sontec 1 RU build thread

Harpo said:

Leonardo_007 said:

just for official clarification.. the codes "0207" "0204" on resistors are size indications in mm, for instance: "0207" means the resistor is 2mm wide and 7mm long.

Click to expand...

Look up the resistors datasheet for the 0204 and 0207 types to get the difference (parts size / power rating / voltage), maybe from this manufacturer ...
http://www.yageo.com/documents/recent/Leaded-R_MF0_2011.pdf

Use ohms law to check, if it matters for a specific part in question.
(hint: with a +/-24V supply, 0.25W rated resistors with value lower than 2K3, 0.4W rated resistors with value lower than 1K4 or 0.6W rated resistors with value lower than 960R might need a 2nd look, if their power rating will be sufficient in a specific spot in this application)
For this EQ build, RPS1...5 (and R16 in a shorted output condition by maybe connected broken XLR cable) better have a higher power rating than 0.25W or 0.4W.

Click to expand...

Xicon resistors, even at values such as 68R maintain the following specifications:

Power Rating: 250 mWatts (1/4 Watt)
Voltage Rating: 250 Volts
Temperature Coefficient: 50 PPM /

For a person who is not that much of an expert but does their homework, it'd be nice to know where or what these spots / resistors are by simply indicating a higher mWatts Power Rating you'd only attain by getting the respective bigger values.

It is not that I'm asking and won't do nothing, I've put the BOM together so far but lacking the knowledge I need to be 100 % sure of my choices. Also, with projects that lack a clear BOM, for people like me, I always provide the community with my mouser BOM.

atticmike said:

Harpo said:

Look up the resistors datasheet for the 0204 and 0207 types to get the difference (parts size / power rating / voltage), maybe from this manufacturer ...
http://www.yageo.com/documents/recent/Leaded-R_MF0_2011.pdf

Use ohms law to check, if it matters for a specific part in question.
(hint: with a +/-24V supply, 0.25W rated resistors with value lower than 2K3, 0.4W rated resistors with value lower than 1K4 or 0.6W rated resistors with value lower than 960R might need a 2nd look, if their power rating will be sufficient in a specific spot in this application)
For this EQ build, RPS1...5 (and R16 in a shorted output condition by maybe connected broken XLR cable) better have a higher power rating than 0.25W or 0.4W.

Click to expand...

Xicon resistors, even at values such as 68R maintain the following specifications:

Power Rating: 250 mWatts (1/4 Watt)
Voltage Rating: 250 Volts
Temperature Coefficient: 50 PPM /

For a person who is not that much of an expert but does their homework, it'd be nice to know where or what these spots / resistors are by simply indicating a higher mWatts Power Rating you'd only attain by getting the respective bigger values.

It is not that I'm asking and won't do nothing, I've put the BOM together so far but lacking the knowledge I need to be 100 % sure of my choices. Also, with projects that lack a clear BOM, for people like me, I always provide the community with my mouser BOM.

Click to expand...

