So, having got the computer/usb board side of things working well its time to expose the paucity of my electronics knowledge...
I want to try filtering the DSD from my JLSounds USB board to recover the analogue as per Hazard's starting point with this thread. I don't have any line transformers available. My amps are quite sensitive (0.8V). But I need to;
Some guys in Italy have had some success using a simple LP filter and I thought I would try their approach as my starting point;
http://www.webalice.it/meneghettig/Un%20DSD%20player%20autocostruito.pdf
If I use their filter approach and follow it with a unity-gain buffer with a cap on its input that should handle the DC issues? It will obviously also provide the drive for the interconnects?
For volume control, I have a 10K switched attenuator available; can I simply insert that, or something similar (if a higher impedance is required), between the LP filter and the buffer?
Sorry if this is noddy stuff but I'm conscious that I don't know about the output impedance of the LP filter, nor understand the interactions of the LP filter and the other elements. I'll be grateful for the offer of a helping hand.
This is what I had in mind for the buffer;
New Octal Aikido Cathode Follower PCB and Kit
Cheers
Ray
I want to try filtering the DSD from my JLSounds USB board to recover the analogue as per Hazard's starting point with this thread. I don't have any line transformers available. My amps are quite sensitive (0.8V). But I need to;
- manage any DC
- drive several metres of interconnect cable
- control the volume of the output
Some guys in Italy have had some success using a simple LP filter and I thought I would try their approach as my starting point;
http://www.webalice.it/meneghettig/Un%20DSD%20player%20autocostruito.pdf
If I use their filter approach and follow it with a unity-gain buffer with a cap on its input that should handle the DC issues? It will obviously also provide the drive for the interconnects?
For volume control, I have a 10K switched attenuator available; can I simply insert that, or something similar (if a higher impedance is required), between the LP filter and the buffer?
Sorry if this is noddy stuff but I'm conscious that I don't know about the output impedance of the LP filter, nor understand the interactions of the LP filter and the other elements. I'll be grateful for the offer of a helping hand.
This is what I had in mind for the buffer;
New Octal Aikido Cathode Follower PCB and Kit
Cheers
Ray
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Hi Ronny, I was browsing the JLSounds website and spotted this little board - maybe useful?
JG buffer - I2S over USB Audio
Any progress?
Ray
Hi Ray, I can't speak Italian - but I can see the LP filter they use - a first order with R = 3.3k and C = 1n. If you use a 10k attenuator, then the series R will form a voltage divider with your attenuator, and you will lose about 25% of the gain. Since you already have the attenuator I assume that you are not going to replace it - so you may want to consider a smaller R (and bigger C) in the LPF. eg R = 1k and C = 3.3n (you will still lose 10%). And make sure you have the DC blocking cap before the attenuator.
I am sure that the Akido cathode follower will sound great, and it will drive your interconnect cable just fine. My system is totally balanced so I don't use akido techniques - but I have read every Tube Cad Journal blog by John Broskie since 1999 and I have learnt so much from each blog, so I reckon you can buy this kit with confidence.
My initial tests with the DIYINHK kit showed that it had low output when set up like this - its much better with the flip flop. Its hard to tell if this is normal or if there is something on the board that is causing a low output. I might well buy the JLSounds card and try it out.
I've been trying to find out a bit more about this board that I linked to earlier;
JG buffer - I2S over USB Audio
this is the circuit that it implements;
http://jlsounds.com/uploads/JGbuffer.pdf
That looks as though it could be quite useful in our context. I'm thinking of getting one and using the filter section for the very simple 1st order filter that I picked up from the Italian site, with the buffer providing a good output capability (though no gain). I'm concerned about the DC issue though so, picking up on Hazard's most recent comment I'm wondering if I could hack the board a little and insert a capacitor immediately before the buffer section? If so, what sort of value?
Thoughts?
