I added it here.
https://github.com/stefaweb/Q17-Amplifier/blob/main/Q17-Project-Description.pdf
Please note, there are errors on the component numbers.
iTiberius has disappeared from the surface.
https://github.com/stefaweb/Q17-Amplifier/blob/main/Q17-Project-Description.pdf
Please note, there are errors on the component numbers.
iTiberius has disappeared from the surface.
I've downloaded files from Tiberius's github.
https://drive.google.com/drive/folders/1v48mDzgeiGWka17qroqA9q4CpzaoyaP0?usp=drive_link
https://drive.google.com/drive/folders/1v48mDzgeiGWka17qroqA9q4CpzaoyaP0?usp=drive_link
Hello,
I have completed testing for the input sensitivity of 0.7Vrms (0dBu).
There is not much modification. Only resistor R17 changes from 3k3 to 5k1. This gives a gain of 5.31 for the opamp and 35 for the whole.
As a reminder, I also advise you to upgrade R17 to 47k and C7 to 2.2uF for better bandwidth linearity.
I will update my Github repository when I have done the other sensitivities (1.2V and 1.4V). There will be more modification for these two sensitivities as the opamp gain should be at minimum 4 (best is between 5 and 6).
In terms of the amp's sound signature, there is not much change. The low mid is more balanced and the bass a little firmer.
Regards,
Stef.
I have completed testing for the input sensitivity of 0.7Vrms (0dBu).
There is not much modification. Only resistor R17 changes from 3k3 to 5k1. This gives a gain of 5.31 for the opamp and 35 for the whole.
As a reminder, I also advise you to upgrade R17 to 47k and C7 to 2.2uF for better bandwidth linearity.
I will update my Github repository when I have done the other sensitivities (1.2V and 1.4V). There will be more modification for these two sensitivities as the opamp gain should be at minimum 4 (best is between 5 and 6).
In terms of the amp's sound signature, there is not much change. The low mid is more balanced and the bass a little firmer.
Regards,
Stef.
Attachments
Linear (an analog lab power supply) for the measures and a Q17-Mini (one pair power mosfet) stereo block with a 160VA toroid at 50Vdc on a pair of JBL L75 and a pair of Triangle Titus for the listening session. The spectrum measure is not perfect as I don't have a notch filter after the oscillator. In any case, the measurements are only there to verify that the amp is not doing anything bad, only the final sound matters.
For sensitivity, I took a margin so as not to reach the clip at 0.7V. The clip is at 27V.
Stef.
For sensitivity, I took a margin so as not to reach the clip at 0.7V. The clip is at 27V.
Stef.
Last edited:
OOPs, sorry.
R16=47k (was 22k)
R17=5k1
C7=2.2uF
The R16 47k value is already up to date on the Github diagram.
Stef.
Call for volunteers to test 1.2V sensitivity.
After having tested several ways of doing things, I suggest you test the sound result of this configuration before making it official.
The measurement data is practically the same as the 0.7V version except for the damping factor which increased to 350.
Here are the values under test for 1.2Vrms (+4dBu)
R16=47k
R17=4k75
R27=560
R6=182
C7=2.2uF
opamp gain: 5.6
overall gain: 22
Output @ 1.2Vrms = 26V
Respect the values because a small difference in resistor causes the gain to vary by a significant proportion.
I left a margin before the clip at 28V.
Let me know if you do the test.
Regards,
Stef.
After having tested several ways of doing things, I suggest you test the sound result of this configuration before making it official.
The measurement data is practically the same as the 0.7V version except for the damping factor which increased to 350.
Here are the values under test for 1.2Vrms (+4dBu)
R16=47k
R17=4k75
R27=560
R6=182
C7=2.2uF
opamp gain: 5.6
overall gain: 22
Output @ 1.2Vrms = 26V
Respect the values because a small difference in resistor causes the gain to vary by a significant proportion.
I left a margin before the clip at 28V.
Let me know if you do the test.
Regards,
Stef.
Attachments
Hello,
I shouldn't lower the sensitivity any further (1.4V and 2V). This does not work (see curve examples ). I have tried several methods (including R27) and none give good results. Given that below a gain of 4 for the opamp with R17/R6, I cannot reduce it further.
Unless anyone has an opinion/idea on that.
Stef.
Spectrum at 1W.
I shouldn't lower the sensitivity any further (1.4V and 2V). This does not work (see curve examples ). I have tried several methods (including R27) and none give good results. Given that below a gain of 4 for the opamp with R17/R6, I cannot reduce it further.
Unless anyone has an opinion/idea on that.
Stef.
Spectrum at 1W.
Attachments
Hello,
Do not take into account the last 2 or 3 spectrum curves I posted. They are all bad (THD). After suspecting a bad setting of the USB interface, I agreed that through testing I ended up breaking something on the Q17 test board.
I went to get my Q17-Mini stereo block (updated 1.2V) from the living room and put it through the bench. It's OK. See the attached curve.
Sorry for that.
All I have to do now is repair the test board (Find what is broken above all).
Stef.
Curve at 1W output.
Do not take into account the last 2 or 3 spectrum curves I posted. They are all bad (THD). After suspecting a bad setting of the USB interface, I agreed that through testing I ended up breaking something on the Q17 test board.
I went to get my Q17-Mini stereo block (updated 1.2V) from the living room and put it through the bench. It's OK. See the attached curve.
Sorry for that.
All I have to do now is repair the test board (Find what is broken above all).
Stef.
Curve at 1W output.
Attachments
Last edited: