[gyraf]

For the bridge rectifier is 1.5A OK?

Yes.

Measure your voltages with reference to 0V. Check that the 7818 has good input voltage (>+21V). Check that the +voltage reservoir cap is good, connected and working.

Jakob E.

[cannikin]

thanks Jakob

I had my PSU wired incorrectly.  now I'm getting voltage through my unit.
I switched to 15v PSU.  

Pin 8 of my 5532 is reading 13.78Vdc  (too Low?)

I'm still not getting audio through either unit.   Did a third check of solder bridges .. found nothing suspicious.

Other than that..... Any thoughts as to a next step?

[gyraf]

- Check if any of the opamps gets hot. Replace if one is hotter than others.

- double-check all electrolytics that touches the +15V rail, one may be reversed..

- Look for DC at all opamp outputs - if there's more than say 100mV, something is wrong either in that stage or in a previous one.

- Trace signal through the unit. Look at the schematic - and check signal after each eq stage.

- make sure that all ic's gets both + and - supply (measure from top, directly on pin) Also check that none of the opamps has pins bent underneath them when inserted in sockets.

[cannikin]

HI jakob,

I want to thank you for all your help.  I found my issue by tracing the signal- it was such a silly over-site, I'm embarrassed to post what it was :oops:

Sounds great!

One thing I noticed is that if the High Freq Pot is "all the way up" and db Pot at 80%.  the unit will squeal.. ouch :roll:

I'll re-check everything.. but the unit is still quite usable.. thanks again.

[Gustav]

I finally got my two channels powered up , sent some signal through and have a minor things.

1.The bypass switch on one channel has no "click"  :?  - It doesnt work, even if I hold it in. Anything I could check there, or do I "just" need to replace the switch ?

2.Ive seen this mentioned somewhere, but cant find it in any of the threads linked from the Calrec meta - I have a boost with the eq in set flat. Was there any solution for this ? Its not a big deal, but for A/B I would like it to be even.

Gustav

[JayDee]

I also have a boost while all pots are flat. But I don´t really like it as I think the gain is a bit too high in general.

What do you guys think will be the best way to reduce the gain.

Attenuation at input ?

Changing amplification at output ?

[cwatkins]

I've been dealing with it in the daw.

I'd still like to know a mod way to fix it, because h/w bypass is useless
This way.  If there could be a simple attenutor knob when ingaged, that would rock, that way you could match to bypass..

But I'm not smart emough.

[gyraf]

How much of a boost is present with controls flat and balanced input and output?

You could try changing the two 10K series resistors at the balanced input to something larger - say 22K should take you down 6dB etc..

I have no proto of this unit around anymore, so I'd appreciate if you could report back with a solution..

Jakob E.

[cwatkins]

Hmm.  Ok, should try that, it's after bypass so that should be cool.
I tried changing the 10k in the bal opamp feedback loop, but I don't understand it well enough..

[Emperor Tomato Ketchup]

Jakob,

I'd love to have a gain adjust on the output of mine, as makeup gain/attenuation for the unit.  I also lack the design skills to do this.  Do you any suggestions?  Perhaps placing a rheostat where the 10K series resistors are?

Thanks,
Chris

[gyraf]

Not a really good idea, as you need very good tracking of the two resistors to acheive good CMRR on the balanced inputs..

[Emperor Tomato Ketchup]

So would a stepped attenuator switch loaded with metal film resistors be OK then?

Thanks,
Chris

[gyraf]

yup, I don't see why not. It will change input impedance though - but this may not be a real problem..

Jakob E.

[cannikin]

Hey Gyraf,

Can you help me..

I'm trying to figure out how to wire some switches off the board.

I have no idea where to start, I have been looking at the schematic but I can't see it ...

First, what switches should I use SPST, DPST.. etc..

[Zee1usa]

Has anyone ever resolved these questions?  I just finished one channel of the EQ, with Gustav's latest board (rev 5?) stuffed according to the silkscreened legend.  Everything works, but I also have the extra gain everyone else does.  So the two unresolved calrec issues seem to be:

1. Extra gain.  Has anyone tried swapping the 5.1K's for 1.5K's?  However, I might actually use this gain to my advantage, as a make-up gain when cutting dB.  I plan on putting an attenuation pot on the output (unless there is a better approach availible for output gain control).

2.  Backwards polarized caps.  Tracing the layout I find two elecrolytic and two tants that don't agree with the schematic.  They are the 22u and 33u located beneath the lo-mid Q switch, and the 22u and 33u located below the Hi freq dB pot (33u not on latest rev).  Gustav, I can't see the pics that you posted earlier.  Is this what you found too?  Finally, are there any issues with these caps being backwards if they aren't seeing a strong DC bias?

An by-the-way, the EQ sounds absolutely wonderful.

This is what I have found also. "the 22u and 33u located beneath the lo-mid Q switch"  the + is labeled wrong on gustav pcb and perhaps the pdf since I believe his pcb was printed from that . According to the schematic it is reverse of the + printed on the pcb.


Jacob & Gustav may want to take note of this if they havent corrected this already. If you could take a minute and confirm this and let me know if i am just blind.

Also there are a few + that did not show up on the pcb, but looking at the schematic will show you the polarity in which they should be oriented.

 :cool:

[Gustav]

Hey Guys.
I dont remember what I had circled on the drawing, but I ended up just following the PCB layout PDF, and I have a kewl stereo eq with no problems. It does have the gain thing, but it hasnt caused me any problems, If it gets too hot I just back of the sends on my DAW insert points.  :?

Gustav

[gyraf]

Yes - don't worry too much about the wrongly-polarized caps, as they all are placed at spots with no DC potential. We'll try to fix it at the next update (which could take a while..)

David,

To use "external" switches, you'll need to consult the schematic AND the PCB layout..

Chris,

How did the attenuated-font-end turn out ?

Jakob E.

Just to let everyone know who's having gain problems, the fix that jakob gave up top fixes the problem of extra gain. I swapped the two 10k's with 22k's, and I have the same gain with the eq engaged as I do when it is bypassed. Woo hoo! thanks jakob.

Erik Wofford
Stapes Audio

[gar381]

Erik

Which 10k's did you swap??

GARY

[gyraf]

Thanks for the feedback, Erik!

Gary - look earlier in this thread: it's the two resistors in series with the input at the balanced input stage.

Jakob E.

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