this thing is pretty cool. not exactly what i was expecting.
I was really worried on this one that I would have to trouble shoot it, but luckilly the only trouble i ran in to was a wire i forgot to solder, which took no time at all to find.
i made a minor mod to it, by using a 100k pot for the delay time.
this thing seems to be pretty close to 1000ms delay time with out any nastyness.
self oscilation is a little more shrieky than i thought it would be, but i dont really have any use for that anyways
I'll post some clips next week.
and thanks again mark for the regulators
Brian
pretty cool. do you like the sound of it?
I havent seen any instructions for a pt-100 - is there a schem available? I'd be interested to see what chip can get to 1000ms.
i think you meant pt-90 ?
its available at generalguitargadgets, www.generalguitargadgets.com.
using the PT2399 chip its really convenient for the delay time as the delay time is set by resistance. my pt-90 is modded with a short/long delay switch thats switched in by a dpst switch that switches in an additional resistance ( i think 47k) in series with the pot. (ala moos' mod on his website)
Han
PT-80?
http://www.generalguitargadgets.com/v2/index.php?option=displaypage&Itemid=80&op=page&SubMenu=
aha... my apologies.....
its not PT-100 nor PT-90 but PT-80 !
named after ibanez's AD-80 i think.... according to Scott's notes.
Han
im a dumb ass.... oops.... PT80
anyways, yeah.... it sounds good.
I took a really good listen to the longer delay times tonight.... played clean. yes it is a little distorted at the longer delay times, im sure if you went any longer it would start to sound really bad.
I timed it tonight, it is more like 1100ms..... cool... it sounds pretty.
now i have a DD3, a rehoused DOD fx90 and the pt80 for delays.... plus some other rack gear, but that is more studioish stuff.
Now i just need to finnish my green ringer..... of the 3 projects i started..... green ringer, pt80, and dod 440, you would think the green ringer would have been done first...... but nope.... Soon.... :roll:
i love my pt80 too...i added a triangular lfo,from the memory man delay schematic,with the switch to change capacitors,that drives a led,that modulates an ldr in parallel with the time pot...cool chorus and vibrato...i also wired a 250 k pot in series with the ldr as a depth control...some modulaton always bleed,though...but i love it...
heyo maneco,
for it to have a chorus effect, wouldn't the delay time have to be in the range of say about 20ms ? hence the ldr chosen should have a resistance light/dark resistance value in that range ?
and hmm... is 250k too big a resistance value to be in series ? since I think that it would drive the delay time way beyond 20ms, and hence it would not sound chorusy anymore ?
I was thinking perhaps a 5k pot in parallel with the ldr actually.
but i guess if it works....its fine!
Han
I've always meant to get around to this... I have a ton of PT2399's, and plan on building a few things of my own.
-Colin
cool.
i thought the pt-100 was an upgrade :)
I didnt realise that you could get 1000ms from a PT2399 chip - i thought it was more around 500ms. I've been looking for something that could handle 1000ms as i play dub guitar at around 60-70bpm - and need 1:1 beats - so this could be the one for me. (now very excited)
Are there schematics available for the LFO mod? I was going to build a flange pedal guts and stick this between the delay and feedback loop - but maybe there is an easier way.
With the switchable resistance - can you put a resister in the chain to cut the delay time to 1/4 of the original delay time? ie I could set the max delay time to match my beats at 1:1, so for example at 65bpm i'd set the max delay time to 920ms, would pressing the resitance switch then cut my delay time to 230ms and get me 1/4 beats? (whilst if the max delay time was set to 800ms, swithing this resister would give me 200ms delays). If this is how it works then i'd be over the moon, its exactly what ive been trying to work out for my delay pedal - if anyone has any pointers on this i'd be very grateful (diagrams are great as im still a reletive newbie)
thanks heaps - muizac
Quote from: Yuan Hanheyo maneco,
for it to have a chorus effect, wouldn't the delay time have to be in the range of say about 20ms ? hence the ldr chosen should have a resistance light/dark resistance value in that range ?
and hmm... is 250k too big a resistance value to be in series ? since I think that it would drive the delay time way beyond 20ms, and hence it would not sound chorusy anymore ?
I was thinking perhaps a 5k pot in parallel with the ldr actually.
but i guess if it works....its fine!
Han
i explained it wrong... :) i use an ldr in series with a 250k depth pot...that series goes in parallel with the time pot (50k on mine) ...the modulated delay produces a chorus effect,even if it's on the 300 ms range...
Quote from: anonymousexperimentalistI've always meant to get around to this... I have a ton of PT2399's, and plan on building a few things of my own.
-Colin
hey colin.... it is a very worth while project. lots of stuff in there.... I'm going to eventually go over the schematic with a fine tooth comb soon, and see what if i can have some fun with it later.
