Re: CVX-2 : covox adapter
Posted on 2017-01-17, 21:52
Whoops! Okay, made the changes, and 1.083 Vdc now achieved! I'll make some new recordings.
Re: CVX-2 : covox adapter
Posted on 2017-01-17, 21:19
Jepael wrote: On CVX-1, R10 needs to be a short (zero ohms), and if it had 100k/200k R2R network, 25k in parallel or in place of the 4.7nF cap C1. I did that: https://goo.gl/photos/L1ykmzuJrgxB6ZSC9 ...but I'm still getting 5.06 Vdc measurement from the device...?
Re: CVX-2 : covox adapter
Posted on 2017-01-17, 20:22
Well, heck, with such exact directions, I feel obligated to make the changes and see how it goes 😀 All I have are 22K and 27K resistors on-hand; I'll use 27K and then report back.
Re: CVX-2 : covox adapter
Posted on 2017-01-17, 19:23
Well, that was educational: CVX-1 Prototype: 5.04 vDC CVX-2 Prototype: 4.80 vDC 10-pin Covox: 1.024 vDC 11-pin Covox: 1.025 vDC
Re: CVX-2 : covox adapter
Posted on 2017-01-17, 18:40
Real Covox R2R network output has also 100k output impedance, but with the extra 25k load resistor, it divides the voltage down to 1/5, so driven by 5V parallel port, it should output 1Vpp audio signal - much better amplitude for audio. Just for curiousity, I decided to do just that (I had a 22K …
Re: CVX-2 : covox adapter
Posted on 2017-01-17, 03:50
Oh no, don't do anything, it's something you already measured, it is within the resistor array package. Okay, cool. (Slightly relieved, since I didn't make the video with OBS, I had to use two cell phones, lol) And the most important part, there is 25 kohm resistor between output and ground, so …
Re: CVX-2 : covox adapter
Posted on 2017-01-16, 21:42
Oh! Okay, I'll attempt measuring that (if it exists) tonight and reply back.
Re: CVX-2 : covox adapter
Posted on 2017-01-16, 18:06
I wrote "there's no need to destroy the pack". Re-read what I wrote more carefully, perhaps? The values have already been measured. As for using an actual DAC, that would obviously produce higher-quality results and probably not cost that much (simple DAC ICs were about $3 in the 1990s, they are …
Re: CVX-2 : covox adapter
Posted on 2017-01-16, 17:18
^ maybe you can send one to dreamblaster to analyze that custom resistor pack I meant send the CVX-1 and CVX-2 prototypes. The Speech Things stay with me :-) now that we've confirmed the ladder uses R=100K and 2R=200k; there's no need to destroy the resistor pack. If there is sufficient …
Re: CVX-2 : covox adapter
Posted on 2017-01-16, 00:49
Yeah, the real covox is probably just a resistor pack, without caps. So a last attempt could be to short the coupling cap as well, on MobyGamer's CVX-1. Okay, this is done: ftp://ftp.oldskool.org/pub/misc/temp/LPTDAC_comparisons/CVX-1%20using%20100k%20resistors%20-%20no%20filtering%20-%20no%20cap% …
Re: CVX-2 : covox adapter
Posted on 2017-01-15, 05:03
Replaced CVX-1's R10 resistor with a 0 resistor (I guess this is good practice for learning to solder :-) and made recordings: ftp://ftp.oldskool.org/pub/misc/temp/LPTDAC_comparisons/CVX-1%20using%20100k%20resistors%20-%20no%20output%20filtering%20-%20R10%20shunted%20-%20crystal%20dream.flac ftp:// …
Re: CVX-2 : covox adapter
Posted on 2017-01-14, 20:39
dreamblaster wrote: Hi Moby, please try by shunting R10, it will sound brighter Okay, will do that and reply back with audio links. I'm going to use a 0-value resistor (instead of a small wire which is what I had to do with the SMC version).
Re: CVX-2 : covox adapter
Posted on 2017-01-14, 18:52
Okay, CVX-1 using 100k resistors, no shunting or filtering: ftp://ftp.oldskool.org/pub/misc/temp/LPTDAC_comparisons/CVX-1%20using%20100k%20resistors%20-%20no%20output%20filtering%20-%20no%20shunting%20-%20crystal%20dream.flac ftp://ftp.oldskool.org/pub/misc/temp/LPTDAC_comparisons/CVX-1%20using% …
Re: CVX-2 : covox adapter
Posted on 2017-01-14, 18:02
MobyGamer wrote: I could shunt the same resistor on the CVX-1 and make recordings, but since it also uses 7.5k/15k resistors, I don't think it will sound any better. Wait, I'm wrong -- I just looked at the CVX-1 Serge sent me and it uses 100k resistors. I'll make the same test recordings and post …
Re: CVX-2 : covox adapter
Posted on 2017-01-14, 06:06
CVX has 1 additional resistor R19, we should test by shorting this resistor Okay, I was able to do that this evening (surface-mount resistors are smaller that I realized!) and made some recordings: ftp://ftp.oldskool.org/pub/misc/temp/LPTDAC_comparisons/CVX-2%20no%20resistor%20R19%20shunted% …
Re: CVX-2 : covox adapter
Posted on 2017-01-12, 01:53
OK, will work on that and reply back with a new set of recordings.
Re: CVX-2 : covox adapter
Posted on 2017-01-11, 22:21
I don't think the adapter should "add bass" or color the sound output; that should be left to the user... What about the resistor ladder/arrangement in the FTL adapter?
Re: CVX-2 : covox adapter
Posted on 2017-01-11, 08:40
Okay, here's the moment you've all been waiting for: The reference recordings! I received the CVX-2 from Serge a few days ago, set up a testing rig with my E-MU 0404, checked for ground loops, and captured Crystal Dream as well as a test corpus on the following configurations: Covox Speech Thing (10 …
Re: CVX-2 : covox adapter
Posted on 2017-01-11, 08:20
The Media Vision "Dongle" is highly complex compared to your average Covox-a-like tho. Sadly I don't have any pictures of the internals at hand but I think it basically came down to being a ThunderBoard on a LPT port instead of having an ISA interface. Someday I'll open up my "m-sound" LPT box. It …
Re: CVX-2 : covox adapter
Posted on 2017-01-02, 23:24
I think that the Covox, similar to the GUS, was mostly a darling of the demoscene. No, it had a lot of use outside of the demoscene for computers that couldn't use ISA sound cards, like laptops and PS/2 systems. It was probably the most common device connected to laptops so people could play audio …
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