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[Bob Leonard]

Art,
I'm going to show my age here, but I've had a few of the oil can delays. I liked them but lost interest when my pet dinosaur stepped on them. The problem with these delays is that eventually they all leak. But that's not what you're after. Go to the link below and you'll find all of the schematics you'll ever need. Look under delay, then further down you'll find oil can delay. There is also a site out there dedicated to these beasts if you really get the bug.

As for parts to build a circuit similar to the Fender circuit (there were 3 versions), I probably have them, including the transformers, in my basement. Once you decide on what you need let me know and I'll dig out what I have and get it to you.

Also note. The 12AX7 is a suck tube for reverb. Try a lower gain 12AT7 in it's place and you'll be happier.

http://schematicheaven.com/effects.htm

 http://schematicheaven.com/effects/fender_echoreverb_II_oilc an.pdf

Here is a much more clear schematic of the circuit above. There are two 12AX7's used and has been said above the 300V B+ hasn't been rectified in the schematic. You'll need two 1/2amp DIODES to complete the circuit. Typical Fender circuit for this purpose.

http://schematicheaven.com/effects/fender_echoreverb_III_oil can.pdf

[Bob Leonard]

Art / all,
If you want to know how they work here's a great article about the original oil can reverbs made by Tel-Ray. Like I said above, they always leaked.

http://www.geocities.com/tel_ray/home.html

[Chuck Harrigan]

Sorry, posting at 2 am is not recomended.

it looks to me like the first stage of the write stage is used to drive the second stage, which creates a high voltage signal that is stored in the capacitive oil drum.  If the control pedal is a switch, it would mute the second half of the write stage, or if it was a potentiometer pedal, it would vary the strength of the signal being written to the oil drum.

The read stage looks similar to a phono preamp without the RIAA equalization.  It is using negative feedback, and it also sends the output signal back to the input of the second stage of the write path.  The potentiometers would be used to set the amount of signal being sent back to the write stage, as well as the output level.  I'm guessing that the capacitor is used to decouple the output from the high voltage, so you aren't sending 450V to the next device in the chain.  I think the echo level is setting the gain of the final stage through the amount of negative feedback.

Memory would be the oil can.  It is rotating and the high voltage signal is being "written" to the plates or whatever is in there capacitively.  The drum acts like a hard drive, but using charges stored in oil instead of magnetic plates to store the information.  I'm thinking that the reading of these signals would be destructive.

edit: grammar

[Andy Peters]

David Buckley wrote on Thu, 16 July 2009 20:54

Some useful info here: http://www.geofex.com/Article_Folders/oil_can_delays.htm There are some patent numbers in there which I've just started reading.

My pal Dave Amels, who wrote the original Tel-Ray plug-in that's now sold by Digi, told me how the thing got its name. Allegedly, two of the guys were working on it, and when they got it "right," one said to the other, "We have to tell [Jamie] Ray [the third partner] that it's working."

Probably apocryphal.

I do have a Tel-Ray t-shirt.

-a

[Art Welter]

Chuck Harrigan wrote on Fri, 17 July 2009 15:32

Sorry, posting at 2 am is not recomended. it looks to me like the first stage of the write stage is used to drive the second stage, which creates a high voltage signal that is stored in the capacitive oil drum.  If the control pedal is a switch, it would mute the second half of the write stage, or if it was a potentiometer pedal, it would vary the strength of the signal being written to the oil drum. The read stage looks similar to a phono preamp without the RIAA equalization.  It is using negative feedback, and it also sends the output signal back to the input of the second stage of the write path.  The potentiometers would be used to set the amount of signal being sent back to the write stage, as well as the output level.  I'm guessing that the capacitor is used to decouple the output from the high voltage, so you aren't sending 450V to the next device in the chain.  I think the echo level is setting the gain of the final stage through the amount of negative feedback. Memory would be the oil can.  It is rotating and the high voltage signal is being "written" to the plates or whatever is in there capacitively.  The drum acts like a hard drive, but using charges stored in oil instead of magnetic plates to store the information.  I'm thinking that the reading of these signals would be destructive. edit: grammar

Chuck, and anyone else who understands tube pre amps and drive circuits,

As I wrote in my initial post, I have tried using pre-amps, small power amps, various input and output transformers, and can get lots of echos from my oil can, but the signal to noise ratio is about 1/1, actually more noise than signal. Oil can echos are normally noisy, but not like that. I do have fresh oil of the special kind (and quantity)that makes the device work in it.

