Relay Volume Control for BLS

[Rarkov]

For a LCD (price starts at 7€, i have some on hand) we would need more free pins, such a larger PIC. Else no problem

On the JAL List, many have contructed 2-wire LCD interfaces. (I seem to recall a competition for a one wire interface too!) Email me if you would like details...

Well done guys...looks good...Unfortunatly I've already splashed out on the APOX stuff!

Gaz

 

[promitheus]

Well the Apox kits are very cool.

 

[sianturi]

The problem with posting the boards is that I can´t convert the pcb or gerber files into pdf or jpeg.

If anybody has an idea how I can do that please help.

Promitheus,

U can use Neevia docuPrinter pro (trial version) at:
http://www.neevia.com/prodDP.htm#docuPrinter

I use protel dxp, and when I want to convert the PCB to PDF, I just print to the layout like printing the normal way, but the printer I used is DocuPrinter (after installing the docuPrinter).

Ciao!

 

[promitheus]

Thanks for the tip !
I will try it out.

 

[jwb]

Very nice work. If you want, just zip the gerber files and post them.

 

[zygibajt]

Nice work Promiteus.

Till
I've seen your website with the information about relay attenuators.
Did you actually compared the relay attenuator with good (Elma for example) stepped attenuator ,series or ladder type.

I'm not that enthiusiastic about that constant load solution,becouse all of the relays are always in series with signal.That means 16 solder joints and 8 contacts in relays.

I have never bulit that kind of attenuator.I use stepped attenuators.

Looking in to service manuals of Aleph P (both of them) I can see how nice it is done.The drawback is that input impedance isn't steady,but in exchange we get 64 (Aleph P 1.0) and 256 (Aleph P 1.7) diffrent combinations.
I'm considering trying relay volume control.I'm wondering how does it compare sonicly to good ,ladder type stepped attenuator.
I even like the one from Aleph P 1.0 better.It is simplier solution,only 6 relays per channel.And what do I need 256 settings for? 64 is quite enough for me.

Did anyone compare relay type to stepped attenuators (true ladder type) sonicly?

Bartek

 

[till]

Rarkov, The LCD version will come in two versions, one with one PGA, one for multichannel or balanced stereo. It will use a 16F877, i´m working on the first test PCB right now. It will be possible to use with relays for volume control or PGAs in different firmware versions. The PCB at the pic attached was made by Pieter from Belgium, we collaborate on this project.


The apox is very nice, but much too expensive for me. Also i prefer to do it more diy.


zygibajt, i don´t have a stepped attenuator and the good quality ones are much more expensive than my solution. If i have taht much money for this hobby, i will spend it on some nice horn drivers or coax speakers before i buy expensive switches.

I built the aleph P 1.0 volume control before, and 64 steps are not enough for me. 255 are ok, if you want less its easy to modify the code to sort some out.

Also there is more than one way to use the relay attenuator.

I think about useing one for the D1 stage volume control in a DIY DAC with AD1865NK.

 

[promitheus]

So I made some pdfs. They should be in original size.
I zipped all of them in one file.
It´s the pcb from the components side with the overlays and parts list.

Info on programmimg the PIC you can find on Till´s website here:
http://home.tu-clausthal.de/~tpa/relais/index.html

Please note I am using another resistor system as Till is. Don´t mix the 2 up. Everything works the same but the attenuator is totaly different.

 

[sianturi]

Hello promitheus & till,

Looking at the schematics for the microprocessor part, I think we can use just 1 rotary encoder for 2 balanced channel (L + R balanced, that is for 2 relay boards, we use only 1 rotary encoder connected in parallel). Is that right?

Promitheus, could you kindly made the pdf file again? I think you missed to print the holes. There's no holes in your pdf files. Btw, very nice boards!

Thanks,

 

[promitheus]

Normaly the holes don´t show up when you print the pcbs.
What do you need the holes anyway? They will be drilled.

 

[promitheus]

You can use as many relay boards as you want with the same data bus.

You can use 3 relay boards for a surround system with a 6 channel volume control.

You can calculate any Load resistor value you want. for instance a 6 X 47Kohm volume control.

