VOGONS


First post, by darry

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Whenever I try to record anything from either the EMU8000 or line in in Windows, I hear a constant very low volume tone (will attach sample soon) in the recording . This is not heard on line-out, no matter what I unmute . Nothing is connected to the line-in jack . The issue is present when recording the input corresponding to EMU8000 even when no MIDI is playing .

This is not hum due to a ground loop (occurs when recording internally and higher frequency than 60Hz).

Anybody had that issue before with an AWE64 ? My guess is the that either the ADC, the mixer chip, or something related is going bad or is it simply a crappy design that picks up noise ?

Last edited by darry on 2020-09-21, 21:01. Edited 2 times in total.

Reply 2 of 16, by darry

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kolderman wrote on 2020-09-19, 07:30:

Gold or value?

Value or original. Will check tomorrow . Definitely not a Gold .

Forgot to mention I have a Simmconn Revival on the card .

I have never tried to record with this card, so issue might be present from factory .

Another sound card in the system has no issues with recording .

Reply 3 of 16, by darry

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Here are some sample recordings . I had to zip them as the forum does not allow .wav attachments, for some reason .

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Here is a frequency graph of one of them .

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EDIT : What is that annoying tone just above 1000 Hz ?

Reply 4 of 16, by darry

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Ran some more tests.

The card installed is a CT4500 . It is noisy while recording even if I remove the Simmconn (no surprises there).

I was able to dig up a CT4520 in my parts stash and tried that instead .
The result : recording is subjectively much quieter (no 1KHz bump), BUT playback is worse than my CT4500 in that it has very quit level pulsing/breathing noises that the CT4500 does not . Since I can always record through line-out using another device, I am better off with the CT4500 in the end .

The CT4520 has Nichicon capacitors, suprisingly. I did not bother checking the CT4500 .

Conclusion : Granted, these cards are over 20 years, but I was hoping for something a bit better . In comparison, my Audiotrix 3D/XG is much better at recording .I can't wait for the AWE64 Legacy .

Reply 5 of 16, by darry

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Curiosity got the best of me, so I ordered a supposedly NOS (large batch being sold) CT4520 . I will try its playback and recording abilities when I receive it (I need an actual usable spare anyway).

The board I am using is a 2006ish vintage (AFAICT) industrial one and the PSU is a Corsair RM850x , so I do not expect the PC environment to be unduly noisy .

Reply 6 of 16, by Joseph_Joestar

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darry wrote on 2020-09-20, 15:16:

Curiosity got the best of me, so I ordered a supposedly NOS (large batch being sold) CT4520 .

Piece of advice, check your CT4520 for the Vibra distortion bug. Doom offers an easy way to test it.

Mine has it, and it manifests whenever the in-game volume for digital audio is above 50%. This is very annoying for older games that don't allow you to adjust digital audio volume in-game. The SB mixer volume settings appear to have no effect on this particular bug.

Using Audigy drivers with a Sound Blaster Live
Installing DOS drivers on an Audigy2 ZS
OPL3 vs. ESFM vs. CQM vs. SBLive
OPTi 82C930 review

Reply 7 of 16, by darry

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Joseph_Joestar wrote on 2020-09-20, 15:50:
darry wrote on 2020-09-20, 15:16:

Curiosity got the best of me, so I ordered a supposedly NOS (large batch being sold) CT4520 .

Piece of advice, check your CT4520 for the Vibra distortion bug. Doom offers an easy way to test it.

Mine has it, and it manifests whenever the in-game volume for digital audio is above 50%. This is very annoying for older games that don't allow you to adjust digital audio volume in-game. The sbmixer volume settings have no effect on this particular bug.

Thank you, I have heard of that issue. I will test it with the CT4500 for now and try to remember to test the CT4520 for it too . Does this issue only occur when the card is used in SB compatibility mode ?

Reply 8 of 16, by Joseph_Joestar

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darry wrote on 2020-09-20, 16:29:

Thank you, I have heard of that issue. I will test it with the CT4500 for now and try to remember to test the CT4520 for it too .

I'm curious if the CT4500 and the AWE64 Gold also have this bug, since their PCB layout is quite different from my CT4520.

Does this issue only occur when the card is used in SB compatibility mode ?

I have mostly heard it in DOS games using SB16 mode. However, it does occasionally manifest in native Win9x games as well.

Using Audigy drivers with a Sound Blaster Live
Installing DOS drivers on an Audigy2 ZS
OPL3 vs. ESFM vs. CQM vs. SBLive
OPTi 82C930 review

Reply 9 of 16, by darry

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I just remembered that I have another CT4520 installed in an Asus P3B-F . I tried recording from EMU8000 input just for kicks . It's actually worse, noise-floor wise, but a bit less annoying than that 1KHz tone . Those AWE64 cards can't all be bad apples . EDIT: Or maybe they are all very susceptible to noise in their own special way .

freq_ct4520_p3bf_MIDI.png
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Reply 10 of 16, by darry

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I did the Doom distortion test in Re: Creative CT2890 PnP vs CT2940 (Sound Blaster 16 models) on my CT4500 using line-out and running the DOS version of Doom (GOG release) under Windows 98 SE . I did not hear anything resembling the clipping/clicks in the MP3 that was present in that thread . I made sure to max out in-game volume and SB16 mixer first . I do not feel like re-testing with the CT4520 at this time .

