Tuesday, 10 October 2017

Electro-Harmonix Slap-Back Echo

I found this old ehx pedal. It's a slap-back style echo. Model EH-4700.

Slap echo or slapback is a single echo resulting from sound bouncing off reflective surfaces.
Like when you clap your hands and listen for the echo in a large empty hall).
I understand that the Slap-Back pedal was one of EH's first forays into the smaller delay unit market.
She is pure analog and needs 18v to work, using either two 9V batteries or a 18V PSU.
I was initially drawn to it as the pedal uses the hard to find Reticon SAD1040 delay chip which is a bucket brigade IC. The Reticon can be found in the Serge WAD which is my favourite effects unit.
The Slapback delay is limited to 80ms. Just right for thickening guitar, bass guitar and other instrument tones.

A distinct repeat-echo is added to the original sound resulting in a very live sound similar to what you would hear in an auditorium.
The PCB is held in place by the Bend pot. So I was unable to remove the board to get a better look.
Thus these pics from the sides.

The pedal is uber simple.
Just two controls : a large 'blend' knob and a switch to turn a filter on or off.
The BLEND control is good for mixing wet and dry signals. The FILTER is turned on with a switch.
I think its a low pass as it seems to be good for cutting out hi frequencies.

There are standard 1/4" TRS connections

It's not versitle to replace your Memory Man or other delay but is the perfect little pedal to use in tandem with something like that to give you some varying delay tones.

I only have the first version but there seems to have been two other versions.
The Stereo Slap-back Echo edition, and the Slap-back Echo with Full Double Tracking Effects.

The Stereo Slap-back Echo edition, featured a DIRECT OUT output jack and a power indicator LED. There one of only 2 small EH pedals that ever used LEDs. The other unit was the small clone
Both units used the Reticon SAD1024 delay IC.

The Slap-back Echo with the Full Double Tracking Effect had a delay that was switchable between 50 and 100ms. The BLEND control was retained and the FILTER switch was replaced by the MS DELAY switch. It was produced around 1979 and used the Panasonic MN3005 delay IC.
EH seems to have replaced the Reticon chip with the Panasonic in nearly all of their effects. According to the net, the Panasonic chip was capable of doing the same delay effects, but with better bandwidth and less noise.I kinda like the reticon though.

The PCB is labeled EH1315

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