Where best to post about diff between Fender and Dumble?

[ViperDoc]

That sounds awesome.

[imo1]

Thanks! Im really happy with it! What I realized is that a lot of the designs Ive been emulating were used in conjunction with other amps. So, what works for this amp if it is paired with a modded super and vibroverb, or a steel string and a bandmaster, etc, is different than what the amp needs to do on its own.

[imo1]

Well, turns out the cold is covid, so I'm isolated for a bit. Good news is I feel ok and can spend the time messing with the amp.

Let's hope it remains that way!

So, with the prior tone stack experiment, if I were to try to emulate a Fender tone stack, with mid 100k pot, if I had it at 10k I would be at the same place as the Fender tone stack with mid maxed out?

Correct, around noon if your mid pot is log taper.

I know I keep stabbing at this, but this is the area where the technical, data driven stuff isn't getting me there. I'm sure there is a way to do all of this through technical study, but I don't see it.

There are so many interactions in the human-guitar-amp-human loop that it's very hard to isolate cause and effect. Everything is confounded. The best you can do IMO is to use known (simplified) relationships to guide experiments.

I am gonna keep experimenting with this. I'll try the 10k and see what that does. I'm also gonna tack in all the 15u on the cathodes(outside of the reverb driver).

Here's a plot of the effect of cathode bypass caps 4u7, 10u, and 22u on a standard 100k Ra, 1k5 Rk 12AX7 stage. All of the action is below 100Hz, and even at 40Hz (open 4th string on a 4-string bass), it's only 2dB. As you go lower, the direct effect becomes much less audible, but might cause other issues that are. If those notes get distorted, then the higher order harmonics generated become very audible.

This is interesting. Its probably a little hard to hear on the recording, but what it sounds like to my ears is that there is a less defined end to the bass(possibly explained by where the 20u roll off, which is below most human hearing) and this actually makes the amp sound like the lower mids are more defined. Again, since I know Fender designs so well, i would reference a vibrolux, pro, or super reverb with the bass somewhat low, where there is a really pleasing low mid), but unlike those amps, there is an additional oomph that I could hear really translating well to the stage or studio. When I took the more stock JM100 design and put a mic on it, I found I was having a hard time translating the lightly overdriven sound to tape.

[imo1]

PS, nice tones! You live in that low mid zone, so I can see why carving that out would not be good for you.

I feel like my sound is in the realm of the same sounds that a lot of blues rock oriented players are going for, at least the fender guitar side. Fenders don't have that low mid push that pauls and other more gainy guitars do. I actually grew up playing pretty much all fenders, so I think that is what I'm trying to do, just bigger. Isn't that how we all stumble into the Dumble realm?

I really appreciate all of the help. I love learning things more than anything, and even though there is still a bunch about the Dumble designs that confuses me, I feel like I am starting to grab the parts that work for me.

I'm curious now to see whether these changes will work similarly on my 50's. Unfortunately they are in Austin and I won't be able to mess with them until Im donw there again. My theory is that I will have to compromise some because the bass won't be as big with the 50, so if I go with all the big cathode caps it might flub out more like a Fender. Curious to see how the PT/OT size vs the filtering balance in terms of that dynamic

[imo1]

I've been playing on the amp every day for the last week and feel like I have a pretty good feel for what it does. I love upping the caps to 20U on the cathodes.
I want to go ahead and sub in a pretty standard Fender tone stack, and play on that for a while.

The .001 treble cap into the mid switch(off) has 280pF into the treble pot. These seems pretty insignificant looking on the tone stack chart.

Doesn't the 1.8k from the bass pot to ground change how tone stack reacts? As I see it, this would put the 1.8k in parallel with the 100k pot, which would basically be like a Fender mid pot on 1, which is a pretty extreme setting on a Fender.

I would love the ability to go back and forth quickly, but i feel like the Fender stack this hollowed out isn't really what it sounds like.

Am I tracking this correctly?

[martin manning]

The .001 treble cap into the mid switch(off) has 280pF into the treble pot. These seems pretty insignificant looking on the tone stack chart.

Agreed.

