Tightening bass in Fender blackface

[SixStringBender]

Hey guys, some recommendations please.

I have done the Diaz mods to my DRRI. I'm trying to achieve SRV's mid 80's tone. Think Montreux 1985 Tin Pan Alley. I have noticed on the amp, playing through a 4x12 cab, I have to dial all the bass out. The knob is all the way down, no kidding. I have installed a .022uF mid cap and I still can't get enough mids, so I think I'll put a 25K mid pot in place in the intensity pot location.
10K would probably do it, because it doesn't need much more mids, but I'll do 25KB just in case.

Mods include, Over size OT, SS plug in rectifier, two 50uF 600V main filters in parallel, removed R65 and R66 balancing resistors, installed the 1K and 4.7K drop resistors in place of the 10K resistors in R67 and R68, replaced C11 bypass cap with .68uF, replaced both cathode resistors in V2 with 2.7K (R24 and R17), pulled V1, disconnected tremolo, installed .022uF mid cap installed 100K input grid resistors, 100R in R53 and 120pF bright cap in C10. Plus replaced ceramic caps with equal value silver mica.

The amp is louder, cleaner and it sounds much more like SRV's tone, but it still has too much bass. I can get his early tone with it easily, and his mid 80's tone somewhat, with the bass turned all the way down.

Since I have the tremolo intensity pot disconnected I'm thinking C18, the third stage coupling cap, should be reduced to .022uF. I'm also thinking the bass cap should be reduced since I have the bass pot all the way down and it still has too much bass. It has a .1uF now.

I was also recommended by a tech minded guy to reduce the output stage coupling caps. C27 and C28. Recommended values of .047uF at 630V.

I need to tighten the amp up a bit. I'm thinking a .022uF bass cap. Since the bass pot is all the way down it would make sense to begin there after the C18 swap to compensate for the tremolo disconnect.

I want more of the SSS King Tone Console tone than a Vibroverb. I checked out the SSS 002 schematic and the treble cap is 360pF (increase upper mids?), the mid cap is .047uF and the bass cap is .1uF. I was shocked by the tone stack values as tight as the SSS amps sound.

Also the mid control seems to be a 100K. I assume that is audio taper? I'm nearly blind, so my wife reads the schematic to me. We tried to find the PI tube to track down the coupling caps, but she couldn't find V5. I'd like to know the cathode bypass cap values in the preamp too.

So with that tone stack, how does an SSS have such a tight bass that isn't so extended and boomy like a blackface with the same .1uF bass cap?

Please help me get the extended boomy muddy bass out of this amp. I'd like to be able to adjust the bass to taste, not have it set all the way down and call it close enough. I was thinking to change the bass cap to .022uF, but since the SSS uses a .1uF I'm thinking the tightening should happen else where, but where? Or is it the step filters allowing for the tighter bass? Wouldn't a smaller bass cap do the same thing?

[Colossal]

SSS is tight in the low end with the 0.1uF bass cap because the gain stages are only bypassed with 5uF (among other things).

I helped a guy with a couple of his Fenders which sounded bloated and woofy and he liked the effect of lowering the bass cap to 0.022 uF.

I think I would start with the SSS approach first and if that doesn't float your boat, start making incremental changes...tone stack, output coupling caps, etc.

[TUBEDUDE]

Maybe reducing the size of the first stages coupling and cathode caps would be the way to go. Reducing unwanted bass early on saves gain and energy to amplify the bandwidth o interest, rather than wasting energy on bass that is eliminated later anyway.

[cxx]

Hey guys, some recommendations please.

I have noticed on the amp, playing through a 4x12 cab, I have to dial all the bass out. The knob is all the way down, no kidding.

Might be part of the problem. Some amps are voiced for open back cabs and will sound very bassy with large closed cabs. The SRV fender setups were combos.

[SixStringBender]

I drilled holes in the back of the 4x12 cab with a hole saw. I do prefer an open back. I can not get great tone from a combo. I like a large open back cab. SRV used cabs with his SSS. That is when his tone became amazing, IMO. Plus, I don't like tube rattle in combos and combos beat the snot out of the tubes.

Okay, so two of you made about the same recommendation. I remember reading the SSS had 5uF cathode bypass caps. I'm already at .068uF in one half of V2 (can't remember witch half). So do I replace every 22uF 25V bypass cap with a 5uF? Even the V3 reverb driver and the PI too?

What about the cathode resistors?

So would you guys reduce the third stage coupling cap to .022uF to compensate for the tremolo being disconnected or leave it at .1uF? I guess I should try the 5uF bypass caps first, then proceed to C18 if the bypass caps don't do the trick.

