Resonant Lopass Gate PCB's (New Batch 4/29/12)

djthomaswhite · Joined: Nov 22, 2007 Posts: 140 Location: Orange, CA

Yes, I can't think of anything that has changed. Maybe 1 less 100K resistor but I think is is accurate. (Just ordered parts for 3 LPG's and 10 Vactrols myself today).

Has anyone got any experience with VTL5C2 Catrols from Vactec? Slow/Fast?

Thomas

/mr · Posted: Wed Oct 01, 2008 2:45 am Post subject:

Speaking of "slow/fast" Vactrols:

I hope you guys are aware that faster is not necessarily better. An ideal VCA or VCF should have infinitely fast CV response, but part of the character of the Buchla 292c is the sloppy response of the Vactrols. The short envelope that is introduced can give the sound a more "physical, acoustic" character. I experienced similar effects recently when I built my Vactrol based Korg PS resonator clone, it sounded really nice when connecting very glitching CV cables, much more interesting than sweeping it with an LFO... Smile

The question is what Vactrol the user would consider "the best" for a modern day 292c... it might be different from the model that Buchla preferred to use in the '70s. Might be interesting to try out, or build some different ones!

chrissugar · Joined: Sep 23, 2008 Posts: 34 Location: ROMANIA

XeNoN23 · Joined: Oct 06, 2007 Posts: 16 Location: AuStRiA

Wow, the demo on y.t. sounds great!!!

If possible, please put me down for 2 boards!
Prepay is no problem!!

thx and b.r.

djthomaswhite · Joined: Nov 22, 2007 Posts: 140 Location: Orange, CA

hanks for the vactrol info! Do you know the approximate decay times of each type of vactrol? You said vtl5c4 is about 1.5seconds... Where does the vtl5c3 fall etc? I will be makin a bank of these will different speeds. If anyone wants to get in on a shared front panel express order in motm format then email me so we can talk about what we want on the panels. Thanks guys!

Thomas

numbertalk · Posted: Wed Oct 01, 2008 8:31 am Post subject:

Depending on how many others are interested/what the total cost per panel would be I would probably be interested in a group buy on MOTM panels.

chrissugar · Joined: Sep 23, 2008 Posts: 34 Location: ROMANIA

djthomaswhite · Joined: Nov 22, 2007 Posts: 140 Location: Orange, CA

Thanks for the cool chart! I'll be making a vtl5c2 unit to sit between my slopass vtl5c4 from the YouTube video and the traditional vtl5c3's.

Update: prototypes shipped today. Will have Friday. Beta testers will have theirs shipped to them on Saturday! Happy times!!!

Now if I could just get my box from bridechamber I'll be 100% ready for testing (fingers crossed and hoping). Time for some serious Deyo-power. Can't beat Scott's price on the Chinese 112a jack clones!

Thomas

Thomas

sourcery · Joined: Feb 16, 2007 Posts: 11 Location: Sweden

If it is not too late, I'll sign up for two pcb's (or more) depending on price...

Thanks!

/Kristian

fluxmonkey · Joined: Jun 24, 2005 Posts: 708 Location: cleve

BananaPlug · Posted: Thu Oct 02, 2008 7:58 am Post subject:

Yes, I'm wondering about that too. See my post a couple pages back. A standard way to test them would facilitate matching people up with matched sets of Vactrols.

/mr · Posted: Thu Oct 02, 2008 8:28 am Post subject: Vactrol datasheets

For the still curious out there; the Vactrol product pages, each with a datasheet:

http://optoelectronics.perkinelmer.com/catalog/Category.aspx?CategoryName=VTL5C+Series

The attack times are spec'ed as typ, whereas the decay times are max values.
If matching is important, I guess the resistance tracking in steady-state operation is at least as important as decay time tracking.

/mr · Posted: Thu Oct 02, 2008 9:12 am Post subject:

urbanscallywag · Joined: Nov 30, 2007 Posts: 317 Location: sometimes

Your V+ and V- should be calibrated pretty well for that to work.

/mr · Posted: Thu Oct 02, 2008 9:52 am Post subject:

urbanscallywag · Joined: Nov 30, 2007 Posts: 317 Location: sometimes

Ah, I see. I guess I was just thinking that you'll never get zero if matched because the -V and +V would have some offset.

hodad · Joined: Jul 31, 2007 Posts: 41 Location: atlanta

I'd like to put myself in for 2 boards.
Thanks!
Tom

Junk Rhythm · Joined: Jan 07, 2008 Posts: 81 Location: San Francisco, CA

Prepay sounds good and a lot safer. Since the there is no cap now, I would like to adjust my order from 2 PCBs to 4 instead.

djthomaswhite · Joined: Nov 22, 2007 Posts: 140 Location: Orange, CA

Here's a photo of the first (old) prototype "slopass version with vtl5c4" in a nice FPE panel (also attached). Express PCB sells 3 of these for 64 US shipped to your door in 3 days. I have a triple Preamp with headphone amplifier I am working on at the moment.

Enjoy the photo!

Thomas

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BananaPlug · Posted: Fri Oct 03, 2008 5:31 am Post subject:

See image about 6 posts back:

intercorni · Joined: Jun 04, 2007 Posts: 69 Location: hamburg

2 for me please.

Thx,

Cornel

Funky40 · Posted: Fri Oct 03, 2008 9:07 am Post subject:

it would be nice to have the disscussion about matching Vactrols in a own thread.
I'm very interested to know how to match them.

djthomaswhite · Joined: Nov 22, 2007 Posts: 140 Location: Orange, CA

Hey guys,

I just received the non-solder masked prototypes and took a couple of quick snapshots. You will see there are two carbon pots mounted on these.

Here are any issues I notice immediately:

I have found one connection that needs to be modified by the pots. Nothing spacing the pots off the PCB won't fix, but I'd rather eliminate any potential for trouble by the final design (as you would expect me to do my best job here). With the smaller Alpha pots, the metal surrounding the pot pins can short out the connection between the pots. The Alpha pots also need to be about 1/8th of an inch closer to the edge of the board to avoid having to bend the PCB when mounting to the panel via the pots.

Nothing else yet. I realize and you will see that the pads for soldering are smaller, but this whole PCB is fairly compact and larger spacing will not work. I needed to make sure the connections don't short out. In my proto's without the solder mask it is more of an issue that it will be when the production versions are created. I can say that Express PCB does not sacrifice quality to be "Express". The PCB's look great and will look even better with any kinks worked out and sitting proudly behind your future panels. I have attached two photos, but two more can be found at my Flickr page.

http://www.flickr.com/photos/26485243@N06/

Thanks guys!

Thomas

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RF · Posted: Fri Oct 03, 2008 7:23 pm Post subject:

Nice Thomas!

trance4ever · Joined: Sep 21, 2008 Posts: 3 Location: Canada

If there is another run or any boards come available, I'll take 2 boards.

thx.