.45 Cowboy Special

[SILVERGUN]

I realized today that if I never post these pics, I'll never post them, so here you go. This forum is my only presence on the internet so the least I could do is show you guys what I'm up to.
When I started the build I wasn't sure exactly what I was building, other than it was going to be SS rectified 2-EL34. I had a Hammond 290CX PT and a Classictone OEM Bassman type (4 ohm secondary version) OT. I used a pre-punched square faced (no angle) Princeton chassis from eBay. I had to enlarge the PT hole to fit the 290CX.

One day last year I just started building a rectifier, out of nowhere, just started cutting G10, setting eyelets and soldering. So, the first pic is just the initial power supply layout.
2nd pic is when I got some more direction. I started looking at different Dumble schematics and wound up basing this off of #183.
I wanted to work with terminal strips, knowing that this was going to be a highly-tweaked build. I wanted to build an active FX loop into the amp and wanted a flexible layout.
I also wanted to "fix" a flaw that I see in most Dumble type amps. I rarely see master volume settings above 2 or 3 because I feel like there is a better choice for a phase inverter in these amps. My intention was to run more preamp overdrive into a PI that could handle it "better". I read a bunch and wound up mostly listening to Merlin's advice about using a 12AY7. I tried a 12AU7 but quickly reverted to the AY7 as it just sounded like it worked better for my goal.

This was the first time I worked off of the schematic and just sat and wired one component at a time and created the layout "Cowboy style", on the fly.
This took an inordinate amount of time but was strangely satisfying to me for some reason. I wanted everything to line up and make sense. So I took way too much time to try to make that happen.

I'll post the pics for now and see if there is any interest. The pics ARE the layout and the schematic is still changing. I had to take some time away from it, but I'll be back on it soon to solder some of the tweaks in "permanently".

Here's another thread where I got some help trying to figure out the FX loop and how I wound up with an amp with no NFB, which I didn't know I wanted until I forced myself to try it.  FX loop MIX control help (el34world.com)

It's cool to see the influence of all of you in my build style. Thank you to all of you who post and continue to help and inspire me to build!

[SILVERGUN]

saving space for power supply schematic

[Rontone]

I'm loving those neat tight heater windings, the teal/turquoise wire colour,

At the end with the rectifier attached, whats that for or where is it going, Heater DC or for another part of the circuit

[SILVERGUN]

I'm loving those neat tight heater windings, the teal/turquoise wire colour,

At the end with the rectifier attached, whats that for or where is it going, Heater DC or for another part of the circuit

Thanks Rontone
That's my 5V relay supply. I would normally use Doug's board but decided to use one of these rectifiers I had laying around. I met this crazy old coot from Texas and he sent me a box full of them. In 8 years this is the first one I have used. It seemed to fit the layout. This was right before I realized I had forgotten the voltage regulator.
This was me being avant-garde.

[Rontone]

Ah ok, and is the relay to let the power on slowly or a speaker output relay,

I've only ever looked at them in a HiFi I had with corroded relays on the speakers that would occasionally not come on,

Edit:- I missed the part about active FX loop, is the relay for that?

[SILVERGUN]

Ah ok, and is the relay to let the power on slowly or a speaker output relay,

I've only ever looked at them in a HiFi I had with corroded relays on the speakers that would occasionally not come on,

It's the channel switch in the schematic. DPDT relay that Doug sells.

[Rontone]

I see it now, you can learn something new every few minutes on this forum,

[shooter]

This took an inordinate amount of time but was strangely satisfying to me for some reason.

ok, it's official, you're now a geek     

[sluckey]

I like the Cowboy style. I may have met the same old Texan. He had noticed the lighted power switches I was starting to use in my builds and said he would send me some with different colors. He had ordered some 12V switches for a boat project but he received 120V switches instead. So he sent them to me in a 6x6x4 box. He used the same diode bridge as in your amp for packing material. Must have been a hundred of 'em. I'm sure he had a good laugh. Folks around here just call him Dummyload. Wish he was still here. He had a lot to contribute to the forum.

[tubenit]

I read a bunch and wound up mostly listening to Merlin's advice about using a 12AY7 as a phase invertor.

That's interesting!  I didn't know Merlin had suggested that.  Experimenting, I actually tried a 12AY7 as a phase invertor for the first time yesterday afternoon and thought it sounded really good.


with respect, Tubenit

[SILVERGUN]

Folks around here just call him Dummyload. Wish he was still here. He had a lot to contribute to the forum.

Yeah, there is plenty of Harold's influence in this build besides that little bridge.
I was very lucky to have his guidance through the years.

