Reddish 500 EQ

[JMan]

Ian,

You are of course correct!

Since it is fed from the input transformer in this case, I suppose what I'm trying to determine is whether I should leave it as a fixed resistor or if I should make it easy for people to play around with the value by using a trimpot - the builder will know better than I what their variables are (even the simple question of whether they are using the Carnhill or UTM transformer, which each have slightly different DCR, I believe).

Personally, this is a little fussier than what I'd want as a builder and I'd probably just leave it at 2k4 and be done. But I can imagine someone who wanted a very particular response and knew they would almost always be feeding it from, say, their soundcard, that person might like to be able to easily adjust a trimpot upon testing to achieve that goal.

Hopefully we'll get some input from potential builders here! If not, I'll just leave it as is.

As always Ian, thank you - your expertise is deeply appreciated and it is why this project even exists at all!

 

[SIXTYNINER]

Hi Everyone,

I'd like to share one of my latest projects with you all. I present the "Redd-ish 500" EQ, a 500 series equalizer based on @ruffrecords amazing work. After building a standalone "RS127 Brilliance Control" box awhile back, I wanted to build a more robust version of the eq in a compact format. This version of the passive equalizer features the Bass and Brilliance sections of Ian's own Redd EQ with an added frequency point in the Brilliance section at 7.2k, and a pushbutton option to engage a treble boost based on the treble control section of the original circuit (the amount of boost is selectable between 2 and 4 dB via a shunt on the circuit board). The makeup amplifier that follows the eq also comes from Ian, and is based around a Burr Brown OPA2134 driving a 600:600 output transformer. I also included a relay-controlled true bypass.

I've used a UTM 2571 on the input, along with their multi-tap inductors in the EQ circuit, and a Cinemag CMOB-3S output transformer. PCBs and mechanical layout are my own, and the front panel was designed by me and produced by the ever-outstanding Frank at frontpanels.de.

Lots of lessons learned along the way here, including "you can't always guarantee that a manufacturer's mechanical drawing and dimensions are 100% precise" and "holy cow, don't ever get yourself into a position where you need to remove an already-soldered Grayhill switch from a PCB."

I can't thank Ian enough for his patience and generosity in answering my questions and giving suggestions. He is a true gem of this forum.

Please enjoy the photos! Just know that in the photos with the front panel, the panel is only loosely affixed (I was still futzing around with things), so you might notice that the metal parts look slightly askew.

Nice Job Jman !

With other 3.4 boards,
each with different frequencies it would become a very so cool multi-band eq.
cheers

 

[HerbertR]

Yes, project completed. As Ian mentioned, the 10k:10K TX Carnhill 9071 (175:175:230:230 DCR Ohm) and 10K:10K UTM 2571 (330:330:400:400 DCR Ohm) inputs are slightly different. So I couldn't get the 10dB gain at the max setting, only 8dB, also the curves were slightly wider compared to the RS127 Rack/Grey plugin. So I set the input resistance to 1K instead of 2K4 Ohm. At 0 Ohm/shorted I get about 12-13dB gain, a little bit too much. I think when you build such high quality EQs you should take the time and trim them to perfection.

I have all the transformers from Igor UTM, including the output Tx. Igor can deliver the fitting size, corresponding to the UTM3523LP laminate size, also with 600:600 ohms. The frequency response with the neutral setting and activated EQ of the entire circuit is excellent from 20-20 KHz. There is not much to say about the sound - an ultimate bomb... The "grey" plugin actually sounds pretty good and very similar, but the hardware here is clearly a step higher. The sun is rising... What else can you expect from this HQ component setup and Ian's scheme... Frank from frontpanels.de supplied the L-bracket and the front panel (my panels are UV-printed on black anodized aluminum), most of the mechanical parts,.. are from Digikey (all 71BDF Grayhills are in stock), the Stockli triangle knobs in black can be bought cheaply from Tayda Electronics in Thailand. I am personally a big fan of old NOS Styroflex Caps as you can see... Many thanks for porting Ian's Redd EQ to the 500 series ... Cheeers

 

[Murdock]

Yes, project completed. As Ian mentioned, the 10k:10K TX Carnhill 9071 (175:175:230:230 DCR Ohm) and 10K:10K UTM 2571 (330:330:400:400 DCR Ohm) inputs are slightly different. So I couldn't get the 10dB gain at the max setting, only 8dB, also the curves were slightly wider compared to the RS127 Rack/Grey plugin. So I set the input resistance to 1K instead of 2K4 Ohm. At 0 Ohm/shorted I get about 12-13dB gain, a little bit too much. I think when you build such high quality EQs you should take the time and trim them to perfection.

