GroupdDIY 511 Racks: round 5.5 available

[rob61]

Just built my third rack, and I guess I've discovered the Xlr pin 1 / ground jumper issue mentioned above for myself. I mounted all the header jumpers on this one from the bottom to provide max clearance to accomodate a 500 module with metal housing. To check all solder points, I used my multimeter in continuity test mode. By touching the header pins I made sure none were shorted.

Next, I mounted the back metal panel to the XLRs and screwed all the screws in. I again tested for continuity... and found that the FEMALE XLR pin headers would always indicate continuity between pin1 and chassis. This would indicate that the use of headers on the FEMALE XLRs will not break the pin1/chassis connection even when put in the pin1/GND position. I assume the FEMALE XLRs must be made with pin1 connected to chassis and you can't override with the pin header setting. I noticed the MALE XLRs do not always have pin1/chassis connected. I think this is an XLR connector issue.

Therefore, it seems there is really no point in putting pin headers on the FEMALE XLR connectors as you can't override them and they will automatically be in pin1/chassis connected no matter where you put the jumpers. I don't know what effect this would have it you put the jumper in the pin1/GND position while the pin1/chassis is always connected.

 

[phasesonix]

Is there anyway to order the kit from the UK/Euro now that the website/email is down?

thanks

 

[abbey road d enfer]

Hi,
Volker suggested I post pictures of my 6-pack.
Done with a handsaw and a drill press from Volker's kit.

 

[abbey road d enfer]

And from behind.

 

[abbey road d enfer]

Now, with the PSU. It uses 4xSMPS and a DC/DC converter for 48V.
There's a filter board inside with inductors and caps.
Rails are very clean. No trace of HF residue in the audio.

 

[mulletchuck]

what are those two modules you got in there?

 

[abbey road d enfer]

what are those two modules you got in there?

A preamp and a HPF+compressor.
My typical recording path is preamp, HPF and dbx-style compressor, so I designed a card with an HPF and a dbx-style compressor, to work in complement with existing preamps.
The HPF is variable. It is a combination of a fixed 2nd-order at 16Hz and a 2nd-order variable from 16 to 300Hz. At the minimum frequency, they combine into a quasi-Bessel. I definitely believe there is no useful signal below 15Hz in music.
The compressor is of the soft-knee (non-adjustable) type. It has Threshold, Ratio and Gain controls and two 8-LED displays, one for gain reduction, the other for Level. The latter is switchable between input and output.  Time constants are non adjustable, similar to the dbx160, with the auto-adaptive detector. There is a bypass switch and a "blue" switch (similar to "thrust").
Inputs and outputs use the 1240 and 1646 THAT chips.
The circuit is compatible between 500 and 51X; in a 51X, the 24V needed for the display is taken directly, in a 500 rack, there is provision for a DC/DC converter.

Also, I decided to revive a preamp I had created in the 70's when I was making mixers.
It is based on a 4-transistor current FB design, uses a specific Sowter transformer with 3 windings, one secondary rated at 2k, one 200r primary and a 20k primary that is used for hot signals. It's much better than a pad; the xfmr isalways properly damped, the EIN is better by about 3dB (not that it matters that much at -30dBu input), and dynamic microphones and transformer-coupled condenser mics see a much higher impedance, making them sound much better IMO. So there is no pad per se, it's rather a "high level" position. The output section uses also a custom-built transformer; it is a quadfilar design and is included in the NFB path for reduced THD.
It is complemented by the same HPF as described previously, so chaining these two modules, you may create an 8th-order HPF (I don't think there's any advantage in doing this ).


While I was at it, I have also designed a dual DI. It is very basic, because I use a multi-channel (8-way) LA Audio rack-mount DI, that I had designed in a former life, and I NEVER have used the pad, gain or Gnd-lift switches, so the front-panel has just 4 jacks (Input and Link) for two channels, not even an LED.

 

[[silent:arts]]

Cool stuff!

 

[mulletchuck]

So, when is that Compressor gonna show up on the white market as a kit and why have you been hiding it for so long?

what are those two modules you got in there?

