Build Thread:PQD2

[miszt]

is there any particular reason that the 220nF polyester caps are listed twice in the BOM? is one of those suppose to be a different value perhaps?


also wondering about the resistors for the switches, how closely do they need to be matched for very good stereo field? I'm looking at ordering 0.1% resistors, because my multi-meter cannot accurately measure 0.1% itself (claims it can, but i don't believe it lol), so there is no point buy 1% and trying to match them myself...but, if 1% difference between them isn't significant, I'd quite like to save myself 5/6's the price...

 

[Gustav]

is there any particular reason that the 220nF polyester caps are listed twice in the BOM? is one of those suppose to be a different value perhaps?

Mentioned for the filter and main board separately.

Did you notice the schematic and board layout files are available? You can check issues like that by comparing. Its a good idea to go through it.

also wondering about the resistors for the switches, how closely do they need to be matched for very good stereo field? I'm looking at ordering 0.1% resistors, because my multi-meter cannot accurately measure 0.1% itself (claims it can, but i don't believe it lol), so there is no point buy 1% and trying to match them myself...but, if 1% difference between them isn't significant, I'd quite like to save myself 5/6's the price...

1% is perfectly fine (imo), for stereo matching, matching filter caps will have  much larger impact.

Gustav

 

[miszt]

is there any particular reason that the 220nF polyester caps are listed twice in the BOM? is one of those suppose to be a different value perhaps?

Mentioned for the filter and main board separately.

Did you notice the schematic and board layout files are available? You can check issues like that by comparing. Its a good idea to go through it.

also wondering about the resistors for the switches, how closely do they need to be matched for very good stereo field? I'm looking at ordering 0.1% resistors, because my multi-meter cannot accurately measure 0.1% itself (claims it can, but i don't believe it lol), so there is no point buy 1% and trying to match them myself...but, if 1% difference between them isn't significant, I'd quite like to save myself 5/6's the price...

1% is perfectly fine (imo), for stereo matching, matching filter caps will have  much larger impact.

Gustav

Yes I went over the board layout, but i couldn't be 100% sure I hadn't missed something, so thought it was worth asking

thanks RE resistors, that's good and bad news, I don't think my multi-meter will give me any useful readings for capacitor matching either tbh, at least not at the % I want - I was reading up on it the other day, and even the "very good" meters can't offer the % match that i think we are talking about here?

I was planning on mostly using this unit in M/S mode anyway, so tbh its not a massive issue, but it would have been nice to have the stereo option aswell; well i'll see what readings i get from my multimeter tomorrow - what % should I be aiming? (obviously as close as possible, but 1%, 5%? or?)


actually i think the real question is, what difference will it make to the frequency band? 5% = +/-1hz or +/-200hz / +-0.1db or +/-6db difference?


this EQ is mainly about color for me, i'll still be doing the core of EQ in my DAW, but if 5% difference means i could have a 3-6db+ difference over a very wide freq range  Left/Right, then that would definitely not be good lol

 

[Gustav]

thanks RE resistors, that's good and bad news, I don't think my multi-meter will give me any useful readings for capacitor matching either tbh, at least not at the % I want - I was reading up on it the other day, and even the "very good" meters can't offer the % match that i think we are talking about here?

You can order a bag of each value and sort them to 1%, or just use 5% rated capacitors for the filters (thats all the caps on the front panel board).

I was just trying to put your worries into perspective,  not create new ones.

Gustav

 

[miszt]

thanks RE resistors, that's good and bad news, I don't think my multi-meter will give me any useful readings for capacitor matching either tbh, at least not at the % I want - I was reading up on it the other day, and even the "very good" meters can't offer the % match that i think we are talking about here?

You can order a bag of each value and sort them to 1%, or just use 5% rated capacitors for the filters (thats all the caps on the front panel board).

I was just trying to put your worries into perspective,  not create new ones.

Gustav

thanks but that doesn't quite answer my question lol or maybe it does and I misunderstood - are you saying that 5% tolerance of capacitors is acceptable for good stereo imaging, or that I should try and match each pair closer to 1%?

tbh I'm not sure my equipment will reliably tell me if a pair of capacitors really are within 1% of one another; I haven't had a chance to check yet - but if 5% tolerance is acceptable for a good stereo image, then that's fine...


(EDIT: going through all my capacitors, I have discovered half of them are infact 10% tolerance, not 5% as I ordered   ffs not in the mood to go through returns)

 

[miszt]

nope my equipment cant even tell me if they are within 10% of each other, i suspect that the capacitors inside the actual meter are probably higher rated tolerance than the ones i'm trying to test!


a definitive answer on the acceptable tolerance of the capacitors in the filter section would be great atm i have a mix of 10% and 5%

 

[Gustav]

a definitive answer on the acceptable tolerance of the capacitors in the filter section would be great

I am sorry, but the answer I gave in my last post is as "definitive" as I can/will get. You will have to bring your own experience into  making the judgement of how close is close enough. If that experience is non-existent, then building a great sounding EQ and getting it working is an ambitious goal in itself (remember to get someone to vouch for the non-lethality of the build) without getting lost in details and super fine tuning.

"I was just trying to put your worries into perspective,  not create new ones".

