quad eight mic pre [pics]

[soundguy]

its a pain in the ass to get them out but a really secure way to get them in and have them stay there.

remove the four bolts in the transformer. Replace with a bolt about an inch or whatever longer. Drill four holes in your chasis to line up with the holes in the transformer. Slide new longer bolts through the chasis. Put a plastic (you may need to use a metal standoff for the one position with the ground trace) standoff on the bolt, 1/4" will probably do. Now mount the transformer and the pcb back onto the bolts and screw the nuts down on top of the transformer. thats the way I mount all that type of stuff horizontally. Its a bit of a production when you need to remove the amps to fix or swap components but its a great roadworthy solution, once you bolt it down, it aint going nowhere.

dave

 

[b3groover]

So the one hole with the ground trace needs a metal stand-off so that it's grounded to the case?

 

[soundguy]

if I remember right it should make its way to ground somehow. Its been a while since I looked at those. I forgot my picture was sitting at the top of this page, thats how those are mounted in the chasis, like I described.

dave

 

[b3groover]

Holy ****! After having this project on the back burner for at least 3 years (if not 4), I finally got all 8 of my Quad Eight cards racked up. I just finished a few minutes ago. Unforunately, I have one bad card, but I think it is the pair of diodes on the rails... should be an easy fix.

Check it out:

It's been so long since I started this project, I've misplaced four of the knobs! Hopefully I can find them or I'll have to buy more. D'oh!

The two holes under channels 1 & 2 are for Joe's direct input kits, however the 1/4" jack's threads are not long enough to go through the thick front panel. I'm still figuring out a way around that.

Lots 'o iron in this bad boy. It's whisper quiet, too, thanks to putting the power supply (one of Joe's kits, naturally) in a separate case.

My wiring is kind of a mess, but hey... it works!

Here's the power supply. I'd like to say I came up with the idea of using an old computer PSU case, but I saw it on the web somewhere. I have a million of these damn things lying around and not only do they have a lot of extra wires that can be used for short hook-up runs, but they make a great case for a small power supply. You've already got a mounted IEC jack and a power switch!

I'm headin out of town for a week starting Tuesday so I won't have time to do any real tests, but I'm really anxious to try these on drums! WOO!

 

[MikoKensington]

Yeah! I just started doing the final layout for my QE's too. These were among the first DIY parts I picked up 4 or 5 years ago. I just need to order up a couple of Joe's DI kits, drill the back panel and wire away.

 

[b3groover]

Poo-ey... replaced the diodes on the bad card and now it is getting juice but it induces a nasty noise into the entire system and doesn't pass audio. Something is wrong... hopefully bad caps?

The other 7 channels are working great and sound sweet! Miko, Joe has a new go-between kit where you can mount the input transformer directly on the card. I wish he would've had those when I ordered my kits, but again, it took me so long to rack these things up...

 

[gang of elk]

sweet!!

 

[rattleyour]

That 8 pack of QE's is staggering... I LOVE my humble pair of them.

Enjoy!

 

[CJ]

hmmm, no Memorex tape on Miko's avatar, what up?

 

[b3groover]

Well, right now it's a 7 pack because I have one card that isn't working. I hope I can fix it. I've had these cards for years and never tested them until the other night. 7 of them are exactly the same, the 8th one (the one that doesn't work) had different diodes on it and some handwriting on it.

 

[SonsOfThunder]

Well at least its not the other way 'round!

Seriously, laying out a good one and taking voltage measurements from it should help you find the fault(s) on the bad one, eh?

HTH!
Charlie

 

[b3groover]

Yes, that's a good idea. I just hope it's not the output transformer.

 

[emrr]

Ohm out the output and see; doubtful IMO. Also see if you can get a current measurement on the individual module to compare.

I've got a similar 8 banger waiting to build, but with these two channel CA-727 cards. They are same as the earlier AM-3 five transistor CA-127's, but two on a card and no attached output trans. Here's an example of a pair I did FS, with Edcor outputs. I've got just enough of some older Jensen outputs for my keepers. Mine are a fairly rare variation that Ken Hirsch of Orphan Audio / Quad Eight Electronics LLC had to ID for me.

 

[rattleyour]

Hey Doug, where did you get those cool QE badges?

I saw them in some otehr pics you posted.

 

[emrr]

I made them. Labels are all old style faux-decal stickers with laquer coating, ala antique WE, military, etc gear.

 

[CJ]

whats this?
is that the stock transformer?

 

[emrr]

That's the stock output transformer found on cards that use them.

 

[CJ]

i see.
i have a 1500,uf instead of 470.
is that an option?

 

[hitchhiker]

Hey CJ!

1500 uf is the stock output on the CA-127. The next v is the CA-137 and it has the 470 uf.

Sure be cool to see one of these output transformers put through the paces.

Lance

 

[CJ]

thanks!
I SAW A 2200 UF ALSO.
Cj