I read where Diaz said they replaced coupling caps with .047 or even .1uF, but it seems that would go against SRV's mid and late 80s tone. Diaz also said he played with the volume and tone controls maxed, but I know for sure that will not get a tone anywhere near SRV's tone. Not even close.

The quote from Diaz says they replaced .042uF caps with .047 or .1uF, but there are no .042uF coupling caps. I guess he meant .022uF or whoever typed it out made a typo.

Here is the quote from the interview.
"The coupling capacitors would be changed to adjust the tone. I’d use a .047 or a .1 in place of a .042 cap. That’s where the tone is—in the preamp."

There is also a ToneQuest article about his Vibroverb and it says it had 33uF bypass caps, but that seems to be going opposite of SRV's tone.

Here is the quote from that article.
"The bypass caps on both channels were changed to 33 mfd, adding a very small amount of bass to the Normal channel, but with very little effect on the Vibrato channel."

These things would be going opposite of what his tone was in the mid and late 80s.

I probably just derailed my own thread. lol So again, where all to put 5uF bypass caps? The cathode of every triode?

[Tone Lover]

Start with V1 has the most effect. Then modify down the line. I wouldnt go past the first couple pre amp stages. it seems everything your quoting from Diaz is going a 180 from were your trying to get to.
just my 2 cents.
Bill

[SixStringBender]

Tone Lover, yes 180 degrees opposite of what his tone was in the mid and late 80s.

By V1 I'm sure, in my case, you mean V2. I have V1 pulled. V2 is the preamp tube for the reverb channel. There are only four triode tubes in use in my amp now. V1 and V5 are removed.

[Stevem]

First a question, is the excess Bass also on the bridge pick up, if not how about just lowering your neck pick up some on the Bass side?

On a guys Strat lest year I installed a roll off cap in series with his neck pickup as this guy needed less bass and lower mids.
He plays thru a cranked Highwatt 50 ( a true 60 watts of clean power!)and its 4 -12 cab which is front ported stock.
Up at the volume he plays at his Bass control needs to be down to 3 to get the bridge pickup sounding good, but it still left the neck too fat and he wanted the neck to be just a certain amount fatter then the bridge and such could not be had with just lowering the pickup height.
I put in a switch so he could get the needed lows and mids back when playing at much lower volumes .

[Structo]

If the preamp cathode caps are 25uF, definitely reduce those.

I found with a couple of my amps, when I reduced the normal .1uF PI caps to
.05uF that it really took the mud out of the low end.

Also, Diaz is kind of known for being a bit vague about his mods.

[Andy Le Blanc]

I get picky about the phase invertor input cap and the caps post of the invertor before noodling with the tone stack... you can also tweak the FB ratio ... tuning the power side

you can inject signal at the PI input and run something like the rightmark program to get a handle on the amps response... tweak that more towards your tastes.

your after critical values of bypass caps... pretty easy to series/parallel
right in the pan with the rig on your bench narrow down your choices

[SixStringBender]

Thanks for the recommendations. I don't play using the bridge pickup. It just isn't a sound I like. I do, however, like the quack of the bridge and middle sometimes and I like the quack of all three pickups in parallel. I most like the neck only and neck and middle combo.

I do already have the bass side of all three pups set lower. It does help, but the problem is in the amp. Even when listening to clips or SRV's early tone before the SSS you can hear the blackface vs Dumble SSS difference. The SSS amp is tighter, less extended and more open sounding in the bass. The SSS clones I've heard clips of (I've never played one) sound tight and clear in the bass too.

This amp is PCB, so playing with caps is difficult. I pretty much need to know what value to put in and risk damage to traces even then. It already has a few jumpers using component leads from the component over to scraped traces to get signal past damaged solder pads.

I'll begin by changing V2A's cathode bypass cap to 5uF. Do you guys think I should go ahead and change the reverb driver, reverb return and PI cathode bypass caps to 5uF? When I use the calculator for cathode bypass caps 5uF doesn't seem to make much difference as far as the numbers show. Remember I am blind, so if there is a graph I can't see it.

V2B, the tone stack recovery amplifier, is already at .68uF (I said .068uF earlier, sorry I meant .68uF). Again, V1 is pulled. .68uF is the value in the 64 Vibroverb Custom Fender sold beginning in 03, I think, and sold for a few years.

Colossal, you wrote, "SSS is tight in the low end with the 0.1uF bass cap because the gain stages are only bypassed with 5uF (among other things)."

What are the other things?

TUBEDUDE, you wrote, "Reducing unwanted bass early on saves gain and energy to amplify the bandwidth o interest, rather than wasting energy on bass that is eliminated later anyway."

