Experience with 100 and 50w JM sig style amps

[imo1]

Hey y’all,

I built a few Dumble style amps over the last couple of years.
I’ve been playing mainly my 2 JM100s. They should great, but are really loud. I use them pushing breakup, for a bluesy sound.
I recently played a fest and jammed with Kenny Wayne. All his amps are dumbles, feel similar to mine, but had a bit more sponginess that works with my tone and style. They were all 50w models. I’m considering dropping in a 50w OT and disconnecting a couple of the output tubes.

Curious to hear if anyone has much experience more in this style, which to me is a “super” fender mode.
There are aspects of the 100w I really like, but it has a stridency about it that makes me miss some of the subtle playing I can get on some more traditional fender models. Wondering if using a smaller OT will be a step in the right direction?

[dorrisant]

Consider reducing the value of the reservoir cap. Look at the schematics of 50 and 100 watt ODS. See the difference, maybe apply the same principal to your amp. It is certainly cheaper to try than a different OT. Add capacitance in series with what you have to drop it. Example: two 100uF in series equals 50uF. Add balance resistors though.

[rccolgan]

Have you played with the GNFB too bringing it down to 4.7k maybe? Perhaps the LNFB on the first tube as well. That will clean things up so I'm not sure if that's something you'd like but I always found the feel more than the cleanliness when I adjusted these two things. I'd love to see your amps!

[imo1]

Consider reducing the value of the reservoir cap. Look at the schematics of 50 and 100 watt ODS. See the difference, maybe apply the same principal to your amp. It is certainly cheaper to try than a different OT. Add capacitance in series with what you have to drop it. Example: two 100uF in series equals 50uF. Add balance resistors though.

Thanks! Definitely will look into that. Power section is definitely stiff. Obviously was not able to look into Kenny’s amps while playing them, but I’m assuming they were probably in line with what Dumble normally did with these style amps. It seems that most of his changes were in the tone circuitry, with power cap section stuff seeming to be pretty consistent.
I have a deal with Mercury, so the transformers aren’t that bad

[imo1]

Have you played with the GNFB too bringing it down to 4.7k maybe? Perhaps the LNFB on the first tube as well. That will clean things up so I'm not sure if that's something you'd like but I always found the feel more than the cleanliness when I adjusted these two things. I'd love to see your amps!

I’m out on the road right now, so hard to get too deep into it. Playing tonight with the Rev! I built two parallel amps, so will experiment with the one at home and if I dig it, implement it on the touring one. I think I have the feedback defeat on V1 on both amps. I do prefer that often on. Haven’t messed with the main one.

I know you are a big Mayer fan. Been to your site many times as I was trying to figure out what I wanted to do. It’s awesome! I think Mayer is an amazing player. I’m looking for a slightly different tone than him. I know it’s so subjective (hence the beauty of the search) a bit more grit and a bit more high mids. I was really blown away by Kenny’s tone when we played together. Just had that thing that I’ve always been looking for two.

[rccolgan]

Thanks for your kind thoughts! Yeah I dove into amp/pedal building as a challenge to build what cannot be bought in Mayer's rig throughout the years. Lol

Oh and another thing to consider is simply pulling two power tubes and adjusting your output impedance to match whichever speaker arrangement you have. You can also try mismatching speakers. Plenty of info over the years of players and even Dumble mismatching speaker loads for different feel. Even the stock Zinky Fender Dual Professional has 4 ohm load coming out of a 8 ohm tap for a certain feel.

Lastly maybe trying 5881 tubes so long as they are the correct voltage rating for less head room. The above "mods" could be easy without too much messing around and still follow the Dumble theme that might be in Kenny's amps. Would love to find out one day but I respect the amp-privacy ha. Kenny has great tone/fingers.

Oh since you're a Mercury artist, maybe they can give you an under-spec OT kinda like the stock Super Reverb?

Last, last, last thing is maybe a speaker swap? Which speaker did Kenny have? Maybe start there

[imo1]

I’m actually gonna build a separate 50w. Trying to find that thread about those passive attenuators. They are supposed to sound a lot better than the attenuators(I have a Weber mass and really don’t like how it compresses the sound.

With this one I took out the triode “half power” switch. I didn’t like what that did. I often use the bypass switch on the NFB loop on V1. To me the amp sounds a little more alive this way. I also did the tone stack like Nik does, which I think he did to account for John using 2 amps in parallel.

