What do you need the spreadsheet for the "Pot center Tweaking" or the "Stepped switch calculator"?
3D "AIR" EQ - "Night EQ" PCB's Complete!
- Thread starter khstudio
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Help Support GroupDIY Audio Forum:
What do you need the spreadsheet for the "Pot center Tweaking" or the "Stepped switch calculator"?
3nity
Well-known member
Pot center tweaking. Thanks
This one opens and it's the one I use
Harpo
Well-known member
Hi Jorge,
excel file is still there from post#564
All that info is in this thread, you will need to read the thread to be able to complete this project there's no shortcut.
The only Pots source with center detents is Audio Maintenance,
switches have no particular requirement you can get them from any store
Parts list attached
steves.mastering
Active member
Hi all, after moving house im finally digging this out of storage, its been half finished for years and now im trying to remember where i was up to.
i also used the 3D-EQ_PotTweaking_2 spreadsheet to calculate the ladder of resistors for the rotary switches.
From what i remember, the values should go from 44k through to 100k.
However, the values i get are wayy higher... up to 866k, is this correct?
I plan on doing the usual.. -5 to +5dB using 11 positions of a 1x12 lorlin.
Cheers,
i also used the 3D-EQ_PotTweaking_2 spreadsheet to calculate the ladder of resistors for the rotary switches.
From what i remember, the values should go from 44k through to 100k.
However, the values i get are wayy higher... up to 866k, is this correct?
I plan on doing the usual.. -5 to +5dB using 11 positions of a 1x12 lorlin.
Cheers,
I have board's as well and would like to do switches. If anyone has pulled this off successfully it would be nice to hear about their implementation. I do have Harpo's excel sheet. I would perfer to do 23 step switch 1/2 dB +-5.5 dB.
Harpo
Well-known member
...and 866,000 ohms in parallel with 113,000 ohms in the orange cell is 99,957 ohms, pretty close to the wanted 99,939 ohms on paper. The little drawing right next to the calc cells shows how to place this paralleled -not on pcb- resistor across the switch in order to make switching lesser jumpy.
steves.mastering
Active member
Cheers Harpo.
Makes sense now. I bought all these resistors years ago. I just panicked when I saw 866K thinking I’d bought the wrong stuff. Makes sense again now
pots from audiomaintenance
With Center Ident/detent?
If there's something I truly advise to anyone doing this project is to only build this using Pots with a Center Detent.
NorthernLight
Member
- Joined
- Feb 17, 2011
- Messages
- 24
Hi guys, I'm contemplating ordering custom made rotary switches for a stereo Nite EQ build, as building these switches myself would be very time consuming and probably not even that much cheaper.
I found this ad on Ebay, the guy can make custom 21-stepped switches and found some posts on the forum that the switches he makes are not bad quality at all: Custom Made (Made to Order) 21 Stepped Potentiometer - 1K B type/Linear 8 pcs | eBay (The ad is for 8 pieces; I only need 6 but do not mind ordering the 2 spares).
I know these are listed as make before-break-which is not optimal. I'll ask if he can make them in break-before-make instead. If not, sourcing the correct switches would be near impossible (even with solder lugs to build my own), so the solution would be not to tweak the knobs while runing audio through the unit I guess.
The Nite EQ PCBs I have are already populated but that was years ago, so I will need to double check every resistor on the board anyway. I do not mind swapping out resistors. Reading back in this thread it was suggested to use 50K pots (or switches) instead of 500K to reduce noise. I'm trying to use Harpo's excel file to calculate the resistor values but I don't have a clue what I'm doing.
So I have the following questions:
1. What would be the ideal total resistance of the stepped pots? 50K or even 10K perhaps?
2. Given the ideal stepped switch value from question 1, which resistors would need to be altered on the PCBs and what values should they become?
3. Which values would R1 to R20 on the stepped switch need to be? I have copied the switch layout from the ebay add and attached it below.
Your help is much appreciated!
I found this ad on Ebay, the guy can make custom 21-stepped switches and found some posts on the forum that the switches he makes are not bad quality at all: Custom Made (Made to Order) 21 Stepped Potentiometer - 1K B type/Linear 8 pcs | eBay (The ad is for 8 pieces; I only need 6 but do not mind ordering the 2 spares).
I know these are listed as make before-break-which is not optimal. I'll ask if he can make them in break-before-make instead. If not, sourcing the correct switches would be near impossible (even with solder lugs to build my own), so the solution would be not to tweak the knobs while runing audio through the unit I guess.
The Nite EQ PCBs I have are already populated but that was years ago, so I will need to double check every resistor on the board anyway. I do not mind swapping out resistors. Reading back in this thread it was suggested to use 50K pots (or switches) instead of 500K to reduce noise. I'm trying to use Harpo's excel file to calculate the resistor values but I don't have a clue what I'm doing.
So I have the following questions:
1. What would be the ideal total resistance of the stepped pots? 50K or even 10K perhaps?
2. Given the ideal stepped switch value from question 1, which resistors would need to be altered on the PCBs and what values should they become?
