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

[mitsos]

Build instructions for the latest version are in this post, as is a PDF for sorting components, courtesy of Udo (forum name Kante).  See the next post if you are looking for the documentation for the older version. Please read through them completely a couple of times before starting. If something is unclear, please ask questions here so that the answers to your questions may help others in a similar position.  The two versions of this EQ share the same circuitry, what changed is mostly metalwork/assembly.  The main difference in components is that the inductor and transformers have molex connectors pre-installed on them for ease of assembly and it is now fully enclosed in metal for the most in EMF protection. 

Please read through the instructions and make sure you have the right document for your module.

Calibrating these is relatively simple, with the EQ in circuit and all potentiometers set to "0", you adjust the trimmer near the opamp to get the same level signal out as coming in.  Of course, this means you need access to the little trimmer near the opamp, if you don't have some sort of "500 series test cable" to allow you to test the module outside the rack, you will need to put the module by itself into the leftmost spot of your lunchbox or 51X rack.  If you are building 500 series kits, you will be well served to buy an edge connector and an edge conector PCB from jeff at classicapi.com and wire your own test cable.  (I think someone sells an extender kit with a ribbon cable now, might be JLM).

As promised, pics of latest version:

FULL METAL JACKET, BABY!!

04/2017 - Updated build doc for new (full metal jacket) revision:
https://www.dropbox.com/s/doha0fdshwt353b/Analog%20Allstars_build_docFMJ_.pdf?dl=0

04/2017 - Component Sorting Sheets, courtesy of member Kante. Thank you!
https://www.dropbox.com/s/s30hx7xlai2dkh1/Sorting%20Sheets.pdf?dl=0

 

[mitsos]

Build instructions for older version (see photos below):
https://www.dropbox.com/s/s30hx7xlai2dkh1/Sorting%20Sheets.pdf?dl=0

Attached to this post (must login to see it) you will see an image of how to set up the amp PCB for standalone (without the filter PCB connected) testing.  As time allows, I will incorporate it into the build document.  With the headers in place, a fully populated amplifier PCB will function as a line amp with minimum gain of about 16-17dB with the trimmer fully CCW. 

In case anyone is stuck troubleshooting, dividing the circuit like this can be very helpful in finding what might otherwise seem like a "needle in the haystack."

 

[Marcocet]

drumroll...

I received my kit late last week. I can't wait to put this thing together! Thanks.

 

[mhuss]

Sort of off-topic: I just looked at the directions (I hope to buy when money is available). If you use 1N4148s in place of LEDs on the little "temp DOA", the output transistors will be biased very cold, close to class B. Note that LEDs provide a nominal 1.1-1.2v Vf, whereas a single Si diode is more like 0.7v.

--mark

 

[okgb]

If you find yourself wanting attenuation with a preamp that doesn't have an output attenuator
and the eq usefull at the same time , I'd think you could set this eq at less than unity depending
on how much attenuation you need and have a nice combo . of course not quickly changeable
I like the neve 1073 types ran in the last two output gain settings so I'll try it ,
Mitsos do you know what the input xfmr will handle level wise ?

 

[mitsos]

If you use 1N4148s in place of LEDs on the little "temp DOA", the output transistors will be biased very cold, close to class B. Note that LEDs provide a nominal 1.1-1.2v Vf, whereas a single Si diode is more like 0.7v.

thanks for that, I admit I haven't done much math on these, it's been used in various incarnations in different amps here in the past. I also remember some talk about regular diodes vs Leds in the Gyraf headphone amp circuit (same stuff) and I don't remember if there was a conclusion reached?  Anyway, to be safe, LEDs it is! will update instructions.

If you find yourself wanting attenuation with a preamp that doesn't have an output attenuator
and the eq usefull at the same time , I'd think you could set this eq at less than unity depending
on how much attenuation you need and have a nice combo . of course not quickly changeable
I like the neve 1073 types ran in the last two output gain settings so I'll try it ,
Mitsos do you know what the input xfmr will handle level wise ?

That's a cool idea for a sort of channel strip.  I would replace the trimmer with a rotary switch though so you could have a position that is known to be at unity.  Good luck and let us know how it goes!

RE: the input trafo, I have not tested it per se, but it's the same stuff/winding as the HS56, which was rated at 20 dBM.

 

[Winetree]

Started build this morning.
Question:  R7 (20k5) resistor on board diagram looks like a 1/2 watt, 1/4 watt supplied. Is that OK?
FWIW;      When installing gray pots, place in right order on bottom side of PSB and place in L-Bracket,
                (make sure front of PSB is touching L-bracket. This required pushing LED back a little)
                install bronze nuts on pots , while holding PSB parallel to L-bracket,
                push down on PSB and solder pins. This keeps them aligned.
                Grayhills: The tabs that touch the back of the gray pots can be bent away
                so when they are soldered they don't melt the plastic. Same with the tab that's close to the rivet.
                Well on to all those wimas.
               

