| chrisb03 |
Sorry if this has already been asked, I did a search but could not find a answer to my question.
I have build a Ucd400 two channel amp in the past. They currently drive a pair of Sonus Faber Concerto. I have a cd player supplying spdif to a P3A DAC which then goes to the amp via a passive volume pot.
I bought my self a sub today and trying to work out the best way to setup.
Can the UcD400 drive the Concerto's and also supply high level signal to the high level sub inputs? Is the UcD ouput stage ok for this kind of setup?
I would prefer to run an active cross over but can't afford one, unless there is a nice high quality kit available.
Chris |
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| Workhorse |
| Why donot you use Line level inputs of Sub??? |
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| chrisb03 |
| I don't have any outputs on dac. Are you saying I should parrallel the line level outputs from the DAC to go to both the UcD and Sub? |
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| Workhorse |
| quote: | Originally posted by chrisb03
I don't have any outputs on dac. Are you saying I should parrallel the line level outputs from the DAC to go to both the UcD and Sub? |
Yes you could parallel....what is the output impedance of your dac |
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| chrisb03 |
| Output impedance is 100 ohms, but I have the passive volume pot on the output. I would be parralleling after the pot. I can't remember what size pot I have, it's about 10K |
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| Workhorse |
| Parallel before pot and adjust the sub level accordingly.... |
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| chrisb03 |
| That would mean I would have to adjust the sub volume at the same time I adjust the passive pot volume. That doesn't make sense. |
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| Workhorse |
| hahaaa, ok then what is the input impedance of your UCD and sub... |
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| chrisb03 |
ummmmmm... don't know.
Am I missing something here. I'm not sure I understand. Are you saying depending on input impedance of ucd and sub that the signal going to sub will adjust linearly with the pot even though it's connected before the pot? |
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| Workhorse |
No you misunderstood....
Ok, if you have access to say 1K-5K pot then you could able to connect both UCD and SUB after the pot.... |
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| chrisb03 |
| Just pull it apart, it's a 10K pot. |
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| Workhorse |
| Could you get a 1K or 5K pot..... |
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| Workhorse |
| Are you using a single or dual pot? |
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| chrisb03 |
Single pot, why does it need to be 1k-5k?
Sorry for the stupid questions, I built this amp a long time ago and I have forgotten the research I did to figure out size of passive pot. |
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| Workhorse |
I love tinkering with newbies...
No need for 1K-5K pot if its single....
You can connect a dual pot and use each half pot for sub and another one for ucd, but you have to use 2 dual pots or a single 4 gang pot for stereo....to control the volume from one knob... |
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| chrisb03 |
| quote: | Originally posted by Workhorse
I love tinkering with newbies...
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:D
| quote: | Originally posted by Workhorse
No need for 1K-5K pot if its single....
You can connect a dual pot and use each half pot for sub and another one for ucd, but you have to use 2 dual pots or a single 4 gang pot for stereo....to control the volume from one knob... |
I need to draw a circuit to understand. |
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| Workhorse |
| quote: | Originally posted by chrisb03
I need to draw a circuit to understand. |
ok draw the circuit..... |
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| chrisb03 |
| Does it matter what size the pots are now? |
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| Workhorse |
| quote: | Originally posted by chrisb03
Does it matter what size the pots are now? |
Good Connections.....
10K maximum |
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| Workhorse |
| Go for Dual 10K for each channel from ALPS priced less than 5USD |
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| runebivrin |
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 |
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| chrisb03 |
| quote: | Originally posted by runebivrin
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 |
Would the logarithmic problem occur with workhorses method? |
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| Workhorse |
| quote: | Originally posted by chrisb03
Would the logarithmic problem occur with workhorses method? |
The answer is NO |
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| chrisb03 |
| quote: | Originally posted by Workhorse
The answer is NO |
Got it ;)
Thanks guys |
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| Workhorse |
| quote: | Originally posted by chrisb03
Got it ;)
Thanks guys |
What did you get..... |
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| chrisb03 |
| quote: | Originally posted by Workhorse
What did you get..... |
Your bold NO :D
Just doing a search for a pot now. Can't find any quads in australia yet.
And I just remembered they need to be log pots |
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| Workhorse |
| quote: | Originally posted by chrisb03
Your bold NO :D
Just doing a search for a pot now. Can't find any quads in australia yet.
And I just remembered they need to be log pots |
Why are you searching for Quads, i think you can go for duals also.... |
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| chrisb03 |
| quote: | Originally posted by Workhorse
Why are you searching for Quads, i think you can go for duals also.... |
I like the fact that I only will have one knob. But I will probably get two duals. |
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| Workhorse |
| quote: | Originally posted by chrisb03
I like the fact that I only will have one knob. But I will probably get two duals. |
Ok happy searching, dont forget to post the photos when you find it...... |
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| eleson |
| quote: | Originally posted by chrisb03
Can the UcD400 drive the Concerto's and also supply high level signal to the high level sub inputs? Is the UcD ouput stage ok for this kind of setup?