I have a long way off idea for the pt2399 as well.... not sure when ill get to it. I wanted to build this basically just to see what it was capable of.
Brian
Definitely man... I'm considering doing something just like the PT80 except with an even more analog-like feedback loop, with the correct LPF value and all... and perhaps even an in-loop 3 band EQ. We'll see, we'll see. It's good to hear it can get up to 1 second, though.
-Colin
Quote from: anonymousexperimentalistDefinitely man... I'm considering doing something just like the PT80 except with an even more analog-like feedback loop, with the correct LPF value and all... and perhaps even an in-loop 3 band EQ. We'll see, we'll see. It's good to hear it can get up to 1 second, though.
-Colin
you can get 1 sec delay.... there is a tiny tiny bit of distortion you can hear on the longer delay times. A lower frequency filter may help quite a bit. Squashing the delay more might help too. The filter is the one thing that i think could use some tweaking.
I think i may add an effects loop for the delay as well. I used to have a digitech processor that allowed me to run the delays thru an envelope filter.... it sounded really cool....
Unless I'm missing something big time, 1000msec from a PT2399 just seems unlikely. The PT2399 has a fixed amount of RAM onboard and tends to poop out around 350ms. I suppose you can tinker with the clocking of it, but the bandwidth would drop noticeably and signal quality too.
In contrast, the PT2395 lets you use either 64k or 256k RAM chips with it for different delay ranges. This is identical to the now discontinued Holtek HT8955, which delivered 800msec delay with a single 41256 chip.
Doesn't mean that folks can't cascade these for long composite delays, though.
QuoteThis is identical to the now discontinued Holtek HT8955, which delivered 800msec delay with a single 41256 chip
Hi Mark,
I think you may have your information wrong. The PT32** chips are nothing like the HT chips as far as I can tell. There is not an option to use external RAM, etc.
JD
Mark is absolutely right about the PT2395...
IMHO, it is possible to even get a 16second delay out of it,
with just a little more memory and a few dividers...
I bet, there are people currently busy on it... :wink:
Drawback: afaik, it`s outa production (currently)...
The PT2395 uses external memory, while the PT2396 and 2399 use internal RAM. The 2399, in particular has 44k of RAM, although I'm never certain from the datasheets exactly what this means. Normally, one discusses RAM under the assumption that word-size is 8-bits, but the sampling is 10-bit here, so that could be 44k of 10-bit addresses, OR it could mean something less. Either way, with a ceiling on RAM of 44k samples in storage at any given moment, that does not permit a great deal of bandwidth once you move out of the 300-400msec zone. Like BBD's, though, that doesn't mean you *can'T* extend the delay time, but you need to accept what it will cost you in bandwidth and additional anti-alias filtering.
The PT23xx series are not pin-for-pin replaceable with the HT8955, so JD is quite accurate there, but they are *functionally* quite similar in that both Princeton and Holtek produced internal and external RAM versions of a 10-bit all-in-one digital-delay chip. Like the HT8955, the PT2395 lets you use a 4164 *or* 41256 RAM chip for either 200 or 800msec. I made one of the latter and it isn't half bad. Could benefit from maybe a little of the companding voodoo that the PT-80 and AD-3208 have, but all in all not bad at all.
What Ton has made me curious about (and he has a way of doing that....) is how one marries up extra memory to the HT8955 or PT2395. The datasheet would suggest that the chip pretty much loses its ability to keep track of where the signal is once you get over the 9 address lines and row/column lines onboard. I gather there is some multiplexing involved?
Heck, even doubling the delay length to 1600msec would be quite useful for purposes of looping. You'd be surprised how much you can stuff in a second and a half.
Hello Mark: no, I`m not the guy who designed the new E-H 16second delay :cry:
but: about 20 years ago I played with a little thing (it had inferior AD/DA conversion than Holtek/Princeton/Mitsubishi(!) ),
and (roughly stated) parallelled the data into a second RAM, which was addressed by the same address-bus, but got its "chip-enable"
from a flipflop (divide by 2) from the last address-line...
Brian-Equally as cool is PITCH shifters and ring mods... man oh man. Did you see moose's site? He did it, might give you ideas. I'm going to see if I can't get it to run off of a 9v all right...
Mark-The way I've always understood it is that halving the clock frequency is as big of a deal, storage/THD/bias-wise, at any delay amount... So if he were to halve the fck to 1mhz, then he'd be getting 700ms without a huge amount of quality loss. Correct me if I'm wrong, though. I had always thought it tangible to get 1000ms out of 2 of these chips underclocked, it surprised me that youc ould get it all right out of one.
