3D "AIR" EQ - "Night EQ" PCB's Complete!

[dissonantstring]

[quote author="fucanay"] Not to mention, that soon there is going to be a nationwide shortage on 500k reverse log pots, thanks to this eq.
Matt[/quote]

hi matt,
this is the reason i contacted colin at audio maintenance to see if he could make them available for us with center detent for added nifty-ness :thumb: (though they would be 470K rev. log). it seems like there is more interest in PCB termination so i will pass this along to colin. there should be enough interest in these pots since the number of PCBs that will be out there is quite staggering and hopefully this will benefit our DIY community as well as make it worthwhile for colin to stock these pots.
cheers,
grant

 

[jensenmann]

:thumb: good idea, Grant

 

[Purusha]

I don't mind buying pots with solder lugs in a group buy (if it happens). I can still wire them to the PCBs.
It takes maybe one hour of extra work but as I said earlier, I insist on my front panel design which doesn't
look so crowded as the original. I am sorry Joachim, but it looks like you will have to design your own front
panel :thumb:

 

[Purusha]

Purusha,
The original unit I have is pretty crowded but it NEVER bothered me.

I know what you mean, I used it before. But since I have the chance to decide how will
my Night cases look in my studio I will take the opportunity and make them less crowded
and improve the weakness on the original design :wink:

 

[dissonantstring]

hi peter,
i wanted to make sure that these were the TYPE of pots that will fit your PCB:

the example pictured is a 16mm single gang pot with center detent, we would be asking for a 16mm single gang 470K rev. log pot with center detent.

i just want to clarify that colin (slenderchap) has offered to stock the 470K rev. log pots at his audio maintenance webstore making it easily available to all of us. this is NOT a group buy, nor am i involved in the selling of this in anyway. i just contacted colin to see if he could help us out since he's already well connected with omeg and carries many pots from them and he has generously offered to do so (for which i thank him).

regards,
grant

 

[Purusha]

Grant, where is this audio maintenance webstore located?

 

[dissonantstring]

hi tat,
it's here: http://www.audiomaintenance.com/acatalog/potentiometers.html

 

[peterc]

i wanted to make sure that these were the TYPE of pots that will fit your PCB:

Grant,

Those look good, as long as the pins have a 5 mm spacing.

I also recommend the P20 (?) pots rather than the P16 pots, as the drawings I have seen on the Omeg site are a bit confusing, giving the P20 dimensions as 15mm & the P16 dimensions as 12.5 - 15 for the shaft centre to PCB pin "shoulder" i.e. the height from PCB top to shaft centre.

Peter

 

[khstudio]

You may want to try one first & see if the center point is accurate. Using 470k in place of the 500k may throw things off a bit... unless, hmmm... maybe you could add a resistor to one leg to adjust the center (FLAT) point :idea:

OK,
I just set ALL the bands of one channel to the center & got readings between 46k & 48k... 3 out of the 5 were closer to 47k.

So 47k it is @ the mid point.

Kevin

 

[Purusha]

[quote author="dissonantstring"]hi tat,
it's here: http://www.audiomaintenance.com/acatalog/potentiometers.html[/quote]

Thanks :thumb:

BTW, are they located in Europe or else where?

 

[Purusha]

Oh, they have £ next to their prices so it must be in UK :green:

 

[dissonantstring]

hi kevin,
unfortunately, since this isn't a stocked item for colin he would be ordering them special, so i would have no way of testing them prior to him ordering a batch. he wants to get the specs right that's why i've been posting on this thread.

i believe you are right WRT the difference between values since the 500K rev. log pot adjusts the proportional-Q so the bandwidth might suffer slightly. if a 470K pot were used then i believe the adjustments on the more narrow bandwidth settings would not be as narrow(?) or in the opposite direction - wide(?) somebody should step in if i'm on the wrong track here as i'd rather not add to any confusion or start thought that's horribly wrong.

as for the center point, i have no clue really. what would actually be affected by the different value of resistance of center? the value might be different, but the center is still the center right? :?
so those who use a 470K rev. log pot would just not get the most narrow or wide bandwidth settings of the proportional- Q on the frequency they are adjusting.
i like your idea of adding a series resistor to compensate for the 470K pot. will this actually work?
cheers,
grant

 

[Slenderchap]

Given the 5% tolerance of the mechanical rotation and the 20% electrical tolerance of an alpha electric pot it is probably all a bit vague as to what the exact value is at the centre point...... you would probably get the same value across a batch..... but it's anybody's guess between batches.

