Digital volume control.

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ed
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#16 Re: Digital volume control.

Post by ed »

good points, one and all.

I am heartened to hear that somebody is on the case regarding drift.
The point about B1 gain was in response to your post to John, saying what he might have liked about the Korg version was the gain...no angle what so ever.

The point about the illegality, or not, still stands as the units I used(nsl-32) are still in use as far as I'm aware. Whether the rule will be rescinded now that we've parted company with the EU remians to be seen. So politics may still be relevant. Again I have no angle so don't care either way. I do recall I gave my stash away at the time, I just don't recall who had them?. If diying this then it's best to have a bunch because they need matching....but if the drift is being addressed then maybe this is not so crucial. But more of a challenge to the diyer.
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#17 Re: Digital volume control.

Post by Nick »

The matching, balance and drift can of course be fixed by wrapping stuff around them. The inherent distortion can't. There are some graphs around here somewhere of some measurements I did. And the THD of the LDR unit that was linked to would indicate the problem is still there. Which is why I quoted it.

IMHO the continuing irony of LDR's is that their original justification was to remove the minuscule distortion introduced by a switch or relay contact, but in the process introduce far higher levels of distortion. There seems to be some odd form of cognitive dissonance going on. "Distortion is bad in switches, we must remove it" : "Distortion in the resistive element is not a problem".

And a final rant, they are called Light Dependent Resistors, and that’s then interpreted as "Resistors, they are passive, so must be fine". But in reality they are semiconducting elements that have all sorts of non linear behaviour.
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#18 Re: Digital volume control.

Post by pre65 »

I've gone and ordered the preamp, sod the expense. :lol:

I decided that remote control volume was necessary, and this seemed a relatively inexpensive way to achieve that aim.

Won't be here for several weeks though. :(

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#19 Re: Digital volume control.

Post by ed »

you can tell I'm looking for distractions, so I'll continue....

superb points Nick....I was almost tempted to resurrect the project with a spare esp32 I have here.....but sanity took over..

from the experience I've had...even when the nsl-32s were new and matched the finished article couldn't hold a light to the original B1 with that bog standard £2.50 Maplin pot...I did have plans at the time to replace the Maplin pot with an attiny and a digi pot so I could add the apple remote but I never got round to it.

I'm not sure, but I'll guess the tortuga uses nsl-32 or similar, so I would still recommend the analog approach..
Yes, I admit, I haven't heard a tortuga unit.....
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#20 Re: Digital volume control.

Post by Ray P »

Were getting two subjects intertwined here so just to clarify (hopefully);

Firstly, LDRs; as I've already said, I posted the Tortuga link for general interest, not to advocate it, so I have no particular interest in mounting a defence of it, or LDRs in general, especially when it isn't even on the market yet. Would be interested to hear one if the opportunity arose but that's all.

B1 buffer; JohnG said he was going to get a B1 after hearing one so would dump his Slagle AVC. What I've said is that he might be preferring the sound of the extra drive being imparted by the B1 buffer and suggested he might want to try a B1 (with or without the Korg device) with the Slagle AVC as its volume attenuator - possibly best of both worlds? I am of course assuming that the Slagle AVC is superior to a standard potentiometer (LDRs didn't come into this at all). I'm not doubting that a standard B1 with an ordinary potentiometer sounds good. Anyway, JohnG seems to have a mysterous 'man in the shadows' who does his builds for him so I guess that will influence whether it gets tried.
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#21 Re: Digital volume control.

Post by Ant »

I've had a passing interest in the pass b1 buffer to go with the f5, never got round to it. Is the b1 the same one I'm thinking of?
One of the nicest passive pre's I've built was the one I put together for Ali using tribute transformers. I've built a lot of different ones, and the ones that stand out are the tribute, the khozmo steppers (I've done loads of them and use one myself) and a glasshouse stepper that was nearly 300 quid. Can't remember what resistors it used but it was very very good.
I wouldn't mind trying a b1 with a khozmo in front of it
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#22 Re: Digital volume control.

Post by ed »

Hi Ant

as soon as I'm allowed out I'll get down to the post office and send you it..if you're interested? It's only got 1 input though, no switching.
let me know.
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#23 Re: Digital volume control.

Post by Ali Tait »

Yes, I’ve had the thought to try a B1 on the end of the Tributes.
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#24 Re: Digital volume control.

Post by Nick »

Or at the front of it. You get even more drive capacity plus the source is driving a resistive load.
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#25 Re: Digital volume control.

Post by Ant »

That'd be great Ed, yes I'd like to try it if I may.
I've got a spare switching box that I scragged up (made a proper one for the different tts now) that I an stick on the end of it
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#26 Re: Digital volume control.

Post by steve s »

Ray P wrote: Sun Apr 05, 2020 9:06 am

Steve, it was me that posted about the LDR volume control modue, not John. As you know, I have a high-resolution system and have tried an LDR-based volume control in the past - I found it transparent and didn't hear any distortion affects - horses for courses I guess.
Sorry for getting you mixed up Ray
My apologies
The session I had with the ldr luckily I had Scott sat next to me, we where both of the same opinion regarding the sound. The same unit was reported as ' improving ' other systems. It would be interesting to do the same test again on one of the modern versions, but as Nick pointed out the distortion levels seem similar to the one I tried.
Maybe Owston (all being well), next year with Phil's if he's ok with that.
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#27 Re: Digital volume control.

Post by Ray P »

steve s wrote: Sun Apr 05, 2020 7:10 pm Sorry for getting you mixed up Ray
My apologies
No prob and no need Steve.
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#28 Re: Digital volume control.

Post by Ali Tait »

Nick wrote: Sun Apr 05, 2020 5:20 pm Or at the front of it. You get even more drive capacity plus the source is driving a resistive load.
Thanks, I’ll keep that in mind.
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#29 Re: Digital volume control.

Post by Nick »

with Phil's if he's ok with that
I don't think what Phil has ordered is LDR.
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#30 Re: Digital volume control.

Post by pre65 »

Nick wrote: Sun Apr 05, 2020 7:45 pm
with Phil's if he's ok with that
I don't think what Phil has ordered is LDR.
Nor does Phil. :lol:
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