I am also gonna play with the possibility of a resistor in the place of a choke(on a switch for now). I will try messing with the first res cap. The tricky thing is truly knowing when changes are actually better as you make them. I shared an AES stage with Eric valentine a few years ago, and his presentation was about aural memory and why a/b testing with audio is a flawed concept. For me, I need to make a change and then use the amp in different settings.

I’m pretty happy with the speakers. It’s kind of hard to put into words the things I want to fine tune, but the easiest thing would be to say it’s a bit clacky(like a twin) and if you do that hendrixy back picky rhythm stuff it kind of barks in a weird way. That is setting the volumes pretty high- master almost all the way up and gain around 11-12
That sound has a nice “dirty” clean thing that allows me to use pedals much more subtlety and is like a steroid version of what I used to use a super for

[WhopperPlate]

A) do you have gut shots of the amps in question?

B) what’s your cabinet impedance? If it’s 16 or 8 try going a step lower : 8 and 4 ohm respectively

C) I bet all of those kws amps have various nos CF and CC resistors in the power supply…and your amps probably have standard fare xicon power resistors …am I right ? Strident comes to mind

[imo1]

Unfortunately no gut shots of Kenny’s amps, and he really didn’t know a ton about what Howard did. I speculate that the circuit was not that different from his often built fender styles. Seems that he mostly did the 100k/1.5k with variances on cathode cap, generally more stuff ps filtering. Kenny’s amp sounded like the classic tone stack that he used (forgetting terminology, but I think low plate classic)
As far as power supply resistors, for the bigger ones I used metal oxide. I guess everything can be part of it, but from talking to my bigger amp builder friends, they tend to largely discount these areas as focal points.

[imo1]

Here is a link from a show last week. You can hear the amp "clean" at the top. It goes to a TS type pedal with just a touch of gain and then a KOT. The mix towards the end(iphone vid) cuts off some of the clarity of the sound as it is obviously being compressed through the phone, but gives you a pretty good idea of the amps sound. this is my favorite setting with the current rig--master almost all the way up and gain around 50-60%

https://vimeo.com/766484728

[WhopperPlate]

Unfortunately no gut shots of Kenny’s amps, and he really didn’t know a ton about what Howard did.

I meant your amps .

As far as power supply resistors, for the bigger ones I used metal oxide. I guess everything can be part of it, but from talking to my bigger amp builder friends, they tend to largely discount these areas as focal points.

Your guess would be correct ime. Look at some Dumble ultraphonix and check out what he used. I like throwing a big CC somewhere in the power supply string. IME this will get closer to what you seek. A little more give and ease if harmonic feedback.

[WhopperPlate]

Here is a link from a show last week. You can hear the amp "clean" at the top. It goes to a TS type pedal with just a touch of gain and then a KOT. The mix towards the end(iphone vid) cuts off some of the clarity of the sound as it is obviously being compressed through the phone, but gives you a pretty good idea of the amps sound. this is my favorite setting with the current rig--master almost all the way up and gain around 50-60%

https://vimeo.com/766484728

I like it . You are having fun ! Great to hear !

Based on what I hear, i think my recommendations would be helpful .

[imo1]

I need to grab some pics off of my dead iphone. I kept pretty good records, but didn't back up the photos.
Fun show! I was able to run amp without attenuator(rare) and that sure makes a difference. I'm pretty happy with the general sound, but always looking for that last couple of percent.

[rccolgan]

Here is a link from a show last week. You can hear the amp "clean" at the top. It goes to a TS type pedal with just a touch of gain and then a KOT. The mix towards the end(iphone vid) cuts off some of the clarity of the sound as it is obviously being compressed through the phone, but gives you a pretty good idea of the amps sound. this is my favorite setting with the current rig--master almost all the way up and gain around 50-60%

https://vimeo.com/766484728

Dang that thing really sings and your playing is great! I can see what you mean about the tone being too fast. I'm curious about where you land on this!

[imo1]

[/quote]

Dang that thing really sings and your playing is great! I can see what you mean about the tone being too fast. I'm curious about where you land on this!
[/quote]

Thanks! I think a lot of folks would mix this with another amp, but I'm already way too loud for many of the venues that I'm playing. It is tricky trying to dial in an amp on that level