I will run further tests once I receive that NOS CT4520 and will think about about a simple way to get some line-out recording samples .

EDIT : It is ironic that I am using a multi-track digital recorder (DSP12) as a mixer but that I do not have simple way to extract audio files from it . I will probably just get an S/PDIF splitter and tap into that for recording .
EDIT2 : Powered optical splitter is on its way .

Reply 11 of 16, by Joseph_Joestar

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darry wrote on 2020-09-21, 04:08:

I did the Doom distortion test in Re: Creative CT2890 PnP vs CT2940 (Sound Blaster 16 models) on my CT4500 using line-out and running the DOS version of Doom (GOG release) under Windows 98 SE . I did not hear anything resembling the clipping/clicks in the MP3 that was present in that thread . I made sure to max out in-game volume and SB16 mixer first .

Cheers!

I figured it might have something to do with the heavily integrated CT4520 PCB. Visually, I see fewer chips on it compared to the CT4500 and the Gold. It also seems to be lacking an oscillator crystal, at least in the case of my card. Let us know how your NOS card fares.

Using Audigy drivers with a Sound Blaster Live
Installing DOS drivers on an Audigy2 ZS
OPL3 vs. ESFM vs. CQM vs. SBLive
OPTi 82C930 review

Reply 12 of 16, by darry

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Joseph_Joestar wrote on 2020-09-21, 06:50:
darry wrote on 2020-09-21, 04:08:

I did the Doom distortion test in Re: Creative CT2890 PnP vs CT2940 (Sound Blaster 16 models) on my CT4500 using line-out and running the DOS version of Doom (GOG release) under Windows 98 SE . I did not hear anything resembling the clipping/clicks in the MP3 that was present in that thread . I made sure to max out in-game volume and SB16 mixer first .

Cheers!

I figured it might have something to do with the heavily integrated CT4520 PCB. Visually, I see fewer chips on it compared to the CT4500 and the Gold. It also seems to be lacking an oscillator crystal, at least in the case of my card. Let us know how your NOS card fares.

If time allows, my plan is to test line-out and EMU8000 recording of silence (nothing playing) on all four AWE64 cards that I will eventually have (one CT4500 and 3 CT4520s) in both my main retro rig (Ipox 3ETI23 industrial board) and my test-bench rig (P3B-F) . This should give an idea of

a) Whether AWE64 noise behaviour is affected by environment (mainboard, PSU, etc)
b) Whether CT4520s vary much from unit to unit and possibly with use
c) Whether or not the CT4500 is always better than the CT45200, noise-wise (limited value due to me having only having a sample size of one CT4500) .

I am still waiting on the AWE64 Legacy, otherwise I would be very seriously considering selling the CT4520s and buying a an AWE64 Gold and a Simmconn Revival Gold version .

Reply 13 of 16, by darry

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I got my powered S/PDIF splitter today, so I thought I would run some preliminary tests, informally .

Some disclosure first :

a) I am no expert in this, so if I am doing it wrong (or you suspect I might be), please let me know .
b) All audio from sound card line-outs is digitized by my Akai DPS12 at 44.1KHz .
c) Sound levels between input on the DPS12 are matched approximately. So take comparisons between cards of different families with a grain of salt . Comparisons between cards of the same family (AWE64 card variants) while be run on one set of DPS12 input, always with same gain settings, and should be comparable between cards.
d) Digital recording card used is a cheap CMI based USB card with S/PDIF inputs connected to my DPS12's S/PDIF output .

First, a baseline of sorts . Akai DPS12 with all inputs muted .

dps12_all_inputs_muted.png
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CT4500 line-out with wave and MIDI (EMU8000) unmuted and at max level on sound card mixer .

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Audiotrix 3D/XG line-out with wave and line-in (Dreamblaster X2) unmuted and at max level on sound card mixer .

dps12_audiotrix3dxg_wave_line_inputs_only_linear.png
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dps12_audiotrix3dxg_wave_line_inputs_only.png
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EDIT: Added linear view of Audiotrix 3D/XG frequency plot .

Reply 14 of 16, by darry

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I think that something may be off off with my DPS12 . The GUS is nice and quiet while playing nothing, except that low frequency bump, same as my other sound cards . So I tested a pair of my DPS12's analogue inputs with nothing physically connected, but the said inputs enabled . I still get that approximately -60dB low frequency bump, which means that the DPS12's analogue circuitry and/or ADC is the one generating it . I can't say I hear an issue, but this is still worrisome to me.

DPS12 with Gravis Ultrasound 3.73 connected and enabled (all inputs on GUS muted except synth and overall).

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DPS12 with one pair of inputs enabled, but nothing connected .

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P.S. I realize that to actually test the noise floor I would need to play a simple tone (say 1 KHz) to prevent a sound card's line-out from self-muting, but my objective so far here was to test noise "at rest" . I will try to run some more rigorous tests when I receive that NOS CT4520 .

Reply 15 of 16, by darry

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I ran even more tests using a 1 KHz test tone . The low frequency bump is still there .

Should I consider junking the DPS12 and getting a proper modern mixer ?
EDIT: Am I just being an anal retentive perfectionist about this ?

CT4500

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Audiotrix 3D/XG

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Gravis Ultrasound 3.73

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EDIT2 : Added results on a Gravis Ultrasound version 3.73