AW: Space Echo sound on sound

[Haible Juergen]

	Mike wrote:

	>I put a switch on the erase head of a 101 (?) space echo
several years 
	>ago. I didn't use a resistor, I just put a switch in line with
one of the 
	>wires. An uneducated mod, but it worked, and didn't add
distortion. 
	>Sounds would eventually fade away, getting darker and darker. A
nice 
	>addition.

	Paul wrote:

	>why not just put a miniature pot in parallel with the erase
head, with
	>the 470 ohm in series? normally this kind of ckt you have probs
with
	>phase shift, c to ground etc but since the erase is
	>fixed frequency, who cares?

Both good ideas.
I have tested with parallel resistors because I didn't want to cut
a wire for testing.
Meanwhile, I have connected an oscilloscope, measured the
amplitude, and found that at approx. 3k parallel resistor the
HF amplitude is reduced to one half.
So the next thing I'll try is connecting a 10k potentiometer
as an attenuator before the erease head. (this time cutting
wires, not just parallel !) 10k would not reduce amplitude too
much when it's fully cw, and should still give a good attenuation
response when it's loaded with the head's 3k.
Unlike the parallel method, it would not reduce record bias, and thus
not cause distortion.
If it will work ok, then I'll sacrifice one of the 2 Mic inputs, and
use the level knob for erease current attenuation.

JH.