Doesn't the 1.8k from the bass pot to ground change how tone stack reacts? As I see it, this would put the 1.8k in parallel with the 100k pot, which would basically be like a Fender mid pot on 1, which is a pretty extreme setting on a Fender.

Yes.

I would love the ability to go back and forth quickly, but i feel like the Fender stack this hollowed out isn't really what it sounds like.

If you were to short the bottom of the bass to the top of the mid, and increase the 1k8 to 11k1 (11k1 paralleled with the 100k mid pot effectively makes it a 10k), you would have a Fender stack, except for the 500k bass (but that is just a variable resistor so it can mach the 250k of the Fender).

If you added a 10k in series with the 1k8 (making 11k8), and then arranged a switch to short the 10k for Two Rock, and then un-short it and short the bottom of the bass to the top of the middle for Fender, you'd be very close. The plot below shows what the Fender mode would look like compared to actual Fender, and note the treble ends look nearly identical.

[imo1]

Man..I want to thank everyone, especially you Martin, for your generosity of time and knowledge.

We are never done in this journey, and as I said in one of the first posts on this thread, I have a hard time truly knowing an amp until it has lived on the road with me lots of different situations and environments. So, it is possible that in a few weeks or months, I will change my mind..

I have to say, that for me, in rolling back the V1 neg feedback, upping cathode caps, and going to the typical fender tone stack, I have what seems to be the perfect single amp for more of the Hendrix/bluesy type of playing(at least for the single coil strat/tele world!)

This most recent rabbit whole started after about a year of using the JM100 style amp on the road. I loved the power and clarity of it but I had a couple of issues. The first was that it was so loud! I'v played a lot of really loud rigs over the years(at one point using 3 Fender(zinky) tonemasters, but with this amp, there was such a huge amount of low end, that even when I was playing a big theater, or outdoor event, the amp would just take over the stage. The other issue I was having is that in order to get a decent "cleanish" base sound, My lead sound was a little tight, which to me compromised some of the more emotional parts of my playing. If you have followed the thread at all, I was thinking it was a lack of power supply "sag" initially.

As I experimented with the circuit, I found that it wasn't the sag I was missing, it was more that the amp was so tilted to low and lower middle frequencies, which have an exponential control of physical space with high frequencies, essentially overtaking a space and drowning them out. When I changed the cathode caps, I found that the low end, to my perception was much rounder and more pleasing. When I switched the tonestack, it shifted the feel of the amp up a bit. I still have a ton of low end, but now I can play a chord hard and it all holds up, and if i put a teeny bit of "heavy hand"(Jesse Davey's marvelous interpretation of a tube screamer) it does that thing that thing that makes the notes really jump off. I also found that when I did these modifications, I found the contour to be more usable. I actually like it now at about 30% giving just a bit of that "scratch" to the mids, whereas before it sounded best completely out of circuit. Lastly, I like changing the 120k that mixes with the 68k to a 220k. I really like the way this pushes the amp. I put this on a switch a few weeks ago, and preferred the circuit to the stock 120k. Of course, this is before I did all of the work on the amp, so I may try tacking another 220k in parallel to see what that sounds like.

The JM100 was designed as a complimentary amp for Mayer to run with his SSS. Because of that he runs it pretty wide open, and all of that low mid information works really well with the bite and chime of the SSS. I know a lot of young players are chasing that sound, and I think you just can't really get there with the one amp stock. There are a lot of different ways to play guitar, but if you are doing a blusier thing and using single coils, taking advantage of Dumbles filtering and build quality tips like lead dress and ground, really does do the thing that a lot of us are looking for, which is the ultimate Fender style amp!

Even the SSS, which I really love, but are so loud, to me sound their best when they are mixed with something like a super reverb or a JM style amp. I don't know enough about the newer Two Rock, in terms of how they are running their tone stacks and such, but listening to Matt Schofield, it sure sounds like a Fender stack to me. I do hear a little bit of that negative feedback in his sound, but I wonder if he is running through the FET at the front end? It definitely has a tighter mid and a nice bite to it when he digs in

[imo1]

Recorded on an iphone, but you can hear the gist of it. To me, you can really hear an important part of what Ive been looking for at 15 seconds in. There is that overtone(on the BB king lick) that makes those notes come alive.

