Crowther Audio - Prunes & Custard

bajaman · Post by **bajaman** » 23 Aug 2007, 03:27

Hello Kaz
check the Hot Cake thread - AG did a schematic for the relay switch board, BUT, it is missing some resistor values - do you know the values?
OR, are you asking us for the values?
bajaman

theblackman · Post by **theblackman** » 23 Aug 2007, 03:58

i think he's asking for them, i didn't realise no one had those part values, i'll check over the daughter board and post a pic.

bajaman · Post by **bajaman** » 23 Aug 2007, 09:28

Thanks Richard

bajaman

krome_magnon · Post by **krome_magnon** » 03 Sep 2007, 21:55

Bump...

I hope the reverse engineering of this cool effect isn't going to die!

Jim777 · Post by **Jim777** » 04 Sep 2007, 00:01

Just what I was thinking....I might draw it out tomorrow if I get some time.

marshmellow · Post by **marshmellow** » 04 Sep 2007, 11:25

Analogguru said he has already drawn it and is only waiting for the resistor values...

Jim777 · Post by **Jim777** » 04 Sep 2007, 17:47

I drew out a schem. I'm not sure how close it is. Maybe I could post it to get things moving?

krome_magnon · Post by **krome_magnon** » 04 Sep 2007, 23:35

I just did a trace of the circuit, had a bit of a stumbling block because the pic with the yellow traces posted before has a small section of copper missing under the guitar/bass switch.

here's the amended version -

Without that small bit of copper the guitar/bass switch would have seemed to chop out half the circuit in the bass position. With it restored as per one of the other gut shots posted, it shorts out a resistor to bring a second cap fully into play to create a bigger roll off in the passive filter that comes before all the diodes.

I can't find the power supply for my scanner so I can't post my attempt at the schem. But that gives me time to tidy it up in my lunch break tomorrow before scanning and posting it tomorrow evening.

Interesting circuit and not a million miles away from the ETI Hyperfuzz, which I also have a scan of somewhere. I'll try to dig that out as well and post it at the same time.

EDIT:

Found the hyperfuzz schem -

Jim777 · Post by **Jim777** » 04 Sep 2007, 23:54

Shame you didn't post that earlier I just took ages looking for that

Here's what I got, see how it matches up https://i199.photobucket.com/albums/aa1 ... crusty.jpg

krome_magnon · Post by **krome_magnon** » 05 Sep 2007, 00:10

Jim777 wrote:Shame you didn't post that earlier I just took ages looking for that
Here's what I got, see how it matches up https://i199.photobucket.com/albums/aa1 ... crusty.jpg

Close, though I have the whole mess of diodes etc. a little differently. The amended trace should go like...

Which, as I said above, makes a lot more sense as it modifies that resistor & cap filter at the start of the diode chain to roll off more highs in the bass mode by shorting out the 100k resistor and bringing the 220n fully into play.

Jim777 · Post by **Jim777** » 05 Sep 2007, 00:29

I already have that connection can't you see it looping under the caps?

krome_magnon · Post by **krome_magnon** » 05 Sep 2007, 18:30

My trace from last night...

I think I included everything.

Jim777 · Post by **Jim777** » 05 Sep 2007, 22:34

Well mine looks a bit confusing the way I've drawn those diodes

I checked it again and it looks ok to me but doesn't look like what you drew. Maybe you could put some resistor values in there? I've never heard one of these do they sound any good?

krome_magnon · Post by **krome_magnon** » 06 Sep 2007, 22:49

Mine redone much in a much more tidy way. Still unsure of resistor values, either my eyes are going or my monitor is crap, but I can hardly tell what some of the resistor colour bands are on the gut shots.

krome_magnon · Post by **krome_magnon** » 07 Sep 2007, 17:31

latest version, with best guess values at most components.

Jim777 · Post by **Jim777** » 07 Sep 2007, 18:50

Looks good. Where did you get the extra 2 diodes and 10k resistor from? I can see on the board where they could go. Were they fitted originally?

RLBJR65 · Post by **RLBJR65** » 07 Sep 2007, 19:40

Great job! Here is the pic theblackman posted I marked the resistors that were not marked as I read them. Couple are tough like the 39 or 390K
looks like a couple of those bands could be smudges. IMO it's probably 390K.

https://img526.imageshack.us/my.php?ima ... ersli3.jpg

krome_magnon · Post by **krome_magnon** » 07 Sep 2007, 19:51

Here's my trace compared to the gutshot. A few values adjusted and I'll further tweak the values as per RLBJR65's posting.

Torchy · Post by **Torchy** » 07 Sep 2007, 20:02

Why would you put a 10V zener on a 9V supply ? Protection against a higher output psu connected by mistake ?

krome_magnon · Post by **krome_magnon** » 07 Sep 2007, 20:03

Torchy wrote:Why would you put a 10V zener on a 9V supply ? Protection against a higher output psu connected by mistake ?

Hence the question mark...