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Author Topic: Oil Can Echo Schematic Questions  (Read 27387 times)

Art Welter

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Oil Can Echo Schematic Questions
« on: July 16, 2009, 07:32:30 pm »

Ray Lubow invented the oil can echo, sold under various brands,  Tel Ray, Dimension IV, Morley, Vox, Standell, and Fender  Echo-Reverb I, II, and III, all useing the same “oil can” with a rotating disk inside, a couple spoonfuls of oil, and two or three rubber- like play “heads”. A third “erase” head is grounded to the case to keep the echos from going too long, without it you can get about 18 repeats!
The combination of the special disk surface and the special oil makes it a capacitive storage device.

I have an oil can unit with no electronics.
I have tried using pre-amps, small power amps, various input and output transformers, and can get lots of echos from it, but the signal to noise  ratio is about 1/1, actually more noise than signal.
The oil can echos are normally noisy, but not like that. I do have fresh oil of the special kind that makes the device work in it.

I admit I can’t tell from the schematic what it does, can anybody tell me what it’s doing?
The tubes are 12AX7, the schematic says 1/2 12AX7.

index.php/fa/23805/0/
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Chuck Harrigan

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Re: Oil Can Echo Schematic Questions
« Reply #1 on: July 16, 2009, 08:29:07 pm »

i think the schematic is referring to each valve separately on the schematic. There are two tubes, but it separates them into halves to make the schematic easier to understand electricly.you'll notice it lists pin one two and three on one half and 6, 7 and 8 on the other.
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Art Welter

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Re: Oil Can Echo Schematic Questions
« Reply #2 on: July 16, 2009, 10:02:14 pm »

Chuck Harrigan wrote on Thu, 16 July 2009 18:29

i think the schematic is referring to each valve separately on the schematic. There are two tubes, but it separates them into halves to make the schematic easier to understand electricly.you'll notice it lists pin one two and three on one half and 6, 7 and 8 on the other.


Chuck,

I know that the device uses two tubes.

What is the circuit doing exactly?
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David Buckley

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Re: Oil Can Echo Schematic Questions
« Reply #3 on: July 16, 2009, 10:31:05 pm »

Assuming it does work as a capacitve storage device - the "write" electrode is driven from the anode of a (half of a) 12AX7 driven by a 300V power supply.  From memory the valve is only good for 250V on the anode, so the 470K must be dropping it a lot.  Anyway, the signal voltage is probably quite large, more so than line level or similar.  In terms of stuff lying around, I'd try a 70V (or 100V if you can get one, common outside the US) PA amp to see if that makes it work better.

Also the input impedence of the "read" electrode is very high, there is 4.7Meg bias resistor.

You could knock up those valvy electronics in a day, getting most of the harder to get bits (particularly the transformer for the HT supply) out of an old valve radio from a junkshop.

I've never seen anything like this.

Just to be a bit clerarer on whats happening - the first two drawn valves are each half of a 12AX7 double tride valve which forms a two stage amplifier.  The amplified voltage version of the input signal is applied to the drum.  There appears tobe two writing heads selected by a three way switch, and the two heads can independently have their levels set, so as to write different "patterns" of signal onto the drum.

The second two stage amplifier (again both stages in one valve) recover the signal from the drum, and amplify it.  This is followed by a two channel passive mixer to mix the delayed and original signals in any desired proportion.

The two controls around the final triode are a bit mysterious - they connect to the anode via a cap and my guess is they screw with the sound tonal "qualities" in some way, either by dulling the tone (reverb limit) or by adding direct signal (reverb control)


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Tom Reid

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Re: Oil Can Echo Schematic Questions
« Reply #4 on: July 16, 2009, 10:41:46 pm »

What I get out of it is 4 stages, marked on the schematic.

If the tubes were replaced with transistors, the B+ side would be the emitters.

Sorry if you already knew all that.

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John Roberts {JR}

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Re: Oil Can Echo Schematic Questions
« Reply #5 on: July 16, 2009, 11:21:20 pm »

The round thingys are tubes... think of them as amplifiers making small things bigger or the same size and stronger.

The round thing in the middle named memory is presumably some kind of ..... memory?  Sorry I can't tell from the picture what it is. Probably not a usb stick.

The circles after the memory circle are more boost stages, and there's some feedback connections from the very output back to the input, perhaps for repeats?

Figuring what the tube stages are doing is math... I have no idea what's in the oil can.. oil?

JR
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David Buckley

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Re: Oil Can Echo Schematic Questions
« Reply #6 on: July 16, 2009, 11:54:19 pm »


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.
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John Petrucelli

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Re: Oil Can Echo Schematic Questions
« Reply #7 on: July 17, 2009, 12:22:51 am »

Art,
Also look here for a collection of oilcan delays from various manufacturers.

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

The Patents for the original delays:
2892898
3072543
3215911

The Fender schematic you posted is missing the B+ rectifier diode (in case you try to build one)   Surprised

JP
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John Roberts {JR}

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Re: Oil Can Echo Schematic Questions
« Reply #8 on: July 17, 2009, 10:14:27 am »

I've designed several delays and thought I was familiar with most of the technologies but this is a new one for me.  

My suspicion is these fell out favor because of inferior sound quality. Tape echos  would be hifi compared to this stuff...  

JR
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Ned Ward

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Re: Oil Can Echo Schematic Questions
« Reply #9 on: July 17, 2009, 02:05:02 pm »

http://www.digidesign.com/index.cfm?langid=100&navid=119 &itemid=1500

Don't remember paying that much for it back when it wasn't owned by digi.

Can't wait to hear how this turns out.
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