G-Sun

D-LA2A, PM 670, D-OAC, prr 176 ?
« on: February 14, 2012, 05:22:32 AM »
I'm looking for a tube-compressor to build, stereo.

The D-LA2A seems like a very good candidate.
But, I could like some attack/release-control.

I'll probably build a 2-1176 first, so those fast needs should be covered.

The Poor Mans Fairchild:
Is it still available?
Is it more expensive/ harder to build?
How would you say it compares to the LA2A?

Are there other good candidates?

Thanks!
« Last Edit: February 16, 2012, 02:55:32 AM by G-Sun »
HJFP2, ssl9k, Harrison Ford Filters
My music


alexc

Re: D-LA2A? 670?
« Reply #1 on: February 14, 2012, 05:43:48 AM »
Poorman 660/670 pcb and part sets are sometimes available from members in the market section.

Yes it is harder to build than a DLA2A or 1176 and takes a lot of playing about to get suitable tubes.
ie matching as best as possible the GR tubes

670 is not as clean a sound imho as the DLA2A - there is more low end distortion probably related
to GR tube matching. the DLA2A is more of an all rounder.

The character of the 670 compression is very smooth but still more pronounced than the DLA2A,
which I think is more transparent and suitable for lower frequency instruments, such as bass gtr.
I think it works well as a tracking limiter and can really bring out instruments in a very nice way.
With suitable time constant parts, the 670 can be made to  respond quite fast as well as slower.

Another alternative could be a DOAC which could be considered quite similar to a DLA2A but without the expensive opto attenuator unit. It uses much cheaper vactrol based opto elements.
I would recommend this for a first tube limiter on ease of build and relative cheapness.
An edcor equipped one can be done quite reasonably in  price.

Then there is the 'prr 176' model - tube compression, solid state side chain.
Could be a very nice one to try.

Other vari mu candidates could be some point-point jobs like an altec 436 type or gates sta-level.

Cheers
« Last Edit: February 14, 2012, 05:47:24 AM by alexc »
I ping therefore I am

G-Sun

Re: D-LA2A? 670?
« Reply #2 on: February 14, 2012, 09:22:18 AM »
Thanks!
Really helpful info.

The prr 176 seems like an interesting project.
But, it's behaving a little like a limiter, right?

I'll be using these things a lot for tracking, and some softer ratio could be a good idea. A soft enough knee would of course help.
Hows are these units regarding low ratio and soft knee? (1176 should be ok with it's 4:1 setting)
(Edit: Yes, la2a cas comp 4:1 and seeing som ratio-curves for the D-OAC here)

Anybody who would give me their opinion on the usefulness and sound of the prr 176 vs 1176 and la2a?

I'm after color, tube-sound, usability on many sources..
« Last Edit: February 14, 2012, 12:31:53 PM by G-Sun »
HJFP2, ssl9k, Harrison Ford Filters
My music

G-Sun

Re: D-LA2A? 670?
« Reply #3 on: February 14, 2012, 01:59:07 PM »
Another considderation:

If I'm first bvuilding a stereo compressor, I should handle stereo-content well.
I've read the D-OAC is not really good at this. Right?
Could I assume getting the stereo-compression right is easier with the 2-1176 and the D-la2a?
HJFP2, ssl9k, Harrison Ford Filters
My music

alexc

Re: D-LA2A? 670?
« Reply #4 on: February 14, 2012, 05:39:58 PM »
Naturally you want it all  ;D

Soft and hardknees, ratio control, stereo linking and so on!

All those things are nice but aren't all available on the diy units I mentioned.

They can be modified to provide these sorts of things, depending on your skill level and determination.

Stereo compression with accurate dual-unit-linked type of control is not so easy, imho especially in diy units unless built with a lot of attention to matching the halves of the unit. I think most of these models are about as easy/hard as each other when doing this.

Maybe an la2a is easiest cause it has fewer controls.

So, for me, not really so important.
Or, if it is important, I'd probably use a more accurate compressor, like a stereo pico.

Anyway, they're all good. I'd focus on the one which you can build and get a good result.
There is no best unit. And you know you'll probably build a variety.



I ping therefore I am

G-Sun

Re: D-LA2A? 670?
« Reply #5 on: February 15, 2012, 05:33:43 AM »
Naturally you want it all  ;D

Soft and hardknees, ratio control, stereo linking and so on!
Yes :) And I would like a pot named awesome. hehe

Quote
All those things are nice but aren't all available on the diy units I mentioned.

They can be modified to provide these sorts of things, depending on your skill level and determination.

Stereo compression with accurate dual-unit-linked type of control is not so easy, imho especially in diy units unless built with a lot of attention to matching the halves of the unit. I think most of these models are about as easy/hard as each other when doing this.

Maybe an la2a is easiest cause it has fewer controls.

So, for me, not really so important.
Or, if it is important, I'd probably use a more accurate compressor, like a stereo pico.

Anyway, they're all good. I'd focus on the one which you can build and get a good result.
There is no best unit. And you know you'll probably build a variety.
Yes. Maybe the la2a is my best shot for first tube compressor.
Well documented, case, comp/limit..
HJFP2, ssl9k, Harrison Ford Filters
My music

Re: D-LA2A, 670, D-OAC, prr 176 ?
« Reply #6 on: February 15, 2012, 12:37:31 PM »
IIRC there's a thread around about trying to match t4b's from a large sample set.  IMO any optical element is going to be difficult to pair, and pricier than transistors to get a good sample size.  surely the rest of the components factor in as well, but being able to match gain reduction elements strikes me as job #1.  i honestly wouldn't worry about it too much though.
There's nothing like the right tool for the job.
And -usually- that's what I end up using...
..nothing like the right tool for the job!

