Expensive diode limiter?

Anyone heard or saw this Prism Sound limiter:

http://www.prismsound.com/psok.htm

http://www.mercenary.com/prismsound.html
The price is over 200$ for a pair. :shock:

Considering Prism Sound is a serious player, I supose it is not a toy.
From what I read at forums it looks like a diode limiter in a tube. Probably it is optimised to start the limiting at the last couple of decibels before AD converter full scale. Maybe there are more diodes and resistors to emulate some kind of logaritmic curve.
I imagine it can be done without problems. What do you think?

chrissugar

I'll betcha it's just some germanium diodes and a resistor or two.

Approximate cost: about $0.50 for the diodes and resistors and $1 or $2 for the XLR barrel.

This bit of copy made me laugh:

stays soft even when large overloads are present and does not become hard like less sophisticated systems.

Click to expand...

no idea whats in the barrell, but those things are big enough to house a small circuit board with an active circuit using standard dip packages, if its surface mount then shit, anything simple could fit on a single sided board, double that for a double sided board. May be more than a few through hole parts.

dave

Dave, it can't be any active circuit (active in sense of powered) because it goes before the AD converter, so it has no source of power. It is 100% a passive circuit and probably it is something simple.
Maybe it is not only two diodes antiparallel and a pair of resistors but it can't be more complicated than some diodes and some resistors.

chrissugar

interesting. There isnt too much info on the website, bummer.

Is it possible to use a choke for audio to achieve the same effect with diodes you guys are talking about?

dave

Zener/FET combination?

Someones opened one up

link

Even simpler than I thought. Ha! What a ripoff!

In a way I guess they can justify the money because of the testing/selection process, but they ought to have some spec on how symmetrical the clipping is. Also they should say how much it loads the source and how much it takes before it blows up.

Low-voltage zeners do have kind of a soft knee, which is usually a disadvantage.

...the sound is in the butta...

Keef

I suppose they consider the maximum peak to peak voltage that you can feed into the converter, they calculate the voltage one or two decibels below, and then select zenners that start to limit at that voltage, so they can avoid AD converter overload. No rocket science.

chrissugar

Da Butta is on da roll!

[quote author="CJ"]Da Butta is on da roll![/quote]

What the hell is the man to the left doing? :shock:
Mastrubating his penis? :razz: :thumb:

He's insane!!
And I need more beer!! :twisted:

Kkrafs

ROTFLMFAO!!!!!!!!!!

I just found my new sig! (he says, giving Analag a break :wink.

Peace,
Al.

Hey this sounds like a very useful piece of kit to have in the toolkit

I'd like to understand a bit better how to do this so I found two examples that seem right.


Assuming there's a back to back pair of zeners similar to that seen in the green pre input section in the tube.

http://1176neve.tripod.com/id10.html

Although I've built a green pre and seen this configuration before, I don't understand how it works quite well enough to make adjustments for a specific input limitation. I assume you use zeners with a rating that equals the voltage equivalent of the db you're after.

so 18dbv has a peak to peak voltage around 22.
http://www.sengpielaudio.com/calculator-db-volt.htm

so 4 22volt zeners, 1 back to back pair off of hot, 1 off of cold, and tied at ground would do it?

or an alternative?

What about a limiter with some germaniums.
how about figure1 from this article minus the input and output pots.
http://headwize.com/projects/showfile.php?file=limiter_prj.htm

I'm missing something here though. (it seems some of the information in that article is clipped :wink: )

I need to test forward bias voltage and then what?
looking at figure 1 what would be the formula to determine r1 if I wanted, for example, 18dbv

also, can you stack germaniums in series like you do with zeners to increase the forward bias voltage? or does the stack just smooth out the clipping.

And then to make this a balanced circuit, It should be component matched and doubled up on both hot and cold lines right?


I think I have some questions about what happens to signal with these two different variations, but that should wait until I know whether or not these configurations will work as planned.

Sleeper

I've been trying to look at this from different perspectives, giving PS the benefit of the doubt and all... But the "How much would a tech charge to design/build it?" argument doesn't make much sense to me, since 1) a diode clamp is a diode clamp is a diode clamp - there's nothing to "design"; b) Once you figure out your requirements, building a test jig to sort the useable diodes would be simple (assuming they indeed hand-pick the good ones); and c) They probably are making enough of them to offset their manufacturing costs.