-Colin
ok, so if we have 44k, and each byte represents one sample. if we set our delay time at 1 sec we would have a 44khz sample rate (or 35.2 if the bytes referred to are 8 bit) so arent we somewhere near CD quality????
anyways, i am pretty sure this delay is rolling highs off well below 15k, probably more like 10k, so even a 35.2 sample rate should be acceptable.
I seem to remember a lot of digital processors from teh 80's having sample rates arround 32 khz...... What am i missing?
Quote from: Brian Marshallok, so if we have 44k, and each byte represents one sample. if we set our delay time at 1 sec we would have a 44khz sample rate (or 35.2 if the bytes referred to are 8 bit) so arent we somewhere near CD quality????
anyways, i am pretty sure this delay is rolling highs off well below 15k, probably more like 10k, so even a 35.2 sample rate should be acceptable.
I seem to remember a lot of digital processors from teh 80's having sample rates arround 32 khz...... What am i missing?
I'm certainly not the digital guy here, but it is important to consider that, ultimately, *usable* bandwidth is a function not of the sample rate but of what you have to do to eradicate aliasing stemming from the sampling process. For instance, if we had a delay sampling at 50khz with a 4-bit resolution, the stairstep-like nature of the resulting sampling, even though higher in sampling *frequency/rate* than CD standard, would be so gritty as to need serious lowpass filtering to get it to sound reasonable. I have no idea what the formal equations are, but I am certain they are packed away somewhere in a back issue of JAES (Journal of the Audio Engineering Society, a fabulous read if you're ever in a university library). What we need to understand at this point is that higher sampling rates (and the RAM capacity that allows them to turn into longer delay/storage times)
assist a given A/D resolution in yielding better sound, but do not, of themselves result in high quality sound.
I will repeat my earlier comment that I have no idea what exactly the PT2399 is packing 44k *of*. If it's 44k of 10-bit memory locations to complement the 10-bit A/D resolution, then we're talking. If it is *nominally* 44k of 8-bit RAM, and the 10-bit sampling process turns that into something of a functionally lower capacity, then that is a separate matter. Itis also worth noting, with reference to thepreceding paragraph, that 10-bits is not God's gift to high fidelity, and faster sampling rates (which reduce what that same memory can deliver in terms of delay time) maybe the only way to make it yield reasonable sound quality.
As for the clock-frequency-equals-double-the-max-audio-frequency, there are realistic limits to that. which are never articulated terribly well While the limits of human hearing make it such that we probably cannot easily tell the difference between an 18khz tone represented by a simple on-off/high-low pulse and the original source, you can bet your sweet ass that once you move down into the sub-10khz range it starts to become VERY noticeable, and reasonable reproduction of those frequencies (and lower) requires something muchmore than merely a sampling rate double the maximum audio frequency in the passband. Indeed, attempting to represent/reconstruct a 1000hz tone by anything less than *maybe* 10khz sampling rate is simple foolishness.
This gets even more complicated when you realize that there are no guarantees that any portion of the signal is aligned with the sampling process in time such that all the snapshots the sampling process is *able* to take are taken at those times that will faithfully represent the waveform. Consider the foolish example of sampling a 2hz signal at a 10hz rate. If the first sample isn't taken at the "right moment" you've essentially missed it. That 2hz waveform could come at ANY time and you'd miss it.
The only way to assure faithful reconstruction without being to guarantee the wave starts only when you're "ready" for it is to up the sampling rate again so that you're just sampling like crazy in the assumption that you'll always cover it.
This is all the long way of saying that 44k of RAM may sound like a lot, but when it's a 10-bit word, and as complicated a signal to reconstruct as an audio signal, 44k doesn't stretch very far unless you rein in bandwidth a LOT..
sometimes a 16 bit audio sample, if at lower volume can be only working with 10 bits of bandwidth..... I think that is why the compander is useful.... it make use of as much bandwidth as possible.
your right though about digial timing an wave form peaks, but the artifacts created by that are sub harmonics, and cant be filtered out with a multipole low pass filter. they really cant be filtered out by anything, because they are so unpredictable. as your sample rate goes up subharmonics reduce significantly, but mathematically they are always there.
I actullally have a pretty decent digital recording studio, and if you record somthing at 8 bit, and 16 bit, and 24 bit at 41KHZ you can tell a difference between all of them.....
If you compress before you record it is much less noticable.
If you cut all the highs about 5 K or so, you cant even hear the difference..... but if you reduce the sample reat to say.... 22khz. you cant filter out the nastyness.
that is my experience anyways.
brian
Brian,
I am about to start on a PT80 build, but I cant loacte any source for the PT2399. I am in Europe but I jave searched far and wide.
No sources whats so ever.
Do you know of one that will ship to France.
Cheers,
Robert