The Dwamp as built

[Williamblake]

Hiho everybody,

when i joined this forum i did so to get some criticism on the amp i came up with but it wasn`t ready then and it isn`t now but getting close to. So here it is.

Jens

[Williamblake]

Took a long time to get it on a single sheet of paper, too. What i left out: Where you see the boneray tonestack at the bottom is a ten-way switch to choose between differnet tonestacks, so beside the boneray there are more to choose from, the fender-tweed i haven`t redrawn yet, though i like it very much.

The attached picture that says midscoop is a middle control that does not have a mid scoop but is nice with humbuckers and full first cathode gain.  The midscoop middle conrol aka framus mid control is in there as well. I took the tone controls from http://chasingtone.com/yourguitaramp/guide-to-single-knob-tone-controls/

[Williamblake]

Since the last time i checked current draw has gone up some and i will lower plate dissipations a tad to get below 90mA but also V3 and V4 seem to draw 10mA which seems a lot for to 6N2Ps.

[Williamblake]

So what does it look like? Well, i redid a lot on this amp and that`s why there is so much crud in there that is really hard to get out that doesn`t look nice at all. Also is this done in a caveman-point-to-point fashion but anyway, it is working and i like the sound so far and it has great reverb.

[Williamblake]

What i am most happy with like the other guy is the reverb. It uses two monacor ME4 tanks which are not really top shelf and a short accoutronics would fit in, too. I like the ME-4 having a rather short delay. And it doesnt drip although sometimes it drips a bit. I guess this is from all the low end i tried keeping out of the reverb and the way i wired the tanks for least hum and max output but mostly from the coupling capacitor from the gain stage in front of the dwell control. Right in front of the dwell-control is a highpass that can nicely dial in the cheese. The reverb recovery EF86 circuit is taken from Merlin.

[Williamblake]

So as i don`t know jack about electronics and this is frankensteined together from different amps there is probably a lot of impedance mismatch and suboptimal resistances to ground. Also the preamp is drawing too much current and the preamp biases might be chosen differently for reasons i might not understand although i have started reading the Merlin-book about preamps several times.

The switch at the plate resistor and cathode of V1 is to be a Marshall 15W Tremolo in position 1 and switchable cathode capacitor at 2, 3 and 4. I might better put in some resistors to be more gentle on that switch and decrease popping.

The bright switch is a 12-way rotary switch i had laying around and i couldn`t decide on the bright capacitor but the way it is i can dial in the clarity i want without the amp being too brittle, probably i just need two capacitors. This amp was about testing out different things and so it became what it is.

The small transformer next to the power transformer is the 9V DC supply i did not mention in the schematic. Also there are jacks to use an external reverb tank and to use the reverb tank with another amplifier i didn`t draw in the schematic.

This was recorded with a cellphone on top of the cabinet.

[kagliostro]

what is that thing to the right of the tube, reverb tanks ???



Franco

[Williamblake]

Two ME-4 reverb tanks. I wanted to try two reverb tanks for hum cancelling but i have to admit i hardly noticed any difference in hum with the outputs in or out of phase and i checked on that some month later again. But the tanks are mounted belly to belly giving nice shielding and more reverb springs is very noticably richer than less. Notice the highpass to cancel hum at the output :-) Also the amplifier is standing with the knobs up on big rubber feet and there is that soft white foam around the tanks, too. And the shiny metal taken from a friteuse around the foam is not screwed to the chassis but dangling around some millimiters (eighths of an inch). Also i put in that extra metal plate between the power transformers an the reverbtanks as i had the impression the springs were moved by the powertransformers. 

I just notice the "K2" marking is wrong, it is connected to ground. But i was wondering if it wouldn't be more effective to connect the screen supply ground directly to the cathode to eliminate feedback from the cathode resistor.

[Williamblake]

So i changed the primary, using one 220 and one 230 winding in series and this gives 6,3V filament exactly. I changed The outputtubes cathode resistors and the dropping resistor supplying B+3 HT to the reverb driver and i am almost at 90mA at the filter choke. I think the power supply is looking almost good now and will try to get less low end out of the preamp now.

Also the tremolo is a bit slow, if i turn the speed up it gets weak and eventually dies. Don`t know, maybe more HT or smaller oscillation loop capacitor/s or a higher resistance from grid to cathode or a bigger plate resistor.