I have all the transformers from Igor UTM, including the output Tx. Igor can deliver the fitting size, corresponding to the UTM3523LP laminate size, also with 600:600 ohms. The frequency response with the neutral setting and activated EQ of the entire circuit is excellent from 20-20 KHz. There is not much to say about the sound - an ultimate bomb... The "grey" plugin actually sounds pretty good and very similar, but the hardware here is clearly a step higher. The sun is rising... What else can you expect from this HQ component setup and Ian's scheme... Frank from frontpanels.de supplied the L-bracket and the front panel (my panels are UV-printed on black anodized aluminum), most of the mechanical parts,.. are from Digikey (all 71BDF Grayhills are in stock), the Stockli triangle knobs in black can be bought cheaply from Tayda Electronics in Thailand. I am personally a big fan of old NOS Styroflex Caps as you can see... Many thanks for porting Ian's Redd EQ to the 500 series ... Cheeers

Really nice build! Congrats!
Did you buy directly from Tayda Electronics?
How was your experience with them?

 

[HerbertR]

Really nice build! Congrats!
Did you buy directly from Tayda Electronics?
How was your experience with them?

Tayda is great. I bought x-times from them. Very good shop and fast delivery at least to Austria/EU with about 2-3 Weeks. But there is a minimum value to order and import fees / Tax are also to pay, like always.

 

[JMan]

I'll echo what Herbert said. Tayda is great. I have heard that their IC selection is a mixed bag in terms of reliability, and although I've avoided ICs from them for that reason (and because I can get most of those from other sources), everything else I've ever ordered from them has been good quality for a good price.

 

[MidnightArrakis]

caught a missing trace that will be dead simple to add

[caught a missing trace] -- WOE be to those who do not listen!!!.....

In all of my previous response comments I have made to you within this thread, I have offered -- TONS -- of PCB-design guidelines, information and techniques!!! And, I have offered you the opportunity for me to only only review your KiCAD PCB-design file, but to also run your GERBER and N/C Drill data files through my "GERBER Analyzing & Editing" program!!! All of this would have caught your missing trace and more than likely would have also probably exposed many other issues within your design that you aren't even aware of!!! But.....who in the heck wants to listen to some "Old Fart" who has been designing PCB's and electronic equipment for over 40-years??? Nobody here.....that's fer sure!!!

And.....I also bet that you didn't run a "Back-Annotation / Forward ECO" routine on your design either, right??? That right there would have caught your missing trace before you even generated your GERBER files!!! But, what do I know?

Offer still stands, though.....

/

 

[JMan]

[caught a missing trace] -- WOE be to those who do not listen!!!.....

In all of my previous response comments I have made to you within this thread, I have offered -- TONS -- of PCB-design guidelines, information and techniques!!! And, I have offered you the opportunity for me to only only review your KiCAD PCB-design file, but to also run your GERBER and N/C Drill data files through my "GERBER Analyzing & Editing" program!!! All of this would have caught your missing trace and more than likely would also probably exposed many other issues within your design that you aren't even aware of!!! But.....who in the heck wants to listen to some "Old Fart" who has been designing PCB's and electronic equipment for over 40-years??? Nobody here.....that's fer sure!!!

And.....I also bet that you didn't run a "Back-Annotation / Forward ECO" routine on your design either, right??? That right there would have caught your missing trace before you even generated your GERBER files!!! But, what do I know?

Offer still stands, though.....

