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Author Topic: Checkout this custom 4-channel Church-Audio CA-UGLY preamp  (Read 10329 times)

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Offline Gutbucket

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Checkout this custom 4-channel Church-Audio CA-UGLY preamp
« on: September 22, 2015, 05:22:50 PM »
I commissioned Chris Church to build me a custom 4-channel version of his CA-UGLY preamp as part of a long-considered effort to streamline several of my recording rigs. I’m posing to here share the particulars and a few photos of the new setup, and to say thank you to Chris for completing a project that I suspect was something of an interesting diversion for him, but also a PITA with everything else on his plate.  Not unexpectedly this took quite a while to bring to fruition, but I want to give big thanks to Chris for making this non-standard odd-ball setup a reality, as well as for his support of this community in general.  Thanks again Chris.

As the TS regulars here know, most of my recording setups are atypical multi-channel arrangements used for making both 2-channel stereo and multi-channel surround recordings, so they differ significantly from typical two channel setups used by most members here.  Up to this point, combinations of standard gear have done the job, but aren't optimal for a number of reasons.  This new preamp is designed for the setup I use most frequently.  It greatly simplifies and error-proofs the entire arrangement, makes it easier to use, and makes it more flexible to accommodate a wider range of recording scenarios.

I'd been using two separate CA-UGLYS in this setup ever since I shifted completely to making multichannel surround recordings about 7 or 8 years ago.  At that time I was using two completely separate recording rigs in combination, in order to record four channels of information- each rig used two miniature DPA microphones, one CA-UGLY and one Edirol R-09 recorder.  Back then I needed to stop and start the two recorders manually, as closely as possible, making a sharp clap at the start and end of each recording as audible "slate-markers" to help with later alignment and sync of the two resulting stereo recordings. 

The availability of the Tascam DR2d provided the ability to record all four channels on one hand-held recorder that would fit into a pocket.  This was a huge improvement, and the single most important one.  However I still needed to manage the two CA-UGLY's and a tangle of wiring, including the four wires from the mics, two microdot-to-stereo-mini-plug 'Y' adapters, and separate interconnects from the preamps to the DR2d.  Also, I only had a maximum of ~5dB of gain adjustment easily available (which is the usable range of line-input sensitivity adjustment on the DR2d and can not be changed while recording) because the original CA-UGLYs featured two gain trim-pots for level control, but no global gain control.

The new preamp immediately cuts the preamp and preamp battery count in half, and the wiring simplification greatly reduces the number of intermittency-prone connectors, interconnections and a mess of wiring.  It has a single 6-pin mini-XLR input, and a single 6-pin mini-XLR output to the DR2d.  All the stereo mini-jack connections have been eliminated up the inputs of the recorder.   Cabling is far easier to route and manage, and the rig can be quickly assembled or disassembled as necessary.

Chris built a very nice breakout cable for the mic input side, with four in-line female microdot connectors, staggered to lay flat and not bunch up.  That allows me to use standard microdot-terminated miniature DPA mics without chopping and re-terminating them.  In this rig that’s four 4060s (In the larger open rig, which I’m also currently reworking, that two 4061s and four 4098s, which will soon be powered by six Naiant PFAs into the DR-680).  I only need to plug in the one mini-XLR input and the one mini-XLR output and am ready to go.  The breakout cable to the DR2d remains attached to the recorder, reducing wear on the only mini-jack connections remaining in the system. 

I’m now considering chopping the four 4060s and terminating them directly to the 6-pin mini-XLR.  This would dedicate those mics specifically to this rig, which I’ve previously been reluctant to do, but would allow for customizing the length of each mic lead, completely eliminating the excess cable loop, and eliminating all in-line connections.

Insertion of the 6-pin mini-XLR output connector switches power on to the preamp.  Alternately, I can leave everything connected and pop out the 9V battery to power it down. The preamp runs on a single 9V.  I like the new battery-tray Chris used, which has spring contacts instead of clamp contacts, less prone to damage over long-term use.  We need to relocate the battery tray however, moving the battery so that it extends from the end of the preamp opposite the input/output connectors.  That will make the preamp much slimmer and less bulky, about the same thickness as the recorder.

For a few years now, the standard 2-channel CA-UGLY has featured a global rotary gain selection switch in addition to the two channel trim-pots of the original version, and this custom four channel version uses that same configuration.  It has two rotary switches (one for ch's 1&2, a second for 3&4).  I would prefer a single rotary switch which controlled all four channels simultaneously, but it's easy enough to set both switches identically.  They are located adjacent to one another and the switch positions are detented.  The switches allow for easy change of overall gain through the preamp to suit different recording situations.