Thanks for taking a peek.
There's plenty of sluckey in there too. There's that can cap serving the plate and screen! I hope Willabe doesn't see it.

[SILVERGUN]

I read a bunch and wound up mostly listening to Merlin's advice about using a 12AY7 as a phase invertor.

That's interesting!  I didn't know Merlin had suggested that.  Experimenting, I actually tried a 12AY7 as a phase invertor for the first time yesterday afternoon and thought it sounded really good.


with respect, Tubenit

Yeah...here you go: The Valve Wizard -Long Tail Pair


The tubenit part would be where I squeezed in the FX loop with no fear and then desecrated the original circuit with whatever tweaks made ME happy.
THANKS for that!

[mresistor]

Folks around here just call him Dummyload

He sure did contribute to the intel one can acquire here fo sho.   

[jojokeo]

Nice SG, your work is very clean. I love working with tag strips too. Eyelet and turret boards are good but dammit I have to make those unless I use a pre-fabbed one or two.


I’ve designed a couple pi’s - one for the Au specifically - and the AY being cleaner & chimier but usually ended up using the AT which goes into most of my builds/and customer’s amps. I get plenty of gain with those and most prefer it too.


I believe HBP explained the deal with chime coming from the transconductance & gain relationship back years ago. I’ve grown away from too much gain and find it easy to attain in various ways, and use it here and there. But I love sweet tube clean chime & punch hearing every nuance coming from my guitars and fingers. Am I getting old? 🤨

[jojokeo]

Folks around here just call him Dummyload

He sure did contribute to the intel one can acquire here fo sho.   

I haven’t been around a lot lately and I’m afraid to ask but isn’t that Pete? And isn’t he okay?

[sluckey]

Yes, that's Pete. He's fine. Just decided to take a break.

[SILVERGUN]

ok, it's official, you're now a geek     

I went back in and cleaned up some temporary mods and this is where we are tonight.
I'd like to say it's done but we all know I'd be lying.

[SILVERGUN]

...... I’ve grown away from too much gain and find it easy to attain in various ways, and use it here and there. But I love sweet tube clean chime & punch hearing every nuance coming from my guitars and fingers. Am I getting old? 🤨

Sounds to me like you're getting better.
I, on the other hand, need the OD to sound better and make the guitar more playable. My clean playing leaves a lot to be desired.
I love the FEEL of 4 gain stages. Especially this Dumble-fied, mid-boosted, feedback machine. It feels like I'm trying to hold back a firehose.
You know me, I like OD with my OD.

[glass54]

Hi SG
Love the neat/sleek layout and particularly like the 25W Ohmite 1k Resistor for Screen supply (have used these myself)
 
Regards
Mirek

[shooter]

I like the sweet line fuses, those ain't your average Radio Shack 25 cents specials

[SILVERGUN]

Hi SG
Love the neat/sleek layout and particularly like the 25W Ohmite 1k Resistor for Screen supply (have used these myself)
 
Regards
Mirek

Thank you Mirek, I respect your opinion and appreciate you having a look.
I like how that resistor fit between the cap and tube socket to keep the wiring tight in that area.

[SILVERGUN]

I like the sweet line fuses, those ain't your average Radio Shack 25 cents specials

I almost no-brained it and threw some glass fuses in there until it hit me what the voltage rating is on those.


The ones I used can be found here:
2 Pack Digital Multi Meter Fuse FF500MA (500MA,0.5A)1000V Fast Acting Ceramic Fuse For DC Digital Multi Meter 6.3 x 32mm - - Amazon.com

[mresistor]

Very cool way to run the PT secondary leads fused to the rectifier and then the first filter.  Good use of space.

[dwinstonwood]

Very cool way to run the PT secondary leads fused to the rectifier and then the first filter.  Good use of space.

Yes, and one short wire from the power tube screen to the second cap can really cuts down on the number of otherwise long and redundant wires (as in my amps). Nice!

[uki]

@Silvergun what is the PI Trim for, balance the PI ? Please could you explain.

[SILVERGUN]

@Silvergun what is the PI Trim for, balance the PI ? Please could you explain.

It is usually used to balance or purposefully unbalance the signal coming out of the PI.

In my case it no longer makes sense because I departed from standard LTP operation when I decided to apply my wet signal directly to it's own half of the PI. I didn't plan it this way.
So, going forward for me, my signal will always be somewhat unbalanced, and I will have to decide by ear where to set my dry and wet levels for best results.

[jewishjay]

Can I ask.....why 56k plates on the PI? #183 has 100k and 110k.....do the lower plates decrease gain?

