calrec PQ1549 help thread

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Uneven distribution of frequencies through the wiper travel. You might or might not care. It will work.
You can buy 100k rev logs @ http://www.audiomaintenance.com/acatalog/potentiometers_carbon.html.
Cheers
 
Hi Guys,

I finished my stereo calrec today... actually I bought the PCBs half done from someone, and they´re two different revisions of the PCB. but I don´t think this will really make a difference, no? (one is rev.4 and the other one is rev. 5)

so the rev. 5 works fine, sounds good from what I can tell after 5 min of testing;
The rev. 4 has a problem... bypass works, but when I switch the EQ on it only works for 4 seconds, then dies... I tried to measure all the currents, and hereby noticed that it works again for about 4 seconds if I short + and -... what is this?? i already checked for bad solder joints and connections, but didn´t find anything. could this be a broken capacitor or some reversed cap?

thanks for a hint!
 
Hey,

can you tell me if you did anything special when building the REV 5 Calrec? what is there to look out for and what are the common build problems when building these eqs?

Has anyone posted any build tips that work?

Michael

ps Mokkinger sorry to hear of your Eq trouble with Rev 4. Hope you get this fixed. Sounds like a reverse cap that's now damaged or a missing jumper. :-\

Can I ask you how you built the Rev 5? I am about to build one or two units and am worried that there is trouble ahead.
 
muffy1975 said:
.... and am worried that there is trouble ahead.

Don't be, just build it as it is. A small mistake is reversed tantal on the silk, schematic is OK, I think
mid section-s.Also read the thread for the "balanced unity gain" resistor change. Even if you don't look at these small mistakes the unit will work, on power on.
 
Indeed, I've built two channels with rev. 5 PCBs and both worked nicely. There's an issue with the voltage rating of one particular electrolytic cap which I've detailed on page 8 of this thread, but as Syn said, the boards work as they are - there isn't too much to worry about.

I ended up adding balanced line receive / drive boards on the input / output, but this was not a fault fix - it was actually necessary in my case to accommodate limitations of other kit connected before and after the EQ. If every source / load the EQ sees is balanced, all should be cool.

Matthew
 
hi! what is likley to have hapend if the 16V cap (the one that gets 30V) has blew?
what should i change first? any ideas? are some of those expensive tantalums probably broken now?

thank you for your help! /jonas
 
hi! maby i was unclear... i ment the one that sits between +ve and -ve, written about on page 8 or so.
so nothing was placed the wrong way... only had to low voltrating... and blew! hmm...
how to think? where to start? thank you! /jonas
 
Hi All,

OMG it has worked first time. I used 16V tantalums and the electrolytics were

22uf 63v
47uf 50v
100uf 25v

At the moment I am giving the unit 16volts. Can I give it 18V with my capacitor choices?

I followed the overlay for the polarity of the caps and have had no problems.
Where there wasn't a + on the PCB I presumed that the hole was covering the + sign up.

Thanks team for a nice sounding eq. Every bit as good as my TC Electronic parametric.

XOX
 
Hi guys!

two simple questions!

1.-For Calrec EQ PQ1549. what is the best opamp: LM833 or NE5532??? and

2.- The PCB Layouts Rev # 4 http://gyraf.dk/gy_pd/calreq/calreq.pdf, the copper PCBs are 100% functional to self-etch?

and thanks Jakob for this DIY thread

PD:please, Jakob maybe you have the PDF file of the PCB copper layout of your Gyraf 4x Intrument Splitter to self etch??? if is possible to post it?  and Is your Tube HeadPhonesAmp DIY Project http://www.gyraf.dk/tmp/Tube_headphoneamp.pdf
100 %  functional?

Thanks again

Mucha suerte
Best regards
chao
Juanjo
 
juanjovincenzo said:
1.-For Calrec EQ PQ1549. what is the best opamp: LM833 or NE5532??? and

2.- The PCB Layouts Rev # 4 http://gyraf.dk/gy_pd/calreq/calreq.pdf, the copper PCBs are 100% functional to self-etch?