Blues riff.m4a

Also attaching a cleaner take. This one suffers from some iphone distortion, so it doesn't do the amp justice. the is harmonic distortion, but no gainy distortion. This is around what I would call a "clean sound" and I love how the chords and low end hold together, lots of definition when I play the low E, but it has that very pleasing sound where nothing pokes out. Before, when i would play some of these big chordal parts, I would find myself using compression to reign in the frequencies.

Angel.m4a

[bepone]

sounds rich! is it some hollow body guitar?

[martin manning]

Sounds great! Very happy to engage on this, and it was an interesting and educational collaboration. I hadn't really dug into the various Dumble stack variations or the Two rock version before. Those clips are both with the faux Fender stack? Love the full bass and Hendrix tones in the second one.

[WhopperPlate]

What’s the signal path in the clips ? Pedals?

[WhopperPlate]

The .001 treble cap into the mid switch(off) has 280pF into the treble pot. These seems pretty insignificant looking on the tone stack chart.

Agreed.

If you are going this far down that rabbit hole searching for your sound then what’s negligible becomes easily arguable . Nuances remain

Recorded on an iphone, but you can hear the gist of it. To me, you can really hear an important part of what Ive been looking for at 15 seconds in. There is that overtone(on the BB king lick) that makes those notes come alive.

Blues riff.m4a

Also attaching a cleaner take. This one suffers from some iphone distortion, so it doesn't do the amp justice. the is harmonic distortion, but no gainy distortion. This is around what I would call a "clean sound" and I love how the chords and low end hold together, lots of definition when I play the low E, but it has that very pleasing sound where nothing pokes out. Before, when i would play some of these big chordal parts, I would find myself using compression to reign in the frequencies.

Angel.m4a

Sounds decent , got any gut shots for reference ?

[imo1]

What’s the signal path in the clips ? Pedals?

The phone is a bit off to the side which does contribute to a bit of a boost in low mids,but..

It’s a replica of my #1. #1 is a ‘62 Strat body with a ‘55 esquire neck. This one is built to those specs, but has a flame roasted neck. I currently have a Lollar Chicago lap steel in the bridge

[imo1]

The .001 treble cap into the mid switch(off) has 280pF into the treble pot. These seems pretty insignificant looking on the tone stack chart.

Agreed.

If you are going this far down that rabbit hole searching for your sound then what’s negligible becomes easily arguable . Nuances remain

Recorded on an iphone, but you can hear the gist of it. To me, you can really hear an important part of what Ive been looking for at 15 seconds in. There is that overtone(on the BB king lick) that makes those notes come alive. Blues riff.m4a

Also attaching a cleaner take. This one suffers from some iphone distortion, so it doesn't do the amp justice. the is harmonic distortion, but no gainy distortion. This is around what I would call a "clean sound" and I love how the chords and low end hold together, lots of definition when I play the low E, but it has that very pleasing sound where nothing pokes out. Before, when i would play some of these big chordal parts, I would find myself using compression to reign in the frequencies. Angel.m4a

Sounds decent , got any gut shots for reference ?

I tried the 330 in parallel with the .001, which puts it right at 250. It is on a switch. To me the difference in imperceptible.


I’m running around right now and have a session later.
I’ll post some pics, but it’s pretty temped right now. All the 15u caps are tacked in, tone stack connection is clipped in.

I’ve been referencing against all of my black faces and it really sounds like taking the best of them all. I have a ‘63 Vibroverb and a couple of really nice supers. This amp has the low end sound, but it holds up better.

The “deep” switch is pretty much unusable now, but for live playing in my style it wouldn’t work even with the 5u cathodes. It’s too much low end for the stage. Sounds great in a bedroom though!

[imo1]

Sounds great! Very happy to engage on this, and it was an interesting and educational collaboration. I hadn't really dug into the various Dumble stack variations or the Two rock version before. Those clips are both with the faux Fender stack? Love the full bass and Hendrix tones in the second one.

Thanks! At some point I’ll properly record them as the distortion. Especially evident on the Hendrix clip is 100% the iPhone. It has definitely been educational for me! I feel like I’ve solved the issue I was up against for decades coming up.
There is nuance to what each player is looking for, but I’m definitely pushing the design limits of what one amp can do