UcD400 and high level sub input

[chrisb03]

Newbie, have you found your pot

Nope, not yet.

Newbie

I may be a novice, but I own one of the first UcD400, serial number 0003 and 0004 which would make me an old timer . At the time, Jan Peter told me I was the first UcD400 customer, but my order must of got mixed up with the second person.

 

[guyv]

I think serial number 0001 and 0002 made their way into Jan-Peter's own system! I said he got UcD700s in his system with these serial numbers so I am guessing it was the same for UcD400.

 

[dublin78]

Hi
This should solve all your problems and keep to your existing set up.
Check out the "Subline": http://www.audiomagus.com/index.php...id=0&option=com_virtuemart&Itemid=27&vmcchk=1
This was designed specifically for digital amps, as they have some difficulties with subs???
I am sure that it is a simple circuit. It would be nice to diy it.
If anyone knows of a circuit that will achieve this, please let us know.

 

[chrisb03]

Hmmm..I think I will stick with the 4 gang pot method for the time being.

I haven't found one yet, but I bought some two gang types and have pulled them apart. I will put a common shaft through them to make a 4 gang.

 

[Iyremenko]

Dual 2 way gang is good approach.

 

[chrisb03]

Does anyone know where to get one of these rotary switches and if anyone has a link with it dismantled. I'm wondering if extra wafers can be added.

http://www.penguinlovers.net/audio/Attenuator.html

 

[chrisb03]

Just connect the amp inputs in parallel after the pots. The worst that can happen is you get a slightly over-logarithmic volume curve. At full and zero volume the pot doesn't matter, and in between it's just a voltage divider.

Rune

Sorry to ask the same questions again, but would the above be the only draw back? If so, I'll just stop looking for an affordable 4 gang pot.

There must be other issues with parralleling the inputs on both the UcD and sub.

 

[richie00boy]

I believe the speaker negative connection on the UcD400 is not at ground potential, so you can't use it to drive an unbalanced input sub.

All you need is an active volume control after the DAC, with two outputs. One stereo pot is all that is needed. It's probably cheaper to build an active circuit than buy a quad pot, if you can even find one. And the performance (and tracking between channels) will be a lot better.

 

[chrisb03]

I believe the speaker negative connection on the UcD400 is not at ground potential, so you can't use it to drive an unbalanced input sub.

All you need is an active volume control after the DAC, with two outputs. One stereo pot is all that is needed. It's probably cheaper to build an active circuit than buy a quad pot, if you can even find one. And the performance (and tracking between channels) will be a lot better.

Hi Richie, I wanted to avoid an active volume control. And I don't have the time to research and built one. The simplest for me would be to just parrallel after the pot.

 

[richie00boy]

What you say is an oxymoron. An active circuit is about the simplest and easiest thing you can design - just slap together a non-inverting amplifier from what you have lying around. Conversely to build a passive correctly would require consideration of all source and load impedances.

 

[chrisb03]

An active circuit is about the simplest and easiest thing you can design - just slap together a non-inverting amplifier from what you have lying around.

I don't have non-inverting amplifiers lying around the house. I don't have the knowledge to do this. I would have to reseach this extensively. I have a day job, an after hours job, I also have three kids (eldest is 4.5 years old) and I also have a wife.

Conversely to build a passive correctly would require consideration of all source and load impedances.

Do you have a link to a site which tells you how to do this correctly?

 

[richie00boy]

A non-inverting amplifier is just an op-amp and two resistors. Google it, you will be able to get it in under an hour I guarantee it.