After routing the wires a bit different the crosstalk is much better(I am still busy finding out the crosstalk dependency of wiring layout). Tested the amp. with music and the sound is very nice.
Will do an A/B test later. Also found out that when using an output relay you have to put a resitor over the relay contacts otherwise it wont switch on. If it does not see a load there is some offset, 1.8V, which stops the relay from closing. Input impedance is a bit on the low side, 10k, it works with a passive pre but att. the volume a bit. Will keep you informed.
Will do an A/B test later. Also found out that when using an output relay you have to put a resitor over the relay contacts otherwise it wont switch on. If it does not see a load there is some offset, 1.8V, which stops the relay from closing. Input impedance is a bit on the low side, 10k, it works with a passive pre but att. the volume a bit. Will keep you informed.
Hello, _another user of coldamp_ !
I found a similar issue with starting. I asked them and told me that there is a slight offset when you start with no load (that's something not very recommendable with any Class-D amp, specially if you inject signal, anyway)
In your case, presumably that small 1.8V (no load) offset is detected by your DC protection circuit and, as you have your relays after the output (correct me if I'm wrong), it won't never switch on properly. They told me to add a 1K-2K resistor in parallel to avoid any problems, also in bridge mode setup (that is on the app.notes, I think).
So that seems to be not an issue at all.
Nor the input impedance, I think that it is even good in order to reduce noise and anyway almost every pre-amp (even passive) can drive it with no problems. I have used it even directly connected to my CD player.
I didn't have any problems with crosstalk, and I must say that I like the sound of my coldamps veeery much. What kind of speakers are you using, Bgt?
BTW: are they being so helpful as they were with me? I think that support is simply excellent.
Best regards,
Pierre
I found a similar issue with starting. I asked them and told me that there is a slight offset when you start with no load (that's something not very recommendable with any Class-D amp, specially if you inject signal, anyway)
In your case, presumably that small 1.8V (no load) offset is detected by your DC protection circuit and, as you have your relays after the output (correct me if I'm wrong), it won't never switch on properly. They told me to add a 1K-2K resistor in parallel to avoid any problems, also in bridge mode setup (that is on the app.notes, I think).
So that seems to be not an issue at all.
Nor the input impedance, I think that it is even good in order to reduce noise and anyway almost every pre-amp (even passive) can drive it with no problems. I have used it even directly connected to my CD player.
I didn't have any problems with crosstalk, and I must say that I like the sound of my coldamps veeery much. What kind of speakers are you using, Bgt?
BTW: are they being so helpful as they were with me? I think that support is simply excellent.
Best regards,
Pierre
Pierre,
The relay is after the output, but it works. Speakers are Driade, the hex shaped towers...well actually more like pillars. The sound is nice, no doubt about it...but different. It is fuller in a way, sounds very powerfull. The UCD is leaner.
Sergio from coldamp is very helpfull.
Pierre, maybe you dont have a crosstalk issue because you perhaps use 2 monoblocs. I use 1 transformer driving 2 rectifier circuits, 1 for every amp. For me it is of utmost importance to have a low crosstalk value and a small amp. Don't like big cases. Low crosstalk gives space/direction/subtlety to the music(if recorded properly).
The relay is after the output, but it works. Speakers are Driade, the hex shaped towers...well actually more like pillars. The sound is nice, no doubt about it...but different. It is fuller in a way, sounds very powerfull. The UCD is leaner.
Sergio from coldamp is very helpfull.
Pierre, maybe you dont have a crosstalk issue because you perhaps use 2 monoblocs. I use 1 transformer driving 2 rectifier circuits, 1 for every amp. For me it is of utmost importance to have a low crosstalk value and a small amp. Don't like big cases. Low crosstalk gives space/direction/subtlety to the music(if recorded properly).
Well, in fact I use a single supply.
Sorry, I don't know that speakers. What is the exact model (it's just that you have awake my curiosity ;-))
Just didn't pay attention to the crosstalk problem because it is totally unnoticeable while listening to music. It is more a purist issue, isn't it?
However, keep us updated on how it goes with your experimentation.
Do you have any other measures?
They told me that they were preparing a custom access for users with forum for direct technical support. I don't know if it is ready by now, they promised to give me a username and password.
Best regards,
Pierre
Sorry, I don't know that speakers. What is the exact model (it's just that you have awake my curiosity ;-))
Just didn't pay attention to the crosstalk problem because it is totally unnoticeable while listening to music. It is more a purist issue, isn't it?
However, keep us updated on how it goes with your experimentation.
Do you have any other measures?
They told me that they were preparing a custom access for users with forum for direct technical support. I don't know if it is ready by now, they promised to give me a username and password.
Best regards,
Pierre
they already have a service forum. Got a username and password. And having low crosstalk values is normal I think. If there is high freq. crosstalk the sound becomes dull, borring. And how I love good sounding amps. so the music can make you feel very comfortable/emotional(if recorded properly). You get spoiled by beautifull sound...well........more addicted.
This is the only pic. of the speaker I could find.
This is the only pic. of the speaker I could find.
