EQP-1S5 500 series PULTEC ---- HELP/BUILD thread

[mitsos]

I hear ya, it took me months of looking and then we just said screw it and did this one based on a silver one I had found.  I assume grub screw = set screw?  Yeah, they have a little screw opposite the pointer.  Send me a PM with your email address, people will get the wrong idea seeing us talking about nice looking knobs in public!    ;D

 

[Marcocet]

Hey mitsos

BOM says R1 is 620R and R3 is 1k
Board screen says R1 is 1k and R3 is 620R

Which one's right?

-marc alan

 

[mitsos]

Hey mitsos

BOM says R1 is 620R and R3 is 1k
Board screen says R1 is 1k and R3 is 620R

Which one's right?

-marc alan

Hi Marc,
thanks for catching that.  I will confirm when I get home tonight, but as far as I can see from an older PCB file on my laptop, the values are correct on the PCB.  To be sure, check that the 620R connects between one pin on the 3-pin header next to it and ground.  I will edit the build doc and repost.

 

[Marcocet]

Got it! Looks great on the scope, can't wait to give a good listen.

 

[mitsos]

Excellent! Let me know what you think of them in use!

 

[mylesgm]

Silly question but just wanted to check that there is no reason not to trim the length of the wires from the inductors...

 

[mitsos]

Should be fine.  Especially considering how much wiring was involved in the originals, where the inductor and caps were in a can bolted to the outside of the case.

 

[nielsk]

trim the inductor & transformer leads to length for your build...
What I do is feed the inductor wires through the holes, hold inductor in place & cut to length. Then I remove the inductor, strip & tin lead ends, then install.

 

[dandeurloo]

Hey guys, I got mine yesterday in the mail and I built my pair last night!  Just need to test them out.

 

[GregNey]

Both units built, calibrated, and tested! These really are terrific. Thank you so much for putting this kit together.

 

[Monoklang]

My 2 kits arrived today here in Sweden. Best package I've seen! And no tax I will start right away.
/John

 

[nielsk]

Thanks for reporting on the successful arrival of your kit in good form, it is a huge sigh of relief for every one that finds it's way home...
I have been very happy about how this came out being a relatively quick & easy build, there was a lot of work put into making it that way!

 

[Mike D]

The kits arrived two days ago. I'm very impressed by the quality of this kit, great engineering. They sound very good too! Thanks guys

 

[sonic02]

Kit arrived Tuesday and built in 5 hours. Great layout and design. The led was a little tight but the rest was very straight forward.

A quick question - How much volume (gain in dB) drop is everyone getting with all the controls set to '0'. I'm getting about 3-5db (with a slight increase in upper harmonics). I can adjust the VR to get unity (no gain drop) but the upper harmonics for 2kHz, 3Khz, 4kHz etc... go very high. Am using with a JLM opamp. Waiting on the GAR2520, will see if there is any difference soon.

 

[Monoklang]

Hi all. I'm almost done with the first module, but now when I'm suppose to secure the transformers, I got this tiny 1mm space between the transformer brackets and the transformers. Without the fiber washer it fits perfectly.

Are those necessary? I could put something thin in that space and solve it that way. Or is it suppose to be like this?

Regards
John

 

[nielsk]

On the transformer bracket, if you have any movement of the transformer, put a strip of double sided tape under the top part of the bracket, this will secure the transformer from any movement and should accommodate any clearance. Without any spacer under the bracket mount tightening the nuts will tweak the sled...
I have seen no harmonic issues (I have been using real 2520s), you do need to adjust the trim-pot for unity gain with eq engaged, no cut or boost. I have no experience with the JLM op amp, it may require a feedback cap, please check with them on their recommended feedback & output set-up. There is a place for an optional output resistor if required, and you can omit / adjust the output transformer loading resistor as required...

 

[Axelerator]

..just got my parcel !
had to explain alot to the MIB 8)
now up do some DIYing..
cheers
axel

 

[Monoklang]

Thanks! Yes I took some tape, and now they sits perfectly. But now when I put the module into my 51x rack to calibrate it, the LED doesn't seem to work. How can I test if this is broken?

I left out the R5-R6 as you suggested. First I thought I wired the on/off switch wrong, and switched but still no light. And no signal

It's so typical, I thought this build was really a quick one, with no strange things, just easy enough for me.
Any clues?

Best regards
John

 

[Monoklang]

One more thing...

Witch way it the right way to wire that on/off switch? I looked at that photo in the white market and is it the middle - SW
left (from above) - EQ

?

Thanks again

 

[mitsos]

Sonic02: That is a new one on both of us. It might help to know which JLM opamp you are using and a bit on your test methods? 

To expand a bit on Niels comment on the JLM, there is no feedback cap used with a 2520. At least there wasn't one in the original and we haven't used any.  There is however a spot for it marked CF, since I didn't know what opamp people would use, and some may want to see one. If you try this, I would try a C0G/NPO or mica cap between 47-100pF. 
 
The resistor in parallel with the cap will allow a bit of DC to get into the transformer winding, and is what API did to "tame" the low end boost in their circuit (I think I may have explained this somewhere, but there is a thread where member Abbey Road d-enfer posted graphs showing what it does).  I will look for it and post a link if I find it.

The 1K8 load resistor on the output transformer would change its response, so if the cause of your problems is the JLM opamp's interaction with the outpu trafo, that might help things. If you decide to try this, temporarily putting a 5K trim pot in there would allow you to find the best possible value.

I would first try the CF.