Couple of #183 derivatives

[bepone]

tubes used in the amp were mixed NOS/JJ + 6P3S-E russian, which are "5881-6L6 family" and have very good sound actually, good to know that for a good sound not needed so much $$ for the tubes..amp finished like this at the end

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sound clips during the process:
overdrive:
https://drive.google.com/file/d/1L6km6H ... sp=sharing
clean:
https://drive.google.com/file/d/1LEZ5UL ... sp=sharing

[bepone]

knowing the influence on the amp sound, in parrallel with material upgrade i was doing extensive research on output tranformers, projecting, winding, testing, comparing influence of various laminations, comparing vintage vs new iron, even rusty laminations!
trying to resolve bass character in the amp with better OT transformer? is it possible? always there is a question to spend money and buy 20 expensive transformers to check the difference? how does it Mercury magnetics sound? it will be very expensive way paying 3x more price than necessary with all the shipping and imported dutys. and what to do with all the rest, not selected.

for me was obvious what to do, and is for sure more fun! waxed and paper interlayer insulation made transformers costs too much nowadays.. but not if you are doing this alone...

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in one of my Marshall JTM project, normal channel is useless, too bassy, same like on Dumbles often.. but i get very nice bass with more definition with one of the iron experiments. so it is exactly what i need to do on my 100w "183 D" amp, which has 3x more bass than needed. ok, new journey begins, all the material change + iron change looks like will happen soon.....one more round, again

[bepone]

following the experiences gained i started to go in direction of new/old project of 100watter with duller sound. how i'm looking at the problem it is like gastronomy, cooking the meal or some good sauce or doing electronics, cooking the sound. all is about correct compensation! lets check the material used there, with years it arrived to this, pics from various tests , some changes in tone stack caps:

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again some wima for treble peak, a lot of MKTs in cathodes instead of elcos, piher in cathodes, some xicon carbon films in signal..dales in anodes they can pass.. carbon comps in PI anodes (too dark, not good position for CC!) MKT instead of tantal in NFB PI tail part..carbon film in NFB circuit. carbon film in input section V1a. dumbleator integrated / V3. too much carbon. 6PS's almost everywhere. V1b coupling cap 418 type (darkest of all).

total too much bass, not so great mid, missing treble.

[bepone]

how pcb was designed with copper side up for faster change of the components, it was fast and easy to do resistor makeover. in half of hour i had allready second test. first i tryed bunch of Draloric carbon films everywhere

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some important changes done:
- V1a Iskra metal fil low noise
- V1b 220k // 500pf ceramic (500pf selected from many 470pF)
- V1 tone stack slope 150k MK3 Resista MF,
- V1/2 a and b anodes, Iskra MF (tried also Dale, tried also MK3s)
- V1 and V2 cathodes metal film MK3s and Beyschlag, and new 4.7uF elcos Vishay from Mouser
- removed V3 dumblelator circuit for the moment
- PI, Draloric in signal, Metal oxide 2W in NFB , Tantal and Draloric 390R in tail, 47nF MKT in second grid cap to
- PI anodes Metal film PR2 Vishay

-------------

Results: quality od middles and highs and some feeling about changed to better.. Iskras i have removed from the anodes because they sound somewhat industrial..precise. MK3 were little bit better.

Bad thing that mud still remain, bass didnt change from flabby too much, and stil it was some treble missing, means need to put treble pot always at 70% of rotation, 3 PM , and bass on minimum or close to minimum , at 8 AM.

[bepone]

Decided to quit with modifying ,and rebuild of the complete new preamp at new pcb and renew the power supply like on 50W.
Elcos Kemet / Rifa, and idea to put more polypropilenes insted aof 6PS and Metal films to gain some presence throughout the amp and make bass tighter.
i used the same pcb like 50w:

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[bepone]

amp wired with the new pcb and parts. for anodes i chose Draoric SMA types for investigation, more about this experiment later
here is Arcotronic PP on the bass, ceramic 390pF for treble, metal films in grids for V2 overdrive, slope resistor 150k some modern metal film (Beyschlag), PI anodes Vishay Beyschlag too. in OD section 220k befor trimer also Metal film!

polypropilenes 715 and 716 everywhere, only at the OD stage there are 6Ps's.