Mike, you know from your +/-24V supply rails, voltage will not exceed this +24V or -24V value, so the voltage limits of your Xicon resistors with 250V rating won't be a problem. Your 1/4W rated resistors can stand a current flow of 0.25W/24V=0.010417A=~10mA. In a short condition (IE solder blob, broken cable), this make or break point will be 24V/0.01A=2K4 ohm. Using a lower resistor value than 2K4 might exceed the resistors power rating, so rating of this part will need a 2nd look, but knowing this value limit, you can simply ignore all resistors with a parts value higher than 2K4. (3/4 of all resistors in this circuit have a value higher than 2K4, so most of this work is already done)
Looking at the schematic, 1st resistor in circuit with value lower than 2K4 is the 100R R7. This has the 20K R8 in series connected, so total resistance is 20K1, more than the 2K4 limit, no problem with 1/4W rating. This R7 also branches to J1-1, further going to the 'boost' rail. This has some 7K5 in series with the 50K center tapped pots in parallel connected. 100R + this paralleled series string doesn't exceed the 2K4 limit, so no problem from this side of the branch as well.
R15 is the same for the 'cut' rail so same as previous branch test and no problem as well.
R9 connects thru J1-5 to the output of the filter stages, each with a 20K or 10K in series in between, no problem expected as well.
R11 connects in series to the 10K R13. No problem.
The 68R R16 connects to XLR-pin2. No problem for usual operation, but if the resistor feeding opamp is steady clipping and can swing up to the voltage rails from a boosted signal and XLR-pin2 gets shorted to gnd by a broken connected cable, there is only a voltage divider forming 10R R23 in between, so your 1/4W resistor power rating will be exceeded, maybe on purpose, acting like a fuse. (Required rating might go up to (24V/(68R+10R)*68R)^2/68R=6.44W for this extreme condition, if your opamp -more unlikely- could deliver this 300mA current draw and the fusible resistors RPS1...RPS4 for whatever reason don't blow up first).
For the 10R R23, Igor already suggested a 0.6W rated 0207 type, where a (24V/(68R+10R)*10R)^2/10R=0.95W would be required to stand this extreme, but a 0.25W or 0.6W rated R16 or more likely the RPS1...RPS4 would blow first, protecting this R23.
No problem for the impedance balancing 68R R17 expected.
The 392R RF1.4...RF4.4 have high enough series resistors connected, so no problem as well.
The 1K6 RF1.9...RF4.10 have a cap in series connected, blocking DC condition and max.voltage will not exceed 24V/sqrt(2). Rating required 0.18W, no problem.
The current limiting/fusible RPS1...5 have to stand the power consumption of all connected opamps. Igor already suggested a 0.6W rated 0207 type.
So all resistors -except RPS1...RPS5- can be fitted with your 0.25W Xicon resistors. As always YMMV.

Harpo said:

atticmike said:

Harpo said:

Look up the resistors datasheet for the 0204 and 0207 types to get the difference (parts size / power rating / voltage), maybe from this manufacturer ...
http://www.yageo.com/documents/recent/Leaded-R_MF0_2011.pdf

Use ohms law to check, if it matters for a specific part in question.
(hint: with a +/-24V supply, 0.25W rated resistors with value lower than 2K3, 0.4W rated resistors with value lower than 1K4 or 0.6W rated resistors with value lower than 960R might need a 2nd look, if their power rating will be sufficient in a specific spot in this application)
For this EQ build, RPS1...5 (and R16 in a shorted output condition by maybe connected broken XLR cable) better have a higher power rating than 0.25W or 0.4W.

Click to expand...

Xicon resistors, even at values such as 68R maintain the following specifications:

Power Rating: 250 mWatts (1/4 Watt)
Voltage Rating: 250 Volts
Temperature Coefficient: 50 PPM /

For a person who is not that much of an expert but does their homework, it'd be nice to know where or what these spots / resistors are by simply indicating a higher mWatts Power Rating you'd only attain by getting the respective bigger values.

It is not that I'm asking and won't do nothing, I've put the BOM together so far but lacking the knowledge I need to be 100 % sure of my choices. Also, with projects that lack a clear BOM, for people like me, I always provide the community with my mouser BOM.

Click to expand...

