Stereo 1176 support - Mnats/Hairball

[dmnieto]

I have a question concerning my board....

While I understand that switching in a .22uF capacitor instead of C27 will increase the attack time to 8ms, I wonder what would be the effect on the release times... Will it be increased as well? Has anybody done an approximate analysis of the time constants in the circuit? Because I would like to increase the attack time without affecting the release too much.

 

[dmnieto]

well, this is the horrible board I have managed to design. I am about to order a prototype of 3 to oshpark unless somebody points me and obvious mistake or a useful optimisation I can do.

Just for info, this is supposed to complement the current stereo kit.

INSERT pad goes to mnat's LOOP
LINK goes to LINK.

15 goes to pad 15, and GR goes to the ratio board.

The meter options change, instead of X/Y you connect M+ to Y on the meter and ground to the X.

This is the OshPark link http://oshpark.com/shared_projects/ADhDjUwa but of course I won't recommend that anybody tries it till I somehow test it :S

 

[dmnieto]

BTW, I will have one extra of those boards... anybody wants it?

 

[dmnieto]

Ok, I got the first prototype boards... last week. I am sending the final design to the board. BTW, this board won't be for sale, but I will put all the gerbers and design files for the grabs if somebody wants them.

Attached the schematic

 

[Piotr]

Hi to all of you !



Having built a stereo rotary version of the 1176 (Mnats boards) and trying to fit it with Hairball's stereo linking pcbs, I've run in the exact same issues stated by Ricothetroll in the official Hairball thread. Stereo switch engaged nulled the ouput to almost nothing...

I've successfully rewired my unit using his drawing so big thanks to him for pointing me in the right direction and helping me understand the issue.

Here's the unit which still needs a little cosmetic work, but is calibrated and works as it should !

Thanks Rico !!!

Piotr.

 

[adrian]

well done Piotr!

ce serai cool qu'on se fasse une session test un de ces 4!

 

[dacapitan]

https://www.wuala.com/ricothetroll/public/Stereo-Link_wiring.gif

From what I am able to tell, according to this diagram, when hooking up the stereo link boards, the only shielded wire required is between pad 17,15,16 and the output pot. The remaining Loop, Link etc. do not need to be shielded, and may be connected using regular hook-up wire?

If shielded wire is required on the loop and link pads, where are the shields connected to? To eachother, cut away, to chassis star ground?

Ive seen many variations of the original, so I am a bit confused as to the correct shielding?

Any clarfication would be much appreciated

 

[dmnieto]

I realize that I have not given an update on the relay board.

The relays work, there is no motorboating (coupling between input and output) and the HPF work as well. The only thing I have not tested is the send/return sidechain, but I have bench measured it and it is ok too.

The only thing is that I am probably provide a new layout. The issue is that there is only one GND pin on the board, and that makes quite challenging nailing the grounding. It is possible, but a pain in the arse to do it properly, i'd like to save the community the nuisance.

The new board will split K101 in two connectors, one with M and GND and the other with +30V and GND.

There will be also GND pins in K103 and P103 (and you really want those if you want to do any sensible shielding)

There is something else, I don't know if anybody would care though.
Upon engaging the bypass relay, the output transformer is disconnected from the XLR, which may cause some load imbalance on the output transformer, so it may be a good idea to terminate the output xfer with a resistor.

Also, and this may be more of an issue, is that upon enabling the bypass, the input is still connected to the input xfr so you will have impedance losses compared with a loopback if the output impedance of your source is not very low. This loss is negligible on the low impedance outputs of my wife's focusrite interface, but it is of about 4dB on the 320Ohm output of the ada8824.

 

[dacapitan]

I finally finished this build, completed the calibration process fine, the unit passes clean audio, no noise etc. every thing seemed to be going fine but I have run into some problems

On both channels, when Ratio of 4 or all (slam) is selected - Meter in GR mode, the VU meter goes all the way to the far right and it seems that there is no Gain Reduction when ratio of 4 or all (slam) is selected (8,12,20 work fine) (+4 VU meter mode works fine/shows level when 4 or slam is selected)

I think this has something to do with the Ratio Swtich, but I wired it according to http://mnats.net/1176_slam_mode_rotary.html - but I must have done something wrong for it be the same problem on both channels

Any ideas of what to do, where to start? - so close but yet so far!

 

[dmnieto]

So finally I managed to finish my dual rev D stereo with the following modifications:

- True bypass with relays.
- Addition of the super-slow attack switch and the ratio 2 (it has ratios 4, 8, 12, 20, SLAM and 2).
- Buffered metering.
- Side-chain high-pass. (with relay switch)
- Side-chain send-return. (with relay switch)
- Link mode (with relay switch)

Oh boy this has been difficult... I had to design and re-spin boards, prototype, sort out routing and grounding schemas, drill more holes than I thought possible, and solder lots of small SMD parts,... But yeah! It works and sounds great!. The feeling of actually designing even a part of it by yourself is very rewarding when it finally works

With the mess of routing I made I am surprised there is no noise, or motor-boating, or oscillation ( even If I know the relays help)... I have to thank mnats, mike, dan and everybody in this thread for their help and for making something like this available to everybody.