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results : changed again the character, adding more presence from before! which is good! bass was only little better, but still not what i wanted....

next plan: flubby and excesive bass is coming from the power supply? so need to be rebuilt-

[erwin_ve]

Very interesting topic, I like your experiments and their sonic changes.
Did you test and mark your caps for outer foil to lowest impedance? For me this was the most significant change for getting a tight bass.

[bepone]

ps went from BC industrial snap-in caps to axial "guitar" types.. diodes from 1N5408 to UF5408 , speed up their work and less rectifier garbage created
old:

¨ps1.jpg

new :

ps2.jpg

result: no change or negligible, direction not worth..

[bepone]

tried also to mix output tubes to see the result - nothing achieved..

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then rewired output section lead dress from OT to the tubes and speaker wires laying on the chassis inside. maybe i get something small, but i need big effect.

all the amp rewired new several times in 10 years, only power transformer remain the same, and bass is still not ok. PT that is problematic? for the bass? cannot be.

i started to think again - output tranformer?? i did 2 changes but, to be replaced again?? 50w and 100w now have the same PCB board, more or less the same components, design is the same.. but here is too much bass..
decided that OPT will be replaced again! i will check what i have from the laminations left..and try to do something

[bepone]

Very interesting topic, I like your experiments and their sonic changes.
Did you test and mark your caps for outer foil to lowest impedance? For me this was the most significant change for getting a tight bass.

i tried both direction for middle and bass in tone stack i dont remember if did something.. which positions you are reffering to? other positions always i leave lower impedance to outer foil.. tried to alter also 100nF bass to 82nF + 47nF but then amp is not good for the pedals any more, i learned not to change 100nF never again

[erwin_ve]

Very interesting topic, I like your experiments and their sonic changes.
Did you test and mark your caps for outer foil to lowest impedance? For me this was the most significant change for getting a tight bass.

i tried both direction for middle and bass in tone stack i dont remember if did something.. which positions you are reffering to? other positions always i leave lower impedance to outer foil.. tried to alter also 100nF bass to 82nF + 47nF but then amp is not good for the pedals any more, i learned not to change 100nF never again

Basically every coupling cap. Except the mid cap, its reversed-->> I use a polypropylene cap there. In a skyliner tonestack I use a .047. This is removing low mid and better for a strat IMO.

[bepone]

yes we are in line... middle cap reversed, outer foil looking to the pots side because on the anode side is bigger impedance than on the pot side (cca 50k internal of ECC83 + 150k slope means cca 200k) and on the mid pot is variable but is less than 200k in use.

47n polypropilene works great also for me for mid cap, using LP guitar with Seth Lover on neck, not muddy at all!
i mean not muddy pickup at all for LP neck position, compared to other neck pickups vulgaris found on LP guitars..

47n for middle gives better mid control and closer to fender cleans.

result for the amp still too much bass, so how i decided to go, for another trafo change..

[bepone]

first i tried to make 50W output, make a test with 2 output tubes.

i chose classic vintage winding pattern, with balanced halves , added little bit more turns (15%) for little bit better inductance than usual , using also hi permeability laminations. all for goal bigger inductance on primary.
paper interlayer insulation,every layer coated with shellac and waited 0.5-1 hour drying for another layer.
finish with nice vintage orange/ brown pressed paper .

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[bepone]

OT finished , coated, mounted, tested in circuit. there is huge difference! extreme difference maybe better to say!
goal achieved/ after 10 years here is how it looks->

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bass problem= no more. now is tight and strong, middles are still good, highs also good not shrill (also was like this before so they didnt degrade i was trying to make "mechanical" low pass filter with waxing and winding geometry)

overall sound is more like it should be, no more bass heavy feeling. bass control is now easy turn to almost half without any problem that will become bummy at neck pickup! i'm very happy with the results and probably amp this will stay with this OT and started to live like 50 watter. until the next change
i did quickly many tests in few days with both guitar (LP/strat) and this OT change lead to many new experiments, like anode resistor replacement and comparation and capacitors changeover and material comparation, effects that are now even more pronounced, not blurried by bass mud!

now is possible to play the amp for several hours without finding some weak spot and is possible to concentrate on playing not on some strange artifacts. before i couldn't stand 20 minutes of noodling in front of the amp

[bepone]

pic with the new OT

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