Hi Patrik,
Check out dantimax.dk
I used control2, relvol3, input2, frontpanel2, an oled display and a 78xxpsu, all from dantimax.
While debugging the problem I had earler with the unconnected ground pad, I wondered if designing a pcb with groumd plain would be worthwhile. If it turns out to be a keeper I may be interested in well designed boards ☺
Regards,
Albert
I'm done with the first schematic, and will make the psu schematic too.
Then I need to think if I will make it close as possible to the original.
1. make one big pcb with PSU and 2 channels + a Relay board pcb
2. Standalone PSU Pcb, 1x Channel pcb ( so you need 2 of them )
3. PSU pcb + 1 pcb with both channels.
4. or something I don't know yet
Then I need to think if I will make it close as possible to the original.
1. make one big pcb with PSU and 2 channels + a Relay board pcb
2. Standalone PSU Pcb, 1x Channel pcb ( so you need 2 of them )
3. PSU pcb + 1 pcb with both channels.
4. or something I don't know yet
i'm using the same setup as you, exept the PSU. i used the standby PSU from Dantimax so the preamp shuts down in standy mode.
also i changed the LED circuit so that the LED lights up in standby and shuts down when the amp is turned on.
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You should ask yourself if you need balanced in & Outs. if you only use cinch you could also use BA3 as pre a Jfet BOZ.
I have build an Aleph P mostly because i have XLR Connections everywhere and wanted to use them.
The P is real good Pre. ive also build some standart B1. All of them are sold. Because i used them not enough.
If I would have to make a decision again, i would use a poti ore something else cheap till P is finished and save the Money and time Needed for a B1.
A few things come to mind about the switching noise. Are you using the attenuator on the output? If so you need to make sure there is no DC input offset on your power amp input. If there is an offset it will vary when the resistance of the output attenuator changes during switching of the resistors when you change volume. Also, if there was any DC from the preamp getting through onto the attenuator somehow it would cause the symptoms you describe. If your control system is powered by it's own power supply, own transformer etc, it should not need a common connection to the audio power supply. If it is powered by the same supply, the current path for the relay coil should be separated from any audio current flow.
If you do not have reverse diodes across the relay coils you could be getting large voltage spikes on the relay supply whenever you switch them. That could lead to noises in the audio signal path. Some relays have the diode built in, others need them added externally.
Hi Bfpca,
Thanks for you tips.
There should not be any DC on the output of an Aleph P1.7 as there are 3 parallel 10uF caps blocking it. Schematic: PASS LABS CLONE - ALEPH P 1.7 DIY Preamplifier PCB layout
The amp is on top of my Aleph J on the floor and being a wheelchair user I cannot measure anything without having it disconnected for me first. I got someone test the + signal of the channels for DC offset and it showed 0V as expected, but I did not get her to test the others.
I have asked Mikkel (of Dantimax) if he has any idea what could be causing the problem but have not yet heard back from him.
At the moment I don't need to adjust the preamp volume so much because I can drop a few dB's digitally without degrading the sound too much. Playing 16 bit digital on a 24 bit dac does have its advantages
Thanks for you tips.
There should not be any DC on the output of an Aleph P1.7 as there are 3 parallel 10uF caps blocking it. Schematic: PASS LABS CLONE - ALEPH P 1.7 DIY Preamplifier PCB layout
The amp is on top of my Aleph J on the floor and being a wheelchair user I cannot measure anything without having it disconnected for me first. I got someone test the + signal of the channels for DC offset and it showed 0V as expected, but I did not get her to test the others.
I agree and assumed they would be completely separate. I had not realised the control boards (input2 and relvol3) each connect audio and control grounds through a ferrite bead. Those I will remove to see if it solves the problem.
The relays came with the relvol3 kit from Dantimax. I assume they are the correct type but would have to check the model to make sure.
I have asked Mikkel (of Dantimax) if he has any idea what could be causing the problem but have not yet heard back from him.
At the moment I don't need to adjust the preamp volume so much because I can drop a few dB's digitally without degrading the sound too much. Playing 16 bit digital on a 24 bit dac does have its advantages
Mostly I just need normal RCA contacts... but I will upgrade to XLR where I can...
