Structo wrote: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
Martian
With the loops built in when I ground the shield either at the source or on the PCB board (which is also common ground to the jacks and pots on the back of the chassis).. I get Hum..Same w/external ones..I don't know why people feel the need to shield here.. Dumble didn't.. This last early 70's one I built has no shielding from the relay to the PI and it is DEAD QUIET!!
Tony
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" The psychics on my bench is the same as Dumble'"
The ground planes on the PCB Loop have a common ground on them pots jacks/ signal..My initial thought is to keep them isolated however Jelle mentioned splitting the signal off and grounding them separate ...So if your designing your own loop boards try splitting the planes..Same with the external..
The cool thing about the PCB loop is it is dead quiet and takes about an hour to build and install.. This to me is a PCB application that works really well (Along with a power supply)..The pots and jacks hold the board on and really is pretty quiet no shielding needed...
Tony
" The psychics on my bench is the same as Dumble'"
I build 4 dlators and I never had 1 hum issue.
Grounding the pots and the jacks with a buss bar.
Also the node/capacitor (at the PS) for the cathode follower is grounded at signal board's ground. That's the way it's done by HAD.
Brandon posted some HQ pics where you can see this.
Structo wrote:Maybe you could offer a pcb kit to the forum members. :D
Sure I would be happy to.. You can PM me or my email is talbany@vvtamps.com
I can also offer a small faceplate for it that you can stick on to label it as well.. If I get enough interest I'll start a dedicated thread...The layout on the PCB is true D-lator..
Tony
" The psychics on my bench is the same as Dumble'"
That seems like a great alternative for the guys that want to have the loop built in to the amp.
Of course you would still need to install the extra tube, right Tony?
That isn't on the pcb is it?
Structo wrote:That seems like a great alternative for the guys that want to have the loop built in to the amp.
Of course you would still need to install the extra tube, right Tony?
That isn't on the pcb is it?
Yes you would need to add the tube on the chassis V3 before PI.. is the spot!!..You would also need to allow for the extra filtering as well.. I used a JJ 32uf X2 can cap right off the screen supply works great if you can find room...Glad to help..
Tony
" The psychics on my bench is the same as Dumble'"
I was wondering if there was a simple way for me to tell where the Send control is to be set for a unity setting?
In other words, if I don't want to add or take away from the signal that is going through the amp, so that there is no distortion introduced, where would that 250K Send control be set?
I suppose on the optional Return pot, since the original Dumbleator has a 220K resistor in that spot, that it would be set rather high on it's rotation.
So that leaves the Send and Recovery amp left to adjust for a clean unity type gain.
Since none of my pedals have a adjustable gain (Reverb and Delay) I was trying to figure out how I can tell where to set them.
I suppose it might just be a matter of adjusting and listening.
And I am probably over thinking this as usual....
I was just wondering if you that have a lot of experience with these loops has found.
Right now I have the Send pot at about 2:30.
That pcb kit sounds like a great idea! I was looking for an easier way to do one. The last one I did (not D-style) had altogether too much stuff hanging off the send & return pots.
Does it really need that much filtering off the screen supply (32+32)??
That might be one of an infinite number of possibilities, and depends upon what is in the loop. The maximum gain of the driver is a little less than 1, but it can be dialed down, then there is the gain of anything in the send-return loop, and then you can trade the recover in and out settings to get the output level to match the input. The settings of the dive and recover in will affect the coloring of the tone by the FX in the loop and the recover stage, so you could adjust those to taste and then set the final output level with the recover out. Your ears are the best judge, as the perceived loudness is dependent upon the frequency spectrum.
Is the point of this to have the speaker volume come out the same with the entire loop bypassed, or just the FX bypassed?
Yeah I was just trying to make the loop volume the same as the amp volume so that when I flip the bypass switch on the loop I get the same volume level in or out of the loop.
I thought with linear pots they reached half value at noon?
This is with a EHX Stereo Memmory Man, Danlectro Chorus and a Boss RV-5 Reverb in the loop.
I thought that linear pots tended to be half their value at noon?
Right now with my amp Volume and Master at noon, for the loop to be the same volume in and bypassed, the D'Lator settings are:
Send - 2:30
Recovery - 1:00
Return - 1:00
Also I noticed when bypassed my amp is much brighter without the loop.
Is that normal?
If I wanted to brighten up the loop, would adjusting the .47uF on the Send side downward be a good place to adjust that or should I change a value in the Recovery side?
I have the 47uF bypass cap in the recovery amp.
I have seen schematics where this is noted as .47uF, which one is correct?
I don't really like the bright switches on the loop so much.
I did lower the value of the 1000pf bright cap to 500pf so that is much better.
If I use either of the bright switches it is the one on the Drive pot.
