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DONE PCBs ordered. Yet another Moog 914 clone...
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dingebre



Joined: Aug 10, 2008
Posts: 270
Location: Salt Lake City, UT USA

PostPosted: Tue Jul 02, 2013 12:31 am    Post subject: DONE PCBs ordered. Yet another Moog 914 clone... Reply with quote  Mark this post and the followings unread

Update 6/15/2020
I updated the web site's 914 FFB pages. Please see the website for details.

Basically:
1. I have re-done the inductor PCB design to work with CineMag inductors. They did the inductors for the Moog modular reissued systems. Please PM me if you want to use them.
2. I found a couple more errors on the Norlin schematics and have offered some corrections. They are very simple. Change a resistor on the I/O PCB, eliminate a couple of capacitors with jumpers and eliminate some resistors on the I/O PCB.
3. On the inductor, I recommend increasing the LP filter capacitors to 1.22uF with a 1uF and a 0.22uF.
4. On all versions, I recommend changing the HP filter capacitors to 2nF with two 1nF capacitors.

Again, details on the web page:
http://analoguerealities.com/projects/fixed-filter-bank-914

I added more photos, added more information regarding calibration, and other stuff.


Update 12/17/2014

My new web store is the best place to buy the PCBs. Start at:

www.analoguerealities.com

click on the Catalog and SDIY "key", navigate the menu to the Moog modules, 914 FFB. It's the only one right now, so should be easy. The checkout is through PayPal.

David

*************************************************


Good news, the GIC and Inductor versions are both finally working. I ordered PCBs today. If anyone is interested in buying a set, email or PM.

GIC - $70.00 per set (A little expensive, but they are 4 layer PCBs to minimize noise and hum)

Inductor - $50.00 per set (Will work with either the large or small core 5 Henry inductors Carsten has made)

A couple of quick comments on construction. I'll put more detail together if people buy the PCBs.

A set consists of 4 PCBs, a top, middle, and bottom PCB adn an I/O PCB which mounts to the bottom filter cell PCB. They have PCB mounted pots, Panasonic EVU-E2JFK4D54, DigiKey P3U0503-ND. You will most likely need to trim the shaft a little depending on the knob you use. the HP and LP pots are not PCB mounted and can be any smallish panel mount pot. I've calculated the values for the capacitors which are on the silkscreen. There are two choices, one for an "exact" cutoff frequency, one that pushes the cutoff either up or down about 6% to mimic what it appears Moog did (as well as Jurgen Haible on his version).

The construction is not bad. The calibration is the problem, here. Ideally, you want the overall "Q" to be about 3.7 (per Yves Usson's testing of an original 914). The trimmers will adjust that, but it's not so straight forward to tell. I've just set my trimmers to point to about 10:00 or 11:00 and the result is very pleasing. you don't want too high a "Q" or you lose some of the harmonics between the cells. Too low and you miss the nice resonance when the input attenuator is fully CW.

Be warned, both versions are kind of pricey to build. For the inductor version, you need a set of Carsten's inductors. for the GIC, you need 29 of the best, lowest noise, op amps you are willing to buy. I ended up using the OPA2227, about 4.50 each for 10-99 pieces. Probably way overkill. Jurgen used an MC4558 at about $0.40 depending on the exact one you pick.

So, enough for now. Please feel free to contact me if you are interested. I've got about 2 weeks til the PCBs are in. In the mean time, I'll work on a BOM and some construction notes.


END EDIT
#################################################


OK, so I built 3 of Yves Usson's EXCELLENT 914 clone modules:
http://yusynth.net/Modular/index_en.html
Thank you Yves.

I purchased 2 sets of PCBs for Jurgen Haible's version:
http://www.jurgenhaible.org/ffb/fixed_filter_bank.html
Thank you Jurgen, rest in peace...

and I've studied the version Carsten Toensmann created:
http://www.analog-monster.de/mmt914_en.html
Thank you Carsten. Also, Carsten is offering real inductors of custom values, particularly the ones needed for the Moog 914.

Despite all these excellent and well done versions, I still wanted one that was laid out to fit in euro rack panel, pots on the PCB to minimize flying wires, and the ability to easily use real inductors should I find a source... I DID find a source! Carsten Toensmann will hand wind inductors! Please check his site for information and all that.

