Vintage Russian 4-bands equalizer - full project

[MidnightArrakis]

The correct type for this type of circuit is a W-taper.
https://www.diystompboxes.com/smfforum/index.php?topic=92918.0
Many units use linear pots by default.

[The correct type for this type of circuit is a W-taper] -- Just a few minutes ago I found some miniature "Fader Sliders" that are available with a "W-taper" and they're small enough to easily fit onto a "500-Series" front-panel horizontally!!! They could be bigger (i.e., "longer") if they were to be mounted vertically, perhaps in 2-sets of 3-faders each. That is a future decision yet to be made.

I am contacting the manufacturer right now as I am writing this response in order to obtain some additional information on them. Kind of like this:





Kind of like this.....only with half the number of sliders:


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[abbey road d enfer]

I used thousands of these 50 and 65mm faders with W-taper. I had to order them with MOQ of 10k.
I think the only possibility to get them in "DIY" quantity is if they are used by a manufacturer and spares are available.
The problem is that most manufacturers have phased out graphic EQ's.
API audio use the 25 (30?) mm version in their 500-series. They may be available there.

 

[MidnightArrakis]

Here, I’m presenting a carefully reworked version of an old Russian DIY radio project. I’ve not only translated the text into English but also selected modern equivalents for the old Soviet radio components.
I chose this project because it allows you to achieve that true vintage sound! It uses LC filters, which are quite rare nowadays.

If you like it, we can collaborate to develop a PCB and have it manufactured. The original design was created by engineer Dmitry Starodub.

View attachment 145741

[I’m presenting a carefully reworked version of an old Russian DIY radio project] -- And, shown below.....I am presenting a freshly drawn CAD-captured schematic recreation of your vintage Russian schematic. And, while I have gone to great lengths to make this schematic shown below as accurate as possible, I am in no way, shape, or manner making any claims whatsoever that the schematic as is shown is completely and totally "error-free"!!! In fact, I -- KNOW -- that it has some errors because I both cannot read Russian nor could I occasionally not decipher what was shown within the original schematic, so.....I just made a "best educated guess" at what I couldn't clearly read.

However, my schematic version is primarily -- just a starting point -- for @Neperdun or anyone else who wishes to chime-in, to help in offering ideas/recommendations/suggestions to the values of the components used within this schematic or the types of parts that could/should be used, such as all of the transistors. As the comments and suggestions are posted here, I will then make updates to my schematic version until no further changes and/or updates are necessary.


>> @Neperdun -- In addition, within your initial circuit description posting up above, you go into a fair amount of detail about the construction of the "toroid inductors". There are a few members on this forum who appear to not only have the specialized expertise in manufacturing and winding inductors and transformers, but they also have the specialized equipment to do so.

Based upon this, I would suggest that you search out these members and contact them in order for you to find out what it will take and what the cost may be of having 1 or 2-dozen of each value inductor made to your specifications for a future "group-buy" for those members on here who may have an interest in building this circuit. It shouldn't be too hard to search and learn who these particular members may be. I have personally seen their response postings in other threads here, but I don't recall their names.

>> WATCH THIS SPACE FOR FUTURE DEVELOPMENTS!!! <<

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[abbey road d enfer]

I believe the orientation of Q1 is wrong. I think its source is up (connected to R4, R5 & R6, and its drain to ground, in order to function as a voltage follower.

 

[Neperdun]

I'm impressed! You’ve done an incredible amount of work! I would sincerely love to collaborate with you again! @MidnightArrakis

I just ask you to correct one mistake: the circuit is designed with a common + (unlike the traditional common -).
Please correst output

 

[MidnightArrakis]

I believe the orientation of Q1 is wrong. I think its source is up (connected to R4, R5 & R6, and its drain to ground, in order to function as a voltage follower.

[I believe the orientation of Q1 is wrong] -- THANK YOU!! See the updated schematic and PDF file in my Post #23.

Anything else???.....

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[MidnightArrakis]

I'm impressed! You’ve done an incredible amount of work! I would sincerely love to collaborate with you again! @MidnightArrakis

I just ask you to correct one mistake: the circuit is designed with a common + (unlike the traditional common -).
Please correst output
View attachment 146995

[the circuit is designed with a common + (unlike the traditional common -)] -- While I "somewhat" understand what it is that you are saying in your response, you will need to -- show me -- what it is that you are describing in your markup of my schematic. In addition, all of the "Pad Numbers" shown within my schematic are the "Pad Numbers" referenced to the PCB edge-fingers of the "500-Series" modules as is shown below. If you could please be so kind as to provide me with a list of how the pads within your schematic coincide with the "Pad Numbers" shown in the "500-Series" edge-finger assignments below, then I can update my schematic accordingly.



[@[B][SIZE=5]inf0[/SIZE][/B] -- I would love to do the front panel design for it!] -- I've already got that covered here on this little project. SORRY!!! While this is still a -- work-in-progress -- as I am still refining the components and various mechanical design details, here is what I have come up with so far:

>> WATCH THIS SPACE FOR FUTURE DEVELOPMENTS!!! <<

>> BASIC FRONT-PANEL SHEET-METAL DESIGN

>> FRONT-PANEL & PCB ASSEMBLY ORTHOGRAPHIC VIEW


>> EXPLODED MODULE ASSEMBLY VIEW ------------------------------------ >> FRONT-PANEL REAR ORTHOGRAPHIC VIEW


>> FRONT ORTHOGRAPHIC MODULE VIEW WITH TRANSPARENT FRONT-PANEL


>> FRONT-PANEL & PCB SIDE-VIEW WITH TRANSPARENT FRONT-PANEL (YEAH!!!.....I KNOW, I KNOW, I KNOW!!! It's still a "work-in-progress, OK???):


>> MAIN CIRCUIT PCB ---------------------------------------------------------------------------- >> FRONT-PANEL PCB

>> ANYONE???.....

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[abbey road d enfer]

View attachment 146998

In the schemo in post #23, the junction of R19/R20RC10 goes to pad 14 ("500 -16Vdc"). Not pad 12.
The polarity of C10 should be reversed.

 

[MidnightArrakis]

In the schemo in post #23, the junction of R19/R20RC10 goes to pad 14 ("500 -16Vdc"). Not pad 12.
The polarity of C10 should be reversed.

[the junction of R19/R20RC10 goes to pad 14 ("500 -16Vdc")] -- Updated!!! THANKS!!!.....

[The polarity of C10 should be reversed] -- I've always had a problem with European schematic symbols. C10 has been flipped over.

THANKS!!!.....AGAIN!!!

>> Post #23 has been updated to a "REV-3" now.

Any comments about the mechanical design and/or PCB-shape details?

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[inf0]

@MidnightArrakis I would personally add the bypass(?) button at the bottom , but you guys know better ! Strictly out of ergonomic / visual aspect

More bands would be awesome if it can be done!

 

[abbey road d enfer]

More bands would be awesome if it can be done!

It's easily feasible, but it may come at the cost of increased noise and a readjustment of bandwidth.

 

[inf0]

It's easily feasible, but it may come at the cost of increased noise.

Interesting , learning every day !