Tape Echo

[gurutzeta]

Hello everyone!!!

I am trying to build a reel-to-reel echo machine or tape echo to use with my guitar. It consist on a cassette tape in a loop with a Record head and a play head both working simultaneously and separeted a certain distance (that creates the echo effect).

I managed to find all the parts I think I might need, but don't have much details about the Bias oscillator that I should use for the erase and record head. I've read that around 100kHz is OK, but what amplitude? any ideas, any easy solution available, any schemtic that I can base my design in.

Thanks in advance!!!

 

[Nigel Goodwin]

Hello everyone!!!

I am trying to build a reel-to-reel echo machine or tape echo to use with my guitar. It consist on a cassette tape in a loop with a Record head and a play head both working simultaneously and separeted a certain distance (that creates the echo effect).

I managed to find all the parts I think I might need, but don't have much details about the Bias oscillator that I should use for the erase and record head. I've read that around 100kHz is OK, but what amplitude? any ideas, any easy solution available, any schemtic that I can base my design in.

Thanks in advance!!!

You will also need bias for the record head, it's probably easiest to simply copy the circuit from an already working cassette recorder - preferably the one the erase head came from (different erase heads will probably require different amounts of power, also the erase head is often an integral part of the oscillator circuit). If it's any help, the old Watkins Copycat had multiple playback heads, so you could switch different delays.

 

[gurutzeta]

You will also need bias for the record head, it's probably easiest to simply copy the circuit from an already working cassette recorder - preferably the one the erase head came from (different erase heads will probably require different amounts of power, also the erase head is often an integral part of the oscillator circuit). If it's any help, the old Watkins Copycat had multiple playback heads, so you could switch different delays.

Thanks for your help Nigel. My plan is to try to do everything from scratch, but I guess I will have to end up doing as you suggest.

About the different playback heads, that was also my idea.

Thanks

 

[bmcculla]

Have you considered a digital solution? I don't think it would be too hard to run the signal into your computers soundcard, process it and output it. The delay function is a simple case of a FIR (Finite impulse response) filter which is not as complicated as it sounds. I'd bet there is source code implementing A FIR filter on the internet somewhere. Using a generic FIR filter instead of a simple delay would allow all sorts of neat filters.

Just a thought
Brent

 

[Nigel Goodwin]

Have you considered a digital solution? I don't think it would be too hard to run the signal into your computers soundcard, process it and output it. The delay function is a simple case of a FIR (Finite impulse response) filter which is not as complicated as it sounds. I'd bet there is source code implementing A FIR filter on the internet somewhere. Using a generic FIR filter instead of a simple delay would allow all sorts of neat filters.

Just a thought
Brent

There's a big revival at the moment for old tape echo units, modern digital ones don't sound quite the same! - WEM Copycats which were being binned a few years ago are now fetching big money (but not from me!).

 

[bmcculla]

I wonder if you could emulate the tape unit with a digital filter? Measure the impulse response of the tape unit and use that as your filter. Or is the difference in sound a product of the digital sampling?

 

[crust]

I would imagine it is probably quite complicated. In this weeks EE times there is an article about synthesizing the sound of a famous pipe organ. Understandably the organ is more complex, but trying to find the transfer function of either one is probably very difficult.

 

[gurutzeta]

I am afraid that the digital way is not a solution, no adc or dac would ever touch the tone of my guitar!!!

Just joking, but as Nigel said, it won't sound as a good old tape echo and besides, having a computer turned on involves noise in the guitar coming from the monitor, fan noise and a pain to carry to gigs.

I found the schematics of an old transistor based tape echo, the roland space echo, so I think I will go for a clone of that one