Mike, you know from your +/-24V supply rails, voltage will not exceed this +24V or -24V value, so the voltage limits of your Xicon resistors with 250V rating won't be a problem. Your 1/4W rated resistors can stand a current flow of 0.25W/24V=0.010417A=~10mA. In a short condition (IE solder blob, broken cable), this make or break point will be 24V/0.01A=2K4 ohm. Using a lower resistor value than 2K4 might exceed the resistors power rating, so rating of this part will need a 2nd look, but knowing this value limit, you can simply ignore all resistors with a parts value higher than 2K4. (3/4 of all resistors in this circuit have a value higher than 2K4, so most of this work is already done)
Looking at the schematic, 1st resistor in circuit with value lower than 2K4 is the 100R R7. This has the 20K R8 in series connected, so total resistance is 20K1, more than the 2K4 limit, no problem with 1/4W rating. This R7 also branches to J1-1, further going to the 'boost' rail. This has some 7K5 in series with the 50K center tapped pots in parallel connected. 100R + this paralleled series string doesn't exceed the 2K4 limit, so no problem from this side of the branch as well.
R15 is the same for the 'cut' rail so same as previous branch test and no problem as well.
R9 connects thru J1-5 to the output of the filter stages, each with a 20K or 10K in series in between, no problem expected as well.
R11 connects in series to the 10K R13. No problem.
The 68R R16 connects to XLR-pin2. No problem for usual operation, but if the resistor feeding opamp is steady clipping and can swing up to the voltage rails from a boosted signal and XLR-pin2 gets shorted to gnd by a broken connected cable, there is only a voltage divider forming 10R R23 in between, so your 1/4W resistor power rating will be exceeded, maybe on purpose, acting like a fuse. (Required rating might go up to (24V/(68R+10R)*68R)^2/68R=6.44W for this extreme condition, if your opamp -more unlikely- could deliver this 300mA current draw and the fusible resistors RPS1...RPS4 for whatever reason don't blow up first).
For the 10R R23, Igor already suggested a 0.6W rated 0207 type, where a (24V/(68R+10R)*10R)^2/10R=0.95W would be required to stand this extreme, but a 0.25W or 0.6W rated R16 or more likely the RPS1...RPS4 would blow first, protecting this R23.
No problem for the impedance balancing 68R R17 expected.
The 392R RF1.4...RF4.4 have high enough series resistors connected, so no problem as well.
The 1K6 RF1.9...RF4.10 have a cap in series connected, blocking DC condition and max.voltage will not exceed 24V/sqrt(2). Rating required 0.18W, no problem.
The current limiting/fusible RPS1...5 have to stand the power consumption of all connected opamps. Igor already suggested a 0.6W rated 0207 type.
So all resistors -except RPS1...RPS5- can be fitted with your 0.25W Xicon resistors. As always YMMV.

Click to expand...

Thanks Harpo, I cannot express how grateful I am for your assistance and the info about how to narrow down my choice of resistors. Hadn't done it without your help.

Although is 10R really part of the build since it is not listed on the BOM provided by Igor? But yeah, I threw a glance at the schematic / drawings and saw that indeed 10R is indicated. Is it just a drawing culprit or really missing on the BOM?

Furthermore, here is my mouser BOM I've put together so far. Anything is on there except the following parts which I already included in my previous mouser order:

Neutrik XLR In / Output

CONNECTORS

POTENTIOMETERS

MISC

DIODES

HEATSINKS

I'd greatly appreciated it if someone could check it for mistakes, it'd be a huge help for anybody as inept as I am

I also have to add that creating a substitute for R55k, I chose two variants since I wasn't so sure which would be the smartest choice of em all:

1. 271-48.7K-RC & 271-1.3K-RC
2. 271-49.9K-RC & 271-100-RC

http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=f65d170554

atticmike said:

I also have to add that creating a substitute for R55k, I chose two variants since I wasn't so sure which would be the smartest choice of em all:
1. 271-48.7K-RC & 271-1.3K-RC
2. 271-49.9K-RC & 271-100-RC

Click to expand...

Sorry, but I'm missing how your suggested substitute will add up to 55K. Just fit a 54K9 and be done with it. The 0.18% difference on paper is within parts tolerances.
No idea why BOMs aren't banned. Most often these are partly wrong, are missing essential parameters or are simply outdated because a vendor changed some order-IDs. You could learn so much more alongside by looking at datasheets when selecting parts of your desire. YMMV.

Harpo said:

atticmike said:

I also have to add that creating a substitute for R55k, I chose two variants since I wasn't so sure which would be the smartest choice of em all:
1. 271-48.7K-RC & 271-1.3K-RC
2. 271-49.9K-RC & 271-100-RC

Click to expand...

Sorry, but I'm missing how your suggested substitute will add up to 55K. Just fit a 54K9 and be done with it. The 0.18% difference on paper is within parts tolerances.
No idea why BOMs aren't banned. Most often these are partly wrong, are missing essential parameters or are simply outdated because a vendor changed some order-IDs. You could learn so much more alongside by looking at datasheets when selecting parts of your desire. YMMV.

