Electro Harmonix - Echo 600

[Scruffie]

As part of my on going interest in EHX I find my self scraping the bottom of the internets barrel for information (although in my eyes, some interesting circuits) and have come to the EHX Echo 600, an expansion on the Deluxe Memory Man using 3 x MN3005 in the vintage slider style pedal box used for the Microsynth etc. with a short/long switch and added output and rate controls.

So far the most I can find is a short mention on our own EH Man's blog of it and 2 gut shots on Effectsdatabase.

Does anyone have a unit they can crack open for some gut shots so I can trace it or the original factory schematics?

While here, I think the last piece apart from this that there is also a shortage of information on is the EHX Solid State Reverb (or possibly reverbatron) so if anyone has anything on that too that'd be an added bonus!

[Mark Hammer]

That looks like something a) ancient, given the size of those caps and the abundance of MN3005s, b) short-lived, in the annals of EHX products, and c) not necessarily worth replicating.  I'm not seeing a compander chip immediately, although the gutshot at effectsdatabase suggests the chip in the corner along the same edge as the BBDs might be a 570.  Still, the presence of an input attenuator and clipping indicator suggests that signal integrity is "challenged".

Interesting historical tidbit, though, since the combination of longer delay capability PLUS modulation is something we wouldn't see again until later Memory Boy pedals.

[Scruffie]

That looks like something a) ancient, given the size of those caps and the abundance of MN3005s, b) short-lived, in the annals of EHX products, and c) not necessarily worth replicating.  I'm not seeing a compander chip immediately, although the gutshot at effectsdatabase suggests the chip in the corner along the same edge as the BBDs might be a 570.  Still, the presence of an input attenuator and clipping indicator suggests that signal integrity is "challenged".

Interesting historical tidbit, though, since the combination of longer delay capability PLUS modulation is something we wouldn't see again until later Memory Boy pedals.

I never mentioned replicating it, just collecting information and seeing how it parallels against the deluxe memory man in design.

There is a compander along with a 4047 clock + 4049 buffer, I can see that much, it was definitely short lived, i'd guess towards the end of the original EHX production period (79 - 84 I suppose) I assume with the popularity of the Deluxe Memory Man, a slight improvement on it with (a claimed at least) 50mS extra delay wasn't anything to turn many heads, but still doesn't mean it wasn't an improvement.

The original and reissue big box deluxe memory man had the overload LED and it didn't have an input attenuator but input gain stage (alright, it could attenuate a bit but was mainly boost) which is what I assume the control on this model is.

I'm quite interested in how the short long switch is working, from the gut shot it looks like it's actually shorting out one of the BBDs.

[Mark Hammer]

Certainly use of a buffered clock to successfully drive a trio of BBDs was VERY far ahead of its time, if the period you've identified is accurate.  Pretty much anything from before 1985 normally defaulted to the MN3101/single-MN3005 structure, treating the use of multiple high-capacity BBDs as a kind of insurmountable obstacle.

One wonders if this was a Howard Davis brainstorm.

[Scruffie]

Certainly use of a buffered clock to successfully drive a trio of BBDs was VERY far ahead of its time, if the period you've identified is accurate.  Pretty much anything from before 1985 normally defaulted to the MN3101/single-MN3005 structure, treating the use of multiple high-capacity BBDs as a kind of insurmountable obstacle.

One wonders if this was a Howard Davis brainstorm.

It certainly was pre 85, this didn't come out in the post 90s/Sovtek EHX reincarnation.

If you look at the factory schematic for the Deluxe Memory Man, there is a 4049 clock buffer with a note "omitted after 12/15/78" the Deluxe Memory Man of course being designed by Howard Davis so i'd say it's probably safe to assume this was too.

EH also used one in their Echo Flanger to drive the 2 x SAD1024 (the schematic states a 4009 but actual units used a 4049) which was designed in 78 and has the initials I think are 'M.A' on the schematic.

I can also think of the Yamaha E1010 unit that had 4 x individual clock buffers for the 4 x MN3005 so buffering clock lines certainly isn't anything staggeringly new.

Why other pedals didn't use more than a single MN3005 I couldn't say, the MN3101 is specified to drive 8192 stages, or two MN3005, guess they mostly figured 300mS was enough.

Edit: Corrected MN3101 specs from 8096 to 8192 stages, got my stages confused

[StephenGiles]

Crikey, I've never heard of it!!

[Scruffie]

I've seen all of 2 units and mention of one other on google, i've contacted one of the owners who'd previously contacted me regards hosting my EHX schematic redraws who is hopefully once he's found it going to get me some gut shots so fingers crossed i'll be able to draw a schematic.

Certainly a rare one!

Reminds me, while I have a schematic for the ambitron using a SAD1024 I found some gut shots of a model that actually had an MN3005 in it, perhaps not the most exciting unit for guitarists but i'll be looking for stuff on that one too.

[Scruffie]

Hey Stephen, while you don't know this unit, I don't suppose you have anything on the rack mounted Dual Analog Delay do you? From outward appearances it seems like a combined Deluxe Electric Mistress & Deluxe Memory Man!

[StephenGiles]

Hey Stephen, while you don't know this unit, I don't suppose you have anything on the rack mounted Dual Analog Delay do you? From outward appearances it seems like a combined Deluxe Electric Mistress & Deluxe Memory Man!

No I haven't I'm afraid, it would be very interesting to see the circuits for that one!