[SILVERGUN]

Can I ask.....why 56k plates on the PI? #183 has 100k and 110k.....do the lower plates decrease gain?

I designed it for use with either a 12AY7 or AU7 PI
#183 was just a jumping off point for me.

Also, that 25K trimpot adds 12.5K in series with either side in a centered setting.

Are you familiar with the Load Line Plotter?...bottom of this page The Valve Wizard

[uki]

When the amp is ready, are you going to make a sound clip or video clip?

[SILVERGUN]

When the amp is ready, are you going to make a sound clip or video clip?

Yes, definitely, uki.

I was doing some home play testing tonight and I'm ready to take it to the rehearsal space and let her rip.
As a habitual tweaker it is hard to know when to stop, but I think I'm very close.
I need to settle on a speaker because this will be made into a single 1x12 combo and I haven't found the right match....yet

[SILVERGUN]

Here's a nuts and bolts shot from behind for all of you amp porn addicts out there.
It's getting ready to leave the bench.

[Williamblake]

Very nice. If you can't let her go you could start painting the solder joints now?

[shooter]

 

If you can't let her go

His playing fingers might be itchin to bad from all the solder fingerin

[tubenit]

The best sounding speakers I've found for my Dumblish inspired builds have been the Warehouse ET65 for a smooth OD tone  & the Emminence Delta Pro 12A for the clean tone (but also a decent OD tone).  I've also tried Emminence  Cannabis Rex,  Red White & Blues and Texas Heat which were all decent but I didn't think sounded quite as good.


This is a great thread and I am grateful you are sharing your innovation and good work on this with the forum.   

IF you wanted to have NFB but also wanted to have a mix control of the FX, you could consider something like this attached schematic?  Not saying you "should" do this simply tossing out a simple idea IF you wanted to do it.  And you could put the NFB on a mini-toggle switch if you wanted to have it a little clearer (w NFB) or more grit  (no NFB)     Just an idea to ponder?


With respect, Tubenit

[SILVERGUN]

Very nice. If you can't let her go you could start painting the solder joints now?

Let's not get crazy now.
I said almost ready, not "paint the solder joints" ready.
I'm a little too commitment-phobic. 

[SILVERGUN]

The best sounding speakers I've found for my Dumblish inspired builds....

Thanks for these suggestions. It's such a critical part of the puzzle and even affects the final tweaking process. I always thought I wanted a Jensen Blackbird (100 watt alnico), so I bought one recently to try with this amp. I broke it in and then plugged it in and it was the exact opposite of what I expected. That was very disappointing and a big step back. So then I bought a Celestion G12M-65 Creamback. (and I am not rich by any means, so this is painful). Same disappointment. So I have been running it at my bench with the Creamback and my old G12H-30 and that sounds very good to me. So, it will be tough to settle on just one speaker, especially when I don't have that much experience with different models. Every time I disconnect one for the other I wind up missing the other speaker. I actually seem to prefer the G12H-30, which is counter-intuitive to what I thought I wanted.

[shooter]

& the Emminence Delta Pro 12A for the clean tone

the &'d part is 'portant 
find a buddy with a 2 by cab, trade the Jensen for an Eminence, add the older creamback.
If you pay the freight you can borrow mine, has an E 12A and an 80's creamback, I can't find amp that makes that combo sound bad

[SILVERGUN]

Sorry for the long post, but I think this is important...

IF you wanted to have NFB but also wanted to have a mix control of the FX.....

I didn't realize that I could have (or would want) this amp without NFB. Dumble is one of those builders where I would be wise to leave it as he made it. But, I wasn't necessarily looking for the same Dumble sound that I hear from a lot of other demos, so I wasn't afraid to try it "my way".
I am a kinda sloppy, not very precise, harder edge'd, classic/hard rock player. I play right on the edge of feedback and love having to control the strings from vibrating, and notes that turn into harmonic feedback. Eliminating NFB made this more pronounced.
If you go back to the FX thread, you'll see that the reason I got rid of it came about accidently. I never thought I was going to work the 2 signals into the phase inverter like I did, but when I did the result was more than I expected.