I'm still having A HELL OF A LOT OF TROUBLE letting go of the idea that people are paying 225 bucks for some diode clamps...

Peace,
Al.

you and me both. its a ripoff pure and simple.

saying that the cost is reasonable because it may cost more to have someone custom design and build something like it for you is not a rational argument.

youre making the very big assumption that they are testing and selecting the zeners. dont forget that the zeners are already sorted at the factory and while there is some small variation in zener voltage etc. the tolerance is not so wide that you would need to spend hours testing and matching. jellybean zeners are about 5%, you can spend a few pennies more and buy 1% zeners. the 'knee' current is not going to vary a huge amount between zeners of the same type. theres no special pixie dust in these things.

if manufacturers made their parts so sloppy that you had to spend hours matching them then they would go out of business. dont forget that the bulk of the market is industry/government who need in-tolerance parts and have no time for the kind of voodoo BS that audio people believe in.

and no its not rational to compare the cost of a commercial piece to a custom job. you can buy a coffeemaker for twenty bucks. if you were to have a talented machinist/glassblower build you one from scratch it would cost hundreds of dollars. so if i tried to sell you the twenty dollar coffemaker for a hundred dollars and told you it was a good price because it was still less than you would have to pay someone to build a coffeemaker for you, how would you react to that?

and a two-diode clamp is a hell of a lot less complicated than a coffeemaker, so lets not get into nonsense about 'design' and 'r&d.'

please dont take this as a personal attack because its not, i just vigorously disagree with your take on the pricing.

I dont really get the idea where some consumers feel like they are owed fair pricing. Too expensive, dont buy it. I get super pissy when I buy something that isnt made well, but so far as price is concerned, whatever, if I cant afford it or cant justify it I dont buy it, big deal. what happens if the company is so small that they only have one tech assembling stufff for them and thats the cost of doing business?

Toothbrushes cost like $3.50 now. Replacement razor blades cost me $10 per pack. Both cost a manufacturer on a large scale less than pennies to make, yet people buy that shit all day long and there is probably a 2000 percent profit on those items.

At whatever those things cost, I dont see anywhere near the same kind of profit margin if they are hand assembled. And if they are made in a factory in china, what are we gonna now blame some guy in business for trying to stay in business. This is the same company that sells a $4K limiter and like a $6K eq, all of which apparently are transformerless. Whats that some great value for the money too?

If its too expensive dont buy it. Seems like an easy enough creed to live by. Rip off, I dont know. If it works and does what it is supposed to do and the price is $200 for a pair, if I am working on location on a movie and need that item, for the time on the clock it would take me to hand build that, even if it is three parts in a barrell, after I get the parts, set up my rig in some motel or on set if Im lucky enough to be on thhe same set for any extended period of time, assemble the thing, test it, rely on it, it is pretty much cheaper and WAY less trouble for me to buy the pair at $200. Try to think of the market these tools are pointed at. Sure, they are advertised to the gearslutz crew and all that crap, but if you are some hot shot and your hourly rate works out to be $200 per hour, it makes more sense to buy something like that than to stop working and build it. All these things are relative and perspective is everything. If its a rripoff for you, dont buy it, its not a ripoff for some other guy so dont crucify him or brand him a sucker for buying the thing. Sometimes a quick solution is worth paying a premium for and sometimes that premium isnt as expensive as it looks. If it wasnt for expensive stuff, some people would never be able to launder the money they are taking out of sessions. Thats a whole other conversation though...

dave

I agree and don't agree with the last few posts.

On the one hand, I totally think this is too much money for ME to spend.
but that's because I think I can DIY this thing If I just had a little more knowledge on correctly addressing the problem. I've always that's what THIS list is all about and I'm happy for it.

But on the other hand, I used to be an electrician and I still do a bit of electrical work for my old clients. I won't leave the house for under 200.
Thats the minimum and people gladly pay it for quality work. If the job is smaller than that it just isn't worth getting in the car.



Back to the problem at hand though, If someone can help me out with a few of the questions from the earlier post, I'd have this thing or something like it cracked.

It's something I could really use... I sometimes do location recording and a limiter like this would be so perfect in my go box...

One other thing.
Does that other post need to have the images inline? or do you guys find it easy enough to jump to links.

Sleeper