Lead Dress: OD V2a Grid wire

[bepone]

litlle offtopic/ontopic about lead dress
i'vu built one Soldano SLO type amp /which is higher gain than Dumble / without any coax, with tube sockets close to the front plate (i consider that for the best layout), on terminal tags, with RF methods (grouped elements for dedicated tube under that socket, anode - grid-cathode resistances) with close reservoir electrolytic capacitor to make short path to the loads (V1-V1 tube) and to test how it can compete with noise and sound...

The result is no any noise , humm, hiss, harsh artifacts in overdrive , /all that what in Dumble amp you get often by default/ the sound result is over all my expectations! here is the clip. at the beginning are the pics of layout, elements are in the air, "ikebana" style but is working very well:
https://www.youtube.com/watch?v=kyi_vo1MTOs

[talbany]

litlle offtopic/ontopic about lead dress
i'vu built one Soldano SLO type amp /which is higher gain than Dumble / without any coax, with tube sockets close to the front plate (i consider that for the best layout), on terminal tags, with RF methods (grouped elements for dedicated tube under that socket, anode - grid-cathode resistances) with close reservoir electrolytic capacitor to make short path to the loads (V1-V1 tube) and to test how it can compete with noise and sound...

The result is no any noise , humm, hiss, harsh artifacts in overdrive , /all that what in Dumble amp you get often by default/ the sound result is over all my expectations! here is the clip. at the beginning are the pics of layout, elements are in the air, "ikebana" style but is working very well:
https://www.youtube.com/watch?v=kyi_vo1MTOs

Dumble experimented around with different layouts and tube placements. He also tried to lower noise floor from the power supply by placing the filter caps closer to the source (plate resistors) but you have to wonder why he didn't continue with the practice?. Perhaps he didn't see the added benefits and or costs (money or time) to convert his manufacturing process and design specs.
IMO even if you change the layout to try and compensate for a particular anomaly or side affect. The question would then be? did the modification change (in your opinion) improve the overall sound and performance of the amp (emphasis on sound)
My fist couple of ODS builds were noisy. It wasn't until I began following Dumbles lead dress and grounding methods exactly that now I would consider them reasonably quiet (for a tube amp) Add on effects loops and reverb (more preamps) and all bets are off..IMO

BTW..I agree that one of the noisiest sections on the preamp board is right at the bottom of the trimmer

[bepone]

Dumble experimented around with different layouts and tube placements. He also tried to lower noise floor from the power supply by placing the filter caps closer to the source (plate resistors) but you have to wonder why he didn't continue with the practice?. Perhaps he didn't see the added benefits and or costs (money or time) to convert his manufacturing process and design specs.

money is out of the equation, because from one amp he can live for 5-10 years IMO it was experiment to develope more his approach and see the result

IMO even if you change the layout to a so called better more improved method to try and compensate for a particular anomaly or side affect. The question would then be? did the modification change (in your opinion) improve the overall sound and performance of the amp (emphasis on sound)

i always hope for YES until i change opinion after i see that is a miss
for me the best sound is always when you put first tube directly below the input socket (now we can discuss why but is trivial ) , this increase the quality of highs to better , more open and organic, heavy, not thin .. if you compare this approach to marshall amp, then marshall is too dull (from tube socket to the pots every wire is 20cm+ and coming back ) .. what does it means? from my experience - shorter paths = more highs, longer paths=less highs. dumble arrived to the same point and probably left all tubes on the back side of the chassis, because OD was maybe way to shrill with some pedals.

i tested idea in my builds/ not following dumble layout/ first tube below input socket, OD tube far away (adding capacitance) and i get some results!
here it is important that feeling of "highs" is generated in the output transformer in conjunction with output tubes and the speaker, with main factor output transformer . if the transformer is not so appropriate, highs are more pronuanced and "unpleasant", the best trafo is filtering them out before the speaker and amp no need / or need only basic tuning. so story about too much heighs in the amp is also a story about the OPT used.

so i want to say that if you follow exact dumbles ideas, you need to follow also his layout and this is difficult because you dont know what the guy thought in that moment..A lot of clips of "Dumble" ODS on the net are fuzzy sounding like "broken" or somebody making holes with screwdriver in the speaker
lead dress? or he pays the tribute that build was custom- dedicated for one guitar only and not good for others? component failure or drift? if you are dumble you will know but for all of us is a mistery....

