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 Forum index » DIY Hardware and Software » Thomas Henry designs
Krunkus does the SNVoice
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Uncle Krunkus
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PostPosted: Sun Dec 16, 2012 3:52 am    Post subject: Krunkus does the SNVoice Reply with quote  Mark this post and the followings unread

A few years ago, Thomas sent me an SN76477 for "inspiration", and a few days ago, Bill (State Machine) sent me a copy of the SNVoice PCB for "distraction", and so I have soldered in the 3 * 12 way molex connectors, (please kiddies, don't solder all the pins before you check that it's flat on the board! Shocked Even us old timers get a trigger happy sometimes. Ask if you want to know how to fix this problem.) and the three IC sockets.
Sometimes, it's nice to take a break from designing things, and trust in someone else's path. This is where I can concentrate on preciscion building, which I just love. It's like meditation for me.

Ummmm,...
A couple of questions,
1. The SN76477 runs off 5V, so does that put it in the same family as the 74XXXX series and therefore not static sensitive, or not?
2. I've heard that most builders solder the SN straight into the board, and that problems with being properly soldered straight to the board are rare. I don't have a socket for it, so that's what I'll do. Last. Any ideas?
3. Is the LF444 critical for both? I only have one. Will a TL074 cut it? for which one? Any other subs? I've got a lot of other quad op-amps.

Okay, that'll do for now, I'll get on with the resistors! Very Happy

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elmegil



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PostPosted: Sun Dec 16, 2012 9:06 am    Post subject: Reply with quote  Mark this post and the followings unread

Dunno about soldering straight in...haven't built mine yet, but I have a chicklet board I plan to solder to which I can then socket.
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diablojoy



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PostPosted: Sun Dec 16, 2012 2:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
but I have a chicklet board I plan to solder to which I can then socket

oohh i have 6 of these to do and no sockets as yet that chicklet board sounds like a very good plan!
as for the LF444 not sure if totally neccesary but maybe because the
offset spec is better than TL series ?

Quote:
and so I have soldered in the 3 * 12 way molex connectors, (please kiddies, don't solder all the pins before you check that it's flat on the board!

yes used to happen to me too occasionally now i hold everything in place with blue tack then solder not foolproof but 99% of the time it works great.

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elmegil



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PostPosted: Sun Dec 16, 2012 2:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

Just looked it up, I got them from bg micro
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diablojoy



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PostPosted: Sun Dec 16, 2012 4:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Just looked it up, I got them from bg micro

thanks i will look them up

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Uncle Krunkus
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PostPosted: Mon Dec 17, 2012 3:29 am    Post subject: Reply with quote  Mark this post and the followings unread

diablojoy wrote:
yes used to happen to me too occasionally now i hold everything in place with blue tack then solder not foolproof but 99% of the time it works great.


Oh, believe me, I should know how to get it right. Rolling Eyes After the ASM2, and prototyping the Klee (have seen how many molex connectors we put on that?! Laughing) It's easy to just solder one pin, and re-heat it while the plastic base is seated, then you finish from the other end. I just found it ironic that after all this time, I'm so rusty, that I'd get the first step so wrong! Laughing
Anyway, all fixed now. Perfecto.

There's no need to add any pics yet, as you've all seen partially populated SNV PCBs I'm sure. But I know from past experience, that the panel should start early, so I''l be looking at that real soon, and so will you. Very Happy

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analog_backlash



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PostPosted: Mon Dec 17, 2012 4:07 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi,

Your question about the LF444 vs. (say) the TL074 has been a source of bemusement for me for a while now. They former are quite often used (especially in Ray Wilson's designs) but I cannot always see why. The TL074 has a faster slew rate, similar output voltage swing, similar input impedance and lower noise characteristics than the LF444. The plus points for the LF444 seem to be that it requires a lower supply current and its input offset voltage is lower. I'd like to know if it's for one of these characteristics that it is chosen (or something else that I've missed). I'd like to know more about this since (a) the TL074 is considerably cheaper and (b) I don't hold out much hope for the long-term future of the LF444 (the LF441 is now obsolete, I think).

Gary

P.S. Good luck with the SN Voice. I've always been put off by the cost of the 76477!
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Uncle Krunkus
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PostPosted: Mon Dec 17, 2012 5:23 am    Post subject: Reply with quote  Mark this post and the followings unread

analog_backlash wrote:

P.S. Good luck with the SN Voice. I've always been put off by the cost of the 76477!


So have I! Laughing
If only I'd bought up 100 or so back in the 80s when I first played with one.
Well, all I can say there is that it is solely due to the generosity of my two major benefactors, Thomas himself, and Bill (State Machine).
I must have had more karma in the bank than I thought. Very Happy

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State Machine
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PostPosted: Mon Dec 17, 2012 5:50 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
1. The SN76477 runs off 5V, so does that put it in the same family as the 74XXXX series and therefore not static sensitive, or not?


The best approach is to treat all IC's the same and use reasonable practice to avoid any damage from static electricity, 5V, 3.3V, 2.5V, or whatever voltage they are powered from. The SN76477 is a mixed signal device with a fair amount of circuit integration and thus may be less robust than say a 7404 inverter IC to the effects of static discharge. Also the 76477 chip is comparatively more expensive, and less available, and even more reason to treat it with care.

Quote:
2. I've heard that most builders solder the SN straight into the board, and that problems with being properly soldered straight to the board are rare. I don't have a socket for it, so that's what I'll do. Last. Any ideas?


Its rare these IC's are bad and if operated within it's specified parameters, will last a life time. I would say that if you don't have a socket and you really want to get this thing up and running, go ahead and solder it to the board. If you had to replace it in the future, through hole devices are not that hard to remove.

Quote:
3. Is the LF444 critical for both? I only have one. Will a TL074 cut it? for which one? Any other subs? I've got a lot of other quad op-amps.


If I had two and had to choose, I would use it in the U3 position simply because it (LF444) has a better offset specification. I chose U3 because the role of the operational amplifier in this position serves partly in the critical role of CV to Expo conversion and HF compensation. The U4 position is serving in a more mundane role and thus is not critical as far as I see.

Bill
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Uncle Krunkus
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PostPosted: Mon Dec 17, 2012 6:35 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Bill,
I was wondering when you might turn up. Very Happy
Thanks for the answers, I may end up getting some more 444s, as I need to find some tempcos here in Australia anyway. It's good to know U4 is up for some experimentation, if need be.
Of course my handling of the SN76477 will be with all due care for such a prize, but I don't think I'll be swapping it out. So I think I'll go ahead with the hard-wired (soldered) idea.

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analog_backlash



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PostPosted: Mon Dec 17, 2012 7:06 am    Post subject: Reply with quote  Mark this post and the followings unread

State Machine wrote:
Uncle Krunkus wrote:
3. Is the LF444 critical for both? I only have one. Will a TL074 cut it? for which one? Any other subs? I've got a lot of other quad op-amps.


If I had two and had to choose, I would use it in the U3 position simply because it (LF444) has a better offset specification. I chose U3 because the role of the operational amplifier in this position serves partly in the critical role of CV to Expo conversion and HF compensation. The U4 position is serving in a more mundane role and thus is not critical as far as I see.


That seems to answer my question - it is down to the superior voltage offset spec of the LF444. Thanks for that Bill. I've looked back at previous circuits that I've used them in and they are usually associated with the expo section. I'll remember that for future reference.

Gary
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