/

Well, Midnight, I guess you don't remember that when I started this project a year (or more) ago, I did converse with you through PM about helping me, and even sent you my files as they were at that time. The design wasn't in its best shape at that time, admittedly, so you were generous enough to provide me a critical reply much like the one you've given here, but never gave me any specific or useful help -- just told me I was doing it wrong and that I should know how to do it better. In the end, I brought this project to fruition through my own hard work and the help of a few select individuals who gave real assistance. The one missed trace had nothing to do with back-annotating, because I in fact missed it when drawing the schematic -- no Gerber analyzing software was going to catch this baked-in human error, regardless of how many thousands of dollars you paid for it. I respect your expertise (I'm nothing more than an amateur hobbyist), but given that you had the chance to help right from the start and instead offered nothing more than pedantic admonishments, I don't know that coming in now to clutter the thread with no less than sixteen video links and then criticizing me for doing my due diligence by having Herbert lend me a second pair of eyes is a very tactful move.

Now, maybe we can move away from this unpleasant side conversation and refocus the conversation. I have made the corrections to the board that I mentioned earlier, and am going to give it a final once-over this evening. After that, I'll get an estimate of cost, and hopefully by tomorrow I'll be able to post here with that info and start taking names of those who would like PCBs.

 

[JMan]

Hello everyone!

I took some time to check things over last night, as well as to look into cost. It looks like I'll be able to do a set of boards (a single channel involves a main board and three auxiliary pcbs) for $20 USD, and that could even come down a bit depending on how many folks join in. To keep the cost down, I will only have the main board manufactured with the ENIG gold plated finish (essential for the 500-series backplane connector), but will have the aux boards done with HASL, which is less expensive and likely what you're already accustomed to seeing on your PCBs. Otherwise the cost nearly doubles, rather needlessly in my humble opinion.

I will need to get shipping estimates once I have a sense of where I will be sending boards. For reference, the cost to ship boards to Ian in the UK and Herbert in Austria came out to ~$45 USD in each case. Shipping within the States will obviously be less, and shipping elsewhere in the world might be the same or more. This was the least expensive option I could find, but since I know we have members here who have more experience shipping things internationally, I'd be open to any pearls of wisdom you might have!

So I guess this is it! I will start taking names of those who would like to purchase PCBs. For now, I'm going to limit this to a single run of boards. I do not know if this is something I will do more than once, so if you have the interest and the means, please heed that disclaimer. Send me a PM or leave a post below expressing your interest and how many sets of boards you'd like to have. I'll keep it open for two weeks (ending April 10th), at which point I'll finalize the list and we can move forward with next steps!

 

[keninverse]

I’m in for two sets.

 

[nielsk]

I'd be up for one (better make that two!), will there be something worked out with Frank to get front panels and sleds?
If there is enough interest stateside, it would be good to do a group buy on the parts that have to be shipped internationally...

 

[JMan]

I'd be up for one, will there be something worked out with Frank to get front panels and sleds?
If there is enough interest stateside, it would be good to do a group buy on the parts that have to be shipped internationally...

I have provided Frank with the files for the front panel and L bracket, and he has already added them to his online shop (I'll link it in the BOM). The project also uses a small right angle bracket available from him. You can add everything needed on the same page of his shop.

My front panel file specified powder coating as the finish, but as you can see in Herbert's post, he ordered them with anodized aluminum instead and they still look amazing, plus I believe this will reduce the cost a bit, so keep that in mind when communicating with Frank about your order. I think either option is great, I just have a personal preference for the look of powder coating.

 

[TimG]

Please put me down for 2 sets! Thx!

 

[noizetoys]

I'll take two sets.

 

[oldskool1]

I'd like 5 sets please.

 

[MidnightArrakis]

I will need to get shipping estimates once I have a sense of where I will be sending boards.

>> I "could" put you in touch with some low-cost "International Logistics" companies, but...............I don't feel like being shredded again!!! I've done over $3,000,000.00 (i.e., 3-million) dollars worth of "Electronics Purchasing".

/

 

[afdobbert]

Hey!

I'm excited for this project - please put me down for 4 boards. Thanks!

 

[NOON]

I'm interested in a pair. In Melbourne Australia, I'll see if I can round up a few others to share postage costs

 

[NOON]

I'm interested in a pair. In Melbourne Australia, I'll see if I can round up a few others to share postage costs

Got least one more pair, potentially more.

 

[dirtfish]

I am in for 2 sets