Henrik
But in my Bosoz i already tuned r15 to about 80 Ohms.
do you have experiences, how distortion increases, by decreasing r15?
In my Bosoz the transistors are matched for that reason. is this o.k.? or is it better to use 430 ohms in r15, with lower distortion and better sound?
regards,
Ralf
Henrik said:Hi Ralf
You proberly need more gain from either preamp or SOZ.
If You cant drive Your SOZ to clip at 15v rails, You will not get more power out at 35v rails, until You get more input voltage swing at Your SOZ.
I don´t know if this is the problem, but it could be.
But in my Bosoz i already tuned r15 to about 80 Ohms.
do you have experiences, how distortion increases, by decreasing r15?
In my Bosoz the transistors are matched for that reason. is this o.k.? or is it better to use 430 ohms in r15, with lower distortion and better sound?
regards,
Ralf
As an experiment, try to lower r15 even more to se if You get mor power at the SOZ.
On my old BOSOZ it was hard to hear the difference between 125 and 400 Ohm values of r15, but I think r15 at 80 Ohm is proberly the lowest value, but try lower it anyway to se if You gets more power. I f You do, then gain is the main issue.
On my old BOSOZ it was hard to hear the difference between 125 and 400 Ohm values of r15, but I think r15 at 80 Ohm is proberly the lowest value, but try lower it anyway to se if You gets more power. I f You do, then gain is the main issue.
After a really long time I finally started testing a choke input filter for SOZ.
I am using an adjustable AC power supply with a 2K Va transformer for testing.
Its a monoblock design.
The chokes are Hammond 195P5 iron cores rated at 5 amps 30 mH .23 DCR and about 6.5 ibs each.
Each Rail has a choke connected right after the bridge rectifier and then to a 80,000 uF bank of 100V caps. Each cap is 10,000 uF. For a total of 160,000uF per channel.
One channel looks like this:
----------------------------30 mH choke---80,000uF caps--- + rail
Transformer--- bridge
----------------------------30 mH choke---80,000uF caps--- - rail
I do not have a scope so all I can do is use my ear and a digital meter.
I listen for noise from the speaker with out the chokes and noticed some low level hum with my ear almost touching the driver. Adding the choke the hum was very faint. I would say almost cut in half. Not easy to hear.
I listen to music with and with out the choke. I preferred the choke. The sound became more relaxed and smooth. I need to listen more it may just be a bias. Listening over a long period of time and then switching back to no choke will be needed.
Running some test with my digital multimeter I found a huge loss in voltage with the chokes in place. In fact it appears to be much more than the .9 commonly used.
A/C in------ D/C after choke.
10.19 V , 4.73V + rail 5.94V (-) rail
35.20 , 11.47 + 11.26 (-)
53.00 , 16.51 + 16.14 (-)
Maybe some one can comment on this loss.
The voltage difference in each rail I think is due to the slight difference in each choke. They are rated + or (-) 15% on both inductance and amps. The A/C going into the the bridge was very stable so that is how I came to this conclusion.
I cramed this SOZ into a small case and the chokes are mounted one over the other with about 1 3/4 inch between each choke winding. I do not think this is the cause of the large voltage loss as from what I understand the magnetic field of iron core chokes stay close to the core. Plus the inductors seem to be working as the noise at the speaker went down by a lot. But, maybe I am wrong and wil have to test them with more distance between them. Maybe some one can comment on this.
Another problem with the choke is as the voltage is increased they tend to buzz. At 60 volts A/C (19V D/C) you can hear it when music is not playing. I do not believe the chokes are getting overloaded as they a just warm to the touch.
A bigger problem is that the chokes vibrate with increased voltage. At 19V D/C if you touch the amp chassis you can feel it. If you touch the capacitors you can feel them vibrate as well. I read some place that I can place a .22 uF cap in parallel before and after the choke to reduce the buzz/vibrations. I will have to try it out or maybe some one can comment on this as I will have to buy the part and report back.
I did make provisions in the design to be able to remove the 500Va transformer( have not tested yet), chokes and bridge.
Hope to have pictures some time in the distant future.
I will continue testing and report back.
Feel free to comment on any thing here.
I am using an adjustable AC power supply with a 2K Va transformer for testing.
Its a monoblock design.
The chokes are Hammond 195P5 iron cores rated at 5 amps 30 mH .23 DCR and about 6.5 ibs each.
Each Rail has a choke connected right after the bridge rectifier and then to a 80,000 uF bank of 100V caps. Each cap is 10,000 uF. For a total of 160,000uF per channel.
One channel looks like this:
----------------------------30 mH choke---80,000uF caps--- + rail
Transformer--- bridge
----------------------------30 mH choke---80,000uF caps--- - rail
I do not have a scope so all I can do is use my ear and a digital meter.
I listen for noise from the speaker with out the chokes and noticed some low level hum with my ear almost touching the driver. Adding the choke the hum was very faint. I would say almost cut in half. Not easy to hear.
