50w highgain mod

[John_P_WI]

Cool Stephan,

Thanks for the details. I went to Hoffman's site and the schematic was much more clear. I will cross reference to the details listed below, thank you very much.

Glad to see some interest here in high gain, I just don't have enough time anymore to follow the threads over at slo..... I cut my teeth in the early 80's and still love Lynch etc.

Take care, happy Holidays.

John

[dukeamps]

Nigel and Gldtp99,

I did not follow the link too closely but it looks very similar to Kevin O'Connor's 4 stage high gain marshall mod from TUT. Roccafortes HG100 amps follow a very similar design. KOC maintains the low input between the 2nd and 3rd stage for clean tones.

Instant Zakk Wilde pinch harmonics if that is what you want. If you dump some of the high freqs across the plate resistors and a cap to ground after the master volume you can get the Splawn tones easily.

My guess is the 10k on the input cathode helps limit the noise which would be amplified all the way through.

John

Hi John, thanks for the info on that mod.

Here is that schem in better quality

http://img707.imageshack.us/img707/8835/dbm39v11.gif

Cheers

Nigel

[John_P_WI]

Thanks Nigel! I still think the modded express to AFD clips you posted are some of the best going....

John

[dukeamps]

Thanks Nigel! I still think the modded express to AFD clips you posted are some of the best going....

John

Cheers John, thanks for the feedback Glad I could help with the schem.

Nigel

[Darkbluemurder]

I cut my teeth in the early 80's and still love Lynch etc.

John,

If you're into George Lynch tones you may want to check the Splawn Quickrod discussions on sloclone. I modified a 100 watter to QR specs and it sounds more like Lynch Mob than my #39 modded amp ever would.

Cheers Stephan

[John_P_WI]

Thanks again Stephan. Now it is just about finding the time and money to build these amps up.

John

[rocketeer]

I worked from this schematic made by DBM:
[IMG:800:566]http://i46.photobucket.com/albums/f112/ ... FD-DBM.gif[/img]

The amp started life as a Laney AOR 50 made in 1987--- i gutted the PCB and built a 50 watt (turret board) version of a Krankenstein from the schematic online--- it sounded much like a real 100 watt Krankenstein owned by the former studio engineer across the hall--- but it wasn't my cup of tea so i made some changes (changed plate-driven tonestack to cathode follower driven and some value changes)---i still wasn't all that happy with the amp's tone.
Then i found DBM's #39 schematic online and re-did the preamp along those lines----- but keeping the much higher power supply filtering values from the Krankenstein-type design. The Krankenstein power supply also doesn't use a choke, so it's been removed. I'm too tired now to trace out the amp but here are gut pics:
http://s46.photobucket.com/albums/f112/ ... AFD%20Mod/
This amp is running a nice pair of RFT EL34's---- V1:RFT ecc83--- V2: JJ ecc83s---V3: Mazda (England) ecc83----PI:EI 12ax7.
This one has a Resonance control between Treb and Mid pots (was the Sweep control in the Krankenstein circuit)---- and it has a "Power Dampening"-type 2nd MV instead of a Lar/Mar PPIMV.
It's not all that pretty inside after being built as three different types of circuits----- but it works well and has a thicker/fatter tone than the #34-type, 3 stage amps IMO.
If anyone would like me to go through the amp and identify the values on the preamp tubes like i did on the other amps ----- just let me know and i will------ otherwise the pics and DBM's schematic should provide enough info to get what's going on with this one........................gldtp99

I'm curious as to B4 & B5 voltages on this build. THANKS!

[gldtp99]

I worked from this schematic made by DBM:
[IMG:800:566]http://i46.photobucket.com/albums/f112/ ... FD-DBM.gif[/img]

The amp started life as a Laney AOR 50 made in 1987--- i gutted the PCB and built a 50 watt (turret board) version of a Krankenstein from the schematic online--- it sounded much like a real 100 watt Krankenstein owned by the former studio engineer across the hall--- but it wasn't my cup of tea so i made some changes (changed plate-driven tonestack to cathode follower driven and some value changes)---i still wasn't all that happy with the amp's tone.
Then i found DBM's #39 schematic online and re-did the preamp along those lines----- but keeping the much higher power supply filtering values from the Krankenstein-type design. The Krankenstein power supply also doesn't use a choke, so it's been removed. I'm too tired now to trace out the amp but here are gut pics:
http://s46.photobucket.com/albums/f112/ ... AFD%20Mod/
This amp is running a nice pair of RFT EL34's---- V1:RFT ecc83--- V2: JJ ecc83s---V3: Mazda (England) ecc83----PI:EI 12ax7.
This one has a Resonance control between Treb and Mid pots (was the Sweep control in the Krankenstein circuit)---- and it has a "Power Dampening"-type 2nd MV instead of a Lar/Mar PPIMV.
It's not all that pretty inside after being built as three different types of circuits----- but it works well and has a thicker/fatter tone than the #34-type, 3 stage amps IMO.
If anyone would like me to go through the amp and identify the values on the preamp tubes like i did on the other amps ----- just let me know and i will------ otherwise the pics and DBM's schematic should provide enough info to get what's going on with this one........................gldtp99

