Very high fidelity volume control chip with serial control

wapo54001

Senior Member
A company in Japan is producing a very high quality volume control chip that can be controlled with 3-wire serial. I would dearly love to develop a Picaxe-controlled front end for my preamplifier using this chip, but I don't understand the documentation well enough to do this.

Could someone have a look and comment on compatibility and if possible, how to proceed with making this work? I can write code for the Picaxe, but understanding the documentation is beyond me.

Muses Volume Control
 

steliosm

Senior Member
Having a quick look at the datasheet for this chip, it should be doable to control it through a Picaxe. The 3 lines are actually a Clock/Data combo and a Latch line. You pull the Latch pin low and start clocking in the data. For clocking the data in you will need to bit-bang it.

A good starting example can be found for the command "shiftout" here: https://picaxe.com/basic-commands/advanced-io-interfacing/shiftout/
Looking at the code examples provided for the chips that doesn't support this command natively, can give you an idea on how to bit-bang the data. You can also search the forum for bit-bang i2c protocol examples.
 

Goeytex

Senior Member
A Picaxe should be able to control the chip via the serial protocol. Just clock in 16 bits. Then send a latch pulse.
The application circuit should get you started. If the manufacturer offers a development board I might get that
to help speed up the develepment procecss.
 

inglewoodpete

Senior Member
I used PICAXE's hSPI for the volume controls using a lower quality chip for a 5+1 channel preamp that I built a few years ago.
 

julianE

Senior Member
I used PICAXE's hSPI for the volume controls using a lower quality chip for a 5+1 channel preamp that I built a few years ago.
If at all possible I'd like to see the work you've done with the less expensive chip. The NJR Muses line of op amps and their other high end offerings look to be a marketing campaign, I doubt I can discern the difference and they are very expensive chips.
 

wapo54001

Senior Member
If at all possible I'd like to see the work you've done with the less expensive chip. The NJR Muses line of op amps and their other high end offerings look to be a marketing campaign, I doubt I can discern the difference and they are very expensive chips.
I installed a Muses volume control chip with IR in a vacuum tube preamp I just finished. It is really, really, fine. Totally transparent, no strain, no veil, I love the sound. Academy Audio Volume Control -- but the thing is, I really like to listen to equipment I built myself.
 

julianE

Senior Member
I installed a Muses volume control chip with IR in a vacuum tube preamp I just finished. It is really, really, fine. Totally transparent, no strain, no veil, I love the sound. Academy Audio Volume Control -- but the thing is, I really like to listen to equipment I built myself.
I too am a fan of music and along the way have listen to a lot of good equipment. i'm getting up there in years and i'm sure my hearing acuity has diminished. Over the summer i went and made an A/B box using a picaxe with IR control and relays to switch signals. It was an eye opener. I would have wagered that a Tube preamp sounds superior to a transistor one. I matched the levels precisely and used the same source, switching between a tube preamp and a transistor one, sadly, the difference was miniscule and what difference there was I could not tell which was superior.

I also tried comparing different op amps from the very expensive ones to very inexpensive, again i failed to tell a difference. There was a difference between op amps on the oscilloscope when driven beyond audio frequencies.

most of my life i have had season tickets to the symphony and the opera, recorded music is a pale replica of real performance.

oh, btw, even with AB tests, vinyl is 10 fold better than best digital. a very good vinyl bests any digital format.

Thanks for the link to the volume control, very reasonably priced. I also agree that there is something to self made equipment. Sounds like you are making a very nice system, I've been listening to Deutsche Gramophone's complete recordings box set of Martha Argerich, highly recommended...even tho it's on CD :)
 

wapo54001

Senior Member
I too am a fan of music and along the way have listen to a lot of good equipment. i'm getting up there in years and i'm sure my hearing acuity has diminished. Over the summer i went and made an A/B box using a picaxe with IR control and relays to switch signals. It was an eye opener. I would have wagered that a Tube preamp sounds superior to a transistor one. I matched the levels precisely and used the same source, switching between a tube preamp and a transistor one, sadly, the difference was miniscule and what difference there was I could not tell which was superior.

I also tried comparing different op amps from the very expensive ones to very inexpensive, again i failed to tell a difference. There was a difference between op amps on the oscilloscope when driven beyond audio frequencies.

most of my life i have had season tickets to the symphony and the opera, recorded music is a pale replica of real performance.

oh, btw, even with AB tests, vinyl is 10 fold better than best digital. a very good vinyl bests any digital format.

Thanks for the link to the volume control, very reasonably priced. I also agree that there is something to self made equipment. Sounds like you are making a very nice system, I've been listening to Deutsche Gramophone's complete recordings box set of Martha Argerich, highly recommended...even tho it's on CD :)
Ha! Very interesting comments. We are in the same boat, years-wise and no doubt hearing-wise. Tubes have the advantage of generating even-harmonic distortion vs solid-state which generates odd-order harmonic distortion. My new preamp's distortion can be dialed in between more of one or the other and be set to a minimum of distortion simply by adjusting tube bias, and there is further discussion of positive-going vs negative-going harmonics doing different things to the music. Now that I've listened, this lifetime cynic is now a believer. If you could not hear the difference between a tube amp and a transistor amp, perhaps you were listening to the wrong amps? My new preamp has transformed the sound of my all-SS system -- for the better.

Here is a discussion of the effect of harmonics in music reproduction 2nd harmonic distortion

and the preamp I built Korg Nutube Preamp -- this features two vacuum tubes in a package the size and shape of an old 8088 chip, and runs off 24vdc. The cathode still glows, but green instead of yellow.

Before this, I was using an LDR-based volume control -- calibrated and controlled by a Picaxe, of course -- which provided some 2nd order harmonics. With the tube preamp it was too much of a good thing and too big to fit in the chassis, hence the Muses volume control which sounds totally neutral as though it's not there.
 

julianE

Senior Member
Here is a discussion of the effect of harmonics in music reproduction 2nd harmonic distortion

and the preamp I built Korg Nutube Preamp -- this features two vacuum tubes in a package the size and shape of an old 8088 chip, and runs off 24vdc. The cathode still glows, but green instead of yellow.

Before this, I was using an LDR-based volume control -- calibrated and controlled by a Picaxe, of course --
I have been curious about the Korg tubes, Nelson Pass made a preamp kit with it and the only negative i've read about is the microphonic issues, where the tubes ring when you tap on them which i see as nitpicking, who taps on their tubes. I have used a bunch of different tubes in my designs, what i love the most are the ones from the 50's and 60's they just look too cool and there is something about tubes that are older than i am. I have also tried brand new tubes and they sound nice too. I too have given LDR volume controls a try, they do work well. i must admit you have me curious to see if i can discern a difference. i do have dynaudio based speakers and a variety of good power amps but to my mind the ultimate resolving gear are headphones, i have a pair of high end sennheisers that i will take off the shelf and try to detect differences between different components.

all the best
 

wapo54001

Senior Member
I have been curious about the Korg tubes, Nelson Pass made a preamp kit with it and the only negative i've read about is the microphonic issues, where the tubes ring when you tap on them which i see as nitpicking, who taps on their tubes.
Korg now ships their tube with a small square of double sided sticky foam to put between the tube and the pcb -- I used it and I have zero microphonics -- I can tap the tube itself with volume at max and hear nothing.
 

wapo54001

Senior Member
I too have given LDR volume controls a try, they do work well. i must admit you have me curious to see if i can discern a difference.
This is my Picaxe-based LDR volume control. One guy measured the L-R and log curve accuracy at 0.1dB. My only competitor is Tortuga audio who use a whole handful of chips to do what the Picaxe does with four mosfets.

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