My best guess is, if I hadn't made the resistor/cap comparison, you would have populated the boards and never thought of it.

If you want to match caps to 1%, the solution is to buy a bag of each value, buy a meter that can measure capacitance and match the relative values.

Gustav

 

[miszt]

a definitive answer on the acceptable tolerance of the capacitors in the filter section would be great

I am sorry, but the answer I gave in my last post is as "definitive" as I can get. You will have to bring your own experience into  making the judgement of how close is close enough.

"I was just trying to put your worries into perspective,  not create new ones".

My best bet is, if I hadn't made the resistor/cap comparison, you would have populated the boards and never thought of it.

If you want to match caps to 1%, you have to buy a bag of each value and a meter that can measure capacitance.

Gustav

you aren't answering the question I am actually asking lol which is, what tolerance (for the capacitors in the filters) do you recommend for this project?

as I've said many times, I'm new to this, I have no "experience" to draw on, I have no idea how much of an impact/difference a +/-10% capacitance will have on this circuit, in comparison to +/-1%

(the only reason I have not asked this question before now, is because I have been trying to research the answer for myself, and avoid asking questions which may have already been answered, but I cannot find a definitive answer, but i can assure you it is a question I have been thinking about since discovering the pultec clone and starting to think about building one for myself!)

 

[Gustav]

a definitive answer on the acceptable tolerance of the capacitors in the filter section would be great

I would recommend you to aim for 5%..

Gustav

 

[dribro]

Its been ages to finish these... Only lettering to finish. Sounds very very good. Thanks Gustav.

 

[dribro]

Onde more pic

 

[dribro]

Onother

 

[dribro]

I think thats enough..

 

[Gustav]

Its been ages to finish these... Only lettering to finish. Sounds very very good. Thanks Gustav.

Glad you like it  - it wouldn't have existed without Jakob's excellent design. I just moved some things around and did a few measurements to make this.

I see you put resistors in series to make the values on the gain switches, so just for future builder reference.

I did calculations for the switches, but they were off in real-use, so instead, I measured. The table shows the measured values rounded off to real values. It won't make any difference if you have a 220R or a 211R resistor on a  step, as long as they are the same in both sides.  Just try to make them add up to the right total and stay within reasonable limites for rounding to more common values, and you should be fine.

Gustav

 

[dribro]

Just my exact thoughts, Gustav.  Its time consuming but resistors in series is a must! Not entirely neat, though. This thing is quiet as a mouse.
And forgot to mention: big thanks to Jakob!

 

[miszt]

in use as an EQ, what is the difference between the way the board is laid out, and the way the above was made? just a difference between the gain/atten curves or is there more to it..?

(i'm just going to follow the board, just asking out of interest...)


My PCB's just arrived cant wait to get stuck in building this! the pcb's look great (as do all the others I ordered, thanks Gustav!)


Looking at the PCB I'm a bit confused by the tube socket type I need, I bought a pair which where listed as suitable for ECC88/6992's, but they have an extra pin in the middle? I put a little pressure on the pin to see if it moved, but I guess it doesn't come out and I have the wrong socket type?

 

[dribro]

I always have a good assortisment of resistors and, when i decided to order the values from the BOM, i figured maybe i should put in the real right values. So series it is! Maybe it won't matter much but as a filter, almost a tiny bit changes things.

 

[miszt]

just want to double check, the only electrolytic capacitors which need to be high voltage are the 330uF?

I ask because the 10uF and 470uF electrolytics I have are significantly smaller than the screen print sizes (10uF is 16V and 470uF is 35V, and if i'm following the board correctly, it seems they are not on the 250V path?)

 

[Gustav]

just want to double check, the only electrolytic capacitors which need to be high voltage are the 330uF?

I ask because the 10uF and 470uF electrolytics I have are significantly smaller than the screen print sizes (10uF is 16V and 470uF is 35V, and if i'm following the board correctly, it seems they are not on the 250V path?)

The large supply caps (at least one of them) should be higher than the rectified voltage of your HV rail, so that depends on the trafo youre using. (If its 250V, that will be roughly 350V).

The 4700 and 10uF caps are in the heater supply path, so needs to be higher than the rectified voltage of your heater supply 16 6 and 35V are fine.

I would advise you to have someone experienced with you to keep you safe when you're ready to power up this unit.

Gustav

 

[miszt]

just want to double check, the only electrolytic capacitors which need to be high voltage are the 330uF?

I ask because the 10uF and 470uF electrolytics I have are significantly smaller than the screen print sizes (10uF is 16V and 470uF is 35V, and if i'm following the board correctly, it seems they are not on the 250V path?)

The large supply caps (at least one of them) should be higher than the rectified voltage of your HV rail, so that depends on the trafo youre using. (If its 250V, that will be roughly 350V).

The 4700 and 10uF caps are in the heater supply path, so needs to be higher than the rectified voltage of your heater supply 16 6 and 35V are fine.

I would advise you to have someone experienced with you to keep you safe when you're ready to power up this unit.

Gustav

thanks for the info!

I'll be fine powering this up, although I do not have a clue what is going on in the filter circuit, I've been building mains voltage appliances of all kinds for decades (only had 1 electric shock off the mains, 22 years ago, i don't plan on another haha)