Autoformer volume control problem
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
Autoformer volume control problem
I have a really strange problem going passive or active, when I play DSD sounds bad, isn't the system because when used a stepped attenuator goind passive or active the DSD plays superb.
-
- Posts: 2091
- Joined: Sat Jan 22, 2005 3:54 am
- Location: NYC
- Contact:
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
-
- Posts: 2091
- Joined: Sat Jan 22, 2005 3:54 am
- Location: NYC
- Contact:
could there be DC on the output? I see the Legato doesn't have output blocking capacitors and relies on the user to null the DC offset.
dave
dave
Get Your Fix
www.hifiheroin.com
www.hifiheroin.com
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
-
- Posts: 2091
- Joined: Sat Jan 22, 2005 3:54 am
- Location: NYC
- Contact:
Hey,
sorry for the late reply, I was out of town.
If the AVC is after a #26 and IT then there can be no DC. The only possible issue is the parallel combination of the AVC inductance and the IT inductance might be too low for the 26 causing a loss of low frequency info. Since Vinyl sounds good, I don't suspect this is the issue.
Is it possible that the grid of the #26 is causing issues for the Dac?
dave
sorry for the late reply, I was out of town.
If the AVC is after a #26 and IT then there can be no DC. The only possible issue is the parallel combination of the AVC inductance and the IT inductance might be too low for the 26 causing a loss of low frequency info. Since Vinyl sounds good, I don't suspect this is the issue.
Is it possible that the grid of the #26 is causing issues for the Dac?
dave
Get Your Fix
www.hifiheroin.com
www.hifiheroin.com
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
-
- Posts: 17
- Joined: Tue Jan 29, 2008 2:43 am
Hey guys,
I don't have enough on the ball to figure this out, but I can't stop thinking that the quantisation noise inherent to DSD has something to do with this. I'll let you guys with enough on the ball actually figure it out.
Felipe,
Is there any way you can play a DSD track and see if there's any DC offset, as you stated you measured none with no signal present ?
Cheers, Crazy Bill
I don't have enough on the ball to figure this out, but I can't stop thinking that the quantisation noise inherent to DSD has something to do with this. I'll let you guys with enough on the ball actually figure it out.
Felipe,
Is there any way you can play a DSD track and see if there's any DC offset, as you stated you measured none with no signal present ?
Cheers, Crazy Bill
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
I used the AVC as passive and 300 Ohm headphone to avoid grid & OPT tx and playing DSD files I still have Left channel -1.6VDC Right channel -0.8VDC, another curiosity is when I stop playing DSD files still remain the DC offset Left channel -1.6VDC Right channel -0.8VDC, only goes to zero when I play PCM files, another test done is changing the volume setting don't change the amount of DC offset so DC offset isn't related to volume setting.
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
-
- Posts: 2091
- Joined: Sat Jan 22, 2005 3:54 am
- Location: NYC
- Contact:
-6Vdc at the output will not make the autoformer or the grid of a 26 very happy.
dave
dave
Get Your Fix
www.hifiheroin.com
www.hifiheroin.com
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
I never used the AVC between the DAC and the grid of 26, I used the AVC between the Lundhal LL1660 OPT and the SS power amp (100K input impedance) or between the DAC and the headphone Sennheiser HD600 (300 ohms nominal impedance).
I know AVC doesn't works ok with DC offset, also I know using a cap input can fix the issue.
What the question is: why if I use a cheap ladder resistor DSD files don't produces any kind of DC offset at the cheap ladder resistor input?
I know AVC doesn't works ok with DC offset, also I know using a cap input can fix the issue.
What the question is: why if I use a cheap ladder resistor DSD files don't produces any kind of DC offset at the cheap ladder resistor input?
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
-
- Posts: 2091
- Joined: Sat Jan 22, 2005 3:54 am
- Location: NYC
- Contact:
1ma will take it down. 6V across the 60ish ohm DCR will allow for 100ma but I'm sure there is no way that amount of current can be delivered.
the effect of the saturated core should just be loss of bass.
dave
the effect of the saturated core should just be loss of bass.
dave
Get Your Fix
www.hifiheroin.com
www.hifiheroin.com
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
-
- Posts: 2091
- Joined: Sat Jan 22, 2005 3:54 am
- Location: NYC
- Contact:
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
-
- Posts: 2091
- Joined: Sat Jan 22, 2005 3:54 am
- Location: NYC
- Contact:
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm
-
- Posts: 2091
- Joined: Sat Jan 22, 2005 3:54 am
- Location: NYC
- Contact:
what is the output impedance driving it?
you can create a file with some LF sinewaves to see if you are really rolling off.
dave
you can create a file with some LF sinewaves to see if you are really rolling off.
dave
Get Your Fix
www.hifiheroin.com
www.hifiheroin.com
-
- Posts: 64
- Joined: Fri Aug 15, 2014 2:48 pm