#183 revisited (mods to my liking)

[ElectronAvalanche]

So I was unhappy with the bass content in OD of my #183 clone....

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.

It is supposed to run in parallel with the cap. Otherwise the bass cut is not correct.

Next I addressed some of the fizzines in OD mode:

250 input trimmer

47pF across V2b anode resistor (kept the LNFB caps of 27pF from anode to cathode on V2a and V2b)

Again one of Gil's gems: Treble Cut mod: 0.002uF cap with 250k trimmer after 180k resistor going to OD Volume (Ratio).

This really brought the amp to new life. Now I can use the Neck PU of my Tele without synth like bass string OD. The bridge PU still has plenty of meat. A Strat sounds very nice as well, as do Humbuckers in a Love Rock Tokai.

Whilst I was at it, I modded my Flexloop (Dumbleator copy from Flexamp) to 1k8, 27k, 47uF specs, as well as changing the LNFB cap from 0.27uF to 0.22uF (I installed the 0.27uF years ago, since I did not have a 0.22uF at hand. I think originally Ulrich from Flexamp used a 0.1 uF there, together with the 1k5 4u7 combo and 15k.

I am really happy with the amp as is. I might have to back down the input trimmer a bit, now I have the OD set really gainy. One other thing I might try is to put a 100k across the 250K OD Drive Pot for a better transition.

I will post a pic of the amp once my cameras battery is fully charged again.

Take home message for me:

Somehow one has to really tweak each amp to his on likes. Sticking to the original schematic might not always get the results.

Thanks again to everybody involved in the #183 schematic and of course to Gil.

Cheers,

Electron

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.

[Structo]

The OD entrance mod I'm familiar with was a .05uf cap in series with the 220K resistor on V2a and a 10M to ground from the cap.

What that does is put the .05uf cap in series with the V1b coupling cap which is shown as .02uf.

Making a total of .014uf instead of the .02 or .05 of the stock amp.

The 10M to ground is merely to stop any popping from the charged cap when switching.

Can you show me where you found the mod you are talking about?

[ElectronAvalanche]

Hi Tom,

here:

https://tubeamparchive.com/viewtopic.ph ... sc&start=0

https://tubeamparchive.com/viewtopic.ph ... ght=#92567

The Gil mod is usually a 47n with a 10m to ground.

For what it's worth, that it not actually the case. What I did -- and never in an amp with 100K plate load resistors -- is put a .0047uF (so, 4.7nF, NOT 47) in PARALLEL with a 4.7 Meg resistor before the 220K pre OD trimmer (100K).

Cheers,

Gil

Electron

[Structo]

Thanks a lot, now I remember the confusion at the time when that was talked about.
May have to give that a try again.

[markusw]

Thanks a lot for sharing your observations!
Great looking amp!

How did you do the face plates?

Peace,

Markus

[stelligan]

Good info. In the middle of tweakin' mine, too. Thanks.

[ElectronAvalanche]

Hi Markus,

Thanks for the compliments!

I had them made in 2001 by a local company in Regensburg when I built my first ODS amp. They are silkscreened black adonized aluminium (1mm).

I ordered 5 sets (front and back) and have one set left for yet another amp

Are you situated in Germany?

Cheers,

Electron

[markusw]

Hey Electron,

close to Germany, in Vienna.

A couple of years ago I did some etched Alucorex face plates for my amp.
(see below).
Cool thing is that they last forever since the white lettering is done by removing the black anodised alyer.

Later we had some Alucorex face plates done for a friend of mine at http://www.elcontec.de/alucorex.html.

They turned out quite nice.
Also the price is reasonable. IIRC, something like 40 Euro for one set of plates (front and back) including cutting, development of the plates and shipping.

Do you remember what you paid for your plates?

Regards,

Markus

[Structo]

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?

[ElectronAvalanche]

Hi Markus,

Vienna. If you ever get to Munich, let me know.

I think the plates were 50 DM each (so 25 Euros).

The Alucorex plates look very nice. So you sent your pdf file to the company and they did the exposition and development?

Nice faceplate layout and great looking amp btw, what software did you use for the faceplates?

What Reverb circuit and any chance to see a pic of the innards? Clips?

Btw I am still trying to figure out what Font Dumble used for the labeling of the controls on the blackface amps. Anyone know??

Cheers,

Electron

Hey Electron,

close to Germany, in Vienna.

A couple of years ago I did some etched Alucorex face plates for my amp.
(see below).
Cool thing is that they last forever since the white lettering is done by removing the black anodised alyer.

Later we had some Alucorex face plates done for a friend of mine at http://www.elcontec.de/alucorex.html.

They turned out quite nice.
Also the price is reasonable. IIRC, something like 40 Euro for one set of plates (front and back) including cutting, development of the plates and shipping.

Do you remember what you paid for your plates?

Regards,

Markus

[markusw]

Hi Markus,

Vienna. If you ever get to Munich, let me know.

I think the plates were 50 DM each (so 25 Euros).

The Alucorex plates look very nice. So you sent your pdf file to the company and they did the exposition and development?

Nice faceplate layout and great looking amp btw, what software did you use for the faceplates?

What Reverb circuit and any chance to see a pic of the innards? Clips?

Btw I am still trying to figure out what Font Dumble used for the labeling of the controls on the blackface amps. Anyone know??

Cheers,

Electron

Hey Electron,

thanks for your offer!
Will let you know if I manage to visit Munich.

Exactly, we sent them a pdf file.
They do everything. Cutting the Alucorex, developing and etching.
No drilling though (we didn't ask for it).
IIRC, I did the layout for the face plates in Visio.

The innards are less nice

I already built the amp in 2006.

https://tubeamparchive.com/viewtopic.ph ... highlight=

Any chance for some gut shots of your amp, btw?

A few changes happened since then. I moved the OD trim to the back. Also the PI trim is now panel mount.

Kind of embarrassing that I didn't manage to do any clips yet.

The reverb is Gary's single tube reverb. Not over the top but clearly sufficient for my taste.

Sorry, no idea what font Dumble used.

Regards,

Markus

[ElectronAvalanche]

Hi Markus,

as promised, some pics from the inside of the amp.

The preamp board is a tad smaller than a real Dumble, since I had to work from pics back in the day. The Power Supply PCB is larger than the original ones (ahh those were the days when not much detailed info was available).

This amp started it's life in 2001 using plain-jane solder-boards and sported a Fender style reverb (3M3//15pF mixer) and a dual pot (250k, 500k) that allowed changing the HF-taper on the fly). Nice amp, but I ripped it apart in 2005 and installed the new preamp board.

Then it was a HRM for some time, but I never liked the sound of the HRM in this amp (another amp performed really nice using the same values, albeit a different OT (Hammond) and PT.

Now it is (as stated before) a clone of #183 but I am again moving toward something else. I had a very nice transparent loop inside the amp, but threw that out since I wanted to use my Rodenberg Flexloop with the amp.

I plan on building some 19" Phoenix style preamps with the different circuits (#102, #124, #40) and see what fits best with the OT (Fender Schumacher from PA100 Fender head).

Cheers,

Electron

[Structo]

What are the output coupling caps?
The look small, are they .02uf?

[ElectronAvalanche]

Hi Tom,

no they are 0.05uF (MPP).

Cheers,

Electron

[Guitarman18]

Hi Electron,

Thanks for sharing your experiences with #183 design, I can't wait to hear some clips!

Cheers Paul.