Low distortion, pure resistive I/V stage for Sabre Reference DAC - Page 5 - diyAudio
Go Back   Home > Forums > Source & Line > Digital Source

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 5th November 2012, 05:46 AM   #41
diyAudio Member
 
Join Date: Jan 2011
Location: Germany
Would it be possible to get 4 Vrms output instead of 0,6 Vrms?
If so, how?



/S

Quote:
Originally Posted by roender View Post
Nope ... should be around 600mV rms.
It is designed to be like that because my RMI-FC100 amp allow only 600mVpp at input for full output power.
  Reply With Quote
Old 5th November 2012, 05:50 AM   #42
roender is offline roender  Romania
diyAudio Member
 
roender's Avatar
 
Join Date: Sep 2006
Quote:
Originally Posted by staccatiss View Post
Would it be possible to get 4 Vrms output instead of 0,6 Vrms?
If so, how?

/S
Why do you need that?
The distortion will be higher for 15V Vcc, power dissipation also if you will be forced to increase Vcc in order to keep the same THD spectrum.
  Reply With Quote
Old 5th November 2012, 05:08 PM   #43
diyAudio Member
 
Join Date: Jan 2011
Location: Germany
I use a line amp in between the IV converter and the power amp. And all my gear follow the standard output voltage, ie 2Vrms single ended and 4Vrms balanced. Makes life so much easier. Having only 0,6Vrms is far to low.

Some extra heat is fine, and a higher rails is OK. I often use 24 - 36VDC myself.
With this in mind, how would you change your design to get 4Vrms output voltage?


/S

Quote:
Originally Posted by roender View Post
Why do you need that?
The distortion will be higher for 15V Vcc, power dissipation also if you will be forced to increase Vcc in order to keep the same THD spectrum.
  Reply With Quote
Old 6th November 2012, 05:49 AM   #44
roender is offline roender  Romania
diyAudio Member
 
roender's Avatar
 
Join Date: Sep 2006
This are the results for 4V rms analog output at 0dB digital output.
The power supply voltage was increased at 30Vdc, hence R7 and R10 dissipates now around 1W, Q1 and Q2 dissipates 250mW and were upgraded to 2sa1360 (must be placed on a small heatsink)
You need to supply a very clean power voltage, preferably from a shunt regulator capable to give 30V/150mA per each channel.

Fourier components of V(vout-,vout+)
DC component:-0.00077357

Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 2.000e+04 5.532e+00 1.000e+00 -1.61 0.00
2 4.000e+04 1.170e-07 2.115e-08 179.69 181.30
3 6.000e+04 1.199e-04 2.167e-05 42.36 43.96
4 8.000e+04 6.279e-08 1.135e-08 -177.48 -175.87
5 1.000e+05 5.828e-07 1.054e-07 -124.63 -123.03
6 1.200e+05 3.940e-08 7.122e-09 176.83 178.44
7 1.400e+05 2.358e-08 4.262e-09 173.40 175.01
8 1.600e+05 2.870e-08 5.189e-09 177.14 178.75
9 1.800e+05 4.302e-08 7.777e-09 172.44 174.04
Total Harmonic Distortion: 0.002168%
Attached Images
File Type: jpg schematic.jpg (85.3 KB, 258 views)
File Type: jpg 20k_thd_4Vrms_out.jpg (30.9 KB, 253 views)

Last edited by roender; 6th November 2012 at 05:53 AM.
  Reply With Quote
Old 6th November 2012, 10:09 AM   #45
diyAudio Member
 
Join Date: Jan 2011
Location: Germany
Thank you!
God work getting very low THD with this output voltage, too!

I am doing the simulation now. May I ask what currents go through
R8
R10
R11
?

Kind regards,
S

Quote:
Originally Posted by roender View Post
This are the results for 4V rms analog output at 0dB digital output.
The power supply voltage was increased at 30Vdc, hence R7 and R10 dissipates now around 1W, Q1 and Q2 dissipates 250mW and were upgraded to 2sa1360 (must be placed on a small heatsink)
You need to supply a very clean power voltage, preferably from a shunt regulator capable to give 30V/150mA per each channel.