 

[mitsos]

Question:  R7 (20k5) resistor on board diagram looks like a 1/2 watt, 1/4 watt supplied. Is that OK?

Well, I still haven't gotten MY kits yet(!) but 20K5 is the feedback resistor, not sure if/why I used a larger footprint, but 1/4W is plenty in this position.

Thanks for the build details. Good to see how someone else does it.

 

[Winetree]

Just checking that the input and output transformers are the same C-4545?
Just cross the leads to the boxes.
                             

 

[mitsos]

Just checking that the input and output transformers are the same C-4545?
Just cross the leads to the boxes.                         

Yes, the trafos are identical. Follow the color codes on the PCB and take the Brown and Red from the input trafo to the bottom box while the ones from the output go to the top box. The boxes should be marked "IN" and "OUT".  Hope that helps! Sounds like you're getting close!

Here's some general wiring info on the trafos:

Single Primary 600 Ohm:
Brown+
Red -


Secondary tapped for 600:600 or 250:600 operation
(the original Pultec used an HS56 backwards and wired 250:600).

Secondary wired for 600 Ohm:
Orange +
Yellow unconnected
Green unconnected
Blue -

Secondary wired for 250 Ohm:
Orange unconnected
Yellow +
Green -
Blue unconnected


Black connects the internal shields and goes to ground.

EDIT: I added a drawing in the help file.

 

[Winetree]

Almost done. Everything's together just need to solder the colored wires to the transfos.
Got it for the red, brown, black, but your above post has me confused about the others. (Blu, Grn, Org,Yel)
You just don't solder all 4 wires, on both tranfos,  to their marked holes? You leave some diconnected?
Running a complete +4 balanced studio, and will be running these EQ's in a chain with other Pre's, compressors, etc.
Help.

 

[mitsos]

Sorry, didn't mean to confuse. Just solder each wire to its respective hole. If you look at the holes for the secondary on both input and output, the proper holes (Yel, Grn on input and Org, Blu on output) are, in fact, not connected to anything. They are just solder pads to keep the wires from flopping around.

 

[jandoste]

Hey Mistos,
I received my kit! and thanks again!
I think I got a bad INDUCTOR! the blue wire is out! I just take it and saw the blue wire has any solder and absolutely not connected to the inductor
the second one is awesome! Do you have any idea? Did you check all of them?
Thanks

 

[Biasrocks]

First impressions, damn that sounds good.  8)

 

[mitsos]

Hey Mistos,
I received my kit! and thanks again!
I think I got a bad INDUCTOR! the blue wire is out! I just take it and saw the blue wire has any solder and absolutely not connected to the inductor

That's very unfortunate.  We did not have the means to test every inductor, but we did check some randomly. Just to understand, do you mean the blue wire fell out or that you get no inductance reading on the blue wire?  And the second inductor reads fine? Send me an email and we'll figure out a way to fix this for you.


@Biasrocks: Very happy to hear you like them.

 

[mitsos]

Hi Jandoste, the replacement inductor was sent out today.  Thanks in advance for agreeing to ship the bad one back to us, I'll take it up with the winder to see what happened.

 

[jandoste]

Hi Jandoste, the replacement inductor was sent out today.  Thanks in advance for agreeing to ship the bad one back to us, I'll take it up with the winder to see what happened.

Hey Mistos,
Thanks for sending the new one! Awesome!
Hey guys! you must build one or more this EQ! it's amazing! I think that I'll get two more![ I already got a stereo] it's wonderful!
Thanks Mistos and Niels!
Regards!

 

[ruffrecords]

What size are the knobs on this unit? Who are they made by?

Cheers

Ian

 

[mitsos]

Hi Ian,

I had them custom made to fit our faceplates, because spacing was very tight and no off-the-shelf knob would fit (not 8 of them anyway).  Off the top of my head they are about 12mm diameter.  I think they turned out very nice, but there was a 4-digit(!) MOQ. 

 

[ruffrecords]

Hi Ian,

I had them custom made to fit our faceplates, because spacing was very tight and no off-the-shelf knob would fit (not 8 of them anyway).  Off the top of my head they are about 12mm diameter.  I think they turned out very nice, but there was a 4-digit(!) MOQ.

That is why I am interested in them. Finding small yet good looking knobs is very hard. Are they grub screw fixing or collet?

Cheers

Ian