I understand the device is always going to be a bit noisy, and since the disk is scratched, it also will always have clicks like a scratched record.

Is there anything that the electronics are doing in this circuit other than amplifying the signal going into the can and then amplifying the output?

What does this circuit do differently than all the stuff I have tried already?

Art Welter

[Tom Reid]

Art Welter wrote on Sat, 18 July 2009 13:07

Chuck Harrigan wrote on Fri, 17 July 2009 15:32 Sorry, posting at 2 am is not recomended. it looks to me like the first stage of the write stage is used to drive the second stage, which creates a high voltage signal that is stored in the capacitive oil drum.  If the control pedal is a switch, it would mute the second half of the write stage, or if it was a potentiometer pedal, it would vary the strength of the signal being written to the oil drum. The read stage looks similar to a phono preamp without the RIAA equalization.  It is using negative feedback, and it also sends the output signal back to the input of the second stage of the write path.  The potentiometers would be used to set the amount of signal being sent back to the write stage, as well as the output level.  I'm guessing that the capacitor is used to decouple the output from the high voltage, so you aren't sending 450V to the next device in the chain.  I think the echo level is setting the gain of the final stage through the amount of negative feedback. Memory would be the oil can.  It is rotating and the high voltage signal is being "written" to the plates or whatever is in there capacitively.  The drum acts like a hard drive, but using charges stored in oil instead of magnetic plates to store the information.  I'm thinking that the reading of these signals would be destructive. edit: grammar Chuck, and anyone else who understands tube pre amps and drive circuits, As I wrote in my initial post, I have tried using pre-amps, small power amps, various input and output transformers, and can get lots of echos from my oil can, but the signal to noise ratio is about 1/1, actually more noise than signal. Oil can echos are normally noisy, but not like that. I do have fresh oil of the special kind (and quantity)that makes the device work in it. I understand the device is always going to be a bit noisy, and since the disk is scratched, it also will always have clicks like a scratched record. Is there anything that the electronics are doing in this circuit other than amplifying the signal going into the can and then amplifying the output? What does this circuit do differently than all the stuff I have tried already? Art Welter

Try degaussing the drum.

[John Petrucelli]

Art,
The circuits are fairly typical tube amplifier stages, so no, they are not doing anything special beyond that.
If you've tried a number of different amplifying circuits with no improvement, maybe the disc itself is faulty and can no longer hold an electric charge?

I think Bob L offered some spare parts?

JP

[Art Welter]

Tom Reid wrote on Sat, 18 July 2009 12:26

Try degaussing the drum.

Tom, the disc that rotates in the drum is aluminum.
It can't get magnetized.

There is no magnetic storage, the system uses the oil and special rotating aluminum disc as a sort of capacitor storage.

[Art Welter]

John Petrucelli wrote on Sat, 18 July 2009 17:49

Art, The circuits are fairly typical tube amplifier stages, so no, they are not doing anything special beyond that. If you've tried a number of different amplifying circuits with no improvement, maybe the disc itself is faulty and can no longer hold an electric charge? I think Bob L offered some spare parts? JP

If there is no special impedance match in the circuit, you are probably right, the disc may be shot, so not worth any more experimentation. As Bob also said, (and I knew) oil can echos are low-fi at best.

The people that are most fond of them are really liking the extra tube preamp stage the unit adds, the echo is just nostalgic.

It may have been run dry long enough that the "magic" disc etching is just not thick enough to hold enough of the special oil to get a decent S/N anymore, though the surface does look unusual, almost like a compact disc.

Thanks for the insight.

Art Welter

[Tom Reid]

Art Welter wrote on Sat, 18 July 2009 19:43

Tom Reid wrote on Sat, 18 July 2009 12:26 Try degaussing the drum. Tom, the disc that rotates in the drum is aluminum. It can't get magnetized. There is no magnetic storage, the system uses the oil and special rotating aluminum disc as a sort of capacitor storage.

cool,

Thanks, I get the technology behind the drum.  It's not making a good charge to read anymore.  Didn't know it was aluminum.    

That would be the first place I'd look, the media.  Electronics work fine (since you've swapped out many parts), it's just the media won't imprint anymore.