#183 revisited (mods to my liking)

[talbany]

Electron
I am a bit confuesd.. if you used the 183 layout and have a 250k drive pot and upped the value of the OD trimmer to 250k(regardless of where you have it set) as well and ax'ed the LNFB this will no doubt make the OD woofy as a mofo.. Then added the bass taming mod?

I remembered Gil's great Bass taming mod and installed it. 0.0047uF cap paralleled with 4M7 resistor. BTW most schemos I have seen IMHO have the mod wrong showing the 4M7 resistor going to ground after the 0.0047uF cap.

Sounds like you are going in a kind of circle..
Lowering the values of either OD trimmer and drive pot is a wonderful way of taming bass without adding additional caps to the signal path of the OD which might alter the character of the breakup..I would start by lowering the OD trigger and cut the taming mod and stick with tried and true if I can..Just sayin..Of coarse if you like where you are going..Ignore this post!
Hope This Helps!!

Tony

[ElectronAvalanche]

Hi Tony,

thanks for your input.

The mods I did followed the problems I had:

1. too much treble (this came out when playing loud and over a 4x12 having 2 V30s (I know, not the best Dumble match) -> upping the OD input pot
https://tubeamparchive.com/viewtopic.ph ... c&start=15

I tried the amp with my 1x12 EV and at higher volumes and the OD was mushy/woofy. This was with the circuit as posted (100% original apart from PI coupling caps: 0.1uF).

2. in came the OD Bass cut mod (Ayan mod).

3. changed to 0.05uF PI coupling caps (sticking with 0.02uF PI input cap as per Scott's recommendation)

Still some piercing high content so next step was

4. Ayan Treble cut (HF trim) (250k, 0.001 uF cap)

Better sound in the high freq compartment in OD

Clean is great as was from the beginning

then I put a 47pF cap across the V2b anode resistor, but this I threw out again since I did not do much good to the sound after some serious testing

5. tried a pair of EL34s: better high mids, but since this is a 100W amp and the PT is from a Fender PA100 (Twin PT) I am stuck with using only 2 EL34, so I put the TAD 6L6 STR back in again

6. going back to 100k OD input trim (much better in the bass, set to close to 23k)

7. tried 100k Level (= OD content) by paralleling 220k with pot, but I loose too much OD for my taste

I could play around with the 180k series resistors, but I would get away more and more from the original #183. That is why I think (and wrote) that the iron use has a vast influence on the amp. Me thinks one has to choose the correct schematic for a specific set of iron used.

My other amp (HRM using Hammond OT never was as problematic as this amp using Schumacher OT and Fender Twin PT. Voltages are dead on btw.

The LNFBL was installed all the time (switch with 22M, 44M or off), but I seem to like the LNFB off in clean and at 22M or 44M in OD.

So....
easiest (easier than ripping the amp apart again) would be to use stand-alone preamps (say #102, #124 and even earlier) and see what fits best with the Power amp? Maybe I am all off, but this specific amp with this set of transformers really is though to get right.

I hope this makes at least a bit sense.

Thanks again for all the input!

Ah and by the way:

I would love to hear a demo of a #183 clone or the Quinn #183 preamp with a Strat/Tele on the neck pickup. One usually hears humbuckers (bridge that is) and this is sounding quite nice over my amp btw (Tokai Love Rock, or Tele bridge).

Cheers,

Electron

[talbany]

Electron

I feel your pain Sounds like you've been all through it.. I know sometimes it's very difficult to get a good neck PU tone on a Skyliner always the balancing give or takes there with some amps..Hope you find the magic tubes..
Wishin you the Best!!

Tony

[bluesfendermanblues]

Out of curiosity, I tried adding a LNFB (22m + 47n + 22m) to a #183 EL34-100w clone.

I'm quite happy with this amp, that I recently modded with a mid-switch (100k + 47n mid-cap) - great with all positions in my strat.

(HAD must be laughing his a.. off if he is reading this....)

With the 'new' mid switch engaged AND the LNFB it sounds like a 20w amp and not a 100w - no bottom end at all.......

Conclusion so far, IMO, with a #183, its either a 47n/100k mid or a LNFB, but I'm tempted at stating that the LNFB is not in the original #183 for a reason.