Unfortunately Purple Audio vetoed the sharing of the schematics and the gerbers of the add-in board (as it is their right), but I still have 12 (unpopulated) boards around here if somebody else wants it (but I warn, this has been the most difficult build I have ever done... oh my god the smd parts). I can also describe how I added the 2:1 ratio to the rotatory version (having 5 ratios + slam) and the simple fix that is to add the super-slow mode.

So pictures here:



My wife is really digging the combination of super-slow attack, fast release, 2:1 ratio and hpf sidechain as a master bus compressor

 

[dmnieto]

transformers and stereo boards are placed under the main pcbs, the grounding is strictly not purely star grounding but a two-point tree grounding (as I wanted to keep both boards separated). There is also a sheet of mu-metal under the right-channel.

 

[hymentoptera]

dmnieto, why the orange drops on one channel, and WIMAs on the other? Is that just what you had on hand. or were you looking for different flavors? Why else is diff between the two channels?

Is there any different in sound at all between the two? I'm guess no since this is a stereo unit? Some of us are going out of the way to choose particular caps, especially those doing coupling duty between various stages, so I'm curious as to the what, why and how for different capactitors in the 1176.

 

[dmnieto]

dmnieto, why the orange drops on one channel, and WIMAs on the other? Is that just what you had on hand. or were you looking for different flavors? Why else is diff between the two channels?

Oh I was just experimenting with the sound, the rest on both channels is identical. Transistors are matched within 1% of each other. Resistors. specially on the sidechain and the ratios are matched to 0.1%.
In testing, both channels differ within <0.2dB for all ratios.

[quote author=hymentoptera]
Is there any different in sound at all between the two? I'm guess no since this is a stereo unit? Some of us are going out of the way to choose particular caps, especially those doing coupling duty between various stages, so I'm curious as to the what, why and how for different capactitors in the 1176.
[/quote]

There is a slight difference in tone actually, the right channel is a bit more forward and edgy than the left. The left one is warmer, I planned to experiment a bit more, but my wife liked that she could have such a small difference in tone available.
In any case it is so, so close that you can actually use them as a stereo pair.

I can actually do some comparisons feeding the same signal to both channels (and a rev f clone) so you can hear it. Do you have any wish-list on the kind of instrument/sound and compressor settings that you would like me to run?

 

[hymentoptera]

...it is so, so close that you can actually use them as a stereo pair.

nice  8)

I can actually do some comparisons feeding the same signal to both channels (and a rev f clone) so you can hear it. Do you have any wish-list on the kind of instrument/sound and compressor settings that you would like me to run?

not particularly. I was just curious is all. Thanks!

 

[critterkllr]

The price to make a stereo unit using Dan's case and a mono unit using the Hairball case aren't very far apart. It ends up being $600 for single channel vs under $800 for a stereo unit.  If my end goal is to end up with two 1176s, is there any reason to not go the stereo single enclosure route? It seems so much more economical, but I'm wondering why everybody doesn't just do it?

 

[dmnieto]

The price to make a stereo unit using Dan's case and a mono unit using the Hairball case aren't very far apart. It ends up being $600 for single channel vs under $800 for a stereo unit.  If my end goal is to end up with two 1176s, is there any reason to not go the stereo single enclosure route? It seems so much more economical, but I'm wondering why everybody doesn't just do it?

It took me a day to build the mono version, months to build the stereo :S

 

[critterkllr]

It took me a day to build the mono version, months to build the stereo :S

Yours was pretty heavily modified right?

 

[dmnieto]

It took me a day to build the mono version, months to build the stereo :S

Yours was pretty heavily modified right?

To some extent, true. But what I want to make clear is that is far more complicated to build the mono than the dual as the mono comes neatly packaged and ready, and there is much more planning in the stereo version

 

[velo-hobo]

Hey all,

Built a mono Rev A from Hairball last fall and it came out great.  Now I'm jumping in with both feet and building two stereo Rev A units and one stereo Rev D - just got enclosures from Dan, boards from mnats, and the stuff from Hairball is in the mail.  I'm putting together a massive Mouser order for most of the remaining bits and I have a question about which rotary switches to get.

I found the Lorlin 4-pole 3 position switch for the metering selector but for ratio, the Alpha 5-position 2-pole that I see on the mnats site and elsewhere (SR2921F-0205-19R0B-E9-S-W) is out of stock at Mouser til late July, and I'm hoping to get these well on their way before then.

Any suggestions on a good alternate that you folks know of?

thx,
Aaron

 

[dmnieto]

Use the six positions one

http://www.mouser.com/ProductDetail/Alpha-Taiwan/SR2921F-0206-19R0B-E9-S-W/?qs=sGAEpiMZZMvNbjZ2WlReYnqYHrQfuERsVYNhUxQIdK0%3d

You can even wire a 2:1 ratio on the last one as I did...