Wren and Cuff Phat Phuk B

[rocket88]

so i posted a request for this a long time ago, but i actually got my hands on one and traced it. i posted a layout for it on the main page, but figured i would post up some pictures of the board front and back, my trace, and the schematic so that it can be looked over to make sure i've got it right.

Front:
<nabble_img src="photo_1.jpg" border="0

Back:
<nabble_img src="photo_2.jpg" border="0"/>

Trace:


Schematic:


a couple of notes:
1 - there are a few tracts hidden by components, which i figured out by placing a light behind the board, and carefully moving some of the components out of the way.

2 - the Ge transistor has its markings removed, as well as the FET being sanded down. the only markings that can be seen on the Ge is what looks like AX9 which matches up to Chinese Ge transistors, but i do not know if it's PNP or NPN, and the FET is clearly a J201.

3 - the FET buffer makes sense to me, but the Ge section just seems really odd, and doesn't resemble a booster or buffer that i've ever seen before. which is why i figured it would be a good idea to have others look over the trace and schematic.

4 - the build quality is incredibly disappointing. the soldering is shit, the board is very low quality making it hard to remove components which is why i didn't/couldn't, and the wire is complete garbage with each one breaking at least ones while moving the board around. honestly incredibly disappointing coming from a "boutique" company, and all everyone here should be incredibly proud of the quality of all your builds.

[Emil]

Nice one!

Sad to hear about the build quality though. But great to hear that our builds are really holding up well! For me, who is just starting out, that was inspiring to hear.

[johnk]

the tranny is a PNP. here's a pic of the PCB that i etched and tested for it.




thanks for posting the schematic!

[johnk]

BTW, i redrew you schematic so it's a little clearer:

[johnk]

i also built another one with the bias control mounted externally as a pot. i like it better than the trimpot version so you can dial it from absolutely clean to overdriven.

here's my PCB layout for it:

[johnk]

i just finished boxing mine up. YAY!

[rocket88]

nice. what did you do for the phatness control? i was looking at a picture of the board for the suppa phat phuk and it looked like a lot more was done the a simple input cap blend, which is what i thought it was originally.

[johnk]

rocket88 wrote

nice. what did you do for the phatness control? i was looking at a picture of the board for the suppa phat phuk and it looked like a lot more was done the a simple input cap blend, which is what i thought it was originally.

i tried the input cap method but it didn't work at all because of the Jfet buffer. then i tried the coupling cap into the germ transistor and that didn't work either (and it changed the amount of gain/overdrive so that wasn't right either). finally, i had success with a 250K linear pot blending between a 4n7 & a 10u capacitor going into the output level control.

[rocket88]

nice. i wonder if it's really just that simple. i know someone posted that they have some pictures of the board, so hopefully they post it so i can trace it to be sure. btw, here's the gut shot i saw:

[johnk]

yeah, i've seen that. i didn't see a Jfet on that one, and it has a chip on it so who knows what's going on in that one?

[rocket88]

shit. didn't realize that surprisingly. i'm going to go out on a limb and say it's a IC based buffer rather then JFET based, but hopefully we'll get some pics that can make it traceable.

[johnk]

rocket88 wrote

shit. didn't realize that surprisingly. i'm going to go out on a limb and say it's a IC based buffer rather then JFET based, but hopefully we'll get some pics that can make it traceable.

that's what i was thinkin' too. it's probably a TL072 (or a TL071) which is a Jfet opamp. i generally tend to llke the J201 method better though.