So, now more than ever I want a PCB set that has the Moog I/O circuits and real inductors. There may be a difference because I believe the Moog inductors were toroids and I believe Carsten's are cylindrical. Other more bright people than I can comment on whether or not that matters.

I'm struggling with the idea of offering these for general consumption because I do not want to step on anyone's toes, especially Yves, Jurgen, and Carsten. While virtually all of the design will be unique, it will also resemble Jurgen's and Carsten's closely by necessity (at least at the schematic level not at all at the PCB layout) and borrows ideas from Yves' design. So, if anyone thinks I'm out of line, I won't offer the PCBs, but will post progress and the learning experience at the least. I'm not making money on this stuff, believe me nor do I want or need to (I still have several thousand dollars of Synthasystem PCBs gathering dust in my basement to prove it Smile ) I just want to share some fun stuff and maybe make back some of the hard expenses of getting a PCB made and in hand... Back to the project.

So, understanding not everyone will want to buy the inductors or even like them, I also decided to have some type of active filter cells or simulated inductor based filter cells. I am pretty convinced I want to use an Antoniou inductance simulator [eg: Sedra and Smith, "Micro Electronic Circuits", Oxford University Press, 2010. Starts on page 1285] Jurgen took this approach as opposed to the Deliyannis multi-feedback structure that Yves used.

So, the ultimate question is what were the "selected" capacitors on the original 914 schematic? With some help from Yves (thank you again), some careful math, looking at the details of Jurgen's design and Carsten's design, and Yves' design, I think I have a handle on what the design goal was for the capacitors.

Please, please, please enlighten me if I am off base here. Selecting the capacitors ultimately has the biggest effect on the sound and behavior because all the other values are specified, and I want to get this right.

It appears the two sections of the cascaded bandpass filters are not tuned to the same center frequency. When I tune them to the same center frequency in SPICE, I get a response which doesn't resemble the SPICE simulations of the real inductors, or Yves' active cells, or Carsten's real inductors, or Jurgen's design either with simulated inductors or real inductors, OR the response published by Moog (see http://moogarchives.com/ Drill down to instruments then modules, then 914 and scroll down for the chart). Yes, I've spent way too much time puttering about in SPICE with this thing.

As of now, I am convinced the design goal was to set the center frequency of the first section in the cascade, with the higher inductance, to a frequency about 5 to 6% lower than the desired center frequency for the given cell and the second section in the cascade to about 5 to 6% higher. The result is a bandpass which has a wider pass band, but the desired center frequency. With these capacitor values, the response is very similar to Jurgen's and Carsten's. There are some subtle differences with Yves', but visually, it's close. Unfortunately, I can't hear it til I build it!

Bandpass done which leaves the high pass and low pass cells. Now, the high pass cell and low pass cell are different. The high pass cell is easily done with the above mentioned simulated inductors (or of course real ones). The capacitors can be selected to get a cutoff of about 7000 Hz by Yves' website or about 10000 Hz by Jurgen's or Carsten's designs (if I trust my math). It looks like both cells are tuned to the same cutoff frequency in this case.

The low pass requires a 'floating" inductor, that is, the coil is in series with the signal path and does not have one leg tied to ground. So, the low pass needs to be an active filter (Jurgen and Yves use a similar structure with different values for components) or I've read where using two Antoniou GICs back to back will simulate a floating inductor. So, 4 op amps instead of 2. I like the idea of inductors, real or simulated, so I'm tinkering with a simulated floating inductor. We'll see how it works out... I think the low pass cells shared the same design philosophy as the band pass cells. That is the first section has a lower cutoff, about 72 Hz, and the second cell has a higher cutoff, about 105 Hz for an average of about 88 Hz.

For the input, I'm going to have the Moog original, but also a transistor one with a bipolar supply source selectable with a DIP switch(s) on the PCB.

For the output, I am borrowing the idea of even and odd cell outputs from Yves because it is one of my favorite features of Yves' design; brilliant Yves, brilliant.

These outputs will have a simple non-inverting amplifier section with an active gain control.

The combined output will have the original Moog output amplifier section as well as the same "modern" amplifier section. Which one is in use will be selectable with a DIP switch(s) on the PCB.

Jurgen designed a faithful output amplifier section which I may just use rather than re-invent the wheel. A dilemma.

The input section will also have an active attenuator which will have it's own input jack to attenuate some of today's higher level signals particularly if you are using the Moog amplifier section. The design will be such that this input jack is switched out when you put a plug in the "normal" input jack.

