My Dumbleator

[heisthl]

http://www.unicornelex.com/categoryall.php?cat=E42
is one place, there are many others, In Phoenix some of the Art Supply stores carry them.

[JimiB]

I am thinking Structo had it right. I have 2 #124 schematics that show the RC filter is only active when the loop is unplugged. (see odourboy's 124 schematic in the files section)

yeah but look at the pic of #124

[Structo]

Thanks Henry!
I forgot to check my local crafts store.
I haven't seen that brand before. I used to see the Datamark packs at a local electronics place but that place has be gone now for years.
I don't think many kids tinker with electronics anymore and Ham radio guys seem to be a dying breed as well. That's too bad, those guys really step up to the plate when there is a major crisis and there are no telephone communications.


I agree that the 220K/250pf is only in circuit when there is a plug in the the return jack.

[Tonegeek]

I am thinking Structo had it right. I have 2 #124 schematics that show the RC filter is only active when the loop is unplugged. (see odourboy's 124 schematic in the files section)

yeah but look at the pic of #124

I stand corrected. The schematics show the same too, I just missed it somehow- too much year end partying, no doubt!

[Structo]

I've updated my schematic after a little adjusting of the power supple and voltages.
I removed one 47uF and put the choke between the 47uF and 30uF.

Changed the dropping resistor to 56K

Voltages are notated on the schem.

[CHIP]

Tom,
I ordered the same PT and Choke from Antique Elec. Supply that you used. I plan on going ahead and building the D'lator. I was wondering about the voltages you ended up with. I read in a recent thread that your getting close to the D sound with the D'lator. So the slightly different voltages are OK?

Greg

[Structo]

Hi Chip,

I recently adjusted my preamp tubes voltages higher when I installed a choke in place of the power resistor on the filter board.
A combination of that plus the Dumbleator has really turned my amp around in a good way.

Be aware that there can be a voltage swing between 12ax7's so the numbers can change by as much as 5-10v when you try different tubes.
So it is a good idea once you get it going to try a bunch of different tubes for tone and voltage.
You should have at least 30v on the cathode follower cathode.

Here is a schematic of my final numbers.

Be aware that the Reverb PT is a little too tall to mount in a rack enclosure.
It is just over 2" tall.
Maybe if you got creative you could make it fit if that is your plan to use the rack mount box.

Hope this helps.

[dcribbs1412]

Thanks Tom
I'm going to go ahead and redo some wiring in my D'lite
..add choke,get voltages up to par,clean up leads.
thinking about adding the reverb tube(internal) and replacing the (ironsides)fx loop with the external d'lator.
This is assuming you are still happy with the changes?

[Structo]

Yes, tonally, there is no comparison between the Ironsounds loop and the D'lator.

At low volumes the Ironsounds didn't sound too bad but when you had the master volume up it didn't sound good. Hard to put it into words but I think it was clipping.
It can only handle a 30v swing so that is probably why.
I even ordered several different opamps to see if that would help.
It did help a tiny bit but still had the clipping issue.

The D'Lator is such a cool piece of gear. Really makes the tone happen.
It takes a little while to figure out where to set the knobs since it didn't came with a manual.

I had a ground loop initially that was a really bad loud hum.
I snipped the ground wire on the cable from the recovery to the circuit board (I think that was the one) and the hum went away, so I didn't over analyze it after that, it just worked.
Also, the 1000pf bright cap on the Send is way too much and sounds very harsh.
Don't know why HAD put that there, perhaps he had some high pf cable or something.
I used a 500pf ceramic there and it is much better, probably could go lower.
I don't use the two bright caps on the loop much, really the only time is when I have the volume very low to help the articulation.

The reverb would be cool to have internal.
Leleduke has a Monkey 88 that has a really good reverb in it.
I thought he had processed the mix with reverb but he said it was all the amp reverb.
Very natural sounding.

As I mentioned in the other thread, the plate voltages are really key on these amps.
If you get them in the ballpark, it really does make the amp sound more Dumbly.
So that is the recommended first seies of tweaks.



Be sure to use shielded cable on both OD pots (4 total)

The mid cap mod is a good one so you can change the response for single coils and humbuckers.

I also installed a switch on the Local Feedback loop there.
It opens the amp a bit more and is most notable when the amp is let out a bit and breathing heavily.

So first get your voltages in line.
I still have the stock BN PT in my amp.
I believe that I still have the 1K first dropper, then an 18K and 2K2.
And a 150K FET simulator at the end of the string to ground.
I think I will adjust the 2K2 a little higher since V1 is a bit high sometimes depending on the tube that is in.

Here is what you should shoot for:

V1= 195-200v

V2= 200-205v

V3= 285-290v
I have the 110K/120K plates on V3 and a 10K trimmer.
It really does help with the tone to have that trimmer adjusted for maximum bloom and harmonics.
I have a choke.
High plates on both V1 & V2

4.7uF 50v bypass on all.

Bright cap on Master 47pf

OD entrance mos (.05uf 220K, 10M to ground)
330pf snubbers on V2
Mid boost on push/pull 250KA mid cap.

.01uF mid cap on board and a .047uF on a switch that puts it in parallel.

Switch on the .05uF LNFB. The cap comes off pin 6 then two 22M resistors.
One lead from the switch goes to the joint between the two 22M resistors with the other switch lead going to ground.
I labeled that switch Smooth and Raw.

The mid cap switch I labeled Fat and Thin.

That's about it.

Oh and I moved the OD trimmer to a pot on the back panel.
I can't remember the value I used, I think it is a 50K and a 2K7 pad to ground.
This puts the desirable 20K-40 range at the top.
I put a chicken head knob on it so I can reach around and feel where it is set.

Hope this helps,
Tom

[talbany]

Tom
GREAT POST!!...

Yeah the Dlator w/100k plate resistor gives you roughly 100v swing 3 times that of the Ironsounds..If you do the built in D-lator and use shielded wire going to the loop you have to watch where you ground the shield..As long as you run the wire from the master to the loop down tight to the chassis most of the way the chassis will provide adequate amount of shielding to keep quiet..

Tony

[dcribbs1412]

Thanks Tom
this will keep me busy for awhile
I very much appreciate you and all the other major players on this forum

here are some links to my latest edition I converted a 18TMB to a TC-15
a kind of a lightning/AC-15 clone with a ef86 channel.Trinity Amps hardware
and iron (thanks Stephen).Jangly cleans with a little grit.I'll be breaking this in while the d'lite is on the blocks.

http://i1018.photobucket.com/albums/af3 ... -15021.jpg

http://i1018.photobucket.com/albums/af3 ... -15020.jpg

http://i1018.photobucket.com/albums/af3 ... -15036.jpg

[Structo]

That looks pretty sweet man!
So EL84's?

I want to build a Rocket type amp one of these days.

How do you like the VVR in that amp?

[dcribbs1412]

I ended up taking the VVR out
one of these days I might try a big bottle Rocket Reverb
RJ,Rawnster,Normster have documented some very nice builds.

[Structo]

Yes that Rocket that Ron built is pretty sweet alright.
I liked everything about it.

That may be my next one as well.

[martin manning]

I had a ground loop initially that was a really bad loud hum. I snipped the ground wire on the cable from the recovery to the circuit board (I think that was the one) and the hum went away, so I didn't over analyze it after that, it just worked.

Is this a known issue with D-lators? It does seem that if all of the jacks are grounded there is a big loop formed by the cable shields to and from the D-lator box.

MPM