So, just to be as clear as possible because I think this is something that might be worth trying (for you or others), here's the Cliff's notes:
- The FX mix control (in my original schematic, similar to the idea you posted) appeared to be cancelling out a lot of signal when set to 50/50 mix (maybe why some people don't love certain FX loops  )
- I looked at the design and realized that I was mixing 2 signals that were 180 deg. out of phase with each other, therefore causing the cancellation effect.
- My solution (based on Merlin's writings) was to split the signal into each half of the PI and see what happens.
- To do that I had to eliminate the global NFB loop which added noise and volume and a general sense that I was making a big mistake.
- But, I bought in because I wanted to see what would happen, so I tweaked the amp to have less treble bite and ran with it.
- My thought process is this:
If us hard rock guys think everything sounds better when cranked and NFB gets reduced or eliminated at full output, then why not eliminate the NFB loop so the amp will have that same "cranked feel" at lower volumes....maybe?
- Once I committed to this extreme design change I haven't looked back
- It is amazing to me that the amp sounds just fine if I only have the dry signal turned up or if I only have the FX signal turned up-
The PI still somewhat balances itself and I wind up with a decent output tone.
- BUT, when I turn them both up at the same time, HOLY COW, it's a Big Bad flame thrower type tone that I was looking for.

I believe that by using a 12AY7 in the PI I now have the ability to send 2 big OD signals into the PI and not have the extra clipping that a 12AX7 would cause. I believe that this is partially why I am loving this amp so much right now.
To me, it is gritty and heavily over-driven but not like a chain-saw tone that I would normally associate with other very high gain amps.

I hope this makes sense and helps someone, or at least helps you understand me.

[SILVERGUN]

One more thing..
If I would have designed this properly in the first place I would not have the opposing signals cancelling each other out.
Then I would've kept the NFB and probably never tried it without it.

The biggest mistake I made was to have a breadboard and not use it. I just started building when I could have laid it out on the BB and tweaked all of this before I started trying to squeeze it into this chassis.

[sluckey]

If you also want to have NFB option look at the Bassman AB-165 circuit. It would be easy to make it switchable or variable.

Have you tried an EVM-12L speaker?

[SILVERGUN]

If you also want to have NFB option look at the Bassman AB-165 circuit. It would be easy to make it switchable or variable.

I wasn't aware I could do that. I will try it this weekend and see what's what. I still have the pot mounted from my initial variable NFB circuit and I would love to have the option.
Thanks for the heads up.

Have you tried an EVM-12L speaker?

I haven't. Once I get it in the right location I will. I haven't been able to really wring it out yet in the basement here at home.
I haven't loved the EV in anything else, and it would create a problem due to it's weight.
Good thing I haven't built the combo cab yet.
This and next week will be the official start of The Speaker Trials.

[jojokeo]

Applause is warranted SG. I want to call BS on the "just winging it" layout build cause it looks very well planned and thought out. At least without having a rough sketch to work by. If true, you are the Rembrandt or Van Gough of amp building. :) And depending on your sound file samples we'll know which one (no pressure ;)) Hahaa! Honestly, thoroughly impressed my man! Well done. (Somebody in St. Lou is very jealous?) I have so many remarks and comments, but the hammer & lighter under the cradle are great metaphors I'll leave it at that. Lastly, I don't know your political affiliations but when I saw "45" in the build name I couldn't help but get a little smile. I hope this doesn't change anything and will keep the politics out of it?

[SILVERGUN]

I want to call BS on the "just winging it" layout build cause it looks very well planned and thought out....
......I don't know your political affiliations but when I saw "45" in the build name I couldn't help but get a little smile. I hope this doesn't change anything and will keep the politics out of it?

[SILVERGUN]

If you also want to have NFB option look at the Bassman AB-165 circuit. It would be easy to make it switchable or variable.

sluckey, the results are in....yes, yes, and YES!
This is a perfect, last, tweakable addition to this amp. I officailly have enough knobs and switches to play with and I can take it and tune it in at band volume with each different speaker and try to find my happy place.
Thank you once again for delivering the coup de grace!

[kagliostro]

Nice amp

Franco

[SILVERGUN]

Graci FRANCO! 

All of my hanging around here has paid off.
I am glad that it is you who has prompted my 3,333 post
It's good to see my old friends around.

[kagliostro]

For Dante Alighieri 3 is the perfect number

 

 

Franco

[tubeswell]

I love the way this amp has been built.  Ultimate tweak-able layout and construction. And so tidy. Neat trick with the FX loop too

[SILVERGUN]

For Dante Alighieri 3 is the perfect number

 

 

Franco

Maybe I'll change the name to The Inferno

[SILVERGUN]

I love the way this amp has been built.  Ultimate tweak-able layout and construction. And so tidy. Neat trick with the FX loop too

It goes to show, if you hang around the right people long enough, they start to rub off on you.

Thanks for all of your posts and knowledge that you share on this and other sites. When I'm not building, I'm reading, and I am a big fan.
I'm glad you like it...it is a direct reflection of everything I have learned from all of you guys.