One thing of note. The capacitors used really have to be selected. To that end, I will not specify capacitor values on the PCBs, but will have copious notes on how to calculate the values depending on the value of the simulated or real inductors.

I will do the same for the capacitors in the Antoniou GIC inductors, too. That way, you can make it any way you want it to be.

I will have some suggested values you can start with, in particular for the simulated inductors. But, to get that real Moog sound, you will need to break out your calculator, and with real inductors, an inductance meter to get the capacitors right.

OK, done for now.

I do not require pre-orders, or anything like that. When I do a project, I like to keep extra around and if I run out of PCBs (assuming they do get offered), I simply order more. I don't buy in a huge batch, typically no more than 50 at a time and I use PCB-Pool.com. They do a high quality job, they do it in a pool so I do save some money, and they accept a lot of different formats, including Eagle, so there you go...

I welcome comments and questions. Remember, I'm still developing the schematics, but the input/output, and the basic filter cell is done, I just have to duplicate and do the layout.

There will be 4 PCBs, uses Panasonic pots, similar to the ones Blacet uses but available at Digikey.com Panasonic #s EVU-E2JFK4B54,
EVU-E2JFK4D54, and EVU-E2JFK4D14. Transistors from Mouser, except the 2N2926 (I got a bunch from Hicham Dalbani at http://www.dalbani.co.uk/forums.html Great source for a lot of harder to find parts)

Other parts:
Inductors - Carsten Toensmann www.analog-monster.de . The only source I have ever heard of or found. I have two sets on the way and will let everyone hear who it compares next to Yves' module mostly because I have two of the three I built to compare with and Yves was able to compare and measure his against a real Moot 914, so it's the best test I can give it.

Everything else is standard type stuff.

David

_________________
David M. Ingebretsen, M.S., M.E.
Collision Forensics & Enginering, Inc.

dingebre@3dphysics.net
http://www.xmission.com/~dingebre/Synthasystem.html

Last edited by dingebre on Mon Jun 15, 2020 8:59 pm; edited 3 times in total
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LFLab



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PostPosted: Tue Jul 02, 2013 1:42 am    Post subject: Reply with quote  Mark this post and the followings unread

LOL! I also did a layout for a FFB a few weeks ago, used Juergen's discrete input/driver and discrete output. Mine is going to be 10 band.
All inductors (since I had a bunch of ferrite laying around, waiting for a project Very Happy )
Pots are PC-mount, I used Alps RK11K112. No experience with them, but they do have a nice feel.

Tested the input and output stages and these work like a charm (as you'd expect with something with that pedigree).

Good luck with your project!
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dingebre



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PostPosted: Tue Jul 02, 2013 3:07 am    Post subject: Reply with quote  Mark this post and the followings unread

LFLab wrote:
LOL! I also did a layout for a FFB a few weeks ago, used Juergen's discrete input/driver and discrete output. Mine is going to be 10 band.
All inductors (since I had a bunch of ferrite laying around, waiting for a project Very Happy )
Pots are PC-mount, I used Alps RK11K112. No experience with them, but they do have a nice feel.

Tested the input and output stages and these work like a charm (as you'd expect with something with that pedigree).

Good luck with your project!


Thanks! How did you decide what capacitor values you will use?

David

_________________
David M. Ingebretsen, M.S., M.E.
Collision Forensics & Enginering, Inc.

dingebre@3dphysics.net
http://www.xmission.com/~dingebre/Synthasystem.html
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LFLab



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PostPosted: Tue Jul 02, 2013 3:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

I am going to use the same values Juergen Haible did.
Bought big polyprop caps. Haven't decided on the type of inductors. I have a bunch of pot-core ferrite, but the original used toroidal inductors (not that it will matter much).

I can wind the potcores pretty easily, but the do need a lot of windings (the > 1H Probably need to go on a transformer core).
On the other hand, the toroidal cores are a royal PITA to wind but need far less windings. Decisions, decisions.
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dingebre



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PostPosted: Sun Jul 07, 2013 10:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

OK, so I've been agonizing over an inability to get the AC response for the bandpass cells to match that of the Moog filter (See www.moogarchives.com). I was able to find some photos of two different 914 modules and I noticed an additional resistor in parallel with the inductor/capacitor pair in the second second section of each cascaded filter cell. The value was different in each of the two modules, and I wasn't convinced of the color bands, but I found that adding a 5.6k to 6.8k resistor at this point brought the AC response right in line with the Moog and with Yves Usson's design (which Yves tested against a real 914).