I listen to music with and with out the choke. I preferred the choke. The sound became more relaxed and smooth. I need to listen more it may just be a bias. Listening over a long period of time and then switching back to no choke will be needed.
Running some test with my digital multimeter I found a huge loss in voltage with the chokes in place. In fact it appears to be much more than the .9 commonly used.
A/C in------ D/C after choke.
10.19 V , 4.73V + rail 5.94V (-) rail
35.20 , 11.47 + 11.26 (-)
53.00 , 16.51 + 16.14 (-)
Maybe some one can comment on this loss.
The voltage difference in each rail I think is due to the slight difference in each choke. They are rated + or (-) 15% on both inductance and amps. The A/C going into the the bridge was very stable so that is how I came to this conclusion.
I cramed this SOZ into a small case and the chokes are mounted one over the other with about 1 3/4 inch between each choke winding. I do not think this is the cause of the large voltage loss as from what I understand the magnetic field of iron core chokes stay close to the core. Plus the inductors seem to be working as the noise at the speaker went down by a lot. But, maybe I am wrong and wil have to test them with more distance between them. Maybe some one can comment on this.
Another problem with the choke is as the voltage is increased they tend to buzz. At 60 volts A/C (19V D/C) you can hear it when music is not playing. I do not believe the chokes are getting overloaded as they a just warm to the touch.
A bigger problem is that the chokes vibrate with increased voltage. At 19V D/C if you touch the amp chassis you can feel it. If you touch the capacitors you can feel them vibrate as well. I read some place that I can place a .22 uF cap in parallel before and after the choke to reduce the buzz/vibrations. I will have to try it out or maybe some one can comment on this as I will have to buy the part and report back.
I did make provisions in the design to be able to remove the 500Va transformer( have not tested yet), chokes and bridge.
Hope to have pictures some time in the distant future.
I will continue testing and report back.
Feel free to comment on any thing here.
After some more tests.
The 20 mH chokes are too close together causing them to buzz more as the voltage increased. I will have to separate them more.
I think the large voltage loss had to go some place. And that turned out to be really hot inductors after 20 minutes of music.
So I am not going to use these. But, have others to try.
For the record the A/C ripple at the speaker was .002 volts with 112,000 uF caps per rail, it took about 80 volts a/c in to get 29 volts d/c per rail. This is about 15 watts per channel SOZ. I had to change the caps to make more room and that resulted in using caps that I have on hand that had more capacitance. I got a good stable quite supply but it cost too much voltage.
Next, I paralleled two 15 mH 6 amp .337 DCR 14 ga iron core inductors per channel. This worked much better. The heat went down a lot. And these can be used. Voltage loss was also reduced. A/C in was 48 volts and D/C out per rail was 29 volts. Ripple still came to an acceptable .003 volts at speaker. Still have a pretty big voltage loss. I have other values of inductors to try.
SOZ draws a lot of power. It's looking like inductor input on SOZ may not be the best approach. I had a double pi filter on SOZ and that was much easier to do and produced a quiet supply. But, for fun I will continue to experiment with lower value inductors. I had calculated that the smallest value to use for the choke to work is about 6 mH for a 15 watt SOZ.
Inductor input looks good for a pre amp though. In the future I plan to remove the regulation on BOZ power supply and use just a choke input.
The 20 mH chokes are too close together causing them to buzz more as the voltage increased. I will have to separate them more.
I think the large voltage loss had to go some place. And that turned out to be really hot inductors after 20 minutes of music.
So I am not going to use these. But, have others to try.
For the record the A/C ripple at the speaker was .002 volts with 112,000 uF caps per rail, it took about 80 volts a/c in to get 29 volts d/c per rail. This is about 15 watts per channel SOZ. I had to change the caps to make more room and that resulted in using caps that I have on hand that had more capacitance. I got a good stable quite supply but it cost too much voltage.
Next, I paralleled two 15 mH 6 amp .337 DCR 14 ga iron core inductors per channel. This worked much better. The heat went down a lot. And these can be used. Voltage loss was also reduced. A/C in was 48 volts and D/C out per rail was 29 volts. Ripple still came to an acceptable .003 volts at speaker. Still have a pretty big voltage loss. I have other values of inductors to try.
SOZ draws a lot of power. It's looking like inductor input on SOZ may not be the best approach. I had a double pi filter on SOZ and that was much easier to do and produced a quiet supply. But, for fun I will continue to experiment with lower value inductors. I had calculated that the smallest value to use for the choke to work is about 6 mH for a 15 watt SOZ.
Inductor input looks good for a pre amp though. In the future I plan to remove the regulation on BOZ power supply and use just a choke input.
Try this thread for a place to buy Inductors.
http://www.diyaudio.com/forums/showthread.php?s=&postid=117104#post117104
Anthony
http://www.diyaudio.com/forums/showthread.php?s=&postid=117104#post117104
Anthony
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