API 312 Thread!

[chrissugar]

Greg, the MM990 was designed bi Fred and you can find the schem here:
http://www.forsselltech.com/JFET%20Opamp.PDF
Fred mentioned several time that it is not capable to drive low impedance transformers.

chrissugar

 

[pmroz]

...

Fabio, did you try your original way? (REG48/R10/REGsw)

How about without relays? 4ch / 1psu possible ?

...

 

[louder]

alo fabio
that is what happened with me.7805,drops.
i got r10 connected to 48v,and i think it behaves better.
best regards
pedro

 

[Bauman]

Hey pedro, what are you using for r10?

 

[louder]

alo fabio
i use 470 ohm/5watts,for r10.
best regards
pedro

 

[pmroz]

Pedro, is your project 1PSU / 4 pres? did you check it works with most or all of the relays on?

 

[omeiko]

The low voltage relays can draw a lot of current. I used four 5v relays in my api/JE-990 preamp and the regulator got really hot. I measured the DC- resistance from 5V-supply to ground and it was only 17 Ohms!
That's almost 300ma.
I also get some buzz when the relays are in.

I think I'll have to change them to higher voltage (resistance) types to get the current down.


-Okko

 

[fallout]

Hey Fabio, I'm still gonna try to stuff 8 of these into a chassis.. I have a good PSU that will most likely power the +/- 18v and the 48v with no problem. However, would it be a problem to use a wallwart to power the +5v switches? If the tq2's are going to pull approx 300ma per PCB (4 relays), i'd assume i'd need a bit of grunt on the wallwart..

-Jay

P.S. Does anyone get any 'buzz' on Fabio's PCBs w/ the relays? Just curious becasue of omeiko's comments...

 

[omeiko]

would it be a problem to use a wallwart to power the +5v switches?

I think it would be simpler to use 48V relays instead of 5V relays.
Usually they draw a lot less current.
In my application the 48V relays takes the current from 300ma (5v relays) down to about 20ma so it should be no problem using the phantom supply.
I don't know if this arrangement is going to make some switching noise though...
I'm going to try it out anyway.

cheers,

-Okko

Edit: The aromat TQ2-5V is ratet for 140mW (mine are 400mW :shock: ) so the current for 4 relays is roughly 120ma.

 

[fallout]

Hmmm.. Let me know how the 48v relays work out.. I still havent placed an order for the TQ2-5v's so if all is well, maybe I'll get some 48v relays. I'd rather not use a walwart but if I have to, I guess i wont have a choice but I'd rather keep it neat.. Thanks!

-Jay

 

[Rob Flinn]

Why don`t you guys use an individual dropper resistor for each relay, like Tekay does on his Neve 1290 board ? If you use individual resistorsd then the voltage will be the same for each relay regardless of how many are energised.

If you know the dc resistance of the relay coil & the fact that it is 5v you can easily work out the current you need flowing. You then work out what resistor you need to pass this current over 48-5v =43v.

 

[Bauman]

Yea, the TQ2-5V are 30mA each! Same current a 992 opamp needs! :?

Anyway, I did this PSU to be used on 2 channels....

Pedro, will try the 470R/5W as R10. Are you running 4 channels with 1 PSU board?

Now I´ll stick with Tq2 cos I got a lot of them already... if you find a 48V relay that fits the TQ2 footprint and have the same quality PLS let me know.

:sam:
Fabio

 

[Greg]

Just to let you guys know... I have R10 as 470R/5W at the R1/C1 junction running two boards. When all the relays are engaged, that baby get super hot, however, nothing craps out. It's a wirewound resistor so it can disapate alot of heat.

 

[fallout]

Hey Fabio... FYI they make a TQ2-48v

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=61148&Row=46443&Site=US

-Jay

 

[omeiko]

BTW my api isn't build on the Fabios board. It's a weird switchable op-amp configuration and the relays are different too.
I'm having slight buzz when the pad or the phase relays are on. Could this be because of the high current the relays are pulling (75ma each)?
They are located pretty close to the input tx.

That's why I'm thinking I should change the relays to 48v types (the PSU would run cooler too).

-Okko

 

[pmroz]

From Digikey catalog p.1231:
TQ2-5V coil current = 28.1ma (255-1001-5-ND) 1x$2.65
TQ2-48V cc = 6.25ma (255-1801-5-ND) 1x$4.05
Looks like same footprint. But TQ2-48V not in stock.

 

[louder]

alo
i am running 4 channels with one psu.
i do not remember 7805 getting hot,cause i placed a finger in the heatsink,and i got no burnes.
best regards
pedro

 

[louder]

alo
what about a jlm audio psu?.
the big one.
best regards
pedro

 

[laitue5]

I found "Grayhill 71BD30-01-1-AJS" on Farnell: is it correct ?
(it?s not "71BDF30-01-1-AJS", it?s "71BD30-01-1-AJS" but I don?t know the difference).

Maybe someone know ? Thanks. :wink:

 

[fallout]

[quote author="laitue5"]I found "Grayhill 71BD30-01-1-AJS" on Farnell: is it correct ?
(it?s not "71BDF30-01-1-AJS", it?s "71BD30-01-1-AJS" but I don?t know the difference).

Maybe someone know ? Thanks. :wink:[/quote]

You wont be able to mount them on the PCB but can just wire them up though.... The missing 'F' from the farnell part # is for PCB mount style..

-Jay