[jazzbass]

Hello Bepone, dear neighbor of the country,

you write:
"money is out of the equation, because an amplifier can live for 5-10 years: P IMO was an experiment to develop his approach more and see the result"

I believe that this is not exactly the reason, although H. Dumble had charged a lot for his amplifiers in relation to the average costs of the time I do not think that with the income from the sale of an amplifier he could live more than three / four months.

If my opinion has any value, the rest of your analysis is logical and poses a healthy challenge to those who passionately follow TAG and his discussions.

Discussion like this should find more people with the desire to question themselves, especially among those who, after the first period of study and classification of H. Dumble's achievements, use the acquired knowledge to take the achievements a step forward, having the courage to to dare and to question oneself.

I understood that those who have turned passion into a profession, and I speak of Taylor Amplified Nation, Bludotone, Fuchs , Tony Albany, Rootz, Erwin_ve and a few others (I apologize to those I have not named), used the study of H. Dumble's projects as a springboard to make a step forward, perhaps also by correctly interpreting the needs and development of musicians and music over the last few years.
Discussions like this are welcome.

Thanks

Un abbraccio.
Franco

[bepone]

thanks Franco!
to avoid too much dry theory, here is practical example , one dumble-ish hybrid with explained layout from previous post. it was built on Randall RH50 donor amp (where i need to say, how goood is the output transformer in that cheap amp!) . for 200 USD you get chassis, PT, OT, and tolexed cabinet! perfect. throw all from inside and proceed with anything.
unusual material for the build, mallory output capacitors which are sondwise in the middle of 6PS caps and 715, arcotronics PP polypropilenes in the tone section..carbon film , carbon comp around..added gain stage AFTER OD stage (yeeees.. ), layout with a lot of space between and many other things. some pics from the progress below. here is the sound,
clean:
https://www.youtube.com/watch?v=WOm2eqJ2Jok
cab: open loop mahagony / maple cabinet with EVM12L inside

drive (non- intentional recording ):
https://drive.google.com/file/d/1bLhQwF ... sp=sharing
cab here: 1x12" with celestion 70-80 inside

[ijedouglas]

Excellent thread! I read everything and made me think about, thank to all for bringing this up revealing a lot of things and artifacts that were strange!
Sure that layout and lead dress are crucial for any amp! To me happened that changing one power tube socket in Fender 75 Rivera with rat's nest of wires below changed the bass, 35% to better. Why and how? Bass pot was uselles (to much bass so amp was played with bass on 0 or 1) and after the change, bass pot was useful up to 5! Means moving only few grid and anode wires on the socket.
Sometimes during repair you cant understand how something happen because effect is invisible.. would be easier if electric field around wire can have color, per example yellow. And magnetic field pink so we can clearly see the parasites and would be easy to avoid them, but things are invisible (at the moment ).

The theory behind this is constant changing of the electric field and grid wire which is inside, means electric coupling, between those
Similar is explained here https://learnemc.com/electric-field-coupling
In ODS is even more pronounced, because we have high resistances in the circuit and because source 1 (grid) is taking feedback coupling from source 2 (plate) through capacitive coupling but is even complex, source 1 is controlling directly source 2 through normal tube operation! Taken from this formula cures are to increase the capacitance between the A and g wires, in practice only to lift grid wire from the ground at first, and second to move it away from plate wire.