So, the Moog schematic is incomplete and this resistor needs to be added to properly tune the 914 response.

At this point, I'm also going to use two Antoniou GICs back to back to simulate the floating inductor for the Low Pass, so if built without inductors, it will be a fully faithful simulation of the inductors for each cell.

I'm just waiting to get my inductors from Carsten so I can make sure the footprint I'm using is correct and I'll start laying out the PCBs.

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David M. Ingebretsen, M.S., M.E.
Collision Forensics & Enginering, Inc.

dingebre@3dphysics.net
http://www.xmission.com/~dingebre/Synthasystem.html
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jmejia



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PostPosted: Wed Jul 24, 2013 11:56 am    Post subject: Reply with quote  Mark this post and the followings unread

Lots of great info in this thread - thanks!

Anyone have any insight in to the commercial clones floating around? I wonder if any of them use inductors (seems doubtful), or if anyone knows how they stack up to the other clone designs?

The commercial clones I know of:
dotcom q127
COTK c914b
MOSLAB 914

Maybe there are more? (probably)
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dingebre



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PostPosted: Wed Jul 24, 2013 1:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

First, I got my inductors and they are amazingly small and compact. Great work Carsten! This will make it much easier to fit it all on PCBs which can fit in a moderately deep rack. On to PCB layout!

Next, to jmejia, in my research, I don't think any of the commercial versions use the passive RLC topology. But, it wouldn't hurt to double check with each of them. If you want the RLC topology, you will need to either wind your own inductors, or buy them from Carsten, which I highly recommend. Carsten is also selling his PCBs, but I think you will need to add that resistor discussed above to the band pass cells to get the proper response.

Last option, my design has now become so different than Jurgen's or Yves' that I will probably be offering my PCBs if you want a euro compatible design.

David

_________________
David M. Ingebretsen, M.S., M.E.
Collision Forensics & Enginering, Inc.

dingebre@3dphysics.net
http://www.xmission.com/~dingebre/Synthasystem.html
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jmejia



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PostPosted: Wed Jul 24, 2013 1:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

Great- I'd love to hear a demo - ideally of active vs passive versions Smile

I didn't realize Carsten was selling pcbs.. that's very promising indeed. I wonder what the differences are between his and Yves' version when built up with inducters.
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dingebre



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PostPosted: Fri Aug 02, 2013 2:35 pm    Post subject: Progress Reply with quote  Mark this post and the followings unread

I think I have everything mostly pinned down. There will be four PCBs, three will have the filter cells, and one will handle power and I/O. I am using the Moog input and output amplifiers with the choice of using an extra output amplifier with gain control so the levels can be boosted to those in other modern systems, and the choice of using a buffered input with attenuation or directly into the Moog input amp.

It's pretty easy to saturate the Moog output amp, so I added a clipping indicator so that I can adjust the input attenuation to prevent clipping. I also added outputs for the even and odd cells separately, each using a Moog output amplifier to maintain the same signal path as for the main output. The only difference is I added a high impedance voltage follower in front of the Moog amplifier so these extra output stages don't load the filter cells and change the behavior.

I'm attaching the current MultiSim model as well as a shot of the AC response, as well as the Moog published response for comparison. I think it's a good match. The "Q" of each cell is around 2.7 to 3.0 give or take and I think the relative gain and output is good.

I'm just going to be laying out the PCBs now, so prototype is about a month or two away.


simulation.jpg
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Moog published response of the 914 will all pots open
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Moog FFB simulation.zip
 Description:
Multisim simulation. You can connect the GIC "floating" inductor simulation for the low pass filter, or use the SPICE inductor model version. This simulation is to be used "as-is" with no warranty or guarantee it is correct or useful.

Download
 Filename:  Moog FFB simulation.zip
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David M. Ingebretsen, M.S., M.E.
Collision Forensics & Enginering, Inc.

dingebre@3dphysics.net
http://www.xmission.com/~dingebre/Synthasystem.html
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dingebre



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PostPosted: Mon Sep 30, 2013 5:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

OK, so an update for anyone who cares.

I've got the PCBs for Carsten's inductors laid out and ordered. I re-did the whole layout in DipTrace. Much better than Eagle in my opinion.

Next, will be a layout for GICs instead of real inductors for anyone who would rather go that route.

