Hi, what is the inductance of the IntactAudio AVC at some low useable frequency, say anywhere between 20 and 40Hz ?
Thanks,
LH/S
Hi everybody !
Stijn -> Alps are not so bad, except maybe the motorized one which add some metallic notes, but it is true that they hide some details, as if you place a towel on your loudspeakers...
Yesterday I have removed those towels 😀 You're right, I'm lucky, being an audiovsual technician when you like DIY is very helpful 😛
Maybe I should try to test nice resistors ?
With my little attenuator, I can easily try the shunt mode as you suggest, removing the Cinemags. The only issue is that I'm afraid to loose stereo mode and the return of hums... I have to check that 😉
Anyway, thank you for the motivation 🙂
wlowes -> I will contact the supplier today 😉
Stijn -> Alps are not so bad, except maybe the motorized one which add some metallic notes, but it is true that they hide some details, as if you place a towel on your loudspeakers...
Yesterday I have removed those towels 😀 You're right, I'm lucky, being an audiovsual technician when you like DIY is very helpful 😛
Maybe I should try to test nice resistors ?
With my little attenuator, I can easily try the shunt mode as you suggest, removing the Cinemags. The only issue is that I'm afraid to loose stereo mode and the return of hums... I have to check that 😉
Anyway, thank you for the motivation 🙂
wlowes -> I will contact the supplier today 😉
Hi Ludwig,
There is a FAQ on Dave's site that discusses this. I picked up one Q which might be what you are looking for. You can also ask him a question about your application. He is pretty responsive.
Q - What is the impedance presented to the source?
A - It is the reflected load in parallel with the inductive reactance of the autoformer. When set for no attenuation, the reflected load is simply whatever follows the volume control in the signal chain. However, that load is cut in half (resistance is doubled) for every 3dB of attenuation. At -20dB the reflected load is reduced by a factor of 100. At -40dB it is reduced by a factor of 10,000 which is 10,000 times the resistance!
The simplified approach is to determine the desired load taking into consideration the lowest frequency of interest and doing a few simple calculations. For example: If your source is a CD player with a 50 ohm Z-out and you want to adhere to the 1:10 ratio of source to load many suggest all you need ot do is pick a suitable low frequency (often 20hz) and plug the numbers into the Z=2piFL formula to get, 500=2*pi*20*L. Solving for L gives you a required 4hy inductance to provide a 500 ohm load to a 50 ohm source.
Our Autoformers come shipped with a butt gap which provides approximately 20hy's of inductance. If your situation requires more inductance it is quite simple to restack the lams to get inductance values up to 170hy's.
Any chance you could draw what you are saying above?? I'd like to understand what's going on....
Thanks!
Nick
Thanks ..
The impedance thing is to do with square of the turns ratio and the load presented, different from what I am looking for.
So the answer is configurable to be between 20H and 170H - but he doesn't state at what frequency.
S&B TX102-mk3 is >400 Henrys at 20Hz.. I'm ok with smaller coupling caps for parallel-feed application..
LH/S
Yes 🙂
An externally hosted image should be here but it was not working when we last tested it.
It is pretty the same for the digital line, except that the chokes are in serie and smaller (300mH). And I have a fourth line for BBB + Waveio with 2H chokes.
For separate the differents lines I have cut the trace between the four 47uF caps and the 47 uF cap connected to the LF33's input. I used the hole of this input cap for connected each module together and used a wire connected to the "PS digital raw line".
For analog side, I cut the trace between VB+ and R3, used VB+ for interconnect Left modules and the R3's hole, close to VB+, for connect modules together.
Finally, I supllied each side from the top, positives to the wire which connect the module, and each ground to its own side.
Maybe I will make a draw too 😛
EDIT:
it will be easiest to understand with it:
An externally hosted image should be here but it was not working when we last tested it.
In red are the trace cutting
In green are the wires between each DAC modules, not connected to the mainboard
Et voilà !
Julien
Last edited:
Will you show how grounds are separated please? If not separated, then how you arranged grounds.
I did not change anything to ground (not yet). First, because I don't know if it is possible digital form analog and second, because I'm not sure of "who is who" 😀
I use a common ground point for my separate analogue and digital supplies too. It works perfectly
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For analog supply yes in my case.
Does anyone has meet the following issue: at low level of volume, I have noise, not hum, and the sound is saturated. Everything leave when I put louder.
Strange isn't it ?
First of all, thanks for posting the drawings!!
How are you supplying the current to the main board? I think your LCLC supply returns and main board supply returns flow along the same section of the main board ground fill.
Also, see this, bottom of the page, fig 10-22
KISS 134: Noise Reduction with Lundahl’s Double-Coil Cut-C Core Chokes: a pictorial essay by Andre Jute
Regards,
Nick
Do you use choke based power supply for digital PS ? I'm asking myself if it is really important for those... ?
But does the formula not give you what you are really seeking? It allows you to understand the required Hy required at a given frequency eg 20hz. Also you can solve for the frequency where you hit -3db for a given H. In my case I have source at 600ohms, and amps at 100k. The supplied 20Hy gives me a floor well below useable 20hz and the upper end goes clean way past 100khz. Also sounds pretty good 🙂
With pleasure !
The main board is supplied by another LCLC raw supply. I had the issue before the separation.
In my case the grounds of the DAC boards connect back to my common ground point
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