Click to expand...

Hah, I was dumbstruck at first too since I couldn't make sense of my 50k composure but I've stumbled across the culprit. I put 50k on my piece of jotting paper and transferred it onto my BOM. Will get fixed as soon as I've put the final list together

Why would the BOM be wrong if I asked for assistance from the experienced members of this board and I'm not going to mince matters just because I want to whitewash my weak points.

Even if it was outdated, people would still get to see the parts of a working build someone put together prior to their efforts which will make their ensuing parts procurement a lot easier.

I'm getting the point that you want folks to throw a glance at the build first and try to understand it. I didn't do anything any different by that matter. But it'll be still nice to have someone apt to throw a last glance at it and support the other's effort.

Especially with the Mica capacitors, I wasn't quite sure whether I've done everything correct with my choice of Mica caps.

I will just list everything accordingly to the bom's structure in this thread to avoid your loathed BOM scheme:


OP-AMP


1 x ad706 OR OPA2604(24V PS) 'CAN BE OTHER LOW OFFSET DUAL OPAMP

http://www.reichelt.de/ICs-NE-SA-/OPA-2604-AP/index.html?ACTION=3&GROUPID=2915&ARTICLE=13662&SHOW=1&START=0&OFFSET=16&&SID=10TwCoZ38AAAIAAGkrnrM5241d7b48719e2f0439021072ba7654c&LANGUAGE=EN

2 x OPA604 OR JE990 ETC 'CAN BE OTHER LOW DIST FAST HIGH CURRENT

http://www.reichelt.de/ICs-NE-SA-/OPA-604-AP/index.html?;ACTION=3;LA=444;GROUP=A218;GROUPID=2915;ARTICLE=13669;START=0;SORT=artnr;OFFSET=16;SID=10TwCoZ38AAAIAAGkrnrM5241d7b48719e2f0439021072ba7654c

5 x OPA2604 OR OP275 ETC 'CAN BE OTHER LOW DIST FAST DUAL OPAMP

Same OPA2604 as number one: http://www.reichelt.de/ICs-NE-SA-/OPA-2604-AP/index.html?ACTION=3&GROUPID=2915&ARTICLE=13662&SHOW=1&START=0&OFFSET=16&&SID=10TwCoZ38AAAIAAGkrnrM5241d7b48719e2f0439021072ba7654c&LANGUAGE=EN


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RESISTORS


Anything Xicon 1/4 metal film except these parts:

R68 - 0.6 W

http://www.reichelt.de/Metall-0-1-5-10-Ohm-82-5-Ohm/MPR-68-0/index.html?;ACTION=3;LA=2;ARTICLE=13047;GROUPID=3102;artnr=MPR+68%2C0;SID=10TwCoZ38AAAIAAGkrnrM5241d7b48719e2f0439021072ba7654c

R22 - 0.6 W

http://www.reichelt.de/Metall-0-1-5-10-Ohm-82-5-Ohm/MPR-22-0/index.html?;ACTION=3;LA=2;ARTICLE=12871;GROUPID=3102;artnr=MPR+22%2C0;SID=10TwCoZ38AAAIAAGkrnrM5241d7b48719e2f0439021072ba7654c

2 x 200R 2%

http://uk.mouser.com/Search/ProductDetail.aspx?R=CCF07200RGKE36virtualkey61300000virtualkey71-CCF07200RGKE36

1 x rx+ 3k6 2% for 24v

http://uk.mouser.com/Search/ProductDetail.aspx?R=RL07S362GB14virtualkey61300000virtualkey71-RL07S-G-3.6K

1 x rx- 3k6 2% for 24v

Same as the one above: http://uk.mouser.com/Search/ProductDetail.aspx?R=RL07S362GB14virtualkey61300000virtualkey71-RL07S-G-3.6K

Still, I'm not sure whether R10 is part of the build since it list not listed under the parts list.