So, when they come and I can make time to build them, I'll post the results.

David

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David M. Ingebretsen, M.S., M.E.
Collision Forensics & Enginering, Inc.

dingebre@3dphysics.net
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dingebre



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PostPosted: Sun Mar 30, 2014 9:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

Time for a quick update.

I got a prototype all built and discovered inductors will do what inductors do and pick up every stray EM field in the universe! Smile Seriously, I puttheh prototype in my cabinet and discovered I can't move it far enough away from my open frame PowerOne power supply transformer to eliminate the hum. Sigh...

Despite the excellent inductors from Carsten Tonesmann (many, many thanks Carsten) I find I need to abandon my hope of an inductor clone of the 914. The cost and effort of a new power supply system and/or cabinet and rack redesign is far more than simply using a GIC paradigm which should be a very close emulation of the inductors minus the annoying "cons" of a real inductor.

I have now completed a layout for a GIC based unit using a GIC for each of the grounded inductors and a "back to back" GIC for the floating inductors in the low pass circuit. Circuit boards should arrive next week and I'll post the results. The simulations are very encouraging.

David

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David M. Ingebretsen, M.S., M.E.
Collision Forensics & Enginering, Inc.

dingebre@3dphysics.net
http://www.xmission.com/~dingebre/Synthasystem.html
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elmegil



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PostPosted: Mon Mar 31, 2014 10:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

What's a GIC ?
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dingebre



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PostPosted: Tue Apr 01, 2014 8:37 am    Post subject: Reply with quote  Mark this post and the followings unread

elmegil wrote:
What's a GIC ?

General Impedance Converter. There are several circuits to simulate inductors, but a couple of more popular forms are Riordan's simulated inductor and Antoniou's simulated inductor [see Analog Electronic Filters: Theory, Design, and Synthesis by Hercules Dimopoulos, Springer-Verlag 2012]. Basically using two op-amps, some resistors and a capacitor, you can simulate the impedance of an inductor and avoid the parasitic effects of a real inductor. You get the behavior of an inductor without the problems.

Both of these forms simulate an inductor with one side connected to ground. If you put two of these back to back (ground terminals connected), you can simulate a floating inductor.

Jurgen Haible used these in his 914 clone.

See attached image for the schematic of one of my filter cells.

David


GIC.pdf
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elmegil



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PostPosted: Tue Apr 01, 2014 4:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

Excellent, thank you for the explanation. Smile
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dingebre



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PostPosted: Fri May 16, 2014 11:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

OK, almost done. I'm waiting on the last iteration of the PCBs which get rid of all the input/output attenuators so I can actually spread out the controls more and actually grab the dang knobs and turn them without turning all the adjacent pots at the same time.

I'm attaching a first cut at the response plot. Note the fall off on the low end. There is a high pass filter with a cutoff of about 60 to 70 Hz on the input to the final amplification stage. After some discussion on the sdiy mailing list, I think it was added to the 914 (it isn't in the 907) to eliminate low frequency and sub-audio rumble to clean up the bass. But what do I know? Smile

So far as the sound, I'm very pleased. Side by side with Yves' version, they sound very much the same. I haven't formally "calibrated" it. I'm waiting for the final PCBs, but the trimmers seem to adjust the "Q" just as expected.

When it's done and really working, I'll post the DipTrace schematic, PCB drawings, and BOM for anyone interested.

David


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_________________
David M. Ingebretsen, M.S., M.E.
Collision Forensics & Enginering, Inc.

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LFLab



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PostPosted: Tue May 20, 2014 5:33 am    Post subject: Reply with quote  Mark this post and the followings unread

You really put a ton of work in this, David! Looks great!

I did a layout using PC mount pots, real inductors and Jurgen's discrete make up amp, it works fine, but I still need to wind inductors for it. Not too keen on doing so, after hearing your hum pickup story with the inductors.
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dingebre



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PostPosted: Tue May 20, 2014 5:43 am    Post subject: Reply with quote  Mark this post and the followings unread

LFLab wrote:
You really put a ton of work in this, David! Looks great!

I did a layout using PC mount pots, real inductors and Jurgen's discrete make up amp, it works fine, but I still need to wind inductors for it. Not too keen on doing so, after hearing your hum pickup story with the inductors.


Thank you for the compliment.

