Group Buy - Digital Attenuator (Kevin Gilmore)

[Kerry]

Can you set one of the other relays as a quasi mute just before setting those switching points and then set it back?  It's not so noticeable if the sound drops a bit during the transition.

[Pars]

There are some threads on diyaudio regarding this. One in particular is from Russ White (twisted pear audio) from 2006.


Sent from my iPhone using Tapatalk

[JoaMat]

Thanks guys. Found a post at diyAudio by Russ White. Mr. White said the problem was easily addressed by some change in the firmware. Well, I think this will be a real challenge for me…. will give it try though.

[JoaMat]

Got Kerry’s VolumeController to work. Wasn’t that difficult when I just figured out the output pins for the digital attenuator. Compiles much faster and uses much less memory than my firmware. Nice display, like the relay indicators!

[JoaMat]

I said a few days ago that I’ve given up Attiny85 as controller for the digital attenuator. I’ve done some additional attempts today and it turns out to work all right. I really like that little thing. Can’t be more minimalistic..?

 

Regarding pops/clicks I think I've to give up. Seems to be to complicated for me to solve.

[JoaMat]

I think it might be possible to squeeze in a digital attenuator in Mini Dynalo.

ATtiny85 is in the middle of the breadboard, lots of space for it in the box. Need some 5 volt supply as well.

[nopants]

is that copper clad for the face? i'm a fan

[JoaMat]

Yes, that’s copper clad. I’ve a CNC machine. Nice opportunity to learn have to use it. I’m not ready to mill aluminum yet.

[iwik]

Hi Guys,

Long time no show. T2 still going well. Need to fix a  volume problem with the original Digital Attenuator board. Volume at switch on is not low.

In fact it is quite loud. Need to get another copy of   updated volumecontroller.zip file that Kerry did. Can someone direct me to it.

Did anyone have any trouble with volume at switch on too loud? In my one if i switch on and immediately turn rotary encoder then the volume drops down.

I dont know now which version of the software i have used so would like to reload  the    " updated volumecontroller.zip ".

Thanks

Les

[Kerry]

PM sent 

[starcat]

Anyone has balanced boards left, empty or populated? Please PM

Edited June 24, 2021 by starcat

[Beefy]

1 hour ago, starcat said:

Anyone has balanced boards left, empty or populated? Please PM

I think I've got 4 unpopulated from the original group buy in May 2011. But they might not be particularly useful given the project advanced a long way after that.

[Beefy]

1 hour ago, starcat said:

Anyone has balanced boards left, empty or populated? Please PM

Yep, 4 of the original boards. Plus, I found a full kit for a PGA2320 volume control from @luvdunhill in the same box. I'd forgotten how much I used to overbuy DIY bits and baubles.....!

I really think you might be better served by the newer more compact version, and they would ship from Canada, but they are yours if you want them.

[johnwmclean]

21 minutes ago, Beefy said:

I'd forgotten how much I used to overbuy DIY bits and baubles.....!

I am master of this.

[Ok_Session_9057]

On 6/24/2021 at 2:20 AM, Beefy said:

I think I've got 4 unpopulated from the original group buy in May 2011. But they might not be particularly useful given the project advanced a long way after that.

Hi. What is the problem with these old boards in your opinion and What kind of significant advancement have there been? I managed to buy one of these first version attenuators and been using it with LCDuino in my line stage and cannot think anything I don’t like about it.

I am just starting to build two more for my electrostatic amp. These seem easier to solder and space is not an issue, since the amp is going to be pretty massive, so I was wondering if there is a good enough reason to get the newer version instead?

[Beefy]

2 hours ago, Ok_Session_9057 said:

Hi. What is the problem with these old boards in your opinion and What kind of significant advancement have there been? I managed to buy one of these first version attenuators and been using it with LCDuino in my line stage and cannot think anything I don’t like about it.

I am just starting to build two more for my electrostatic amp. These seem easier to solder and space is not an issue, since the amp is going to be pretty massive, so I was wondering if there is a good enough reason to get the newer version instead?

I actually built and installed a pair of these in a balanced amp recently. There's absolutely nothing wrong with the board on a technical level.

The problems I had that might have been solved with the newer revisions were size and software. This first revision are physically way bigger than the second. And I'm not a programmer, so I rely on grabbing code provided by others, and I couldn't find code that works perfectly with a pot. Kerry's all-in-one code from the other thread mostly gets there, but it opens up at full volume on power up - this is a bit dangerous, and I'm not nearly clever enough to work out why. I believe the code for the second revision was a lot more complete. I have the LCDuino codebase, but haven't been able to get it to work.