[Structo]

Hi Claus,
How are you switching in the 100K slope and 47n mid cap?

Thanks

[hans-jörg]

Hi,
I guess a 330 K parallel to the 150k //a 33n (or an 47n) parallel to the 0,01 mid cap. Both with one dpdt. I have done so.

Hans-Jörg

[renshen1957]

Those look great as well.

I for one think a "tubes up" amp is much more efficient in cooling than the traditional Dumble with the tubes hanging down.

Heat rises....

I wonder why he chose that path for his amps?

Hi Structo,

I would guess that HAD like Randall Smith over at Mesa started by modifying Fender combo amps/heads and just followed the convention.

About the tubes tubes with downward orientation, the heat will concentrate on the tube 'seals' around the pins (shorter life expectancy). Tubes get hot, but last longer and work better if some cooling method is used. How many builders (or manufacturers) add fans for their hot bottles?

Best Regards,

Steve

[bluesfendermanblues]

Hi Claus,
How are you switching in the 100K slope and 47n mid cap?

Thanks

With a DPDT switch. I've quick drawn a schematic

[Structo]

Thanks Claus, I sometimes have trouble visualizing switch installations.

[ElectronAvalanche]

So the saga continues.....

I reworked the amp and arrived at the #124 circuit (low value plates):

200k OD input trimmer, set to 30k
270pF snubbers
still have the Gil Ayan HF trim with 500k trimmer and 0.001 uF cap
made the FET switchable (installed a 10k pot inplace of the FET input) via relay

The amp really shines now (albeit I have not had a chance to hear it a full blast).

So I guess the #124 values fit the OT more in this case. For me this shows that the OT has a huge influence on the sound of the amp.

Only slight problem I have right now:

I use a 5V regulated supply for the relays. With the FET relay and LEDs in the footswitch I run into headroom problems with the supply, the voltage drops below the threshold voltage for the relays to work. I have the FET relay switchable from the back or it can be paralleled to the PAB switch, thus activating PAB also activates FET. This works nicely with the chassis switches but not with the footswitch with LEDs.

I see other people use a 12V regulator for 5V relays, but I think this leads to overvoltage if only one relay is used.

Sinc I currently use a 3 pin XLR out from the amp to FS I might go to 5 pin DIN and use one wire to have the supply voltage for the LEDs seperated. Thus I would need three DPST FS.

What else can be done to remedy this? Anyone out there that uses a L7805 regulator from a 9V supply with three relays and LEDs? Any tips?

Thanks in advance,

Electron

[TheHandsomeOrk]

The 1x12 I built myself some years ago, it is the ported variety sporting a EV12L. Headshell is from Tube-Town (Germany). I really do not care for the looks of the headshell handle, but it is quite comfortable for carrying, moreso than the Fender handles.[/quote]

Nice looking amp.
What length are the ports in your cab? I recently built a ported 1x12 but think the ports are to long as it has too much low end.
thanks

[talbany]

Dominick
If you run the 5v relay with the 3 pin Stereo/or XLR (diode in series w/ relay) you will lose headroom if you are using current limiting resistors in the footswitch..Try losing those and might work (I know it works on a pair) ..The relay series resistance should be enough to help with current limiting ..Also try to keep the run as short as possible ..This is the only method I know of that works w/5v supply and 3 pin jack..Use good quality LED's if you go here!!


Hope it works for you..

Tony

[ElectronAvalanche]

Hi Tony,

Thanks for your reply. I use low curent high quality LEDs. The relays are Meisei 5v BTW and a Alcatel 5v. I measure 5v with no relay activated and 4.80 with all activated (via FS+LEDs). With 2 relays activated I get 5v (dead smack). I will swap one of the Meisi against a spare Alcatel and see what happens.

Nevertheless I will install the 5 Pin DIN socket and get one of them Marshall style 3 button FS.

Will Report back.

Oh BTW: if my memory serves me well, the ports were 12 cm in length.

Cheers,
Dominik

[Structo]

I like the high sensitivity Omron relays.

http://au.mouser.com/Search/ProductDeta ... V-2-H-DC12

Spec Sheet
http://www.components.omron.com/compone ... 2_0609.pdf

Of course that is a 12v relay but they have the 5V as well.

I run four of these relays off of my regulated 12v supply.