Johnson: 800 ms of analog delay ? (coop ?)

[V!N]

Hi folks,

On eBay there are always a few of these, maybe you have seen them before or perhaps you have even played/owned one.



http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2373838993&category=38070

800 ms of analog delay seems like a realy neat pedal, but ! ... Not every owner on HC is satisfied with this pedal:

http://www.harmony-central.com/Effects/Data/Johnson/EAD_2_Echo_Analog_Delay-01.html
http://www.harmony-central.com/Effects/Data/Johnson_Electronics_U_S_A_/Echo_Analog_Delay-01.html

But ! ... It might be a nice base to tweak into a realy great pedal. 800 ms is quite a lot ! lot lot lot lot lot lot lot lot lot lot lot lot


I never gave up on the coop-spirit. EdJ and I are going to build a ourselfs two huge Vibes.

But what if we'd chuck in a few bucks to buy one of these delays, tweak it and clone it ? It wouldn't be half bad to have another delay project.

[Fret Wire]

Sounds interesting. But it doesnt sound like it has 800ms of delay. Taken with a grain of salt, the HC reviews tell me that the pedal has a good foundation, but needs some work. The grainy sound and noise could probably be fixed with good quality components.

I'd be interested in both directions: modding and cloning. If a cheap pedal has the basics of a sturdy enclosure, easily replaceable pots, jacks, and switches, sometimes it's easier to mod the pedal  than clone.

Either way, I'm interested.

[afranks]

Nope... it's crap... I have two, and they sound horrible.  Parts are
crap... enclosure is crap... etc.  I bought them to strip out the BBD,
clock, and compander parts.  I got them really cheap.  By any reasonable
measure, you will only get 300ms out of this pedal, at best.  It uses
two BL3208's which are 2048 cell BBDs, pin compatible with the MN3208,
in the 8 pin DIP form factor.  I don't like the form factor of the pedal
as is... it's longer than a Boss pedal, and the knobs are small and slippery
and really hard to turn.  

I would recommend buying one if you got a really good deal and wanted
to harvest the parts.  At smallbear prices, the harvest-worthy parts in that
pedal are worth about $30.

[Fret Wire]

Ah ha! Somebody owns one. That bad? Not worth modding? Did it have pcb mounted jacks, pots, and switches? Do you think it's basic circuit has any promise?

[Fret Wire]

Speaking of Johnson, check out their pedal case:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2374666704&category=22669#ebayphotohosting

Kinda like a gig bag for pedals. A nice idea, with probably poor execution. It's hard to tell by the photo's, but does the front side fold over itself? If not, it's like you have to step in it to stomp your pedals. That wouldnt be fun for a wah wah!

Then there's the power supply. If it was quiet, and the front folded over or zipped down, it would be a good buy for the money. Funny, the pic shows 6 pedals, and only one is their's.

[ExpAnonColin]

Who knows, maybe the BL series can be clocked lower or something...

-Colin

[afranks]

Well, I can't get more than 300ms out of it, at least to my ears.  I have
a Boss DM-2 to compare it against, and it sounds about the same to
me, as far as delay time goes.  Obviously I'm more fond of the DM-2
for its tonal characteristics. :-)

To answer the question about construction, The pots are on a small
daughter board with cables leading to the main pc board.  The jacks
are similar to the enclosed Switchcraft jacks I like to use, and aren't
physically attached to the pcb.  The switch is a momentary switch
hooked to a FET style switching circuit, like on Boss pedals.  The
power jack is mounted to the pcb.  Basically, it's contructed like a
Boss pedal, but a little longer.

I think you could probably go through it and replace all of the caps
with quality replacements and have a good start.  I haven't traced
the schematic, but I know it's a different circuit from a DM-2, since
the buffering is done with opamps,  unlike the Boss.  For me, I
simply don't like the form factor of the pedal as-is, so I would be
inclined to harvest the parts (including jacks and pots), and build
an AD-3208 out of it.

If anyone has any luck improving the sound of the Johnson delay,
I'd love to hear about it.  I'm just not up for investing the time to
come up with a set of tweaks.  My 1 year old is running me ragged. :-)

-alan

[puretube]

Who knows, maybe the BL series can be clocked lower or something...

-Colin

I clocked them (BL3207) from 1.5kHz to 2Mhz yesterday...
getting a little misty on the scope above 1MHz, and producing nice sine-waves after the output-filter in the audio-range at low freq., though....

[Mark Hammer]

Mike Irwin tells me that the input capacitance on the clock pins of the Matsushita chips is what restricts maximum usable clock rate.  Buffer the clock lines and dump lots of current into them (e.g., parallel invertor sections) and apparently 1mhz and even 2mhz isn't all that much of a problem anymore.  The standard clock driver chips provide adequate current to successfully send a nice sharp clock pulse up to a certain clock rate, but crap out after a certain point.  Most discourse you see about max clock rates anywhere implicitly assumes one is feeding a clock pulse directly from an MN3101 or 3102.  You will note that the A/DA Flanger, prized for its extraordinary sweep width, does not use a Matsushita clock chip but uses a CD4047 instead.

Incidentally, am I the only guy who has ever noticed that the A/DA has an input jack for external control voltages, but also has an on-board envelope follower? (for controlling the FET-based noise-gate)  In theory, it ought to be possible to reroute tha envelope follower to drive the external CV input.

[puretube]

above stated frequencies was with BL3102 (+ 1 BL3207).
Starts drawing heavy current though, above 500kHz...
(dunno yet, if it is the BBD itself, the Clock-gen., or both...).

Of course, when clocking more BBDs, their clock-input capacity adds...

Mark: thanx again for your great BBD-data-sheet collection!

[Paul Marossy]

I've always wondered if the Johnson tube overdrive pedal sounds any good... anyone have any experience with that one?
Saw one on ebay, sparked my curiousity, but I never heard of Johnson until I saw one on ebay...