Build Thread:PQD2

[phelar]

Hi!

Someone got the docs for this build?

 

[Gustav]

Hi!

Someone got the docs for this build?

https://pcbgrinder.com/index.php?route=product/product&path=59_61&product_id=63

Near the bottom

Gustav

 

[andow]

Does anyone else find that the bass cut does too much with the standard resistor values?  ???

 

[Gustav]

Does anyone else find that the bass cut does too much with the standard resistor values?  ???

Easily changed, just lower the resistor values.

The high cut and high boost total resistance are critical, the bass cut total resistance is not, so you can solder resistors in parallel or swap as you like.

Gustav

 

[weiss]

Hey guys, i'm having bit of a trouble here..

my pqd2 passes audio but only in mono and there is no sound processing in any way. i can hear the noise of the device but the bypass or any other switches won't affect the signal. (note: i had to wire two 2x6 switches (high q and high boost) and change their position compared to the pcb. if there was a disconnection somehow, would it affect the complete eq processing pathway?)

Is there a way to begin trouble shooting?
I'm building the device for a client - bad timing  :-[

I hope someone can bring me closer to the problem.

thanks for any help!
Ansgar

 

[Gustav]

Hey guys, i'm having bit of a trouble here..

my pqd2 passes audio but only in mono and there is no sound processing in any way. i can hear the noise of the device but the bypass or any other switches won't affect the signal. (note: i had to wire two 2x6 switches (high q and high boost) and change their position compared to the pcb. if there was a disconnection somehow, would it affect the complete eq processing pathway?)

Is there a way to begin trouble shooting?
I'm building the device for a client - bad timing  :-[

I hope someone can bring me closer to the problem.

thanks for any help!
Ansgar

Hi Weiss..

If there was an error on the wiring of the switches, that would definitely influence the operation of the unit.

You can check the input/output stage by jumping the to/from filter connections.

You can check the filters with a signal, without the gain stage active.

No scope to trace the signal?

Gustav

 

[weiss]

Thanks for the response gustav.
Is it correct, that the numbers on the input and output section refer to the corresponding numbers on the xlr pin?
I'm gonna try to follow the signal with my scope.

best regards

 

[Gustav]

Is it correct, that the numbers on the input and output section refer to the corresponding numbers on the xlr pin?

No - if you look at the PCB, you should be able to see that all the middle pads are connected to one node - common.

Youll have to do 1 hot on the input and 1 cold on the output, or vice versa to have phase coherence.

 

[weiss]

No - if you look at the PCB, you should be able to see that all the middle pads are connected to one node - common.

Youll have to do 1 hot on the input and 1 cold on the output, or vice versa to have phase coherence.

oh thanks, that solved it !!

 

[fonzobrown]

Hi all, please  someone may share the BOM and possibly the schematic of PQD2 because Gustav ( pcbgrinder) don't provide anymore on website ?

I may need even the VECA ones

i've the pcbs from almost 2 years and now i'd like to assembly my units

Your help will be really welcomed

Thanks

Roberto

 

[Vac11]

After some years im actually done. Thanks!!!

 

[Vac11]

Hi all, please  someone may share the BOM and possibly the schematic of PQD2 because Gustav ( pcbgrinder) don't provide anymore on website ?

I may need even the VECA ones

i've the pcbs from almost 2 years and now i'd like to assembly my units

Your help will be really welcomed

Thanks

Roberto

Hi Roberto,

pleas see attached file and follwed link:
https://drive.google.com/file/d/1j54y3SC_FtMufzDibf-tx6QDIriQKlMm/view?usp=sharing

M.

 

[fonzobrown]

Thanks so much Vac11

Now i'm still miss VECA ( Comp ) BOM

https://groupdiy.com/index.php?topic=59576.msg906357#msg906357

Really Thanks for the help

 

[andow]

After some years im actually done. Thanks!!!

What are these boxes on the left?  ???

 

[Murdock]

What are these boxes on the left?  ???

Quite sure these are the output caps. Old russian PIO capacitor

 

[weiss]

...could also be weights, to make the unit seem heavy and valuable  ;D ;D

 

[Vac11]

Quite sure these are the output caps. Old russian PIO capacitor

Exactly... I think 4.7uF...

 

[andow]

Ah, now I see them missing on the PCB...
Wow, these are huge!  ;D

 

[Potato Cakes]

I've a bit of a head scratcher on one of these I just completed. High and low boost controls do not work, but everything else does. The other odd thing is that when I do a low cut, the low boost brings it back up forming a dip in the signal instead of a shelf like it should. But It won't actually boost the low end. I've pulled it all apart and doing my due diligence with checking solder connections whilst tracing signal and comparing it to the schematic, but so far nothing. Oh, and i have about 10dB of boost from the make up gain amplifier, whether the EQ section is in circuit or not. The lead connections from the filter board are connected to the corresponding silkscreen connections and are making an electrical connection. The board is super easy to build and it's pretty spread out so if there was solder bridge it should be easily visible. The audio is clean in and out, but when I turn the bass boost up there is a slight buzz that comes in.

One thing I did notice is that the two header connections on the main PCB are not making identical connections to the transformers. I thought I had found an error when two of the header pins had 13 ohms between them and the same ones on the other header did not, but I saw that the pins with the 13ohms were connected to the transformer. I was testing the wrong pins and also found that there is only one pin connects ground to the filter board as that is all is needed, so the middle pin for channel 2 is not connected because there is no need for two ground connections. The traces for the other pins are identical.

I'll get back to it later this evening and poke around some more. It seems that something is bypassing the high and possibly low boost switches and that same possible thing is causing the 10dB increase of gain, like it's not seeing the loss that you would expect with a passive filter section. If someone has some ideas in the meantime I'd gladly like to hear them.

Thanks!

Paul

See next post

 

[Potato Cakes]

Got back to it tonight and did some listening with pink noise. I can hear the high frequency sweeping with a narrow bandwidth setting and I can see that the amount of boost increases with increase of frequency, but still not to the level of what it should be. The lows are still the same. I did notice that I can only boost the lows to the unity level from where they are cut. When I start to decrease the amount of cut, I can see and hear the frequency notch returning to unity level, but the amount of boost does not change past that. So the controls are doing something, but the other Pultec style EQs that I have built and used there is a significant amount of change when boosting. The HF and LF attenuation seem to work fine as does the bandwidth control. I can measure resistance changes between the switch positions and there seems to be continuity amongst the components to match the schematic. According to the results I'm getting from each test, this should be working. When I crank the lows to 10 it should rattle my teeth instead of what it is doing at the moment.

For the 10dB of gain, is this normal? I checked my resistor at the input and output transformers and I do indeed have a 10k between the secondaries of the input and 2k2 on the output. I double checked to make sure there wasn't a boosted gain stage in my rig by plugging the I/O XLRs together and I get unity gain coming back into the interface.

This is a pretty easy build with minimal interconnects and generously spaced components, so I'm a bit confused why this is not a happy EQ. If the problem was no sound or no change at all I could find it fairly easily, but the behavior that is currently being exhibited is a bit baffling.

I am a disgrace to the DIY community. I had build these boards a while back then they sat until I finally got a case made. Somehow when I initially stuffed these boards I confused the resistor arrays to their respective switches. The good news is I now have a reason to break in my new desoldering pump.

I can't believe how amazing I am...

Thanks!

Paul