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Quick question:
Do someone have a extra set of Kojas pcb?
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Anyway, my goal is to build a preamp to match my Krell KSA 100 Clone I built some years ago. And if i can get something similar to RSTAudios P1.7 it would be cool.
KK still has the board on his website, www.kk-pcb.com so you could ask him. That is the board my friend bought years ago and is in the amp I completed. Having had a good look at the board I wonder if a board with a large ground plane would be better. I do not have enough experience to answer my own question, just intuition.
I have not seen Kojas boards.
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I know, but don't like the layout. They are probably working 100%, but I want another layout, more like Kojas. But it would be nice to have +5/+12 available in PSU for Relays and LCD in future.
If some is interested in another run of new pcb's, drop a pm, and we can decide what will be included or not.
Done with Mainboard, PSU schematics and BOM.
I've looked on some different schematics from various people, and they do have some interesting solutions and I think I might add some of them into my version.
Koja: has Relays for better audio quality instead of a cheap dip switch solution.
R.Sten: has an extended Gain control at RG + couplings caps here and there.
I'm thinking of adding more options to chose different sizes of Caps on: C14, C14, C15, C16 for more easy fitting.
Any more ideas you guys can think of adding ?
I've looked on some different schematics from various people, and they do have some interesting solutions and I think I might add some of them into my version.
Koja: has Relays for better audio quality instead of a cheap dip switch solution.
R.Sten: has an extended Gain control at RG + couplings caps here and there.
I'm thinking of adding more options to chose different sizes of Caps on: C14, C14, C15, C16 for more easy fitting.
Any more ideas you guys can think of adding ?
re: Ralph S's example: I also considered implementing internal gain as relay switched discrete resistors but could not find a mechanical encoder with binary analog combinations (Digikey no longer stocked it); I eventually gave it up for all the pcb real estate required for the added relays. The boards were already pretty big with all those 10uF pp caps.
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As I previously mentioned, I hear distortion when changing volume using my Dantimax RelVol3 attenuator. Removing the ferrite bead connecting powerGND to audioGND had no effect.
In order to make sure the problem was not in the amp itself, I tried did the following:
1. Disconnected all audio connections on RelVol3 board. This left only 5V DC and flatcable to Dantimax Input2 board.
2. Connected DSO Nano signal generator set to 1KHz square wave to RelVol3 INPUT.
3. Connected Analog scope to RelVol3 OUTPUT.
I have uploaded a clip where I change volume by rotating the encoder https://youtu.be/WvkQ2TlmWj4
It is clearly visible on the scope that something is wrong. When I repeat the experiment using an Alps pot, I get nice smooth changes in amplitude.
Bfpca suggested earlier the problem could be due to the type of relay used on the RelVol3 board. I have checked and the type used is Fujitsu FTR-B4CA4.5Z (see attached datasheet). Could these be the cause of this problem?
Have other builders used te same relays or had similar problems?
I have emailed Mikkel a few times but have not had a reply. Any suggestions are appreciated.
Thanks,
Albert
In order to make sure the problem was not in the amp itself, I tried did the following:
1. Disconnected all audio connections on RelVol3 board. This left only 5V DC and flatcable to Dantimax Input2 board.
2. Connected DSO Nano signal generator set to 1KHz square wave to RelVol3 INPUT.
3. Connected Analog scope to RelVol3 OUTPUT.
I have uploaded a clip where I change volume by rotating the encoder https://youtu.be/WvkQ2TlmWj4
It is clearly visible on the scope that something is wrong. When I repeat the experiment using an Alps pot, I get nice smooth changes in amplitude.
Bfpca suggested earlier the problem could be due to the type of relay used on the RelVol3 board. I have checked and the type used is Fujitsu FTR-B4CA4.5Z (see attached datasheet). Could these be the cause of this problem?
Have other builders used te same relays or had similar problems?
I have emailed Mikkel a few times but have not had a reply. Any suggestions are appreciated.
Thanks,
Albert