3. Which values would R1 to R20 on the stepped switch need to be? I have copied the switch layout from the ebay add and attached it below.
Your help is much appreciated!
It's been a while that I finished off my unit, but if I remember correctly, the "problem" with this circuit is that neither a perfectly centre-detented pot nor a perfectly calculated and built rotary-- neither of these two as such alone will automatically give you a flat frequency response -- it can end up all over the place at mid positions and crossovers.
I spend quite some time tweaking the filter caps and resistors !! And, yes, I used C50k pots without detents, matched them as best possible in same positions L and R (from CCW to CW and at eyeballed mid position, where EQ is pretty flat when just eyeballed), and then finished off the unit with a relay-based hard bypass for "fully flat frequency".
So over here, either the broad filters of this EQ can be dialled in and steplessly ridden (if needed) to make program sound better or they can't. Easy process.
If you need full mastering capability, go for a Sontec with rotaries. Costs more but less of a headache
I spend quite some time tweaking the filter caps and resistors !! And, yes, I used C50k pots without detents, matched them as best possible in same positions L and R (from CCW to CW and at eyeballed mid position, where EQ is pretty flat when just eyeballed), and then finished off the unit with a relay-based hard bypass for "fully flat frequency".
So over here, either the broad filters of this EQ can be dialled in and steplessly ridden (if needed) to make program sound better or they can't. Easy process.
If you need full mastering capability, go for a Sontec with rotaries. Costs more but less of a headache
NorthernLight
Member
- Joined
- Feb 17, 2011
- Messages
- 24
Thanks for your reply @Script . I'm not entirely following what you are saying though. Let me clarify my intentions.
I'm not looking for a perfect flat response, I can get that from EQ software in my DAW. I'm looking for a "mojo" outboard EQ, but with (somewhat) hassle free stereo linking of the 2 channels. The idea was to accomplish whis with tightly matched "stereo" stepped switches. In other words, I'm not afraid if a step is a little off, as long as it's off in the same amount on the left and right channels, (within a certain margin of course because component values never exaclty match). I'm not a professional but enjoy DIYing a unit that can match (or surpass) the quality of a professional unit.
Can you elaborate on your statement that whichever solution you choose, "it can end up all over the place at mid positions and crossovers"?
Let's assume for argument's sake that the filter caps on both channels are matched nicely ad that the steppd switches from the ebay ad are also tightly matched on both gangs;
If I would go for 500K stepped switches I would not need to change any resistors on the PCBs, but noise would be slightly higher
If I would go for 50K stepped switches I would need to swap out some resistors on the PCBs (which ones?) and overall noise would be lower (will this even be noticable?)
In other words; is the lower noise on the 50K solution worth the hassle of having to swap out the resistors on the boards?
I'm not looking for a perfect flat response, I can get that from EQ software in my DAW. I'm looking for a "mojo" outboard EQ, but with (somewhat) hassle free stereo linking of the 2 channels. The idea was to accomplish whis with tightly matched "stereo" stepped switches. In other words, I'm not afraid if a step is a little off, as long as it's off in the same amount on the left and right channels, (within a certain margin of course because component values never exaclty match). I'm not a professional but enjoy DIYing a unit that can match (or surpass) the quality of a professional unit.
Can you elaborate on your statement that whichever solution you choose, "it can end up all over the place at mid positions and crossovers"?
Let's assume for argument's sake that the filter caps on both channels are matched nicely ad that the steppd switches from the ebay ad are also tightly matched on both gangs;
If I would go for 500K stepped switches I would not need to change any resistors on the PCBs, but noise would be slightly higher
If I would go for 50K stepped switches I would need to swap out some resistors on the PCBs (which ones?) and overall noise would be lower (will this even be noticable?)
In other words; is the lower noise on the 50K solution worth the hassle of having to swap out the resistors on the boards?
Ah, I see. I'd say for what you want to do, can forget about 50k
Mismatch or uneven frequency response will be more noticeable. (Could measure caps and then calculate resistors to get it flatter. But can do that later, should you feel it doesn't sound right.)
And if all that doesn't really matter that much to you -- which it might indeed not really do for DJing -- I'd opt for easiest build possible. Maybe even forget rotaries altogether and go for dual taper pots ? Definitely cheaper than rotaries.
Out of stock there, but something like that:
https://www.taydaelectronics.com/c50k-ohm-anti-log-dual-taper-potentiometer.html
Mismatch or uneven frequency response will be more noticeable. (Could measure caps and then calculate resistors to get it flatter. But can do that later, should you feel it doesn't sound right.)
And if all that doesn't really matter that much to you -- which it might indeed not really do for DJing -- I'd opt for easiest build possible. Maybe even forget rotaries altogether and go for dual taper pots ? Definitely cheaper than rotaries.
Out of stock there, but something like that:
https://www.taydaelectronics.com/c50k-ohm-anti-log-dual-taper-potentiometer.html
