Yeah, well...perhaps you should try it, the even-order distortion is inaudible. Don't forget, this conversation includes transformers and autoformers. So...you want some really audible distortion? Try one of them.
And if you don't like any distortion, then the volume control chips are the choice anyway.
You'll run into control range issues, tracking issues, noise, distortion...etc. Like I said, this is like audio engineering from the 1950s. I'm sorry, I don't get it. Why?
Funny but I recently heard someone describing a fellow DIYer that was so annoyed with volume control and its influence he had totally omitted it. Just 1 volume level adjusted to his likings.
Radical!
Radical!
Um...check the data sheets. Clickless, and vanishingly minimal distortion. Every speaker, headphone and microphone in the world has massively more.
Every possible volume control has more negative sides than a pair of resistors....
Nothing against electronic volume control but it is a pity that you hear that they're there 🙂
Nothing against electronic volume control but it is a pity that you hear that they're there 🙂
Every single recording you're playing has been run through dozens of "volume controls", some analog, some digital, some with VCAs, and all manner of variable gain dynamics controllers. Ever counted the level controls on an analog tape recorder? And today's digital recordings have lots more done than just volume control. So...we're eliminating the last one, the one that lets us adjust the play level to compensate for different mastering levels, performances, and our own desired play level...we're taking that one out because...why exactly? And what about the dozens of others already in the chain? Distortion? What about your speakers, rooms, microphones, vinyl, tape, heck, pretty much everything you're listening to. Why fuss about distortion in a resister when it's already been through thousands of them?
If there's a logic to this, please enlighten me.
If there's a logic to this, please enlighten me.
That one in your device is the one you can control and that has a direct influence on your chain. All the others are a given just like the material you choose to play back. Besides that differences between volume control are very easy to judge. Try a PGA2311/2310 volume control for instance compared to a RK27.
Even if the precious signals went through hundreds of NE5532 and PGA2310 (and NOT through tubes!!! OMG) then you will still hear YOUR volume control when you try various types 🙂 It is a variable in your chain.
Even if the precious signals went through hundreds of NE5532 and PGA2310 (and NOT through tubes!!! OMG) then you will still hear YOUR volume control when you try various types 🙂 It is a variable in your chain.
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The best recordings are done when not using anything but passive potentiometers. Just
use a DG recording from the 70-80 or, if you are so inclined, popular music from
the 60.
Because we are discussing volume control for a tube preamplifier. If you are going to use ICs, you are cheating. You might as well get rid of the tubes altogether then.
Wow that is a very narrow minded and old fashioned view, sorry. Cheating, are you serious?!?! I thought it was not about topology but about final results. So then the power supplies in tube gear are not allowed to have modern regulators? What about hybrid amplifiers?
This can only happen with tube people I think. What's next? A tube only DAC?
This can only happen with tube people I think. What's next? A tube only DAC?
What I meant is a low source or load impedance is not absolutely necessary as the transformers parameters can be adjusted to handle it. For example if you have a high source impedance say then you need a correspondingly high primary inductance to define the low frequency point. Similarly for the hf extension
Hmmm...
Searching distortion....
CCS loaded #26 preamp, S&B TX102 TVC, 2V RMS output (measured a decade ago).
That's absolutely wrong. The days of nothing but passive faders started to vanish in the late 1970s. Many console manufacturers realized there were benefits to fading groups and minimizing fader movement noise, and VCAs were already quite good. And what was the recording/release medium in 70-80? The path was tape > tape > tape > lacquer/vinyl. Sometimes even more generations. You want to talk distortion??? OMG, tape is "terrible" comparied to any passives. THD, IMD, scrape flutter (the analog equivlent of digital jitter), worse with each generation. Noise too. And those were the days before cap distortion was well understood too. Those were not "clean" recordings in any aspect, even if they sound good. There's no way to "audition", a pot or resistor with material that doesn't already have all that baked in.
Pop music from the 1960s was the era pre high output, low distortion tape. The era of Scotch 111. And Ampex 300 series machines, that couldn't even pull tape at a costant speed head to foot. You can hear the pitch change on record, as well as the flutter and IMD.
There are those griping about passive volume controls here. I'm sensing there's no engineering involved, just myth and legened.
Lets brew some coffee here.
"Cheating" to get a better result isn't "cheating", it's called Engineering. But you have to very clearly define your goal to know what to eliminate and what to add. Tubes for tubes sake is a goal. Best performance is another.
For the Tube DAC (this was actually discussed seriosly several decades ago), you'll need several racks and a room with dedicated air conditioning. Think tube-based computing, 1950s.
Attachments
As far as I'm concerned, when I use tubes, it is usually tubes for tubes' sake, as there are only few cases where there is a clear technical reason to use tubes. There are some, for example, I once used them for strictly technical reasons in the output stage of a direct-drive amplifier for electrostatic loudspeakers. In that case, I used transistors in another stage, as that was technically the best solution. Anyway, everyone can do what they like, of course.
The Americans used digital voice encryption techniques during the second World War, so that was indeed quite serious. Bell Labs published articles about digital telephony and digital closed-circuit television in 1948 and 1950, but those were not very practical yet.
If you don't mind hybrid solutions with solid-state digital signal processing, or limiting yourself to DSD, a tube audio DAC becomes quite practical.
The most astonishing one I saw (I don't know if it was published outside the Labs) was the direct digital receiver (earpiece). The electrostatic diaphragm was divided in 8 sections each twice as large as the one before. 8-bit data was put right to the sections, LSB to the smallest etc. The ear-cup integrated and filtered the pulses. This may have been very late 1960s. And yes, it gets impractical along about 8 bits, unless you do a further division with voltage leves.