I will be using 2 boards for balanced volume control.
a 4 x 5 Kohm volume control.

 

[till]

Hello promitheus & till,
Looking at the schematics for the microprocessor part, I think we can use just 1 rotary encoder for 2 balanced channel (L + R balanced, that is for 2 relay boards, we use only 1 rotary encoder connected in parallel). Is that right?

As Promitheus sayed, the digital part with the PIC is able to drive a serios amount of driver transistors. So you simply hook up as many relay boards in parallel to the PIC as you need. The rotary encoder also could make use of a pushbutton function, if you want for mute, or for a change between 2 sources.

The 16F877 controller with LCD i work on will be able to read 2 encoders for more funktions.

 

[batee]

By extra functions, are you thinking of adding input selection? I've been thinking about how this could be implemented with only one pushbutton rotary encoder and a basic stamp, similar to what you're doing. A backlit LCD display would indicate the mode or function value (source, vol level, etc). Maybe a clock that just flashes 12:00...

Turn knob, change volume. Push button, select function by turning knob, push button to choose function (input source, etc), turn knob to change value of function. No user input for xx seconds, back to volume fumction. Push and hold button for x seconds = mute. Turn knob or push button again to unmute.

Should make a nice clean looking front panel. Any other functions we could add through this sort of interface?

 

[till]

By extra functions, are you thinking of adding input selection?

I use the minimal relay version with 16F628 in my BZLS with 2 sources input selector on pushbutton. The board here http://www.diyaudio.com/forums/showthread.php?postid=360807#post360807
allready has a connector for 5 sources selector.

Any other functions we could add through this sort of interface?

I think about (does not mean all will be implemented soon):
- IR reciver for RC5 code
- support for multichannel PGA control
- support for relay control
- balance funcion ( set left and right channel independent)
- Allready implemented in the minimal version: store volume settings for sources individually, so you can A/B sources with different output levels at same volume level
- simple DSA interface for sending controls to Philips CD transport. This would be usefull for a CD PRO or CDM
based CDP with DAC, the controller tells the transport the Dac mode to use, and volume is set in the D1 I/V stage.
- Trigger outputs to switch on a power amp from the preamps control.


All would be usable with only one rotary, but it may be better to use two: sometimes you want to mute or change volume very fast. So for a multi function device it may be a solution to do mute and volume with one encoder, and all other function with a menue at the other. I just ordered a stock of alps-encoders for a good price.

 

[JC Fardo]

Promitheus

1) Could you please inform Takamisawa relay reference. I think I´ll only find Omron, Tyco or Fujitsu similares around here.

2) Is input load of your power amp 5Kohm?

3) Congratulations and thanks a lot sharing your project

JC

 

[till]

excuse me if i post it,

this relays could be ordered at http://www.schuro.de/preisl-relais.htm

specs : http://www.schuro.de/Daten/Takamisawa/ry.pdf

 

[promitheus]

On the board you can also use the Omron relays DPCO-G6A-234P at 12 volts, you can use the small Finder double relays.

I use the relays that Till uses. They are very good at that price.

The Balanced Line Stage from Pass DIY needs 5Kohm poti at the output for minimum distortion. An amp has 50Kohm input resistance.

 

[promitheus]

Just remembered.
You can check the pin configuration from the file Till has in the previous post. In the pdf file you can see what the pin layout is like. You can use any relays with this layout.

 

[JC Fardo]

Just a litlle clarification here:

The Balanced Line Stage from Pass DIY needs 5Kohm poti at the output for minimum distortion. An amp has 50Kohm input resistance.

And on X-Pro post

http://www.diyaudio.com/forums/showthread.php?threadid=21198&highlight=

he says that the load impedance ( or the power amp ) must have the same pot resistance value. Sorry, I´m new to this Volume Control matter.

Thanks again and Till for relay info and his previous write up

JC

 

[promitheus]

It all depends where you use the volume control. This volume control at 5Kohm was calculated for the balanced Line Stage. Because the Amplifier input has a resistance of normaly 47KOhm it won´t effect this volume control.