amp section keeps the amp pretty much distortion-free up until you get close to a max clean output. At this point the amp hits the wall dynamically, and then the negative feedback starts to get frequency selective and sonically nasty things like blocking distortion can occur." I do see that there is more negative feedback compared to say a Bassman. Could that also be the issue?

Or could it be the Jensen Falcon? It's described as "Lows: Loose/Fat Mids: Firm Highs: Bright Guitarist Description: Warm and full bodied tone with lows that are rich and fat. It responds to overdrive distortion with a colorful crunch.".

[pdf64]

Try disconnecting the 10pF cap between the 2nd and 3rd stages of the reverb channel. It's like a second bright cap.
Yes, reducing the degree of negative feedback is likely to be beneficial; apparently the new custom SF RIs use a 1k5 feedback resistor (rather than 820). Or just disconnect it.
Reducing the 220k power tube grid leak resistors to 100k has several beneficial effects in smoothing overdrive.

[Reeltarded]

Around 7 the bright cap does virtually nothing.

Turn the volume to ten and set the tone controls until it sounds best and loudest. If that doesn't do it you have suffered the 30w snare rule.

[Roe]

Around 7 the bright cap does virtually nothing.

Turn the volume to ten and set the tone controls until it sounds best and loudest. If that doesn't do it you have suffered the 30w snare rule.

the 10pf does quite a lot at any volume

[Stevem]

Added mids will round out the overall distorted tone of the amp, but the larger / fatter signal level will also drive to output stage into clipping sonner and limit your clean head room!
Feedback broadens the amps frequency range, but once the output stage is clipping you have no feedback voltage left to make for that over high end tone.

[Reeltarded]

Yeah the cap on the board does lots, I was speaking to the actual BRIGHT CAP on the VOLUME POT which does JACK SHIT at VOLUME.

So set the volume wide open and turn the bass up until it's loud then turn the treble up until it sounds good. Don't remove the 10p, instead replace it with something much larger to taste.

He wants smooth overdrive. More headroom with a 20 watt amp is impossible. Snare drums likely peak around 150w before the heads break. I doubt the other players have ever heard you play.

As said above, and to repeat, at that volume your amp has swamped the NFB. There is no effect. It's done.

Ok, back to the world.

[pdf64]

See the text here http://www.ampbooks.com/mobile/amplifie ... /feedback/ for explanation why negative feedback can often result in harsh distortion.

[Richie]

Is this a reissue or a real BF?

[Smitty]

Yes the mid scoop is the issue. Try adding a 250KA mid pot to the normal channel. Use the '2' input for the pot. Add a 220K grid stopper to V1B. Then push the whole deal with a clean boost.

[TimmyP1955]

Get rig of the excess low end that Fenders have. Change the PI-6V6 coupling caps from .1 to .01. Or change V1A's cathode bypass cap from 25uF to somewhere between 2uF and 5uF. This worked great in the boss's BF Princeton Reverb.

[rooster]

Man, interesting suggestions here. Here's some from me then.

And I have to conclude that you are using a SC equipped guitar? I dig SC guitars, don't misunderstand, however be advised that guys like Bloomfield did use - occasionally - a LP into a SR cranked to get some of his recorded tones. (The Electric Flag album solo work was pretty much a LP into a fuzz, btw, don't be confused.) This is a fat midrangey instrument compared to a Strat or Tele.

Do not remove the 10pf cap. This is another thing entirely, it is a bleeder cap across the 3.3M resistor, both of which send the original signal of the reverb channel on to the coupler stage that receives the reverb affected signal. Leave it alone or change it to silver mica of the same value.

The BF amp is stripped of midrange, sure, that's why it became so popular at the time - it cut like a knife compared to the tweed type amps that preceded it. This is also why SRV wisely used his Strat and a TS pedal to create a midrange dripped lead tone with cutting treble. If you are skipping his plan, then sure, add some midrange to the signal. Either change the 6.8K resistor on the bass pot to something of higher value, say 18K or change the 100K slope resistor on the tone stack to a lower value, say 56K. (The reverb tone will change slightly by doing this, but the bass is permanently rolled off so no worries there as to the gain/distortion of the verb.)

I'm not sure why you have walked away from OD pedals while continuing to use this amp, and particularly if you are indeed using a guitar with SCs. Reconsider this course, that's still an option, right? Maybe also try the Wampler Ego Comp or something of equal quality if you are still determined to get an non-pedal overdrive sound. Compression will smooth things out quite a bit with an edgy amp although it needs a good player, too.

One last thing, you asked about the Jensen speaker? I don't know this speaker but I would easily recommend a 50 watt Weber Silver Bell ceramic for this amp. Good luck.

[pdf64]

Do not remove the 10pf cap. This is another thing entirely, it is a bleeder cap across the 3.3M resistor, both of which send the original signal of the reverb channel on to the coupler stage that receives the reverb affected signal.

If removing the 47pF bright cap helps but the amp is too bright and edgy on the trem channel (and the normal channel is better in that regard) then removing the 10pF bright cap may be beneficial.

I can see that the original design intent of the 10pF cap may have been to compensate for the treble loss due to affect of Miller capacitance on the high impedance in the grid circuit.
But 10pF is way higher than is required for that, and results in a significant overall treble boost.
http://www.aikenamps.com/index.php/what ... apacitance

[johnny99]

Hi guys, I just wanted to update on this thread.

I'm using an original BF amp, not a reissue. It was originally a silverface that someone messed up trying to mod it, so I rebuilt it to AB763 using orange-drop caps and metal film resistors. The small capacitors are silver mica (including the 10pF at the reverb mixing area) I'm using humbucker pickups through it.

Playing with the duncan tone stack calculator, I could see that to raise the mids I can lower the bass and treble and crank raise the overall volume. So at practice today, I tried the amp with the volume at 10 and the bass and treble both around 3.

It did sound like more mid for sure, and the distortion was a little smoother as well.

I would still like to add a mid pot, even temporarily until I know what value I like. I'm also considering adding a variable negative feedback to try and do the same. Don't get me wrong, I liked the tone I was getting today at practice with these new settings better.. but it's still just a little too ice-picky for me. As rooster said, this amp "cuts" and it definitely does that!

I also tried using a Fuzz Face today as a boost, but it didn't do much.. I think with the amp on 10, there's no room for a boost left to be head since everything is already hitting the wall. The fuzz face just made it sound gnarly and "blowing-up-ish".

[johnny99]

If removing the 47pF bright cap helps but the amp is too bright and edgy on the trem channel (and the normal channel is better in that regard) then removing the 10pF bright cap may be beneficial.

I can see that the original design intent of the 10pF cap may have been to compensate for the treble loss due to affect of Miller capacitance on the high impedance in the grid circuit.
But 10pF is way higher than is required for that, and results in a significant overall treble boost.
http://www.aikenamps.com/index.php/what ... apacitance

Interesting, thanks PDF. Yes, removing the bright cap helped.. but that vibrato channel is way too bright and edgy compared to the normal channel. If I could get trem and verb on the normal channel, I'd be very satisfied. But right now, that vibrato channel is very harsh in comparison.

[pops]

What speaker are you using, i find a 20-25 watt speaker to be much brighter than a 50-100 watt and regardless of amp i try to use at least a 50 watt speaker. Just seem warmer to me.