I like this approach. The coupling caps will be my last step, if necessary. However, would you agree Leo Fender most likely went with a .1uF coupling cap in the third stage due to the 50K to ground at the intensity pot? Since I did away with the 50K to ground shouldn't I counter the choice to use such a large coupling cap in the third stage? That wouldn't harm bandwidth by going to .022uF there would it? Since it is a pretty standard coupling cap value.

[Reeltarded]

You are working it out all backwards.

Coupling is where to start. You should undo everything you have done and stop reading about Diaz.

Use an EV in a closed back cabinet, use an amp with 5x the headroom. Stop trying to do it how you imagine and instead do it like everyone but Diaz. You will NEVER be happy with any .1 couplers. It's not what to do.

Coffee..

Change the first coupler to at least -5x what it is now. Too tight? Ok, half the original value then. Closer but not enough? Tight but wooly?

Ok, that first cathode is fully bypassed at 25u (?) (not looking at anything) so it won't start sounding very much different until you get the stage tuned a few Hz below your lowest note, somewhere around 78Hz. I am liking 2uF-ish..

More shaping?

Decrease slope resistor slightly. Increase midrange resistor slightly. Do a little of each if needed. If your amp was balanced you would use the other pickup settings.

Limit the treble pot to half it's value with an equal value resistor across the outside lugs. Now you can turn the treble up a number and the back pickup is sweet enough to use. Magic balance.

Kick it up. change 1st plate resistor to 220k.

I'm probably liking that setup.

[SixStringBender]

Reeltarded, please reread my posts. I did not install any .1uF coupling caps. I was afraid I would derail my own thread. I even said I would in that post. If you read that post I said the coupling cap change Diaz said he made is the opposite direction of what I want. I said that before anyone else pointed that out too.

Those changes were not SRV's tone. Or at least that was not SRV's tone in the mid and late 80s. Maybe at El Mocambo. I don't like that sound though. A lot of people do, but that is not great tone, IMO. Great playing, yes, but not great tone.

The Fender 64 Vibroverb Custom did not have any of those larger coupling cap or larger cathode bypass cap changes. The 64 Vibroverb Custom is the amp I modeled mine after. Not what Diaz or ToneQuest said. It appears Diaz told Fender a different story. At least based on the 64 Vibroverb Custom schematic.

The coupling cap I keep speaking of is C18. Look at the DRRI schematic. It is .1uF right from Fender as Leo designed it. He probably put that large value there due to the 50K tremolo pot sending signal to ground through the 50K resistance. I no longer have that path to ground. I have more signal going through C18. Shouldn't I reduce C18 to .022uF? .022uF is a very common coupling cap value. The same as C12.

As far as the other mods. They all tighten, firm bass and increase clean headroom. Oversize OT, SS rectifier, the 100uF main filtering, the smaller drop resistors increase preamp voltage to increase clean headroom, C11 replaced with .68uF instead of stock 22uF reduces bass and R53 at 100R tightens bass. All those things are steps in the proper direction. I just need to take it a few steps farther.

Note: I didn't install the 33uF cathode bypass caps like in the ToneQuest article either. I knew that was a step in the wrong direction as well.

I'm not playing in stadiums so I don't think I need a 150W MONSTER. If I had an SSS clone I would have a 100W version and I would have an OT with multiple taps so I could pull the outer two, or inner two, output tubes, change the OT taps to reflect the proper primary impedance and reduce the MONSTER to a lesser 50W monster. When the time comes for 100W I'd reverse the changes. Put tubes in and flip a switch. I don't even see anything wrong with using JJ's 6V6S to reduce volume to put the sweet spot of the amp in a volume level people can tolerate. If I ever have an SSS I will have my power transformer custom wound so I can do just that. I would probably aim for 450V on the plates of the output tubes so I could use JJ 6V6S or JJ 6L6GCs.

I have ideas to make the amp I need, but I am limited due to my blindness. If anyone is aware of a kit for the SSS 002 build with a drilled chassis and a good layout and predrilled boards I think my wife and I could tackle it. It would have a few twists to make it more versatile for sure.

[Reeltarded]

Yep on the .022u coupler.

I would focus on the treble cap and slope resistor next and serious about limiting the treble pot value to balance it.

[SixStringBender]

What treble cap value? 360pF? The treble pot in the 002SSS is 250K as is the DRRI too. Or do you mean to play with low treble settings? I don't play with the treble pot very high. I do change the treble pot setting based on the tone I want.

I haven't checked, but I thought the slope resistor was 100K in the SSS. If it is lowered that will mismatch the impedance from the preamp plate.

I have thought about doing a switchable cathode follower tone stack. If I could find a high voltage DC DPDT switch I would do it so I can switch back and forth from cathode follower fed tone stack to plate fed tone stack. I have V1 sitting there empty to rewire. Or maybe even a MOSFET source follower would be even better.