The individual channel trim-pots are retained and are located adjacent to each other, next to the rotary switches.  Adjusted individually, these are critical for setting up the correct inter-channel level balance between the four channels.  Adjusted together, they also serve to fine-tune the throughput gain of the switch positions, so that the switch positions are properly calibrated to suit the input sensitivity of the DR2d with respect to various recording scenarios.  It takes some time to find a comfortable global-gain setting in combination with the appropriate trim-match from channel to channel.  In the past I arrived at these settings by trial and error, making slight re-adjustments between recording dates.  This time I measured gain through the "entire chain" for each channel using the settings I had arrived at with two original CA-UGLYs, and transferred those settings to the new four channel version.  I did this by sending a test tone through each mic in turn (Behringer cable tester as tone generator, driving airline ear-bud headphones, with the small 4060 capsule placed into the silicone flange of one of the ear-buds) and recorded the resulting peak levels numerically indicated on the DR2d.  I then did the same after switching to the new preamp, with the two rotary switches placed in a middle position.  I then achieved the same gain-staging as before, mapped to a middle position on the gain switches.  I can now increase or decrease gain as necessary for very loud or very quiet recording situations using the switches, without touching the trims or needing to adjust the very limited input gain range available on the DR2d.

Here’s some photos of the preamp and its breakouts connected and ready for use with a DR2d and its remote (the photo perspective makes it look larger than it actually is in relation to the recorder in the last couple photos) -
« Last Edit: September 22, 2015, 05:29:18 PM by Gutbucket »
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline Gutbucket

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Re: Checkout this custom 4-channel Church-Audio CA-UGLY preamp
« Reply #1 on: September 22, 2015, 05:25:36 PM »
Here's a few more of the preamp showing the controls, the current battery tray location, and the intended revised battery location which will make it longer but more slim-
« Last Edit: September 22, 2015, 05:30:14 PM by Gutbucket »
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline OhioHead

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Re: Checkout this custom 4-channel Church-Audio CA-UGLY preamp
« Reply #2 on: September 22, 2015, 09:15:09 PM »
Sweet set up!

Offline Gunner

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Re: Checkout this custom 4-channel Church-Audio CA-UGLY preamp
« Reply #3 on: September 23, 2015, 12:07:38 AM »
Nice! 

This is a beautiful ugly preamp!  :D



Offline rodeen

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Re: Checkout this custom 4-channel Church-Audio CA-UGLY preamp
« Reply #4 on: September 23, 2015, 12:48:46 AM »
Now that is a really freaking Ugly preamp!  And very cool.  Thanks for sharing pics.
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Offline cybergaloot

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Re: Checkout this custom 4-channel Church-Audio CA-UGLY preamp
« Reply #5 on: September 23, 2015, 10:04:54 AM »
Interesting! Chris has always done well for me.
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Offline jb63

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Re: Checkout this custom 4-channel Church-Audio CA-UGLY preamp
« Reply #6 on: September 23, 2015, 04:43:06 PM »
That is totally Awesome!
That's the main reason I didn't like the dr2d, was because i needed too many preamps!
I say chop those microdots and make it a permanent setup!
once again, lost in all the noise

Offline weroflu

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Re: Checkout this custom 4-channel Church-Audio CA-UGLY preamp
« Reply #7 on: September 23, 2015, 05:59:29 PM »
I love all the uglies.

ps my little boards could have easily worked for your deal, but  at the time you ordered I wasn't up to speed.
I have boards/schems for plugin power and variable gains - 4 channels easy peasy.

I have a 2 channel board layout that's 1/4 size of the ugly,  never sent to fab, runs on single a23.

Offline Gutbucket

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Re: Checkout this custom 4-channel Church-Audio CA-UGLY preamp
« Reply #8 on: September 23, 2015, 06:43:38 PM »
I've followed your thread and are quite interested in what you are doing.  As you mention, this was already well underway before you got rolling.  Also, I've been very pleased with the results I was getting using the two original UGLYs so this was an easy, tested, and obvious way to go.  I'm quite pleased with it as is, and will be even more so once the battery location can be reconfigured.

However, I may also consider building an alternate rig using your boards. 