Anyways, there we got R10 - 0,6W, 0,1%, 10,0 Ohm

http://www.reichelt.de/Metall-0-1-5-10-Ohm-82-5-Ohm/MPR-10-0/index.html?;ACTION=3;LA=2;ARTICLE=12769;GROUPID=3102;artnr=MPR+10%2C0;SID=10TwCoZ38AAAIAAGkrnrM5241d7b48719e2f0439021072ba7654c

Do you think it'd be smart to just get all the resistors at 0,6W with a tolerance of 0.1%? That'd be almost 0.9 percent lower compared to Xicon and it'd cover the headroom mentioned earlier everywhere?


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CAPACITORS-ELECTROLYTHIC


2 x 100U CPOL-EUE Pitch: 5 mm Width: 10.5 mm

http://uk.mouser.com/Search/ProductDetail.aspx?R=UES1H101MHMvirtualkey64700000virtualkey647-UES1H101MHM

2 x 100U CPOL-EUE Pitch: 5 mm Width: 13 mm

http://uk.mouser.com/Search/ProductDetail.aspx?R=UFG1H101MPMvirtualkey64700000virtualkey647-UFG1H101MPM

4 x 33U CPOL-EUE Pitch: 5 mm Width: 6 mm

http://uk.mouser.com/Search/ProductDetail.aspx?R=UKW1H330MDDvirtualkey64700000virtualkey647-UKW1H330MDD


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CAPACITORS-CERAMIC


17 x 0.1U 5MM PITCH CERAMIC POWER SUPPLY BYPASS

http://uk.mouser.com/Search/ProductDetail.aspx?R=RPER71H104K2K1A03Bvirtualkey64800000virtualkey81-RPER71H104K2K1A03


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CAPACITORS-POLY ETC.



1 x 0.15U C-10-15/6

http://uk.mouser.com/Search/ProductDetail.aspx?R=160154J250E-Fvirtualkey53900000virtualkey539-160154J250E-F

2 x 0.47U C-10-15/6

http://uk.mouser.com/Search/ProductDetail.aspx?R=160474J63D-Fvirtualkey53900000virtualkey539-160474J63D-F

8 x 1U C-10-15/6

http://uk.mouser.com/Search/ProductDetail.aspx?R=160105J63E-Fvirtualkey53900000virtualkey539-160105J63E-F

1 x 2U2 C-10-15/6

http://uk.mouser.com/Search/ProductDetail.aspx?R=MKS4C042204C00JSSDvirtualkey50520000virtualkey505-MKS42.2%2f63%2f5P15

1 x 1U C-10-15/6

Chose the same one as 8 x 1U since I didn't know what difference it'd make since it was listed separately: http://uk.mouser.com/Search/ProductDetail.aspx?R=160105J63E-Fvirtualkey53900000virtualkey539-160105J63E-F

2 x 2u2 C-10-15/6

Chose the same one as 1 x 2u2 since I didn't know what difference it'd make since it was listed separately: http://de.mouser.com/Search/ProductDetail.aspx?R=MKS4C042204C00JSSDvirtualkey50520000virtualkey505-MKS42.2%2f63%2f5P15

1 x 4u7 C-10-15/6 (PITCH UP TO 35MM, POSSIBLE TO USE 2 CAPS IN PARALLEL)

http://uk.mouser.com/Search/ProductDetail.aspx?R=MKS4C044704D00JSSDvirtualkey50520000virtualkey505-MKS44.7%2f63%2f5

1 ** C-10-15/6

I presume that " 1 ** " indicates the possibility to use 2 caps in parallel?



