EBS - Multidrive  [schematic]

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floris
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Post by floris »

Does anybody have the schematics of the EBS Multidrive perhaps or else some information about the signal switching?
I'm actually not so much interested in the internals workings of the drive but more the switching arrangement and input/output stages because it pops when enabling it.
The foot-switch seems not to be true bypass but a simple one pole switch. This probably implies that the switching is done electronically and that the foot-switch provides a logical 1 or 0 to the electronic switching circuit, right?

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floris
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Post by floris »

bump...
Perhaps somebody can help out? Some info on the used switching technique of the EBS Multidrive or any exprience with FXs that make the signal "pop" when enbaling or disabling them in combination with an EBS Multidrive would be great!

The "popping" signal chain:
Bass guitar -> EH QTron -> EBS Multidrive -> Amp
The signal "pops" when enabling/disabling the EH QTron while it is before the EBS multidrive in the signal chain. It does not matter if the Multidrive is on or off. The EBS Multidrive seems not to be true bypass. Its probably always in the signal chain regardless if its on or off.

This signal chain does not "pop":
Bass guitar -> EH QTron -> Amp

EBS Multidrive circuit board:
http://www.littlefishmusic.net/multidrive01.jpg

Anybody who has any idea or suggestion?

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jrc4558
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Post by jrc4558 »

Solder a 2.2meg resistor from hot to ground on the input jack. input cap seem to be floating.

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Post by darkglass »

Mhhh, I don't think the "missing" resistor is the reason... though if is not there, adding it wouldn't hurt.
Probably the buffer in the EBS is "interacting" with the signal of the qtron, you should check if theres a coupling cap before and after the buffer, if theres not, the reason of the poping maybe DC leaking into your signal form the EBS´output buffer, or even a previous gain stage.

Regards from Chile!

Doug.

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floris
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Post by floris »

Thanks for the reply.

> Solder a 2.2meg resistor from hot to ground on the input jack. input cap seem to be floating.
This has been tried without success. 1M resistors were soldered on the input and output jacks to ground. :(

@ darkglass:
Which "buffer" in the EBS Multidrive are you refering to?

Regards,
Floris

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Post by darkglass »

floris wrote:Thanks for the reply.

> Solder a 2.2meg resistor from hot to ground on the input jack. input cap seem to be floating.
This has been tried without success. 1M resistors were soldered on the input and output jacks to ground. :(

@ darkglass:
Which "buffer" in the EBS Multidrive are you refering to?

Regards,
Floris
I have no idea :D , I've never seen any schematic of the pedal, but it must have a buffers somewhere, besides the fact that is not true bypass says that it should have at least a input and output buffer, but even if it doesn't, a DC voltage could be leaking from any stage, either buffer or gain... but even the worst designer in the world (and I doubt this would the case) would add a coupling cap from a gain stage... but there are some designs that don't include it before and after buffers. But anyways, I'm not saying that a missing coupling cap is the only reason though... it could also be a bad cap conducting DC, thats a rare case, but sometimes it happens!

Any soultions? If byou don't have a schematic, is hard to see where could be the problem, if you could try with another EBS we could dicard a design problem, and focus on a problem with your pedal... If you can't get another one for trying, the only thing left is to measure, a osciloscope would be very useful here... But if you don't have acces to one, measuring DC with a DMT may reveal if you have a DC leaking into your signal. ( I'm not quite sure if this would work, but you can anyways try)

If you can get a schematic, post it, that would really help.

Regards

Douglas.

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Post by Bernardduur »

Got this pedal in as it was cutting out. Turned out some bad soldering and a switch that needed replacement.
EBS - Multidrive.JPG
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Post by ricothetroll »

What the hell is that schematic ? :D

MC14660B doesn't even exist, MC14660 is a 25W power resistor...

My guess is it's either a very weird one, or a joke from the author

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Post by krome_magnon »

ricothetroll wrote:What the hell is that schematic ? :D

MC14660B doesn't even exist, MC14660 is a 25W power resistor...

My guess is it's either a very weird one, or a joke from the author
Possibly a 4066 switch judging from how it's used in the schem.
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Post by floris »

I know Bernardduur is not a joker.
I guess the MC14660 should be a 4066 CMOS quad analog switch?

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Post by Jarno »

Ancient thread, but I noticed this uses a 2164. Note that these IC's can sometimes be destroyed by current peaks when switching power on and off (as is likely to happen in an effects pedal).
Here's an article about the matter:
https://www.njohnson.co.uk/index.php?me ... bsubmenu=3

A schottky diode should be added to protect the IC (at least, that is the easiest solution).
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Post by Ben N »

SSM2164 is a quad VCA. What the heck is it doing here, with 4 VCAs in parallel?

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