You may have different luck than I did. My power supplies use a standard transformer rather than a toroidal transformer and the power supplies are close to the modules. If you mount the module far away from the supply, you might be fine. Carsten Tonnesmann, from whom I bought my inductors, did not have any hum pickup problems.

You could always just wind one coil for one of the cells and see if it picks up any hum?

David

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LFLab



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PostPosted: Wed May 21, 2014 1:55 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, might give it a shot, I use standard 3u rack PSU's, and one of them is a switcher.
I might also have some shielding material (the thicker adhesive backed plastic stuff) around, so I could also make an enclosure for the coils.
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dingebre



Joined: Aug 10, 2008
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PostPosted: Wed May 21, 2014 9:22 am    Post subject: Reply with quote  Mark this post and the followings unread

LFLab wrote:
Yeah, might give it a shot, I use standard 3u rack PSU's, and one of them is a switcher.
I might also have some shielding material (the thicker adhesive backed plastic stuff) around, so I could also make an enclosure for the coils.


Be aware that the Norlin schematics are missing a resistor on the band pass cells that is parallel to the second inductor/capacitor pair to ground. This should be about 5.6k'ish to set the "Q" of the second cell to about 3.0.

There is also a missing resistor in the high pass cell again parallel with the second inductor and should be about 10k.

If you don' t add these resistors, the "Q" is too high and you don't get the appropriate AC response.

And, I think the input resistors to the band pass cells should be more like 4k7 not 47 k, and the high pass should be about 10k.

David

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dingebre



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PostPosted: Tue Jun 24, 2014 2:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

OK, after many, many hours and lots of prototype PCBs, I think I have a good handle on the filter. I just ordered what I hope is the final revision for PCBs for the GIC version. I went to some very extreme measures to minimize outside noise and hum pickup, like a 4 layer board, ulta low noise op-amps (OPA2227), etc. I think I can safely say any noise is due to the original filter design. I think the inter PCB connections carrying the summed output signals may derive benefit from shielded wires due to the low levels from the resulting summed filter cell outputs.

For comparison, I did some quick "ear" checks against my Yves Usson 914 filter clone and I was very happy. I'll work on some more analytical comparisons over the next week or so.

I need to think about the Inductor based version a bit more, but I think I have the final version of those PCBs ready to go, too. I will buy a set of last prototypes soon and will post here as soon as I have them built.

David

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David M. Ingebretsen, M.S., M.E.
Collision Forensics & Enginering, Inc.

dingebre@3dphysics.net
http://www.xmission.com/~dingebre/Synthasystem.html
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dingebre



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PostPosted: Fri Aug 01, 2014 1:00 am    Post subject: Hum GONE! Reply with quote  Mark this post and the followings unread

I stuffed the latest prototypes using Carsten's inductors and I re-did my whole power distribution. There is now no hum whatsoever and Carsten's inductors are great. I discovered one last "fitment" issue on the inductor PCBs and will order what I hope is the last set of prototypes tomorrow.

I also re-did the layout around the summing nodes and I think that has helped as well.

I will stuff the GIC prototypes tomorrow. I'm really quite pleased.

David

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David M. Ingebretsen, M.S., M.E.
Collision Forensics & Enginering, Inc.

dingebre@3dphysics.net
http://www.xmission.com/~dingebre/Synthasystem.html
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LFLab



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PostPosted: Wed Aug 06, 2014 6:13 am    Post subject: Reply with quote  Mark this post and the followings unread

thumright
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dingebre



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PostPosted: Tue Aug 12, 2014 11:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

Done...

Here are photos of the GIC version. I should have the final prototype inductor version tomorrow and I'll stuff as soon as I can. Work is ramping up and I'll be pressed for time. I think the low pass is a little hot, but that can be adjusted by making the summing resistor bigger. I'll try to get audio and a spectrum analysis posted as soon as I can make time.


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David M. Ingebretsen, M.S., M.E.
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LFLab



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PostPosted: Wed Aug 13, 2014 5:53 am    Post subject: Reply with quote  Mark this post and the followings unread

You probably have enough fixed filter modules now Very Happy
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dingebre



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PostPosted: Wed Aug 13, 2014 8:31 am    Post subject: Reply with quote  Mark this post and the followings unread

LFLab wrote:
You probably have enough fixed filter modules now Very Happy


Sigh... sadly, I still want more Smile

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Collision Forensics & Enginering, Inc.

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http://www.xmission.com/~dingebre/Synthasystem.html
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