Effectloop / Dumbleator sound issue

[Richard1001]

I have a question about the ODS effectloop and Dumbleator combination.

I have an ODS like amp with passive effectloop and put together a ceriatone c'lator. I would like some delay in the loop an for this i use a Roland SDE-3000.

When i use the amp with nothing in the loop, it sounds awesome. On all volume levels, clean of OD, with of without PAB or Mid boost, never harsh, nice presence and tight. Even with the singe coil bridge PU of my strat.

But when i put the C'lator in the loop, i lose highs and overtones. With my strat neck PU, it even gets a little muddy. The bright switches on the Clator can make it so there are more highs, but this doesn't sound the same and the overtones are still gone. (Less overdrive)

Before you might think the problem is in the C lator of delay: I use the Clator and Roland delay in the loop of my SSS also. My SSS can produce overdrive and boosted with a TS it sound great. The C lator smooths the highs somewhat, but the tight, thick overdrive tone remains. The Roland has been fully refurbished and has a direct signal bandwith from 10Hz to 100KHz. So i would think not much is lost there.

I wonder if any of you have come across this issue and found any solution for it.
I have seen small caps on the mastervolume, but this wound also change the amps tone when playing without the C lator. I realy don't want that. I have also seen a 220 // 250p in series with the out going signal. I guess this gives the signal send to the dumbleator a little boost in the high an mids. This, if it works, would be ideal since it is out of circuit when the loop is not used.

But before i start experimenting i would like to learn from others so i would like to hear any experience with the passive loop and Dumbleator.

[ayan]

A question for you: how long are the cables you're using to connect the amp's preamp out to the C-lator input and from the C-lator output to the amp's power amp in? I appreciate the fact that you've mentioned things work well with your other amp. However, whatever you stick in the loop will make a difference and shorter, low capacitance cables will help preserve the highs. If, for instance, you have the C'lator on a pedalboard and are running an 18 ft cable to it, I think you'll never make that work well. I keep my D-lator in a single space rack right under the amp's head with 2 ft cables going form/to the amp.

In addition, I don't know anything about the C'lator's design per se. But if it's anything like most actual D-leators, the Send and Recovery pots are high impedance (250 K). If you set the Send pot in the middle of its range, that'll set the output impedance of the D-lator's send jack at its highest and there will be extra loss of highs. So perhaps you can try to dial in the C'lator with the Send pot set either really high or really low, which will lower the output impedance, and see if that makes any difference at all. I personally don't like using the D-lator's bright switches, they're placed too late in the signal chain and will always tend to sound harsh. If I need to use a bright switch, I prefer the sound of the one on amp (mine are 120 pF, no the more common 330 pF value that Dumble used). But most of the time I get the high end response I want by balancing the amp's Master volume setting and the Dumbleator's Send setting.

[Richard1001]

Thank you for your relpy.

I understand your argument on cable length. I keep them as short as possible. I put the rack on the floor next to the amp/speaker. The length is 1,80 meter (5 feet or so?)
I use high quality cables.

I could change the cables between the delay and C'lator. They are spectraflex patch cables and 3 feet in length. I could use something shorter,

Changing settings on the knobs doesn't change much, exept when the bright switches are used.

[erwin_ve]

I use the 220k//250pF on the amp loop connection.
A small bright cap(15pF) on the master. You can use a push pull pot.
Master is set fairly high, about noon.
Recovery bright cap(x5f ceramic is smooth) on the Dlator is on. I turn the recovery pot as far as necessary to smooth out.
Thats my recipe to get the dlator working.

Erwin

[bepone]

would be good to have mosfet follower immediatelly after the master volume potentiometer, this would fix all the problems with Dlator, without adding unwanted capacitance to raise the highs

[Richard1001]

I use the 220k//250pF on the amp loop connection.
A small bright cap(15pF) on the master. You can use a push pull pot.
Master is set fairly high, about noon.
Recovery bright cap(x5f ceramic is smooth) on the Dlator is on. I turn the recovery pot as far as necessary to smooth out.
Thats my recipe to get the dlator working.

Erwin

Thanks Erwin. I tried the 250p//220k. It cleans up the muddyness with the C-lator but does not realy add highs. Together with the drive's bright switch it gets usable.
I read somewhere Robben Ford's amp supposed to have a 68p cap on the mastervolume. Guess i'll have to trie and see how it works out.

[Richard1001]

Yesterday i read about someone measuring the capacitance of different types/brands of jack plugs. According to this, the straight Neutrik plugs i use
supposed to have an avarage capacitance of 33pF. That's only for the plug itself. According to this measurements, Amphenol plugs (ACPM) are 6.6pF. So i will change to Sommer LLX cable and those Amphenol plugs to see if this will help.

[bepone]

it is good to think that master volume value is 1Mohm, when is not at full (and this is.never) is split to 2 resistors, one is in series with the signal, and it is in hundreads od kiloohms. after you add the cables, it is easy to see low pass filter (MV+ coax cables)
to avoid this story in total we need to have mosfet follower after master volume which is reducing this effect but i dont see nobody to inplement this.

when i need i have tube buffered fx loop (aka dublelator)integrated in the amp, to avoid long coax run outside

[pdf64]

… According to this, the straight Neutrik plugs i use supposed to have an avarage capacitance of 33pF. ..

I just checked a Neutrik straight jack plug, it read about 12pF

[rootz]

Captain obvious here: either lower the capacitance of the cable from the amp to dumbleator ánd dumbleator to fx. Or lower driving impedances.

So imho a dumbleator should always be on top or at least very close to the amp.

Maybe a bigger problem is the high output impedance of the Dumbleators CF. Part of its character, but you could considerably lower the value of the pot after the CF, especially when you use a 12at7. A 12ax7 will run out of steam pretty soon.

[Richard1001]

Thanx for all the input.

I know a low impedance driver would prevent losses in the cable, but i've heard that 'the fragile harmonics can't survive in a crystal like structure' ( ) so i won't be going for the Fet option.

Short cables sure would help, but i can't put my rack case on top or under my SSS.

Looking at pictures of Robben Fords rig, he too uses a few feet of cable back and forward from the amp to his rack. I'm trying to find some recipe to get it to work in the same way.

[talbany]

Welcome to the Dumbleator Jungle!



Tony

[Richard1001]

Welcome to the Dumbleator Jungle!



Tony

Brilliant !

[bepone]

but i've heard that 'the fragile harmonics can't survive in a crystal like structure' ( ) so i won't be going for the Fet option.

maybe reverse is true

[Richard1001]

I fixed the problem last weekend and tried the amp yesterday with my band. It sound great when using the C'lator.

I tried different caps (values and type) on the master volume and rewired the effectloop jacks. I ended up with 68p on the master. A cheap 500v ceramic sounded the best. Put in a push pull pot like Erwin suggested. I also put a 220k // 270p (silver mica) in series with the send signal. (added a switch to have the option to switch it in and out)