5003 eq building and help.

[mylesgm]

I'm building the PeterC 553 Eq. The build is finished and I'm testing a few things and need some clarification.  I thought other people would be building these soon and would need the same information hence the new thread.

Its up and running (in my 51x case of course).  I've got the full PeterC kit of transformers, inductors, caps/resistors, etc.  I'v TI 5534AP in the input opamp and a yamaha NE-80100 DOA in the output amp which I'll change later.  The Eq works well and between myself and a friend it was a straightforward build except for some little problems listed below.

So orientation of phase on the output transformer its not listed and I've managed to get the phase reversed so what is the correct hookup of the output tx?

It seems that standard pots dont have a thread long enough to mount them on the pcb and the faceplate.  I've set them up so that the faceplate is held on by the switch nuts but it does mean that the pots are just floating behind the panel.  This works but I don't like them moving and they certainly dont feel good when you move them.  Are there any pots that have a longer threaded shaft or is there another way to mount them?

Lastly and most annoying is there seems to be an 8db drop in level when the Eq is inserted into the signal path and this is regardless of wether the eq is in or bypassed by the front panel switch. Is this to do with the output tx wiring or perhaps the choice of DOA?  They both operate exactly the same so its not wiring etc.

here are some pics and yes I know that the knobs are too big but its what I had lying around, they'll change....

 

[peterc]

Hi Myles

So orientation of phase on the output transformer its not listed and I've managed to get the phase reversed so what is the correct hookup of the output tx?

Flip the Brown & Red wires on the output transformer.

It seems that standard pots dont have a thread long enough to mount them on the pcb and the faceplate.

I used the Omeg 16mm ECO series pots & they fitted well. They have a "deeper" body than the pots on your build.

Lastly and most annoying is there seems to be an 8db drop in level when the Eq is inserted into the signal path and this is regardless of wether the eq is in or bypassed by the front panel switch. Is this to do with the output tx wiring or perhaps the choice of DOA?  They both operate exactly the same so its not wiring etc.

Could be one of the output transformer windings is out of phase. You have wired them correctly according to the legend on the transformer, but there might be an issue with those. The other way to do it is to change the gain of the input stage. I will look into it tonight.

Regards
Peter

 

[mylesgm]

Thanks PeterC.  Otherwise a pretty straight up build and they sound excellent in initial tests.  Will be putting them through their paces for mixing sessions and then a mastering session later this week.

M

 

[3nity]

any boards left? 2??

 

[mylesgm]

Which pot from omeg did you use peter?  Part no?

Any luck on the gain issue?

M

 

[peterc]

Which pot from omeg did you use peter?  Part no?

Any luck on the gain issue?

I used a bunch of 10k centre detent pots that I bought for the Calrec EQ. I will have to work out the number & confirm with OMeg

I will try & check on the gain issue this weekend. I have just realised that I dont have any inserts in my studio, I ran he tests off an aux feed.

A quick fix would be to change the 2 15k resistors marked R7 & R14 on the PCB to  39k.


Peter

 

[Tubemooley]

I received my PCB's and inductors last week. They look great. I'm a cheap sumbitch and I did not buy Peter's output trannie. Will the EA-2623 work in this EQ? Will it fit on the PCB? I have EA-2623's at home in my shop but they're not loose right now. I will get one loose and see if it fits on the PCB. I can modify just about anything so I'm not worried about having to cut the PCB a bit to make a trannie fit. Also, Peter, would it be possible to get a schematic of the EQ? I don't plan to use the IC opamp on the input. I plan to drop a discrete transistor amp in there. Thanks for your help, DANA.

 

[peterc]

Hi Dana

I set up the transformer cutout & hole spacing to accommodate both the Profile & my version of the transformers, so I think Ed's unit should be fine.

I will put up the schem tonight.

Regards
Peter

 

[jsteiger]

I'm a cheap sumbitch...

Now, that goes without saying but I guess you did say it!

Will the EA-2623 work in this EQ? Will it fit on the PCB? I have EA-2623's at home in my shop but they're not loose right now. I will get one loose and see if it fits on the PCB. I can modify just about anything so I'm not worried about having to cut the PCB a bit to make a trannie fit.

The 2623-1 is physically smaller than the 2503. I don't think this will be a good idea though as all the API eq's have a 2503 wired 1:3. You will need a 2503 as the 2623-1 has only 2 secondaries. 

...I don't plan to use the IC opamp on the input. I plan to drop a discrete transistor amp in there...

Hey! Me too! Crazy minds think alike! I plan to use something along the lines of a 5 transistor UREI amp myself. I believe Gary did this in his beta units and fell in love.

Best, Jeff

 

[Sleeper]

I've got Peter's transformers.
I still have to mark my trafo outs on the board and I just quickly stuffed what I had on hand in order to figure out my order.
I have one question straightaway. 

Is the 22r (which looks like it's a termination resistor on the output) specific to Peters trafos, necessary at all, or is that just there as a placeholder for whatever termination resistor might be required??

oh and the 5534 option cap should be roughly 22pf - 47pf according to datasheets.  I usually use 39pf there...

 

[peterc]

Sleeper

Is the 22r (which looks like it's a termination resistor on the output)

This resistor keeps Gnd & chassis isolated, it is not a transformer termination resistor

Peter

 

[Tubemooley]

But will the 2503 fit on the board, Jeff? I gotta' pull out my stuff and see what fits. I do have 2503's which are loose. But they are slated for another project so I would need to order some more. DW.

 

[peterc]

Dana, it should fit, I have used Cinemag CMOQ2 (?) on the board, & as  far as I know, that  is the same size as the 2503.

Peter

 

[Tubemooley]

Beautiful. Thanks.

 

[peterc]

Schematic is here:

http://twin-x.com/groupdiy/displayimage.php?pos=-3946

 

[johnnyscotch]

any luck on the BOM??

 

[gar381]

Dana, it should fit, I have used Cinemag CMOQ2 (?) on the board, & as  far as I know, that  is the same size as the 2503.

Peter

Hey Dana

I can confirm what Peter is saying.
Ed's 2503 fit perfectly in the Cinemag cmoq2 output cutout.
I have done it on several occasions.  

GARY

 

[fazeka]

Any benefit/advantage to using Ed's 2503 rather than Peter's output trannies? Are the lams different, etc.?

 

[desol]

They're both steel quadfilar i think. Peter's has a tad bit of nice top end to it i believe...

 

[johnnyscotch]

OK,

I did the best I could on this.

Here's a Mouser cart with the parts that weren't included in Peter's kit. Save the pots:
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=546ee9f29d

Please anyone feel free to make suggestions/alter this if something won't work, it would be much appreciated.

I tried to size the caps to work, some of them may be too big, but it's all they had in stock.

My other question was about the IC. I put TL071 and 5534 on there (assuming they are the correct parts) and some 39pf caps for the option cap. But, what's the difference?? I'm assuming 5534 is better because it's more expensive? I'm probably going to take the TL071 off the list, but just for reference.

Jeff, will the switch caps you stock work for the switch? What about your PCB mounting hardware?

cheers all
Eric