But if you have the space, and you have code that works for you, then this first revision board should be AOK.

[Kerry]

1 hour ago, Beefy said:

I actually built and installed a pair of these in a balanced amp recently. There's absolutely nothing wrong with the board on a technical level.

The problems I had that might have been solved with the newer revisions were size and software. This first revision are physically way bigger than the second. And I'm not a programmer, so I rely on grabbing code provided by others, and I couldn't find code that works perfectly with a pot. Kerry's all-in-one code from the other thread mostly gets there, but it opens up at full volume on power up - this is a bit dangerous, and I'm not nearly clever enough to work out why. I believe the code for the second revision was a lot more complete. I have the LCDuino codebase, but haven't been able to get it to work.

But if you have the space, and you have code that works for you, then this first revision board should be AOK.

I'll have some time in March to look at the issues you were having.  My setup doesn't open up at full volume.  

[Beefy]

5 minutes ago, Kerry said:

I'll have some time in March to look at the issues you were having.  My setup doesn't open up at full volume.  

I appreciate that, but please don't spend too much effort if it's just me. It's entirely likely I'm doing something wrong! I've used the Arduino IDE and VSCode to customize and build 3D printer firmware, but am really flying blind in terms of proper understanding.

[audiostar]

All this time I was looking into the other thread for the digital attenuator and it took me a while to find this one with the actual discussion 🙂

The latest digital attenuator is a very nice one on a single small board for a 4 channel balanced amp, but without a control board it is not really easy, i.e. useful to people and I mean all people. It seems like Kerry is not giving his control board away as well; it looks to me he did take the Arduino Pro Mini schematic (which is pretty simple and open source btw) and included the encoder, so all on a single board to connect straight to Kevin's attenuator. I think demand is real for this one, and if yes, we should make a control board to pair with the attenuator so we have an easy to use and replicable system to put in our amps. Make the OLED display optional, i.e. connect it or not; this is the easiest part and is actually more software as the hw-part is the I2C connector only and the display itself.
I would suggest using the bigger Bourns encoder (RK16812MG099) as it has more mass and has the more silky and smoother feeling. The IR receiver stays optional as well, use it or not.

The other option would be to make the control board, so that it accepts a commercial Arduino Pro Mini as a mezzanine card, which will make everything bigger but not necessary easier. I think there is appeal in making the control board integrated and sit just below the encoder (this includes soldering the ATmega328p chip, which shouldn't be difficult for the most). The set might include an interface board to go from RK50/DACT to the digital attenuator on existing amps. So three boards in total, where the interface board is optional. 

Checking demand for this? 

 

Edited April 13, 2022 by audiostar

[Pars]

Any experience with the Muses volume controller IC in place of clacking relays?

[luvdunhill]

12 hours ago, Pars said:

Any experience with the Muses volume controller IC in place of clacking relays?

I think it sounds pretty good in fact!

[audiostar]

13 hours ago, Pars said:

Any experience with the Muses volume controller IC in place of clacking relays?

Its very nice, 0 to -111dB with 0.25dB steps, highly linear. Controlled by a 3-wire bus. Sounds pretty amazing, used by Pass in the XP-30 as well.

Edited April 14, 2022 by audiostar

[MLA]

This guy seems happy, though a bit principled on staying with the datasheet circuits 

https://www.audio-perfect.de/muses_72320.en.html

 

[audiostar]

7 hours ago, MLA said:

This guy seems happy, though a bit principled on staying with the datasheet circuits 

https://www.audio-perfect.de/muses_72320.en.html

Looks like he is not publishing the control software!
The ST controller chips are completely sold out everywhere as well. Otherwise flashing the software is pretty easy with a ST-link programming unit and their IDE and the hardware part is straightforward as well.

Btw, nice balance control can be implemented (in software) as the chips can be addressed separately and 2 are needed for balanced anyway.

The newer chip is the 72323, not much difference, if any.

Edited April 14, 2022 by audiostar

[Pars]

I'm building a couple of the UGS Muse preamps from the french site homecinema.fr / diyaudio. The only part done on both of the is the processor boards, and yes, it was easy to flash. These do use the 72323 chips (which I haven't bought yet).