Why V2a wiring is so critical - when I see the standard D layout, maybe is not so ok to form hi-resistance “U” shaped turn (coming from V1b with internal node resistance od 40k, passing 47nF, going to sw. relay, coming back, increasing node resistance even more over 220k, arriving to trimmer, increase node resistance even more over the trimmer 70k+) with 300k od resistance on this “antenna” and sum this to V2b without shield? How I see this point with high resistance is very prone to all kind of problems.

Maybe will be better, this particular distance from sw. relay to the V2a to connect over coax without attenuation, with internal resistance of 40k (tube V1b), then on the socket tag terminal make attenuation with two resistors 300k-30k to the gnd, and center point connect to the tube grid. On this way 300k is grid stopper and attenuator in the same time and because of coax coupling problems can be avoided, signal is arriving on the socket with 5 times less resistance (40k, compared to the 300k before).
See here there is no gain trimmer anymore (no problem if people want to follow 27-30k to the gnd like D, put the resistor, more reliable then cheap trimmer) . Actually I like more sound od 60-100k’ish. I will test these ideas one day just to find free time...

Perhaps the goal was not to reduce noise at this location but to use it to sculpt sound?

[jazzbass]

hi Bepone,

I asked a friend if the idea of placing a socket and its valve near the signal input was correct. His response was:

"A tube close to the input jack is not a good idea, the hum (heating) in the jack is most likely induced."

In your experience, will I really have / will I not have induced hum problems?

A hug, Franco

[bepone]

ejla Franco,
no, i don't have.. but i need to say when is higher gain amp in progress (sometimes also marshall type lower gain), i'm using 12VDC regulated heater on first two valves V1-V2 (12VDC is easier to make than 6.3VDC, lower current, smaller heatsink on the regulator, less heat) to avoid this problems at all..this DC i'm getting from 14.5VAC additional winding on the power transformer (always custom).

that 12VDC im using to power the relays and some indicator lights also..i had in the past humm inducted in volume pots on V1 over dirty relay supply voltage!
so now im regulating all, with some 7812 with small heatsink.. last years also with low drop regulators (LDO) for even less heat dissipated.

if you put V1 to the input jack and want to power heaters with AC? hm. not sure for classic D layout.. now is longer path for the heater wires and in Dumble standard layout there is no place to pass arround.. the best is to pass around the chassis without interference with the other circuits but there is FET circuit. if you dont have FET and chassis is clean on that wall you can do - maybe. here would help a lot to transfer to 12.6VAC heating (but this need to be planned before ordering of power transf.), and using pins 4-5 only so heater is not passing to the other end of the socket (pin 9) where is close always some sensitive grid stopper in tens of Kohms which can collect some humm.
for DC heater - no problems, no electro-magnetic field around the heater wires

[jazzbass]

Hi Bepone,

I promised a friend that I would make him a JM / Wonderland 100W but I can't find the right chassis.

I could ask Nik from Ceriatone for a chassis but this presupposes other different problems.

I thought of putting the V1 next to the inputs but the risk of Hum is great and I prefer not to venture now in a field that I do not know.

I will find another solution like that of drilling a blank TubeTown chassis.

A hug

Franco

[bepone]

i have started JM too and arrive only to half i have chassis and populated boards.. now it is somewhere few years - on seasoning.
in wonderland see how much space is in front, you can do. but i agree, take a new build, drill and experiment, try for the start easy only low gain amp like fender with basic functions, and see how you will like, immediatelly you can feel that highs are better (if you have dull amp this is the recipe for reconstruction)!

[brewdude]

I like building amps with the tubes along the front panel—though, I’ve only employed the method on my own simple original designs. I’ve had very good results, however, I’m skeptical that the layout has made the builds any brighter or less dull. It has made for short wire leads and there has not been any need for shielded cables. I will continue to employ and refine this technique in future builds.

If I was building a Dumble style amp I would use Dumble’s layout.

[jazzbass]

Hi Bepone,

I think you are right, words of common sense.

Un abbraccio

Franco