3 - Please, Jakob maybe you have the PDF file of the PCB copper layout of your Gyraf 4x Intrument Splitter to self etch??? if is possible to post it?  

4 - Is your Tube HeadPhonesAmp DIY Project http://www.gyraf.dk/tmp/Tube_headphoneamp.pdf 100 %  functional?

1 - I like the LM833 for this.
2 - The Calr-eq PCB's are checked and working (the same files are used for the OEM PCB-service)
3 - The 4x instrument splitter never had a layout - the circuit is simple enough to just mount on a piece if stripboard/veroboard
4 - The Tube headphone amp: The circuit is known working, but I haven't tried using the PCB's. It should be simple enough to get working - If you use them, please report back!

Jakob E.
 
I'm having a heck of a time finding 63v polyester caps, can I use a higher voltage rating? It won't hurt the integrity of the EQ will it? Thanks.

-JB
 
63V is a common value, but yes, you could use larger if they can fit (space) on the board. Farnell, Digikey, Mouser should have those. Farnell sells Wima MKS series...
 
Team,
;D

I have 2 channels working straight off the bat. Tight.

I would like to correct the 10k input resistors but I see there are 4 10k resistors connected to the input IC. Which are the two that are in series? IS it the two 10k resistors on the far left of the schematic that are connected also directly to the 47uf caps.

Don't want to change the wrong ones.

Help me ???

Thanks in advance

Michael

 
briomusic said:
I finally got my CALREC eq to work (thanks to some hands-on help from a good friend) and I also noticed a jump in gain with all the band's level controls flat. as I quite like to have a gain control on an eq to compare with the untreated signal, I was thinking of inserting a dual gang pot instead of just changing the 10k resistors to 22k. so I tried the following mod:
calreclevelctrl.gif

This allows me to have resistances from 10k-32k and to make up for moderate cuts and/or boosts. Is this kosher or am I comitting untold crimes on input impedances etc? if - due to pot tolerances - I have a different resistance on the plus and minus rails, what would the effect be?

ETA: I ended up using dual rev log 100k pots (instead of 22k) for the gain (same as the ones spec'd for frequency) to get the required range.


IS it the the two 10K resistors before this chaps idea of the 22k pot?
Are these the two 10K resistors that are also directly connected to the 47uf caps?

Michael
 
muffy1975 said:
IS it the the two 10K resistors before this chaps idea of the 22k pot?
Are these the two 10K resistors that are also directly connected to the 47uf caps?
Yes. Increasing resistance lowers gain of this stage.
With Rin varying between 10K and (10K+22K rev.log stereo pot=32K) this diff.amp has gain varying between 0dB and -10.1dB.
With Rin varying between 10K and (10K+100K rev.log stereo pot=110K) gain range is varying between 0dB and -20.8dB.

Rearranging some connections giving gain varying between +/-10.1dB (with 22K lin stereo pot) or +/-20.8dB (with 100K lin stereo pot), keeping 0dB unity gain at pot center. Linear taper stereo pots have far better tracking and are easier to source than stereo pots with negative logarithmic taper, if you want to go this route (but CMRR will still be degraded).
calreclevelctrl_edit.gif

 
HI, I'm a little concerned about my standard Alpha(pcb) 16mm pots that I'm planning to use in my calrec EQ. Are those good enough in quality for this project?
I've been tryin to contact Omeg for pots that others have used, but haven't got any response from their company! Also, On their web page those ECO? pots has so MANY options for bush, shaft and spindle types, and I cant figure out the exact specs for the pots. That's why I can't make an order from Omeg.
IF someone has those pots (left overs) on the shelf, I would really like buy !!!  But kind of help would be greatly appreciated !
P.S Just wondering , Is there another company that sells Omeg pots for calrec EQ ?
With Kind Regards, jyrki3101
email:  [email protected]
 
HI,

alpha pcb pots are fine in my opinion and those cheap rev log pots from ebay ( 10 for £10 ).
The alpha pots have a great action too!

Michael

ps check out the sontec EQ if yo want a real quality eq unit
 

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