Can I get a BOM or parts list for the bypass PCB? I'm not savvy enough to be able to look at a schematic and know exactly what parts I need unfortunately, so any kind of kit/project setup would be awesome.
TOTALLY depends on your application.
You need 2x DPDT DIP-16 relays, with high coil resistance, for low power consumption,
solder wires to PCB, a switch, 1N4002 kinda diode, and, probably, if you need light when ON, a LED and resistor.
Relay's voltage:
EXAMPLE1: if this goes to GSSL, you have about 42...50V between power supply capacitors right after rectifier,
than, I'd use 2x24V relays in series.
Possible to hook to +22 right after diode rectifier and gnd, and use 2x12V in series, but it is less funny imho.
EXAMPLE2: If I have +5V supply inside of a unit I need to hardwarebypass, I use 2x5V relays in parallel connection.
Same about +12V: 2x12V relays in parallel; BTW, here possible to use 2x5V relays with coils in series.
Termination and proper load/Zobel for your trannies: search NET for trafo datasheet etc. I have to do same to answer.
In general, "the way" is.
IF your unit have an output transformer and it IS unterminated and have no Zobel network, bypass PCB allows to put it here.
RL: in general, 600R.....3k for most of trafo's. Rz, Cz: depends on transformer.
Search this forum about how to figure out Zobel network. I saw it 10 times at least described better than I may do.
Scope, square wave, some resistors and some caps to try, 10 min, done.
No scope and square wave oscillator? Search net, maybe, somebody had this experience with this transformer.
In 75% of situations, it is enough right load resistor and NO Zobel network at all.
If you have el. balanced out, forget about all this load/zobel stuff.
Great post about API out transformers terminating BTW:
http://recforums.prosoundweb.com/index.php/m/118457/0/
Hello everyone!
I have a newbe question and will be very thankfull if you help me
According to attached schematics bypass board requires +/-12 or +/-24 V for relays. But for example if I'm building an EQ based on BA283 (which requires +24/0 V) can I use the same PSU for both of them (I mean bypass board and BA283 board)?? And consequently connect "negative terminal" (V_REL-2) of the bypass board to "earth" terminal on the PSU? Or maybe the most preferable variant is to have two separate PSU's?
Welcome! You can use 2x12 v relays in series or 2x24v relays in parallel. Hook V_REL to 24V, - to gnd and + to +24V of you audio PSU.
Is there anyone that can help me to understand which values I need to get for the Zobel network in the Bypass pcb:
*R_L *CZ *RZ
The Bypass is going to link the output of the SRPP stage of the DUAL EQP1A of Gyraf Audio which I have equipped with 2 LUNDAHL LL5402 Transformers (the scheme below) to the XLR IN and OUT of a Dual Eqp1A.
As I can see there is no zobel network at the secondaries of LL5402 in Gyraf's schematics! Consequently you don't need R_L, CZ, RZ at all
In general: you just have to load the out of your trafo with proper resistor. Feed square wave to the input of your SRPP,
get out BEFORE the SRPP clips, load treafo with 10k pot, and see what happens with overshoot. I think, for this kinda circuit, less termination is better. IMHO, no need Zobel. If overshoot is more than 10%, use 200R....1k+4n7....10n, something in this range I guess should work.
DOCS:
http://ij-audio.com/downloads/BYPASS.zip