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CAPACITORS-SILVER MICA OR POLY



1 x 3n3 C-7-10/5

http://uk.mouser.com/Search/ProductDetail.aspx?R=CD19FD332JO3Fvirtualkey59850000virtualkey598-CD19FD332JO3F

2 x 2n70 C-7-10/5

http://uk.mouser.com/Search/ProductDetail.aspx?R=CD16FD272JO3Fvirtualkey59850000virtualkey598-CD16FD272JO3F

1 x 100P C7.5/3

http://uk.mouser.com/Search/ProductDetail.aspx?R=CD5FC101JO3virtualkey59850000virtualkey5982-5-300V100

1 x 150P C5/2.5 NOT NECESSARY WITH OPA604 2 330P C7.5/3

http://uk.mouser.com/Search/ProductDetail.aspx?R=CD5FA151JO3virtualkey59850000virtualkey5982-5-100V150

2 x 330P C7.5/3

http://uk.mouser.com/Search/ProductDetail.aspx?R=D105F331JO3virtualkey59850000virtualkey5982-10-500V330

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CAPACITORS-SILVER MICA OR COG



5 x 5p C2.5/2

http://uk.mouser.com/Search/ProductDetail.aspx?R=CD5CC050D03virtualkey59850000virtualkey598-CD5CC050D03

2 x 12p C7.5/3

http://uk.mouser.com/Search/ProductDetail.aspx?R=CD5CC120JO3Fvirtualkey59850000virtualkey598-CD5CC120JO3F


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DIODES


4 x 1N4004 D20, D21, D22, D23

http://uk.mouser.com/Search/ProductDetail.aspx?R=1N4004G-Tvirtualkey62110000virtualkey621-1N4004G-T

4 x 1N5400 D16, D17, D18, D19

http://uk.mouser.com/Search/ProductDetail.aspx?R=1N5400G-Tvirtualkey62110000virtualkey621-1N5400G-T


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IC'S


1 x 317 LM317 IC1

http://uk.mouser.com/Search/ProductDetail.aspx?R=LM317HVT%2fNOPBvirtualkey56960000virtualkey926-LM317HVT%2fNOPB

1 x 337 LM337 IC3

http://uk.mouser.com/Search/ProductDetail.aspx?R=LM337T%2fNOPBvirtualkey56960000virtualkey926-LM337T%2fNOPB


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PS Ceramic Caps


4 x CERAMIC CAPS 0.1UX50V PITCH 2.5MM

http://uk.mouser.com/Search/ProductDetail.aspx?R=FK16C0G1H104Jvirtualkey52130000virtualkey810-FK16C0G1H104J


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ELECTROLYTHIC CAPS 50V


4 x 100u CPOL-EUE3.5-8 PITCH 3.5MM

http://uk.mouser.com/Search/ProductDetail.aspx?R=UKW1H101MPDvirtualkey64700000virtualkey647-UKW1H101MPD

2 x 3300u CPOL-EUE7.5-18 PITCH 7.5 OR 10MM

http://uk.mouser.com/Search/ProductDetail.aspx?R=UKW1H332MHDvirtualkey64700000virtualkey647-UKW1H332MHD


---

Hey Guys,

Thanks to Christoph (crisotop), I Just finished reading the whole thread and I think I am motivated to build this precious, maybe two of them, Need to check if anyone  in US (I am in Dallas, TX) is interested in getting the alpha pots and maybe we can order a bundle and split shipping charges, I can re-ship via USPS ?  Or perhaps someone in Germany could receive them for me and re-ship to us?



Please send me a PM or an email to ludwing at usmastering dot com ASAP if you are interested

Wish me luck!!!

Ludwing

the shipping isnt as bad as the actual cost of the pots

Anybody available to take part in checking the parts of my list?

atticmike, I will have check to very soon! 

yeah, pots are a bit pricey.... but I wrote them an email and they can send me twice the amount for same shipping price ($30 eu) to US.    I am just waiting for Igor to respond my email before proceeding to order them.

By the way, who ordered diy-racked cases from USA?  how long did they take?  The ones from collective cases are nice but a bit more expensive than the Europeans

Thanks!

colombian said:

atticmike, I will have check to very soon! 

yeah, pots are a bit pricey.... but I wrote them an email and they can send me twice the amount for same shipping price ($30 eu) to US.    I am just waiting for Igor to respond my email before proceeding to order them.

By the way, who ordered diy-racked cases from USA?  how long did they take?  The ones from collective cases are nice but a bit more expensive than the Europeans

Thanks!

