Prelude 1200 - heavy distortion (and crash) above 27420Hz

[rvo_nl]

I dont know I dont know much about AHI 6. I know there are versions for many platforms, like morphos, ppc, 68k etc. I guess I just have to try it out. Whenever I find the time to do so, I will post the results. Thanks so far!

[whabang]

The maximum frequency a 27420Hz sampling rate can achieve is approx.  13.5KHz, half the sampling rate. And that would be one hell of a crappy  square looking 13.5KHz wave. This is why the higher the sampling  frequency is, the better more accurate representation, even way way  beyond double audiable range. 192KHz is nice, but sampling frequencies  in MHz ranges would be even better at correctly capturing the high end  audiable frequencies and harmonics which just aren't represented at all in todays digital world of crap sound.
Makes me glad I have my Tascam reel to reel mastering machine and a decent vinyl collection.

While most people can't hear anything over 21 KHz , we are perfectly capable of telling different waveforms apart, even at high frequencies. That's where high sample rates come in.

Problem is that 192 KHz sometimes allow distortion, as the resolution is so high it allows other frequencies to "merge" - kinda like aural moiré patterns. There's a few tests that imply that the optimal sample rate for human ears would be around 70-80 KHz.

Regardless, I'm getting older, and seems to be capped at 44 KHz. When I was younger I was able to tell 44.1 from 48 KHz. Now, I can barely hear the difference between 48 and 32. -.-

Anyway, to get back to the topic: 27 KHz at 16-bit resolution means a transfer speed of at least 54 Kbps. Can the clock port handle that much when the CPU needs cycles to feed it with data?

[rvo_nl]

27 KHz at 16-bit resolution means a transfer speed of at least 54 Kbps. Can the clock port handle that much when the CPU needs cycles to feed it with data?

 Especially with my clock port extension cable in place, that is something I am sersiously questioning now, too. I am in contact with ACT and Marc, who is very helpful, is afraid that cable is just not able to cope.
 
 If installing AHI 6 is not helping, Im quite sure the cable has to go. Then I have to find another way of connecting the thing.

[rvo_nl]

AHI 6 didnt help..
 
 @Paul1981 what screenmode is your machine running?

[paul1981]

AHI 6 didnt help..
 
 @Paul1981 what screenmode is your machine running?

It works in any mode/colour depth mate. My Workbench is Euro72Hz Productivity. My Audio Evolution screen mode is Multiscan Productivity. Can't you try your Prelude connected straight to the 1200 motherboard like it's supposed to be? At least that would let you know if it is a cable issue or not.

[rvo_nl]

Thanks!

I wish it was that easy.. But I will try this week.

[Dandy]

...in todays digital world of crap sound.
Makes me glad I have my Tascam reel to reel mastering machine and a decent vinyl collection.

Exactly.
I also still have my 2.5 m vinyl LPs, about 1.5 m vinyl Maxi Singles and roughly 500 vinyl singles from my DJ period (1974 - 1980).

[rvo_nl]

Can't you try your Prelude connected straight to the 1200 motherboard like it's supposed to be? At least that would let you know if it is a cable issue or not.

Hi, took me a few hours, but Ive got the machine running with just 2Mb. When I run a digibooster mod over AHI, there is no distortion. It doesnt matter if the clockport extension cable is connected or not. I was quite surprised by this. The only thing I have removed is the ppc + bvision. Any ideas?

Edit: With PPC+Bvision+256Mb connected, I stil boot into the same Workbench installation I am using now. In that situation, the output will crash the system.

[Dwyloc]

Hi, took me a few hours, but Ive got the machine running with just 2Mb. When I run a digibooster mod over AHI, there is no distortion. It doesnt matter if the clockport extension cable is connected or not. I was quite surprised by this. The only thing I have removed is the ppc + bvision. Any ideas?

Edit: With PPC+Bvision+256Mb connected, I stil boot into the same Workbench installation I am using now. In that situation, the output will crash the system.

@rvo_nl
This is just a whiled guess but it sounds like some sort of timing problem.

So the first think I would try with the BlizzardPPC reconnected is to go into its own early startup menu.

I don't have access to my BlizzardPPC at the moment to check what key combination you hold down on reboot to get into the menu BlizzardPPC setting menu.

But it allows you to change the ram speed and make play with some other performance options related to the context switching between CPU's if I remember correctly.

So I would make a note of the current settings then try changing them one at a time help.

Its also possible that that its one of your RTG setting causing the issue so you could try without the blizzardvisionPPC monitor driver loaded and any other libraries moved out the way to stop them loading if you have not already tried that.

Anyway good luck and I am now wishing I had time and space to get my A1200 Tower out of storage and refit my BlizzardPPC and BlizzardVision instead of using my mediatorSX and Blizzard040 cards that are currently fitted to it.

I just don't have the space to have it setup at the same time as my Sam440, PC and minimig :-)

[rvo_nl]

I like your thinking, but Im afraid its not going to help. I have just tried with a 030 card and have encountered the same issue. Also, Im doing this on a fresh Workbench 3.1 installation with no CGX installed.

As soon as an accelerator card is in place, the timing is broken. Then again, it could be broken without an accel card too, since the basic 020 is not able to play mods in realtime in that case and it may not have to shift as much as data in that case. Just guessing.

[Dwyloc]

I guess that leaves trying with a different revision of A1200 motherboard or timing fixes to your existing board other than that I am out of ideas sadly :-(

[paul1981]

I like your thinking, but Im afraid its not going to help. I have just tried with a 030 card and have encountered the same issue. Also, Im doing this on a fresh Workbench 3.1 installation with no CGX installed.

As soon as an accelerator card is in place, the timing is broken. Then again, it could be broken without an accel card too, since the basic 020 is not able to play mods in realtime in that case and it may not have to shift as much as data in that case. Just guessing.

Are you making sure you are using the correct ahi.device and paula.audio for your cpu? Do you get problems when using the paula audio driver?

So ahi.device is for 020 through to 040
ahi.device.060 is for 060

Remember to manually rename cpu specific files around when swapping between an 020/030 cards and your 060 card - either that or re-install AHI with its installer and make sure it re-installs for correct cpu. I'm guessing this is how it works, but like I said, haven't installed AHI in 7 years.

Remember that the PreludeTapeDeck program doesn't need AHI, nor does play16 if you set the PRELUDE tooltype... so what happens when you use either of these programs? Does it work?

[rvo_nl]

AHI drivers are the right ones.

I fiddled around with Play16 today and noticed the same issue. Initially the output sounds fine, then a loud hiss follows, which sometimes dissappears, sometimes not, and it results in a crash from time to time.

Ive tried without the Blizzard by holding down '2', but had the same problem. Seems like something is broken or my system generates a lot of noise? Is anyone able to test and repair my Prelude?