Coldamp Six Channels

[DQ828]

I have started a amp build using six of the Coldamp Sonora S250 modules and one SPS80 PSU.

I was hoping to have progressed much further but life has intervened & slowed progress considerably.

To save some funds I have emptied an old Yamaha amp case I have & am using that in the short term (probably long term)

I have drawing a schematic, for sorts that has been checked by Sergio, who has been VERY helpful.

The modules are mounted on the back side of a piece of aluminium checker plate, which turns out not to be as flat as you may hope, so I will use some thermal tape to mount them should they heat up too much. I have salvaged the heat sinks from the Yamaha & will mount those on the checker plate. I will need to build a new front panel which will be timber & aluminium & a new back panel, I have manages to scrounge all of the aluminium & have plenty of timber to choose from. As far as I can tell I have all of the bits I need now all of I need is some more time on the weekends.

There is one thing that I would still like to do, that is have a global (One knob to control all channels) volume control. The amp will be feed by a Squeezebox Touch via a MiniDSP so I can use the Touch for general volume control, but would like to be amp to set the volume to a maximum level manually. Also a balance control would be useful.

Oh, I am a beginner at all of this, just so you know.

Any ideas on the best way to apply volume and balance control over six channels?

[ssanmor]

Hi,
Nice setup, although you should make sure that you use a good aluminium base that is flat and 2-3mm thick. Using thermal tape is not a good idea, it is much easier to get the proper alu panel (some local shop can cut it for you to your desired dimensions). Things that are well done from the start always work much better!
As for the global volume control, what is your sound source, a 5.1 receiver or something like that? Otherwise, if it is stereo and you are going to triamp, for example, the best thing is to use a stereo volume control before splitting at the filters (and possibly add a smal adjustment to each channel individually at the POT header so you can adjust relative levels easily).

[GaloDourado]

You can use the 3-pin conector in miniDSP to a 10K pot to control volume. This is the way I'm doing.

Other way will be using a 6-gang pot after the minidsp unit.

I don't know about balance control, sorry.

[DQ828]

Originally Posted by ssanmor

Hi,
Nice setup, although you should make sure that you use a good aluminium base that is flat and 2-3mm thick. Using thermal tape is not a good idea, it is much easier to get the proper alu panel (some local shop can cut it for you to your desired dimensions). Things that are well done from the start always work much better!
As for the global volume control, what is your sound source, a 5.1 receiver or something like that? Otherwise, if it is stereo and you are going to triamp, for example, the best thing is to use a stereo volume control before splitting at the filters (and possibly add a smal adjustment to each channel individually at the POT header so you can adjust relative levels easily).

The amp will be feed by a Squeezebox Touch via a MiniDSP which will split the signal (tweeter left & right, Mid Left & Right, Bass Left & Right)& to the six amp modules & then to three drivers in each active speaker.

The MiniDSP will look after the driver levelling,

Ideally I would like the volume control as a single knob on the amp case.

I have found this on ebay ALPS 6-gang motorized Potentiometer RK16816MG 10K Pot - eBay (item 350371173403 end time Feb-26-11 08:03:49 PST) would it be the go, then I can have a remote if I want.

David

[ssanmor]

So you have a stereo-triamp setup.
If the connection from the squeezebox to the MiniDSP is analog, why don't you use a stereo gang potentiometer, simply?

[DQ828]

Originally Posted by ssanmor

So you have a stereo-triamp setup.
If the connection from the squeezebox to the MiniDSP is analog, why don't you use a stereo gang potentiometer, simply?

Yes it will be a stereo triamp setup

From Squeezebox to MiniDSP will be digital.

[ssanmor]

Then things are a bit more difficult.

We are also designing a DSP board (to be available by mid of this year I hope), and I am almost sure we use the same family of chips than MiniDSP. Some of these chips have pins associated to a 8 or 10-bit A/D converter. They can be used to connect a DC voltage to control anything inside, for example the volume of all the channels (this require proper software in the board, of course).

Check the datasheet or ask the manufacturer if they can offer this possibility, and then you can use a simple voltage reference and single potentiometer to control the volume of all channels inside the DSP processor.

Just an idea, hope this helps.

[DQ828]

Originally Posted by ssanmor

Then things are a bit more difficult.

We are also designing a DSP board (to be available by mid of this year I hope), and I am almost sure we use the same family of chips than MiniDSP. Some of these chips have pins associated to a 8 or 10-bit A/D converter. They can be used to connect a DC voltage to control anything inside, for example the volume of all the channels (this require proper software in the board, of course).

Check the datasheet or ask the manufacturer if they can offer this possibility, and then you can use a simple voltage reference and single potentiometer to control the volume of all channels inside the DSP processor.

Just an idea, hope this helps.

I can add a volume control to the MiniDSP, but the things I have read about the volume control is at the moment it doesn't work as well as one might hope.

Is there a problem with adding a six gang volume control to the amp?

[holtet]

What problems have you read about? Just curious since I've been testing the minidsp for some time now, using a potmeter to control the minidsp volume. To me it seems to work great.
I guess you will need 2 minidsp units to have 2x3 channels. I think you could use a single-gang volume to control both if they have the same powersupply. If so (probably you should check this), you won't have any problem with level difference between channels.

Originally Posted by DQ828

I can add a volume control to the MiniDSP, but the things I have read about the volume control is at the moment it doesn't work as well as one might hope.

Is there a problem with adding a six gang volume control to the amp?

[Helmuth]

Nice project david you are re-using a electronic enclosure. Can be perfect with new front and en plate and wooden side panels.

That volume control shout be OK. You can use a wire to control the motor and have a remote control by wire or use IR-wireless-control with eletronics to control the motor.

But after this you have to build 6 loudspeaker poor guy