I'm curious as to B4 & B5 voltages on this build. THANKS!

Give me a few days and i'll have this info----- i won't be able to work in my shop until at least Thursday..................gldtp99

[rocketeer]

Thanks man. I'm also interested to see how filtered/stiff you had the PS in the preamp sections. Just curious! Thanks again.

[Colossal]

Rocketeer,

For what it's worth, I built a Tone Lizard modded JCM800 (2x6V6) and used 47uF/47uF/22uF/22uF/22uF. I did try 94uF (47u||47u) in the first position but found it made the amp a bit too hard sounding and glassy. Going back to 47uF for the reservoir cap brought back the smoothness and improved the feel of the amp greatly (at least in my opinion). I also used a 1k/5W and 10H choke between the reservoir cap and screen cap.

I am actually going to be starting work on an AFD/JCM type 25W amp for a fellow very soon.

[gldtp99]

Thanks man. I'm also interested to see how filtered/stiff you had the PS in the preamp sections. Just curious! Thanks again.

Filtering:
EL34 Plates--- 135uF
Screens------ 135uF
PI, V3, V2, V1-- 16uF each

Voltages:
EL34 Plates-- 413V
Screens-- 395V
V4a--329 V4b--327
V3-- 292V
V2-- 248
V1a-- 225V V1b--237V

I played this one and several other amps last night thru an Orange 4x12 i'm considering getting.
I actually liked my '78 Marshall JMP 2203 (near stock w/Lar/Mar PPIMV) the best ---- the higher gain amps seemed too fizzy to me and i liked the crunch and push of the 100 watt 2203 better.
So i'm considering changing this 50 watt #39 Mod head to another circuit, i'll think on this for a while because i have lots of other amp work to do first.
For example: just finished an emergency rebuild of a '65 BF Bassman (AB165 circuit)--- some fried wiring, blown screen resistors, shorted OT---it had a 7.5 amp fuse in it------ now has stock amplification circuit but bias circuit converted to AA864 Bassman specs (can now adjust bias voltage to both tubes)---- installed new Atoms under doghouse.
Same person also brought me a SF Princeton Reverb from a garage sale---no tubes, no reverb tank, ? condition--- looks decent, we'll see.
A few other scratch builds, too before getting back to this #39 Mod head......................gldtp99

[M Fowler]

Stripped out my Ceriatone Express and build DBM circuit into it, loving the four gain stage.

I am going to put in an effect loop next.

Mark

[Tone Lover]

Its really nice to see some high gain stuff on here i seem to gravitate back to high gain every other build.
Bill

[M Fowler]

Next will be either a Chupacabra, Splawn QR or Laney TI-100 hmm which one would I like better?

Mark

[gldtp99]

This thread is still alive, i see---- i re-did the #39/DBM amp into a more modern voiced metal circuit---- ideas from SLO and Dual Rec schematics, but not exactly like either one---- super thick tone on this one now- .
I also re-did another 50 watt build (formerly a Shiva-type lead channel only --w/boost)--- this is now a Quickrod-based circuit---this one was the favorite of a friend that demo'd several amps here the other day---it's in an OD2/Gear 2 configuration (sort of)---i still haven't done the boost (OD1/Gear 3--based) i'm planning on---- i'll add the relay that was in the Shiva-based circuit soon to make the footswitchable boost happen.
My friend was over to pick up his '77 Marshall Superlead (modded long ago by somebody---amp used to belong to a famous German rocker)--- he wanted a Lar/Mar PPIMV installed so that he can use the amp with his band in clubs---he has two Marshall Jub's he usually plays---this one has some sweet tone, too---not modern metal but pretty good sounding----- just a variation of the One-Wire Mod.
Getting ready to build a 100 watt channel switcher with some Quickrod-based configuration for the Lead channel and some paralled gain stage ideas for the clean channel---will have Zero Loss FX loop in this one---when i get some free time, that is- .......................gldtp99