Fourier components of V(vout-,vout+)
DC component:-0.00077357

Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 2.000e+04 5.532e+00 1.000e+00 -1.61 0.00
2 4.000e+04 1.170e-07 2.115e-08 179.69 181.30
3 6.000e+04 1.199e-04 2.167e-05 42.36 43.96
4 8.000e+04 6.279e-08 1.135e-08 -177.48 -175.87
5 1.000e+05 5.828e-07 1.054e-07 -124.63 -123.03
6 1.200e+05 3.940e-08 7.122e-09 176.83 178.44
7 1.400e+05 2.358e-08 4.262e-09 173.40 175.01
8 1.600e+05 2.870e-08 5.189e-09 177.14 178.75
9 1.800e+05 4.302e-08 7.777e-09 172.44 174.04
Total Harmonic Distortion: 0.002168%
  Reply With Quote
Old 6th November 2012, 10:25 AM   #46
roender is offline roender  Romania
diyAudio Member
 
roender's Avatar
 
Join Date: Sep 2006
Please find below the requested values:

I(R8 = 5.14 / 5.19mA
I(R10) = 48.7 / 56.8mA
I(R11) = 10.26 / 12.7mA

The above min and max values are for full output swing.
  Reply With Quote
Old 7th November 2012, 05:14 AM   #47
diyAudio Member
 
Join Date: Jan 2011
Location: Germany
Thanks, roender!

To get 4,0Vrms output, and have the currents you wrote down, I had to change a resistor value into half what you suggested, and I had to increase the 1k1 into 1k75.

THD is about -88 dB in balanced mode as the even order harmonics cancel out. In the real world, where an amplifier does the balanced to single ended conversion, even order harmonics will not cancel out as well.

In SE mode, THD is rather high at -61 dB simulating at 1kHz and 2Vrms out at 0 dBFS (16mAACp-p).

See attachments.

/S



Quote:
Originally Posted by roender View Post
Please find below the requested values:

I(R8 = 5.14 / 5.19mA
I(R10) = 48.7 / 56.8mA
I(R11) = 10.26 / 12.7mA

The above min and max values are for full output swing.
Attached Images
File Type: jpg 4V Version-1.jpg (526.0 KB, 216 views)
File Type: jpg 4V Version--2.jpg (124.3 KB, 203 views)
File Type: jpg 4V Version--3.jpg (139.1 KB, 191 views)
  Reply With Quote
Old 7th November 2012, 05:38 AM   #48
roender is offline roender  Romania
diyAudio Member
 
roender's Avatar
 
Join Date: Sep 2006
If you are using Buffalo II or III DAC the output current is actually 17.2mA pp.
Better use the same source as in my simulation, a voltage source with 1.715V DC offset and 1.69V swing at 0dB output followed by 195ohm series resistor.
  Reply With Quote
Old 7th November 2012, 07:56 AM   #49
diyAudio Member
 
Join Date: Jan 2011
Location: Germany
I should haev told you about my source. It uses 195.3128 resisors which are inseries with the sine generator, and also in series are 1,65VDC batteries. I use an inverter so that only one sine source is used.

So, we are using the same system except that I use the (recommended) 3V3 instead of Twisted Pears 3V5.

What single ended THD do you get with 4,0Vrms output voltage?

/S

Quote:
Originally Posted by roender View Post
If you are using Buffalo II or III DAC the output current is actually 17.2mA pp.
Better use the same source as in my simulation, a voltage source with 1.715V DC offset and 1.69V swing at 0dB output followed by 195ohm series resistor.
  Reply With Quote
Old 7th November 2012, 07:59 AM   #50
roender is offline roender  Romania
diyAudio Member
 
roender's Avatar
 
Join Date: Sep 2006
Quote:
Originally Posted by staccatiss View Post
I should haev told you about my source. It uses 195.3128 resisors which are inseries with the sine generator, and also in series are 1,65VDC batteries. I use an inverter so that only one sine source is used.

So, we are using the same system except that I use the (recommended) 3V3 instead of Twisted Pears 3V5.

What single ended THD do you get with 4,0Vrms output voltage?

/S
Do you mean 2V rms single ended, because 4V rms is pointless for a single ended preamplifier?!
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
ESS Sabre Reference DAC VS Prism sound ADA-8XR, DAD AX24 and weiss DAC? mbl Digital Line Level 12 19th October 2009 09:48 AM


New To Site? Need Help?

All times are GMT. The time now is 10:30 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2