Nyan 1073 EQ =^x^= (formerly Cheap's73 / Poor Man's 1073)

[shot]

Keep up the good work!
I'm following with interest

 

[grid_stopper]

definitely following these updates closely. really interested in trying this circuit out

 

[TheseGoToEleven]

In case anyone is interested, a simulation of the high/low shelving section of the EQ is available at the web version of the tone stack calculator. It defaults to 220Hz for the lows and 10k for the highs. But you can change that by entering in different cap values.

 

[krabbencutter]

Thanks for the info, that's really useful and in some ways even much more convenient than LTSpice!
Speaking of the shelving circuit: how could I reduce the maximum gain to +/- 12dB while keeping the original frequency response? If it was a standard tone control, I would just increase the 620R & 6.8K resistors. But because of the added low frequency bump/dip it's not that simple. And while I could try all sorts of component values until it kinda looks right, I wouldn't say no if there was some method to the madness

 

[TheseGoToEleven]

Thanks for the info, that's really useful and in some ways even much more convenient than LTSpice!
Speaking of the shelving circuit: how could I reduce the maximum gain to +/- 12dB while keeping the original frequency response? If it was a standard tone control, I would just increase the 620R & 6.8K resistors. But because of the added low frequency bump/dip it's not that simple. And while I could try all sorts of component values until it kinda looks right, I wouldn't say no if there was some method to the madness

Not quite sure I understand the goal. Would the desired effect be the same as limiting the potentiometer's range of motion, so that the user could not turn it to the extreme ends? If so, and if you plan to use a digital potentiometer to get recall on the eq settings, you could limit the effective range of motion programmatically while leaving the circuit unchanged.

 

[TheseGoToEleven]

By the way, I am curious whether 6.8K or 6.2K is the original value of the resistors on the low side of the shelving high/low. I have seen schematics both ways and photos of B205 boards both ways. It makes only a tiny difference to the curves but... Maybe the value got changed at some point during its production?

 

[krabbencutter]

By the way, I am curious whether 6.8K or 6.2K is the original value of the resistors on the low side of the shelving high/low. I have seen schematics both ways and photos of B205 boards both ways. It makes only a tiny difference to the curves but... Maybe the value got changed at some point during its production?

I was able to find three different revisions of the schematics.
1073-fullpak.pdf has the first B205 revision from Feb. 71 with 6k8 resistors. The B211 schematic seems to be the original revision from Dec. 70 and has incorrect pinouts on the T530 inductor.
This schematic has the second B205 revision from May 72. The resistors haven't changed but pins A&V have been swapped. The B211 schematic is from Nov 71 and has correct pinouts on the T1530 inductor.
Neve_1073_1084_User_Manual_Issue5.pdf has the latest B205 revision from Mar. 79 and includes the handwritten 6k2 resistor values. The B211 revision is from Jun. 75 and has an additional 220k resistor across the 450mH inductor tap.

The B182C schematic is identical in all three files and dates back to Jul. 71.

 

[krabbencutter]

Built a prototype today and it was a success. I initially planned to use the LM4562 as buffer & EQ amp while the GIC circuit would be built around a TL072. The LM4562 however created lots of interference and distortion, so I ended up using TL072s only, which worked much better.

(Because I was too lazy to build everything from scratch, I modified another circuit I had lying around. The blurred out part is just some leftover components I didn't remove)

 

[melmsmidth]

Hello, first post here...

I'm more a builder than a designer, my knowledge is quite limited yet. I was thinking of doing a "channel strip" with the Amek 2500 preamp on this forum as well, schematic here Cheap Nice and Funky Amek 2500 preamps followed by the NYAN EQ.

The preamp ends balancing the line and the EQ takes a non balanced input, my question is if it's good to taking the signal from the last buffer (IC28) on the preamp and add the driver it at the end of the EQ.

My purpose is to have some new preamp with eq for tracking (and mixing), but right now I must keep it cheap and that's why I'm choosing a transformerless preamp.

Any advice will be very welcome. And of course thanks to everybody here for the great loads of information that someone like me can read and learn a lor from!

 

[krabbencutter]

Sure, that should work.

 

[melmsmidth]

Sure, that should work.

Thanks!

 

[krabbencutter]

I'm finally in the mood for analog stuff again After playing around some more, I have settled for a textbook approach with equal resistance gyrators. Noise performance is still much better than the old gyrator implementation and the circuit needs way less components than my previous GIC approach. I've attached a (slightly convoluted) simulation file, where you can compare the original inductor, old gyrator circuit, GIC & new gyrator circuit.
You'll probably notice that the new gyrator implementation deviates more from the original inductor circuit, than the other implementations. That's because the capacitor values have been rounded to the nearest off-the-shelf component values. It should be no big deal though, because the reference target is an "ideal" 1073 with 0% component tolerance and even a brand new 1073 from the AMS factory will vary in its frequency response. On top of that the deviation from the "ideal" values is always within +/-5%. So if you want a close match, you could just buy a bunch of 10% tolerance caps and choose the ones that fit best.

 

[jhaell]

Nice work! Nyan EQ + Neve 1290 stage with UTM or Carnhill transformers would make a quite affordable channel-strip.

 

[audiomaker]

H folks, new audiomaker here.
This 1073 EQ Looks good - Well done.
Looking at the 'main' circuit diagram, just want to check pot wiring.
Can I assume turning a pot anti-clockwise moves the wiper(2) towards (1) and clockwise towards (3)?
thanks.

 

[audiomaker]

Anyone actually built this EQ? Just wondered how you got on. Still not quit sure on the pots...

TIA

 

[krabbencutter]

Hey, it's a bit embarassing to admit but I actually don't know how the pots in my own design are wired and even when I built it I had to rewire some pots after the fact

 

[audiomaker]

Ahh I see
I think with these kind of EQs when the pot wiper goes towards the input signal, that is'boost'?
So maybe RV1 is the wrong way.

 

[richiyobs]

hi folks ..... very cool project!
discovered only now and read with interest
is the attached the final version?

best
richi

 

[krabbencutter]

Small update: I'm still dedicated to improve the mid band and have ordered a T1280 and T1530 inductor from don-audio to better analyze the original RLC circuit.

 

[Ricardus]

I am eagerly awaiting the results of this project. I want to build about 1000 of these!