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Volume controls - what are you using?

audio_PHIL_e

audioPHILe
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My neighbours control my listening volume
I likes the Lenny Henry sketch where he's in the kitchen with LOUD reggae on, and there's banging on the front door. The Mrs goes to the door, he calls out "If that's the neighbours complaining about the music, tell them to buy their own stereo 'cos ours won't go no louder"
 
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karlsushi

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Some testing was done in 2014 in hifi World, it produced just under 1% 3rd harmonic at mid volume. Nick gorham had similar test results.
They are not really passive as in a resistor. The light source causes the photoelement to make electrons available, sort of a semiconductor.
Note to self...don't try and pretend you know something about something on the Wam as someone will always demonstrate that you don't know as much as you thought you did :)

I'll revert back to my usual response when I'm out of my depth...my LDR sounds bloody good to me!

(seriously though, I am surprised by this, as I always thought it was even order harmonics that are supposed to sound more 'musical' and it is definitely the stepped attenuator of the two that sounds more 'harsh/fatiguing' to me :unsure:)
 

awkwardbydesign

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An LDR is still a resistor and still has inherent noise. I haven't looked at specs, but I would imagine that possibly resistor noise is higher in an LDR than a metal film. The rest of the circuit will presumably have some effect, even if just by minimal coupling.
When I made my Stereo Coffee LDR, I found that the implimentation of the volume control made a big difference. Now that's not in the signal path, but controls the voltage to the light source that changes the resistance of the actual LDR. Using law faking resistors completely messed up the sound. Strange. I have since sold it, and it passes from hand to hand; in fact one purchaser sold it and then re-purchased it! The type 26 DHT pre killed it stone dead.
29364951562_9a0d397d8e_z.jpg
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iansr

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In the past I’ve owned some quite pricey active preamps including a Conrad Johnson and a Pass Labs ( I forget the model numbers).
Then I bought a Prometheus TVC which cost me about £180. It completely blew away everything I’d previously owned - it was so much more transparent and neutral.
If I was in the market today for a neutral /transparent volume control then beyond a shadow of a doubt I would buy an IcOn. They use Slagle AVCs and add a very nifty remote control. But my interest lies elsewhere - a DHT preamp.
 
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sjs

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In the past I’ve owned some quite pricey active preamps including a Conrad Johnson and a Pass Labs ( I forget the model numbers).
Then I bought a Prometheus TVC which cost me about £180. It completely blew away everything I’d previously owned - it was so much more transparent and neutral.
If I was in the market today for a neutral /transparent volume control then beyond a shadow of a doubt I would buy an IcOn. They use Slagle AVCs and add a very nifty remote control. But my interest lies elsewhere - a DHT preamp.
If you follow the Thomas Mayer approach to dht preamp circuit, you can have both dht and slagle avc :)
He tends to run the inputs to the selector switch, then the dht, step down output transformer drives the avc, and out to the power amp. He used to use Tribute tvc, but seems to generally use Slagle now.
Lovely
 
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iansr

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If you follow the Thomas Mayer approach to dht preamp circuit, you can have both dht and slagle tvc :)
He tends to run the inputs to the selector switch, then the dht, step down output transformer drives the tvc, and out to the power amp. He used to use Tribute tvc, but seems to generally use Slagle now.
Lovely
Thank you for that. All being well a member of this parish ;)is going to be making a DHT pre for me and I am hoping to persuade him to use a Slagle for attenuation . . . .
 
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robin

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I have a vdh array A1 they also do a p1, a relay for each gain setting, tough bob has been after it for a few years, the most versatile pre I have heard
 

karlsushi

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LDRs? Read this:
This makes for very surprising reading. As I've mentioned in other posts, I use a Stereo Coffee LDR and love it so much, I have one in both of my systems now. To my ears they are completely transparent and distortion free, but evidently that is not the case.

