Parallel loop - for ampgarage users only :-D

[Structo]

Oh, don't get me wrong, I was able to understand it, it's just that calling it V3 kind of threw me since the tube is not in an amp, at least the stand alone unit isn't.
There are three or four layouts here for internal D'lators.

I hope I didn't come off snarky.

I pulled my layout to fix it.

Hopefully this will work.
I installed the bypass on my serial loop yesterday and it works great.

Not sure if I want to mod my D'lator to parallel or make a whole new loop.

The shielded cable noted on the layout is not official. I just included it to show that the longer runs should probably be shielded for best noise reduction.

Placement of the Series/ Parallel and Bypass switches should be given some consideration. I put my Bypass switch above the jacks for easy access. I may put the Series/ Parallel on the back as well. It will keep the front from getting too cluttered.

Wire colors are just to show contrast with each other and are not official.

[Sven]

The idea is to have a D-lator INSIDE of an amp, thus the obvious choice of V3 to be used as a dobule-triode for that function, whereas PI valve becomes V4, of course.

Furthermore, the width of a card used for D-lator circuit is less than 65 mm (cca 2 1/2 inch), so that the card could be inserted vertically into the amp, next to V3.

I have not yet built D-lator circuit into D-amp, so I wander if the original intention of having an outside, freestanding D-lator, was: not to INTERFERE with the pre-amp and PI circuits electronically thus causing noise, reduction of sound quality or any other performances of an amp. If such bad consequences could be avoided, than definitely a D-lator place INSIDE of an amp would be much preferred, generally, rather than carrying around yet another extra box to a show or in studio, let alone higher cost of a freestanding D-lator.

So, yes, my layout is for INSIDE placement of D-lator, with the card placed vertically, preferrably.

It would be nice to get some input from people who actually built D-lator circuit on the same board where PRE amp and PI components are placed, to find out whether some bad interactions in electronic domain are taking place between D-lator ckt. and pre-amp and PI ckt.? When building a D-amp from scratch, one could than place all pre.amp, than D-lator, and than PI components on one long board, together. I wander if that would be causing some phase cancellations between D-amp and its D-lator, and how would one go about building it on one board, all components, while avoiding damaging effects?!

[Structo]

Hi Sven,
Some guys that have built in the D'lator have done so point to point off of the socket.

In my case with a Brown Note D'lite amp, there is not room for another tube the way my amp is configured.
I have the OD trim pot on the back panel plus a switch for the Local Feedback and a switch for selecting two different mid caps.

The chassis used for my amp is not as long as a typical ODS amp so it is rather cramped inside.
So an outboard unit was my only choice.

I think when HAD designed the Dumbleator in the 80's, rack systems were popular with bands. So he designed the rack mount unit.

[FUCHSAUDIO]

I think when HAD designed the Dumbleator in the 80's, rack systems were popular with bands. So he designed the rack mount unit.

I think it was also another sales opportunity as well....

[Structo]

Say it ain't so Andy!

Hmmm, the amp is $4K and for it to sound really good, you need this $2K tube buffered loop........
Capitalism at work.

[llemtt]

It would be nice to get some input from people who actually built D-lator circuit on the same board where PRE amp and PI components are placed, to find out whether some bad interactions in electronic domain are taking place between D-lator ckt. and pre-amp and PI ckt.? When building a D-amp from scratch, one could than place all pre.amp, than D-lator, and than PI components on one long board, together. I wander if that would be causing some phase cancellations between D-amp and its D-lator, and how would one go about building it on one board, all components, while avoiding damaging effects?!

In my own experience putting the buffered loop (not D-Lator, different design) inside the amp has been a little nightmare because of the interactions you mention.

One thing you have to mind carefully is input impedance at the grid of the cathode follower actually being higher than 10Meg -> it's like having a radio antenna potentially receiving any signal inside the chassis...

At very first try there was enough leakage around that I was comfortably able to play the amp at very bedroom level even with the master turned full off!!

Teo

[Luthierwnc]

I never had any trouble with mine. I split the rail at the screens so the loop has it's own dropping string. The picture shown was a non-HRM at the time. I later put in the modern power section and HRMed it. The picture probably dates to 2007.

I'm selling that amp to a friend and building a 100 watt version now. It won't have the internal loop -- mostly because I have other amps that sound good with the loop and a rack unit can be used for those too.

Good luck on yours, Skip

[Luthierwnc]

Here's another shot.

[llemtt]

Try this:

- set OD on
- turn OD ratio control completely off
- play

can you here any sound coming out of the speaker?

[BobW]

I pulled my layout to fix it.

Hopefully this will work.
I installed the bypass on my serial loop yesterday and it works great.


Wire colors are just to show contrast with each other and are not official.

Tom, thanks for the layout. It looks correct, and electrically it will work, but if you move the ground wire on the series / parallel switch to the other 220k, it matches the schematic that Bluesfendermanblues posted. ie the same 220k resistor is either connected to the send pot or grounded.

[Structo]

Not sure I follow Bob.

What other 220K?

Claus' schematic did not show the Output pot, just the 220K fixed.

I just incorporated the pot since it seemed that most of the guys were building their loops with the pot vs without.

If you see a mistake on the layout can you please describe in more detail?
I want this to be correct for people that want to build it.

BTW, I did install the bypass switch and it works well on my loop.
Helpful to check the balance between the loop on or off.

[BobW]

Tom, electrically your layout works but the leftmost 220k connected to the series/parallel switch toggles to either the bypass or to ground. According to Claus' schematic his resistor toggles to either the bypass or open.

Your 2nd leftmost 220k toggles to either the send pot or to open. Claus' resistor toggles to either the send pot or to ground.

Electrically they are the same since both switched 200ks share a common node, but following your layout and comparing it to Claus' schematic may get confusing for some. As you stated, it's obvious Claus is using a fixed 220k as a recovery, you are using a 250 pot. So simply moving the ground wire on your parallel / series switch to the bottom left contact would then make your layout match claus' schematic minus the recovery ckt.

Just something I noticed and though it would help others understand the differences between the schematic and the layout posted. hth

[gilgalad101]

Nvm

[ampdoc1]

Just wondering....? I've used what I believe to be the oldest d'lator schematic (attached) with great results. Do the "current" resistor/cap values markedly improve the sound?

[Structo]

The main difference I see Doc, is the 47uF cathode bypass the the tail resistor on the cathode follower which is 10K on yours and 27K on the newer schematic.
I think it was Scott that said the real deal has a 47uF there.
And of course the 250K pot on the return instead of the 220K fixed.
That extra pot is nice as it acts as an volume control to the return of the pedal signal.

I'm sure yours sounds fine as is.

The main thing I discovered when I built mine was to have around 260-270v on the first plate, 30v on the cathode follower cathode and 210-220v on the second plate.