Click to expand...

i got cases from Tat... im in Mexico and in less than 2 weeks they were in my doorstep. he is a legend

Gracias Patron!!!

me alegra que un Latino tambien este en esto!  ya terminaste el tuyo?  si puedes dame tu email para escribirte!

Un abrazo!

Actually, I have to correct myself.  Tat's and Dan's cases are about the same price.

Thank you

I emailed Alphastat about pots a month or so ago and was quoted 45 eu for postage, emailed him recently and was quoted 30 eu. Glad I held off for that 15 eu saving hehe..

Still one silly question about stepped switches 

How do you wire the gain switch? Ok the center is 0r but are you supposed to connect the -1/+1 resistor legs to center lug or just leave the center empty and jump the -1/+1 over the lug? In alpha pots it seems that there is 4 legs and one of them goes to ground, do I need also ground the center lug of the stepped switch?

Thanks!

3 connections to your 'center lug' (maybe pin12 from a 23 position rotary switch).
Both +/-dB resistor legs next to the +/-0dB step position and 0V reference voltage.

Harpo said:

3 connections to your 'center lug' (maybe pin12 from a 23 position rotary switch).
Both +/-dB resistor legs next to the +/-0dB step position and 0V reference voltage.

Click to expand...

Great thanks again!

And just to clarify before stuffing the resistors (using 21 position rotary):

For freq I'm using Harpos xls I stuff the both decs (2x21) as 100k rev log, one side of the resistors connected to a switches throw lug and all resistors other side to a common ring?

For Gain, 0.5db steps 20x2.5k connected in a series string and change summing resistor from the boards twice as higher 40k/20k?

on the pcb_io it says ad706, does that mean it is better to employ ad706s for that purpose or can I stick with an OPA2604 since on the bom, it says  "ad706 OR OPA2604"?

Placed in between the two 604s.

Also, what options are there to procure the front panel?

Anything European by any chance? Wouldn't mind to import from the states also though.

sedit1 said:

And just to clarify before stuffing the resistors (using 21 position rotary):

Click to expand...

Don't miss the line 'Update the cap.values in the red cells with measured real world capacitance of your fitted parts' before ordering resistors for your frequency setting rotary switches (caps come with tolerances from +/-2% up to +80%/-20%).

For freq I'm using Harpos xls I stuff the both decs (2x21) as 100k rev log, one side of the resistors connected to a switches throw lug and all resistors other side to a common ring?

Click to expand...

Single resistors, connecting to a common ring, require a MBB switch to prevent an open loop. I'd prefer the calc right next to it for strings of series resistors (adding up to a total of about 100K), so either MBB or BBM switches could be used. YMMV.

Harpo said:

sedit1 said:

And just to clarify before stuffing the resistors (using 21 position rotary):

Click to expand...

Don't miss the line 'Update the cap.values in the red cells with measured real world capacitance of your fitted parts' before ordering resistors for your frequency setting rotary switches (caps come with tolerances from +/-2% up to +80%/-20%).

For freq I'm using Harpos xls I stuff the both decs (2x21) as 100k rev log, one side of the resistors connected to a switches throw lug and all resistors other side to a common ring?

Click to expand...

Single resistors, connecting to a common ring, require a MBB switch to prevent an open loop. I'd prefer the calc right next to it for strings of series resistors (adding up to a total of about 100K), so either MBB or BBM switches could be used. YMMV.

Click to expand...

Will do so.
Great advices especially the importance of measuring the caps.
Again thanks a ton!

Harpo said:

sedit1 said:

And just to clarify before stuffing the resistors (using 21 position rotary):

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Don't miss the line 'Update the cap.values in the red cells with measured real world capacitance of your fitted parts' before ordering resistors for your frequency setting rotary switches (caps come with tolerances from +/-2% up to +80%/-20%).

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Just measured capacitances. Allmost all the values were in line with eatchother but how colose do you need to match the channels?
My 0.47uf caps were littlebit off 3x~0.47 and one 0.49uf. Is it better to order more 0.47uf and try to match the caps better?