Combined with the fact that reverse log pots from different manufacturers have different laws [hence why they sneakily call them "audio" laws] you cannot even compare manufacturers.

We can have a set of samples made if you wish.

Colin
www.audiomaintenance.com

 

[khstudio]

ATTEN:!:
About the Alpha pots from Small Bear -

I just measured several of these & they range from 450k to 490k.
The "CENTER Points" measured between 75k & 85k.
:shock:


All these pot will "Work"
I'm just reminding everyone of where my Original units FLAT Point is.

The circuit was designed around this I'm sure... when the knobs are centered, that band is "FLAT". This is at 47k.

I do not think other pot values will affect performance... just perception of.

The only reason I'm driving this point is because the PCB mount pots can not be rotated to adjust for the center point... they're stuck there.

 

[fucanay]

[quote author="khstudio"]
The only reason I'm driving this point is because the PCB mount pots can not be rotated to adjust for the center point... they're stuck there.[/quote]

True, but you could always just move use the set screw on a knob to adjust for this, right? That's assuming you used knobs with set screws I suppose.

But this does raise an issue about how much you can cut or boost if the centers (47k) are not at the correct place in the rotation. Out of curiosity, how many of the original pots did you check in terms of the center position value? EDIT: Oops, I just read this at the top of this page.

It seems to me that this could be a poor design if the pots are needing to be a very specific value when most are in the 10-20% tolerances. Or am I not understanding this right? Did you see a part number or manufacturer on the original pots?

Matt

 

[clintrubber]

[quote author="fucanay"]It seems to me that this could be a poor design if the pots are needing to be a very specific value when most are in the 10-20% tolerances. Or am I not understanding this right? Did you see a part number or manufacturer on the original pots?

Matt[/quote]
Perhaps this is the moment to skip all-things-pot & focus on rotary switches from now on ?
What do people think, how many taps would be acceptable ? Have some 12-pos. rotary switches here, but that might be too rude I'm afraid...

 

[fucanay]

[quote author="clintrubber"][quote author="fucanay"]It seems to me that this could be a poor design if the pots are needing to be a very specific value when most are in the 10-20% tolerances. Or am I not understanding this right? Did you see a part number or manufacturer on the original pots?

Matt[/quote]
Perhaps this is the moment to skip all-things-pot & focus on rotary switches from now on ?
What do people think, how many taps would be acceptable ? Have some 12-pos. rotary switches here, but that might be too rude I'm afraid...[/quote]

If you could figure out what they all needed to be to gain the gain steps where you wanted them, I think it would be a good idea. And just imagine how great it would be for recall purposes. But of course sometimes you want a half db cut or something and this wouldn't be good for that.

Seems that the best solution is the right pots, but maybe that's impossible.

Matt

 

[khstudio]

[quote author="clintrubber"][quote author="fucanay"]It seems to me that this could be a poor design if the pots are needing to be a very specific value when most are in the 10-20% tolerances. Or am I not understanding this right? Did you see a part number or manufacturer on the original pots?

Matt[/quote]
Perhaps this is the moment to skip all-things-pot & focus on rotary switches from now on ?
What do people think, how many taps would be acceptable ? Have some 12-pos. rotary switches here, but that might be too rude I'm afraid...[/quote]

Good idea but your NEVER going to fit 12 Lorlins acrossed the front... what else is there that's cost effective?

 

[clintrubber]

[quote author="khstudio"]Good idea but your NEVER going to fit 12 Lorlins acrossed the front... what else is there that's cost effective?[/quote]
Staggered perhaps ? Maybe case-meister Purusha can do some magic tricks with the parallel front panel he usually uses - space it a bit further away so that say all odd rotaries are directly mounted on the front panel and the even ones on the mentioned additional panel ?

Must admit I have some mini-Elma's here, so that would work fine already as is.

But I'm not sure if 12-pos would be enough.

 

[jdbakker]

[quote author="khstudio"]Good idea but your NEVER going to fit 12 Lorlins acrossed the front... what else is there that's cost effective?[/quote]
Has anyone ever used the Grayhill 56-series (or other half-inch rotaries) ? It would appear that Purple Audio use 'em, so they might not be total crap. Digi-Key stock 'em (GH5601-ND). At US$10.61@1 / $8.48@25 they're not as cheap as the Lorlins, but not quites as expensive as the Elmas.

JDB.
[the ITT/Cannon half-inch switch (Digi CKN6049-ND) is somewhat cheaper]