Having gone down the route of lower powered Class A amplification of late however, I am starting to wonder if I need more preamp gain, so am debating whether the better next step is either a preamp with some gain or more sensitive speakers.

Never tried a TVC pre, although I have debated using one. Am I right to assume they have no gain, unless incorporated with some sort of additional gain device (such as the DHT combo mentioned above)?
 

greybeard

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Never tried a TVC pre, although I have debated using one. Am I right to assume they have no gain, unless incorporated with some sort of additional gain device (such as the DHT combo mentioned above)?
Some have a switch, to add up to 6db of gain.
 

zeta4

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Some have a switch, to add up to 6db of gain.
Remember though if you use the gain control you do tend to loose one of the advantages of TVC's. For example if the TVC (or AVC) is at a -6db setting ( 1:2 step down ) the reflected source impedance is reduced by 2 x 2 so if the source impedance was 1K it appears as 250R. Similarly the load impedance is magnified by 2 x 2 so 47k becomes 188K. This makes it easier for a source to drive a load.

Now with the +6db the reverse happens so at +6 db (1:2 step up) the 1k source impedance becomes 4K and the load impedance is 11k. Now
its a little harder for the source to drive the load. In this case it may not be too much of a problem but if the source impedance is a bit high or the load impedance is a bit low it can become a problem. So its important to be aware of this if you intend to use this feature.

Its the reason why +6db gain is the limit implemented on TVC's. It would be perfectly possible to go higher but the above problem rapidly becomes very much worse.
 

iansr

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Remember though if you use the gain control you do tend to loose one of the advantages of TVC's. For example if the TVC (or AVC) is at a -6db setting ( 1:2 step down ) the reflected source impedance is reduced by 2 x 2 so if the source impedance was 1K it appears as 250R. Similarly the load impedance is magnified by 2 x 2 so 47k becomes 188K. This makes it easier for a source to drive a load.

Now with the +6db the reverse happens so at +6 db (1:2 step up) the 1k source impedance becomes 4K and the load impedance is 11k. Now
its a little harder for the source to drive the load. In this case it may not be too much of a problem but if the source impedance is a bit high or the load impedance is a bit low it can become a problem. So its important to be aware of this if you intend to use this feature.

Its the reason why +6db gain is the limit implemented on TVC's. It would be perfectly possible to go higher but the above problem rapidly becomes very much worse.
Can I just check my understanding. If you have an AVC on the output of a DHT preamp, the preamp will see a much bigger input impedance on the power amp its driving, thus making the power amp easier to drive. Have I got that right?
 

zeta4

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Can I just check my understanding. If you have an AVC on the output of a DHT preamp, the preamp will see a much bigger input impedance on the power amp its driving, thus making the power amp easier to drive. Have I got that right?
Yes, assuming of course that you not using the AVC to provide gain.
 

Hornucopia

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When I made my Stereo Coffee LDR, I found that the implimentation of the volume control made a big difference. Now that's not in the signal path, but controls the voltage to the light source that changes the resistance of the actual LDR. Using law faking resistors completely messed up the sound. Strange. I have since sold it, and it passes from hand to hand; in fact one purchaser sold it and then re-purchased it! The type 26 DHT pre killed it stone dead.
29364951562_9a0d397d8e_z.jpg
[
At least you made yours Battery powered, to lose the mains input degradation. THAT, and the remote control, attracted me (I'm the repeat buyer!) Charging as I type.
 

awkwardbydesign

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If you follow the Thomas Mayer approach to dht preamp circuit, you can have both dht and slagle tvc :)
He tends to run the inputs to the selector switch, then the dht, step down output transformer drives the tvc, and out to the power amp. He used to use Tribute tvc, but seems to generally use Slagle now.
Lovely
Isn't the Slagle an AVC?
 

zeta4

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You have to be a bit careful following one transformer with another as you can get funny resonances occuring with the first transformer
seeing the inductive load of the second. It can be dealt with if your aware that it can happen and go looking for it.
 

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