http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3702418171&category=41415
Now that is just plain wrong.
The "magic" of the old green box delay was that it had a tracking filter where the high-frequency rolloff was yoked to the same clock that set the delay time in a very specific way. The notes they post indicate the need for a dual-ganged pot for setting the delay, which I gather is intended to simultaneously adjust the delay time on the PT2399 with its own internal clock AND adjust the delay-time of the original board to get the tracking filter function.
I'm not suggesting the hybrid is going to sound awful, but the likelihood of the delay time and lowpass filters tracking each other the way they did on the original (a divider circuit made the lowpass filter rolloff at a frequency very specifically determined by the HF clock) is pretty low.
This is NOT the same thing as replacing a bunch of SAD1024's with a trio of MN3007's. Not by any stretch.
I've got a broke one of those that I use for parts. I couldnever find the chips for it. It had if you look where they modded that one, removeable chips on it....
Quote from: Mark Hammer
Now this is just plain wrong.
The "magic" of the old green box delay was that it had a tracking filter where the high-frequency rolloff was yoked to the same clock that set the delay time in a very specific way..
+1,000
-Colin
the mxr analog delay schematic looks intersting,but i could not see much of it...maybe i need new glasses
Maneco
Just would liek to add a note . I bought one of the MXR100 boards from these guys for $40 and wired it up and it sounds fantastic. These guys are for real if anyone was on the fence about buying anything from them.
I know the chips are impossible to find - but if anyone wants the green MXR traced - I have a perfectly good working one here.
"-)
that would be great!!!
Quote from: MarkBI know the chips are impossible to find - but if anyone wants the green MXR traced - I have a perfectly good working one here.
"-)
Cool! It seems that the implementation of the tracking filter would be good information to extract.
ok - when I get a few minutes, I'll pull it out and take closeups of the board... so everyone can take a look and we can trace and check it.
"-)
That would be great Mark, i've been after one of those for years but they're really rare, especially here in the UK. A schem or layout would be boss!
Jim[/quote]
thanks again,Mark,
if you can take some scans of the board,i can start "filling the blanks " in the impossible to read schematic from the bid posted...i'll work hard...
Maneco