Multiple PT2399 in series for mega long delays - what have folks done?

[earthtonesaudio]

To achieve the minimum delay time it has to go pretty close to 0V.  But that's an extreme case.

R.G., your comment reminded me of the power systems engineering class I just took.  My teacher would say all the time, "...but we're going to use the simplified model instead".   

[R.G.]

R.G., your comment reminded me of the power systems engineering class I just took.  My teacher would say all the time, "...but we're going to use the simplified model instead".   

Yep. Engineering in the corporate world (that is, you get to use big toys) often comes down to:
1. get results
2. get it out to the paying customers on time
3. don't let it blow up in the company's face before or after shipment
4. make it work better in the second release
5. take the blame for the rising-star boss that got the company into this mess in the first place.

The simplified model is often the most practical tool for that.

One working definition of education can be what you have left when you can't remember what caused all these scars. 

[merlinb]

To achieve the minimum delay time it has to go pretty close to 0V.  But that's an extreme case.

R.G., your comment reminded me of the power systems engineering class I just took.  My teacher would say all the time, "...but we're going to use the simplified model instead".   

What matters is the current you pull out of the pin, and for minimum delay it's about 3.5mA, even when shorted to ground. You could achieve this with a 2V source and a 140R resistance, for example ((2.5V-2V)/3.5mA). Remember, if you connect a voltage source to the pin, all you're really doing is making a voltage-to-current converter using whatever resistance is between the two- even if it is just the resistance of the chips' internals.

[earthtonesaudio]

Remember, if you connect a voltage source to the pin, all you're really doing is making a voltage-to-current converter using whatever resistance is between the two- even if it is just the resistance of the chips' internals.

Yep, that was my point exactly.  The PT2399 does this job internally, so one need not bother with current mirrors, or resistance converters, or other esoteric methods.  A voltage buffer with (relatively) infinite current drive, but hard limits on the voltage swing (0-2.5) uses one op-amp and allows you to directly interface with the voltage outputs of the world.

[merlinb]

The PT2399 does this job internally, so one need not bother with current mirrors, or resistance converters, or other esoteric methods.  A voltage buffer with (relatively) infinite current drive, but hard limits on the voltage swing (0-2.5) uses one op-amp and allows you to directly interface with the voltage outputs of the world.

They are the very opposite of esoteric. Pin 6 is a voltage source, so if you connect another voltage source to it, it may do funny things (like latch up, which we're all aware of). You can force it to work, but in general it's bad engineering to try and connect a voltage source in parallel with another voltage source. It's a circuit bender's mentality, not an enlightened one. And all you need is one resistor to make it a sound engineering approach...

[asatbluesboy]

Princeton Technologies was not interested in changing the innards or even telling me more about the insides for less than a 100K unit order.

Old thread, but still worth asking. Did they ever quote you that 100K? Maybe if we got enough members down... Just a thought.

[Jazznoise]

Haven't I read somewhere that this is how the Belton Reverb brick is designed? Multiple PTs 

A pair of them with seperate delays with some decent feedback routing would get you there, some all-pass filters don't hurt either!

I remember reading a huge forum discussion on Diyaudio I think on programming reverbs, getting a smooth reverb tail is nothing short of an obsession with some folks!

[deadastronaut]

old thread but very relevant..

ive been messing around with 3...now 4 pt's...on breadboard/s

any advice/comments would be appreciated.

http://www.diystompboxes.com/smfforum/index.php?topic=105183.msg948619#msg948619