Ray
JG buffer - I2S over USB Audio
this is the circuit that it implements;
http://jlsounds.com/uploads/JGbuffer.pdf
That looks as though it could be quite useful in our context. I'm thinking of getting one and using the filter section for the very simple 1st order filter that I picked up from the Italian site, with the buffer providing a good output capability (though no gain). I'm concerned about the DC issue though so, picking up on Hazard's most recent comment I'm wondering if I could hack the board a little and insert a capacitor immediately before the buffer section? If so, what sort of value?
Thoughts?
Ray
Hello Ray,
last week i have received the amanero board and some other hardware i need.
This week i have time to try some things. I will try several option:
- Just outputtransformer and filter
- Just filter
- Just iso7640fm and filter
- flipflop with filter
The board in your link has similar filter setup as i use. I like to make my own pcb's.
Hazard500, can i use this thread to report my findings or shall i open a new thread? I ask because this is your thread.
I hope its not just my thread. A few of us are experimenting with this approach and I'm very eager to share our knowledge. I've tried 2 configurations (DSD to transformer and DSD to flip flop then transformer). I much prefer the latter, but thats not to say that its best. I'm very interested to hear how you go - I wish I had time to try more configurations.
Good luck with your experiments,
Good luck with your experiments,
Ray, this DC issue is causing some issues for us. Are you able to read Italian? In the link that you provided above, are you able to interpret what they did to block DC? This assumes that there is DC!.
Regards, Hazard
Sorry hazard, my Italian is very limited and I just interpreted the pictures; I don't think there is a solution to DC in there.
However, the DC has been troubling me and I think I've found a solution that will suit me, it's not fully formed yet but in outline and to critique;
1. Pass the DSD outputs from the USB card through a FlipFlop as you have done, producing differential digital signals.
2. Apply a LP filter, of choice, to each differential signal.
3, Feed the filtered differential signals into the inputs of a Broskie unbalance. Read the section about using the 'Unbalancer as I-to-V Converter' down near the end of this article;
The Unbalancer
In fact, the Unbalancer has pads on its board for components for a simple 1st order filter.
As I read it that should give me a healthy, clean, single-ended output.
So where is my mistake?
If it works I will gradually develop/refine, if not I can reuse almost all the parts in another project.
Ray
Here's a link to the Unbalancer manual, though I think it might be a little out of date wrt power supplies.
http://glass-ware.com/User_Guides/Unbalancer 9-pin -PS.pdf
Ray
http://glass-ware.com/User_Guides/Unbalancer 9-pin -PS.pdf
Ray
Hi, I´m following this thread silently, very nice idea, indeed.
Maybe it already came up, but this guy had a very similar idea:
6moons audio reviews: PS Audio DirectStream PerfectWave DAC
He explains his method of lowpass filtering and powersupply-concept a little bit...
Maybe it already came up, but this guy had a very similar idea:
6moons audio reviews: PS Audio DirectStream PerfectWave DAC
He explains his method of lowpass filtering and powersupply-concept a little bit...
I don't know, that seems to be overly complex for what your trying to achieve.
Yes, maybe a little more complex than I would like too, converting to differential and then back to SE grates a bit but I think it will extract the audio from the DSD data stream and eliminate the DC offset issue without using a 'conventional' DAC. We're learning about this stuff. Would be glad to hear of a simpler approach...
Ray
Exactly, DSD by its very nature is very close to analogue.
However, you would also get very good results with a native DSD DAC. it's usually the case that several to-and-fro conversions of DSD degrades the sound.
I don't consider it audiophile software. However, HQ Player is. Try that one for real-time DSD up-conversion.
Where do you think it happens, Gopher?
It's actually a very good question and the answer may surprise you.
The D/A happens at the pin output itself.
This is why it can be filtered simply with an analogue lowpass filter.
DSD is digital, but analogous to analogue
Not my idea but, how about feeding DSD into a tube, anyone..?
Precisely what I wanted to do: get the pure DSD out and then feed that into tubes.
So, got my native DSD DAC as well as a made my SET tube amp with the PCB from George of Tubelab.
The next step would be to tap that direct DSD and use my own analogue filter. One of the DSD boards looks fantastic for a DIY solution.