Catalinbread - Dirty Little Secret [traced]

[loylo]

Which multimeter do you use?
There is a huge difference between your readings and the theoretical resistors' values, according to their colour codes.

They have both 5% tolerance, so the first CC one shouldn't read lower than 950R and the second one 640R...

[pietro_moog]

it's a cheap multimeter, like everybody else have. it's precise for all the other stuff.

[loylo]

OK.

I asked because I used to have a very cheap multimeter (less than 3€/5$).
Until I realised all my readings were rather wrong (especially while measuring tube amp transformers).
So I bought a better one, anyway at a reasonnable price (around 30€/50$), which is very accurate.

[jymaze]

Sometimes my cheap multimeter drifts randomly when the batteries are not too fresh. I periodically check for accuracy on some 1% resistors i have at hand.

[Ripdivot]

Best thing to do is just lift one leg of each component before you measure it and even your "cheap" meter should be pretty close.

[Ice-9]

Best thing to do is just lift one leg of each component before you measure it and even your "cheap" meter should be pretty close.

+1 on lifting the leg to read a resistor. You will not get an accurate reading with the resistor in circuit. Either lift one leg of the component free of the circuit and read with a meter or better still read the colour codes on the resistor.

[HHR18]

Are we ready for a vero guys? Or do we still think some values might be off?

[pietro_moog]

the schematic is good, the values are ok. we definitely are ready for a vero layout. are you working on one?

[roseblood11]

the schematic is good, the values are ok.

Are all other resitor values definitely verified by reading the color codes? You can't measure parts values in circuit, unless you're dead certain that there's nothing in parallel...

[pietro_moog]

yes, color codes are real.
i can't remove the resistors from the circuit. those traces are very tiny and the CC resistors legs are big, there is a big risk of damaging the pcb.

[lukatosh]

so... the MKIII can't be built using 5457?

[imaradiostar]

Sure it can- you just can't be sure it'll sound exactly the same.

By adjusting the gain control, source resistors and bypass caps you should be able to get the same sound, more or less.

We don't know what they're doing to build them- they might be selecting transistors of specific gains anyway. My guess is no but it's possible.

jamie

[roseblood11]

Uwe stocked the MPF 4393:
http://uk-electronic.de/onlineshop/prod ... df4c9f94b8


But his link to the datasheet doesn't work. I guess it's this one, but it's possible that he sells transistors from another manufacturer...
http://pdf1.alldatasheet.net/datasheet- ... F4393.html

[mmolteratx]

Sure it can- you just can't be sure it'll sound exactly the same.

By adjusting the gain control, source resistors and bypass caps you should be able to get the same sound, more or less.

We don't know what they're doing to build them- they might be selecting transistors of specific gains anyway. My guess is no but it's possible.

jamie

Nic has stated that they select FETs before, IIRC. Dunno what parameter they select for in particular, but my guess is pinch off voltage.

[roseblood11]

Is it possible to do that with a cheap multimeter?

[Intripped]

http://www.geofex.com/article_folders/f ... tmatch.htm

[HHR18]

Once the schematic is verified, it might be nice if pietro_moog could post the voltages of the original one so we can compare the two. I never checked the voltages on any other of my Catalinbread builds so I don't think it matters that much.

[pietro_moog]

the schematic IS verified. unfortunately i sold the pedal, i can not do any more check

[biglouis]

I can make a layout for this project, but, i don't know how to make layouts on vero.

If i make a pci layout, someone proposes to build?

[HHR18]

Vero would be greatly appreciated, don't have the skills to make it myself!