A preamp and a HPF+compressor.
My typical recording path is preamp, HPF and dbx-style compressor, so I designed a card with an HPF and a dbx-style compressor, to work in complement with existing preamps.
The HPF is variable. It is a combination of a fixed 2nd-order at 16Hz and a 2nd-order variable from 16 to 300Hz. At the minimum frequency, they combine into a quasi-Bessel. I definitely believe there is no useful signal below 15Hz in music.
The compressor is of the soft-knee (non-adjustable) type. It has Threshold, Ratio and Gain controls and two 8-LED displays, one for gain reduction, the other for Level. The latter is switchable between input and output.  Time constants are non adjustable, similar to the dbx160, with the auto-adaptive detector. There is a bypass switch and a "blue" switch (similar to "thrust").
Inputs and outputs use the 1240 and 1646 THAT chips.
The circuit is compatible between 500 and 51X; in a 51X, the 24V needed for the display is taken directly, in a 500 rack, there is provision for a DC/DC converter.

Also, I decided to revive a preamp I had created in the 70's when I was making mixers.
It is based on a 4-transistor current FB design, uses a specific Sowter transformer with 3 windings, one secondary rated at 2k, one 200r primary and a 20k primary that is used for hot signals. It's much better than a pad; the xfmr isalways properly damped, the EIN is better by about 3dB (not that it matters that much at -30dBu input), and dynamic microphones and transformer-coupled condenser mics see a much higher impedance, making them sound much better IMO. So there is no pad per se, it's rather a "high level" position. The output section uses also a custom-built transformer; it is a quadfilar design and is included in the NFB path for reduced THD.
It is complemented by the same HPF as described previously, so chaining these two modules, you may create an 8th-order HPF (I don't think there's any advantage in doing this ).


While I was at it, I have also designed a dual DI. It is very basic, because I use a multi-channel (8-way) LA Audio rack-mount DI, that I had designed in a former life, and I NEVER have used the pad, gain or Gnd-lift switches, so the front-panel has just 4 jacks (Input and Link) for two channels, not even an LED.

 

[abbey road d enfer]

So, when is that Compressor gonna show up on the white market as a kit...

I don't feel like getting in the kit business. All the components are quite easy to source, but some would want different knobs or want to use components they already have.
I could sell the PCB and front-fascia. The mechanical design is finished but I need to place an order of about 50 to make it attractive. Maybe I could post a feeler... it' just a matter of having enough people interested. Another possibility is to have front fascias made by Schaeffer, but I think the bracket/shield is necessary, so anyway I would have to place an order from my metal fabricator.

...and why have you been hiding it for so long? 

I started designing these modules end of 2012. I just wanted to make sure they work as expected before talking about them.

 

[bhs-audio]

Can you tell us more about your PSU?
Inside-Pictures?

Bruno

 

[sharpeleven]

Any idea when those racks are gonna be back in stock?

 

[[silent:arts]]

Any idea when those racks are gonna be back in stock?

Yes. Soon  8)
I can only speek for me, awaiting some missing parts the end of next week.

 

[jsteiger]

For North American customers, I will have the stock posted to my store sometime on Monday.

 

[Spiritworks]

How long till power supply  floor boxes will be ready to ship? I would like to buy two racks and and a dual-lead power supply.

 

[jsteiger]

How long till power supply  floor boxes will be ready to ship? I would like to buy two racks and and a dual-lead power supply.

The racks are ready now. I do have 3 Floor Box kits that I can add to the store but don't plan to do that until I get caught up on other open orders. I have a ton to pack right now so it will be a few days at least.

 

[Gustav]

Any idea when those racks are gonna be back in stock?

Yes. Soon  8)
I can only speek for me, awaiting some missing parts the end of next week.

....Will check again end of next week!

Gustav

 

[[silent:arts]]

Gustav, received the missing parts yesterday - and some 25 pieces of cool floor box PSUs from Jeff  8)

 

[bruce0]

I am doing a GROUP BUY of the second and last run of the DB25 connector PCB's for the 51X rack

I want to make sure anyone with a 51X rack gets a chance to play.
Here is the thread, first post describes the PCB and the Group Buy.

http://www.groupdiy.com/index.php?topic=47653.20 (Updated)

PCB's are at cost.



I hope it is ok to post this here, if not let me know by PM and I will delete it.

 

[[silent:arts]]

We are now at round 5.5  8)