Space Echo sound on sound

[media at mail1.nai.net]

At 2:15 PM +0100 11/21/97, Haible Juergen wrote:
>Wasn't there a Space Echo that could do Sound-On-Sound ?
>I have the RE-201 model, which cannot do it.

I also have a RE-201.  I also had an RE-501, but I traded it away.  Imho,
the 201 has a better sound.

RE-101 -- Space Echo -- 3 input mixer, no reverb,
RE-150 -- Space Echo -- ????
RE-201 -- Space Echo -- 3 input mixer, spring reverb, bass and treble
RE-301 -- Chorus Echo -- same as 201, with BBD chorus, Sound-on-Sound,
                         A & B outputs, footpedal speed control
RE-501 -- Chorus Echo -- no mixer, no footpedal control, S-o-S level control,
                         footwsitches for chorus and S-o-S, balanced XLR
RE-555 -- Chorus Echo -- same as 501 in rack mount version

Lets look at the description of the Sound-On-Sound feature as described in
the RE-301 manual: "Sound-On-Sound: When set to ON, input sound is
reproduced 10-30 seconds later.  You can double the performance or add
another effect sound on your performance simply by handling this switch."

The Sound-On-Sound is implemented with a fourth playback head placed
several inches away from the other three playback heads.  The RE-201 has
three playback heads.  The RE-301 and RE-501 have a total of four playback
heads.

>I tried to short the erease head (with 470 Ohm to prevent damage),

Would disconnecting it with a switch (or just snipping the wires) cause
damage??

>Sure, I could control the HF current to the erease head *only*,
>but then, wouldn't the HF bias
>in the recording head still partly erease the previous material ???

Yes, it would.  Even if there is no signal coming from the recording amp it
would still try to "record silence" onto the tape.

Anyway, on the RE-201 the 60kHz bias on the PS-15C PCB goes from point 53
to the record head at point 14.  Point 54 on PS-15C goes to the erase head.
You may note C101 (250pf) and the trimpot for adjusting bias (VR21, 50K)
are in series between 53 and 54.

>Before I go on experimenting, I need schematics of commercial units
>that have this feature built-in. Preferably Roland models, if there are
>any, but others are welcome too. What would I have to look for?

I also have the RE-501/555 schematics in front of me.  I do not see
anything that would suggest that the Roland Sound-On-Sound feature changes
the current to the erase head.  However, that does not mean that doing so
could not be a useful modification.

I'll admit that I'm confused by the RE-501 schematics -- they aren't drawn
very clearly.  It seems that pots are labelled with one function in one
diagram and labeled differently in another.  Certain switches seem to be
missing altogether.  From what I can tell the output of the Sound-on-Sound
playback amp is switched by a transistor (n-channel J-FET) on the way to
the expander.

>From the RE-501 Block Diagram also seems that the Sound-on-Sound output is
treated differently in regard to the Echo Intensity control ie. the
Sound-On-Sound output is not fed back to the record head.  However, I can't
see how they do that from looking at the schematics.

I hope this has been helpful.  If you like I can mail you the RE-501
schematics.

>PS.: This was a mail I sent to Looper's Delight - I thought I include it

What is Looper's Delight??

PEACE OUT :)
MARK





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