Hi BarryBlue,
Yes, it is correct. The main star ground is at the point where speaker ground is connected.
This topology is called star in star ground. If you have problems with hum noise (speakers over 91dB SPL), you should cut the PCB connection between front end ground and main star ground and connect those grounds together through an 2R2 resistor. In this case, the front end PSU ground wire will be connected at the junction of the 0.1uF front end decoupling capacitors.
I will look forward for your listening impressions.
Cheers,
Mihai
Yes, it is correct. The main star ground is at the point where speaker ground is connected.
This topology is called star in star ground. If you have problems with hum noise (speakers over 91dB SPL), you should cut the PCB connection between front end ground and main star ground and connect those grounds together through an 2R2 resistor. In this case, the front end PSU ground wire will be connected at the junction of the 0.1uF front end decoupling capacitors.
I will look forward for your listening impressions.
Cheers,
Mihai
Rafael.luc said:
Hi Rafael,
I don't know if I get your question right, but if you speak about turn on thump, that phenomena is related with the ability of an amplifier to quickly stabilize his bias currents.
To get a thump free amplifier, one must avoid using any electrolytic caps in LTP and VAS current sources supply lines and also avoid using bootstrapped CCSs
Cheers,
Mihai
Sorry , my english not goodroender said:
roender said:
Yes it was
The electrolyte you talking (power supply?), in your project you regulated the voltage to supply the LTP and VAS (in power supply), I am sure?
I could use Zener between the V+ V- to the neutral, I believe that could neutralize turn on thump, Leach amp did this configuration
thanks
Front End PSU
Hi Mihai,
After a few weeks of too much work and commitments I have finally powered up the first channel tonight. No big bangs or serious issues at first sight but the front end power supply is dropping too many volts (it was OK off load).
So I can figure out if it is the PSU or front end of the amplifier can you tell me the nominal current drain for the front end of the amplifier please?
Thanks for your support as always.
Hi Mihai,
After a few weeks of too much work and commitments I have finally powered up the first channel tonight. No big bangs or serious issues at first sight but the front end power supply is dropping too many volts (it was OK off load).
So I can figure out if it is the PSU or front end of the amplifier can you tell me the nominal current drain for the front end of the amplifier please?
Thanks for your support as always.
Voltages
Hi
That matches the drain I measured last night - well 25ma anyway
The front end Psu voltage is 37 volts on both the positive and negative rails off load. I then put a 1K resistor across the positive rail and the voltage stayed at 37 volts. So that seems fine.
However when I connect to the amplifier the postive drops to around 19 volts and negative drops lower again nothing seems to get warm.
I will double check the amplifier front end and let you know what I find.
Cheers
Hi
That matches the drain I measured last night - well 25ma anyway
The front end Psu voltage is 37 volts on both the positive and negative rails off load. I then put a 1K resistor across the positive rail and the voltage stayed at 37 volts. So that seems fine.
However when I connect to the amplifier the postive drops to around 19 volts and negative drops lower again nothing seems to get warm.
I will double check the amplifier front end and let you know what I find.
Cheers
Testing
Hi m2003br
Yes
Yes
I have found that the positive and negative rails are both OK when they are individually connected to the amplifier with the 0 volts but not when both the rails are connected at the same time.
I have just been looking at the voltages on the amplifier board and the LEDs that do not light up......
Hi m2003br
Yes
Yes
I have found that the positive and negative rails are both OK when they are individually connected to the amplifier with the 0 volts but not when both the rails are connected at the same time.
I have just been looking at the voltages on the amplifier board and the LEDs that do not light up......
Sheldon said:
Add some for the drivers, and I believe total dissipation is around 42W for the original 25vac transformer. If 30vac is used for power supply, total dissipation is up to around 71W. Roender recommended .35C/W for a 25vac supply. If using 30vac supply, something in the order of .30C/W or better may be needed
pooge said:
The original transformer was 34vac http://www.diyaudio.com/forums/showthread.php?postid=1349109#post1349109. At 6.8W per device, total dissipation for the output devices is 41W. With the latest set-up http://www.diyaudio.com/forums/showthread.php?postid=1705663#post1705663 (100mA through the drivers), the drivers add about 7W, for a total of 48W.
Output dissipation will scale with bias, emitter resistor value, and supply voltage (20mA, 0,1R, 34vac, for this example). Driver dissipation scales with supply voltage and R5 (12R for 100mA).
Sheldon
pooge said:
I'm not sure how to add the link so that only the relevant post is shown, but I copied the post link for post 8. The schematic in post 8 is a clear as it can be, 39v frontend, 34v output. Either way, the calculation is straightforward.
I did not include the front end power dissipation in the above calculation, but it will be a little over 1W.
Sheldon