Re: D-LA2A, 670, D-OAC, prr 176 ?
« Reply #7 on: February 15, 2012, 02:09:45 PM »
D-la2a has never been really known for drums. It's too transparent. I think what your saying when you say you want a tube compressor is that you want a vari mu. ie: Sta Level. Good on pretty much everything...and gives you that bouncy 'tube' vari mu thing.

G-Sun

Re: D-LA2A, 670, D-OAC, prr 176 ?
« Reply #8 on: February 15, 2012, 03:44:54 PM »
D-la2a has never been really known for drums. It's too transparent. I think what your saying when you say you want a tube compressor is that you want a vari mu. ie: Sta Level. Good on pretty much everything...and gives you that bouncy 'tube' vari mu thing.
Thanks! That's in la2a-land regarding cost right? And no stereo?
My main application is bassguitar, vox, guitar.
HJFP2, ssl9k, Harrison Ford Filters
My music

G-Sun

Re: D-LA2A, 670, D-OAC, prr 176 ?
« Reply #9 on: February 15, 2012, 03:45:40 PM »
IIRC there's a thread around about trying to match t4b's from a large sample set.  IMO any optical element is going to be difficult to pair, and pricier than transistors to get a good sample size.  surely the rest of the components factor in as well, but being able to match gain reduction elements strikes me as job #1.  i honestly wouldn't worry about it too much though.
Ok, I'll keep that in mind. Thanks!
HJFP2, ssl9k, Harrison Ford Filters
My music


Re: D-LA2A, 670, D-OAC, prr 176 ?
« Reply #10 on: February 15, 2012, 05:25:40 PM »
D-la2a has never been really known for drums. It's too transparent. I think what your saying when you say you want a tube compressor is that you want a vari mu. ie: Sta Level. Good on pretty much everything...and gives you that bouncy 'tube' vari mu thing.
Thanks! That's in la2a-land regarding cost right? And no stereo?
My main application is bassguitar, vox, guitar.

Probably...more or less. Drip has what appears to be a nice sta level board and a nice 660 board...these are obviously, originally point to point. 660 would be very nice...but more $$$.

G-Sun

Re: D-LA2A, 670, D-OAC, prr 176 ?
« Reply #11 on: February 16, 2012, 02:57:58 AM »
Probably...more or less. Drip has what appears to be a nice sta level board and a nice 660 board...these are obviously, originally point to point. 660 would be very nice...but more $$$.
I'm not up there with the original 660/670. PoorMans maybe :)
Sta level seems nice, but I think I'll build a compressor, not a limiter only.
HJFP2, ssl9k, Harrison Ford Filters
My music

G-Sun

Re: D-LA2A, PM 670, D-OAC, prr 176 ?
« Reply #12 on: February 16, 2012, 02:59:09 AM »
Any way. You've given me many nice options here.
I'll let things sink in a little and decide later ;)
HJFP2, ssl9k, Harrison Ford Filters
My music

Re: D-LA2A, 670, D-OAC, prr 176 ?
« Reply #13 on: February 16, 2012, 09:40:46 AM »
Probably...more or less. Drip has what appears to be a nice sta level board and a nice 660 board...these are obviously, originally point to point. 660 would be very nice...but more $$$.

Sta level seems nice, but I think I'll build a compressor, not a limiter only.

Sta level IS a compressor. ;)

http://www.retroinstruments.com/sta-level.php

G-Sun

Re: D-LA2A, 670, D-OAC, prr 176 ?
« Reply #14 on: February 16, 2012, 10:14:38 AM »

Quote
Sta level IS a compressor. ;)
Ok, sorry :) Do you know what the ratio is like?
HJFP2, ssl9k, Harrison Ford Filters
My music

Re: D-LA2A, PM 670, D-OAC, prr 176 ?
« Reply #15 on: February 16, 2012, 12:00:24 PM »
"Compression and limiting are not the same. Stock from the factory, the Sta-Level was only a modest 3.3 to 1 compressor (a 3.3 dB increase in input produces only a 1 dB change in output). An advantage of starting with a high-level DC control signal is that you can send it through an RC (resistor and capacitor) network to vary the attack time (how fast it controls) and release time (how long it holds down the level) as well as the compression ratio.

Radio engineers tinkered with these values to get that perfect operation to fit/complement a given format's music and voices. Compression ratios of 6:1 were possible and release time constants could be made minutes long."

http://www.radioworld.com/article/the-sta-level-effective-audio-control/553


G-Sun

Re: D-LA2A, PM 670, D-OAC, prr 176 ?
« Reply #16 on: February 16, 2012, 12:22:16 PM »
"Compression and limiting are not the same. Stock from the factory, the Sta-Level was only a modest 3.3 to 1 compressor (a 3.3 dB increase in input produces only a 1 dB change in output). An advantage of starting with a high-level DC control signal is that you can send it through an RC (resistor and capacitor) network to vary the attack time (how fast it controls) and release time (how long it holds down the level) as well as the compression ratio.

Radio engineers tinkered with these values to get that perfect operation to fit/complement a given format's music and voices. Compression ratios of 6:1 were possible and release time constants could be made minutes long."

http://www.radioworld.com/article/the-sta-level-effective-audio-control/553
Nice reading :)
HJFP2, ssl9k, Harrison Ford Filters
My music


 

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