Wow! Bgt, I have also received an username and password: I am now able to communicacte with them directly at a secure personal page, with forums directly attended by technical support. They also offer a folder where we (users) will be able to see the latest documents.Great value, I think. I hadn't seen something like this before from a supplier.
Hello, Bgt.
Any news with your tests of the coldamp modules?
From my side, I have done some testing in bridge mode, getting 800W of clean power out of them! As the load, I used a couple of 2x15" JBL towers in series, for a total of 8 ohm nominal. It's incredible to see how such tiny modules can drive that beasts so loud!
I have just decided to buy another one for my home subwoofer. (I got more motivated when I saw the new ESP article):
http://sound.westhost.com/project116.htm
Any news with your tests of the coldamp modules?
From my side, I have done some testing in bridge mode, getting 800W of clean power out of them! As the load, I used a couple of 2x15" JBL towers in series, for a total of 8 ohm nominal. It's incredible to see how such tiny modules can drive that beasts so loud!
I have just decided to buy another one for my home subwoofer. (I got more motivated when I saw the new ESP article):
http://sound.westhost.com/project116.htm
Yes, in fact I got two for home and two for "PA" use.
The ones at home sound simply excellent to me. (In fact I have stopped my own DIY class-D developments for a while and I am planning to purchase some more for a multichannel 5.1 setup
The other two that I have are intended for more abusive use with my JBL loudspeakers at open air parties.
The ones at home sound simply excellent to me. (In fact I have stopped my own DIY class-D developments for a while and I am planning to purchase some more for a multichannel 5.1 setup
The other two that I have are intended for more abusive use with my JBL loudspeakers at open air parties.
Pierre, I am redoing the housing with the coldamps. Still not satisfied with the crosstalk. When listening to them they sound really nice. They seem to have more bass, lowend. They have a full sound. When switching to the UCD's...they are different. Maybe you can describe it as a bit thinner, leaner....but excellent quality.
When you look at the pcb you'll see the 5532's and they are cap.coupled. Have to try another opamp. I guess. First get rid of the crosstalk. Ahhh...there are always so many things that influence the sound.
When you look at the pcb you'll see the 5532's and they are cap.coupled. Have to try another opamp. I guess. First get rid of the crosstalk. Ahhh...there are always so many things that influence the sound.
OK, redid the housing and the problem was still there but less.
This is the latest housing I use.
First 1 was much smaller.
Well, to solve the crosstalk I had to add a ground wire from the coldamp to the - of the speaker terminal. Originally the - is taken from the 0V at the PSU PCB as you will see in the recommended wiring diagram of coldamp.
Twisting the wires is a necessity with the coldamps. The power supply lines have a lot of high frequency EMI on them. The crosstalk decreased about 40Db @ 15khz. Still not finished, some missing parts for the housing. Will keep you updated.
Here you see the extra groundwire.
This is the latest housing I use.
An externally hosted image should be here but it was not working when we last tested it.
First 1 was much smaller.
An externally hosted image should be here but it was not working when we last tested it.
Well, to solve the crosstalk I had to add a ground wire from the coldamp to the - of the speaker terminal. Originally the - is taken from the 0V at the PSU PCB as you will see in the recommended wiring diagram of coldamp.
Twisting the wires is a necessity with the coldamps. The power supply lines have a lot of high frequency EMI on them. The crosstalk decreased about 40Db @ 15khz. Still not finished, some missing parts for the housing. Will keep you updated.
An externally hosted image should be here but it was not working when we last tested it.
Here you see the extra groundwire.
Hi Edl,
I ordered them here the last time:
http://www.schuro.de/preisl-bc154.htm
They are replaced by the Vishay 102ph and 106pedst.
I ordered them here the last time:
http://www.schuro.de/preisl-bc154.htm
They are replaced by the Vishay 102ph and 106pedst.
Thanks, Bgt, for sharing your tests and experiences...
To summarize: in your setup, did you say that you got better results by taking the - output to the speaker from the module GND? It is true that they recommend to take it from the PSU GND. In fact I didn't observe any problems by doing that, but who knows!
You speak about 40dB less of crosstalk at 15KHz. At first you spoke about -55dB, does that mean that you now have -95dB of crosstalk at that frequency? What change did make the biggest difference, twisting the PSU lines togegher or taking the output - from the module GND?
My small contribution: just in case you want to know, I observed that the background noise was (even) smaller when I tied both input GNDs with a small thick wire at the RCAs. Now you have to literally glue your ear to the tweeters to hear something with no signal.
To summarize: in your setup, did you say that you got better results by taking the - output to the speaker from the module GND? It is true that they recommend to take it from the PSU GND. In fact I didn't observe any problems by doing that, but who knows!
You speak about 40dB less of crosstalk at 15KHz. At first you spoke about -55dB, does that mean that you now have -95dB of crosstalk at that frequency? What change did make the biggest difference, twisting the PSU lines togegher or taking the output - from the module GND?
My small contribution: just in case you want to know, I observed that the background noise was (even) smaller when I tied both input GNDs with a small thick wire at the RCAs. Now you have to literally glue your ear to the tweeters to hear something with no signal.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.