Since my primary application is surround recording and playback, I'd ideally be recording 5 (or 6) channels as I'm doing in the big rig instead of 4, but a small, pocketable recorder with 5 or 6 channel analog input does not currently exist.   I even briefly considered attempting to DIY a relatively simple dedicated 6-channel recorder backend with extremely simplified operation, built onto the same housing as the preamp- little more than a 6 channel ADC and control chip providing functionality to write to an SDHC card.  Power it up and throw a single switch to record, no metering, only a power LED and recording LED.  Gain ranges could be preset to a few switchable ranges since the same mics would always be used, making mics to SD card a 'closed system' which greatly simplifies the design requirements so it needn't be as flexible or have the features of most recorders.

Love to build a 6-channel version if an appropriate recorder appears or if that simplified DIY recorder idea becomes a more reasonable possibility.
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline weroflu

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Re: Checkout this custom 4-channel Church-Audio CA-UGLY preamp
« Reply #9 on: September 23, 2015, 07:24:07 PM »
6 channels not a problem, 8 is easy enough as well with two quads.

I thought about a diy recorder for about 30 seconds then came to my senses.

When the dr70d came out I almost stopped because with the op amp replacement mod it should pretty much sound like what I made.

6-8 channel recorders like the dr70d are probably a year away.

You would probably have fun rolling op amps.

check this out...

https://www.by-rutgers.nl/ME6211-PRO37R.html








Offline willndmb

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Re: Checkout this custom 4-channel Church-Audio CA-UGLY preamp
« Reply #10 on: September 24, 2015, 05:45:33 AM »
Pretty cool.
I would leave the battery though, extending it seems like asking for trouble of it popping out easy and of course that wouldn't be good
Mics - AKG ck61/ck63 (c480b & Naiant actives), SP-BMC-2
XLR Cables - Silver Path w/Darktrain stubbies
Interconnect Cables - Dogstar (XLR), Darktrain (RCA > 1/8) (1/8 > 1/8), and Kind Kables (1/8f > 1/4)
Preamps - Naiant Littlebox & Tinybox
Recorders - PCM-M10 & DR-60D

Offline swordfish

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Re: Checkout this custom 4-channel Church-Audio CA-UGLY preamp
« Reply #11 on: September 24, 2015, 06:20:45 AM »
Pretty cool.
I would leave the battery though, extending it seems like asking for trouble of it popping out easy and of course that wouldn't be good
2nd the above...the way it is built is perfect for  >:D

kinda interesting to find out how many Dr2d owners would like to have an ugly pre like the above...BTW I own one too. ;-))

Offline Gutbucket

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Re: Checkout this custom 4-channel Church-Audio CA-UGLY preamp
« Reply #12 on: September 24, 2015, 09:36:06 AM »
I thought about a diy recorder for about 30 seconds then came to my senses.

6-8 channel recorders like the dr70d are probably a year away.

Same here.

The DR70d size is still too large for this application.  I need something DR2d sized, and don't need phantom powering or balanced inputs.

Thanks for the link, I'll take a look.

Pretty cool.
I would leave the battery though, extending it seems like asking for trouble of it popping out easy and of course that wouldn't be good

The battery won't be protruding unprotected from the end of the preamp.  It will be housed in an identical tray to the one currently being used, just relocated and epoxied to the end of the preamp instead of to the side of it, for significantly reduced bulk and bulge.  The even though is not enclosed, the battery clicks into that tray pretty securely.
« Last Edit: September 24, 2015, 10:17:33 AM by Gutbucket »
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline Gutbucket

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Re: Checkout this custom 4-channel Church-Audio CA-UGLY preamp
« Reply #13 on: September 24, 2015, 10:15:43 AM »
One step closer to my imagined ideal of a single device about the size of an Altoid tin, with a single 7 or 8 pin mini-xlr input (accommodating six 2-wire mic channels), record switch, and a 'now recording' LED indicator on the outside, and the circuit boards with an SD slot and the battery on the inside (and maybe a gain switch with a couple positions).

Actually the imagined ideal wouldn't need any user-adjustable gain switching at all.  The signal level through the system set so that the dynamic range of the miniature microphones (~100 dB) would just fit within the total input range of the ADC without need for further adjustment.
« Last Edit: September 24, 2015, 10:18:06 AM by Gutbucket »
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline weroflu

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Re: Checkout this custom 4-channel Church-Audio CA-UGLY preamp
« Reply #14 on: September 25, 2015, 02:22:52 AM »
If you want I'll make a 6 channel plugin-power preamp altoids sized board design. But it looks like you only have 4 recording channels available.

 

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