Chris |
Yes,
and that way you can listen to your SUB while looking for a pot ... |
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| guyv |
Eleson,
I agree that this is the best method (connecting high-level input of the sub in parallel with the speakers on the output of the UcD), but have you tried it yourself with a UcD? I would love to have first-hand feedback if you have done this.
Chris, let us know how it sounds with the high-level input and what sub you are using. The worst that can happen is that the "magic" does not happen. For some reason most sub owners are happy without the magic because they have never heard the magic (the magic is when the sub sounds like it is not there, but all frequencies become smooth and effortless and airy and you can "feel" the concert hall). The test is to power-off the sub and see if the sound becomes flat and boring.
The reason I am asking is because I did not have success doing that with a first generation REL STORM sub and a Tripath TA104 amp (85V DC rails).
REL later admitted that the input circuit on the first generation STORM had to be improved on later releases, but I am also wondering if the Class-D nature of the Tripath had something to do with it - using high-level input worked very well with the output of a Yamaha amplifier (incredible bass combination) but not with the Tripath.
I think the UcD has cleaner output (less super-sonic frequencies that might confuse the high-level input of the sub) but I loved the sound of the big Tripath and I am building more since I had ordered a few at the time.
Eventually I will have to match a sub to both the Tripath (again) and the UcDs.
Guy |
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| chrisb03 |
| quote: | Originally posted by guyv
Eleson,
I agree that this is the best method (connecting high-level input of the sub in parallel with the speakers on the output of the UcD), but have you tried it yourself with a UcD? I would love to have first-hand feedback if you have done this.
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Hi Guy
Why is it the best method? I would of thought using an active crossover would be best method? Especially using units such as deqx where you can tune each drivers crossover. Having said that, it would probably be worst if you don't know what your doing.
Chris |
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| chrisb03 |
| Actually, anyone in Sydney, Australia know where I can find a 4 gang pot? It looks like they are pretty rare. |
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| guyv |
| quote: | Originally posted by chrisb03
Hi Guy
Why is it the best method? I would of thought using an active crossover would be best method? Especially using units such as deqx where you can tune each drivers crossover. Having said that, it would probably be worst if you don't know what your doing.
Chris |
Reasons:
- REL recommends it
- there seems to be a special synergy, I am wondering if the signal gets altered by the characteristics of the speaker coil. I don't have a real theoritical explanation. I've always wanted to ask the REL people why.
- I was never able to get the "magic" using the line level inputs
Guy |
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| deandob |
Chris,
It will be hard finding quad pots in Australia. I did a similar search for similar reasons a couple of years back (single knob for active subwoofer xover) and found one in the UK, at Falcon Acoustics, and it cost me about $15 including post, which was OK.
However I just went to their site to see if they still have them, and it looks like they went or going into liquidation. But it may still be worth contacting them as they have some stuff for sale. email Malcolm Jones at falcon-acoustics.co.uk.
Good luck!
Regards,
Dean |
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| chrisb03 |
Hi Guy
I'm all for synergy, but my original concern was whether the UcD output stage had issues with this sort of setup (cause damage). Also, I didn't want to deteriorate the signal to the main speakers.
If this isn't the case then I would probably setup this way if it has the best synergy. Does it matter what sort of cable is used? Same as main speakers?
Dean, thanks for the info.
Chris |
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| guyv |
I have no concern that it would cause damage or deteriorate the sound on your main speaker, assuming that you use the special high-level input designed just for that.
I am curious to know your sub model and manufacturer. |
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| chrisb03 |
| quote: | Originally posted by guyv
I am curious to know your sub model and manufacturer. |
M&K V75 Mark2
I bought it of a online auction site for a total price of $230(AUS)!! Bargin! It was supposed to be a used item, but after receiving it still had original plastic seals and not a single mark on it.
It's a 12inch sealed sub.
http://www.mksound.com/v75mkii.htm |
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| Workhorse |
| Newbie, have you found your pot |
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| chrisb03 |
| quote: | Originally posted by Workhorse
Newbie, have you found your pot |
Nope, not yet.
Newbie :eek:
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 :D . 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. |
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| 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. |
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| 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...mid=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. |
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| 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. |
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| Iyremenko |
| Dual 2 way gang is good approach. |
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| chrisb03 |
| quote: | Originally posted by runebivrin
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. |
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| 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. |
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| chrisb03 |
| quote: | Originally posted by 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. |
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. |
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| 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. |
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| chrisb03 |
| quote: | Originally posted by richie00boy
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. |
:bigeyes: 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.
| quote: | Originally posted by richie00boy
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? |
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| 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. |
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