Hi,
I have enjoyed my Polaris II for many years. I recently had to refresh the solder joints at one of the inputs.
Most of the SUMO threads here are well-aged, so I'm starting a new one in the hopes we can get some contemporary replies.
I have two questions:
1. I have the corrected amp schematic courtesy of this forum. Does anyone have the power supply schematic?
2. Until I opened the amp up, I assumed the LEDs (CR12, 13, 14 and 15) were Vee and Vdd indicators, as I used to see neon lamps used as B+ supply indicators on some old tube equipment. Looking at the schematic, they are driven by Q8 and Q9 which I *think* are part of the servo circuit. But I'm not sure...anyone know what their function is?
Thanks in advance
I have enjoyed my Polaris II for many years. I recently had to refresh the solder joints at one of the inputs.
Most of the SUMO threads here are well-aged, so I'm starting a new one in the hopes we can get some contemporary replies.
I have two questions:
1. I have the corrected amp schematic courtesy of this forum. Does anyone have the power supply schematic?
2. Until I opened the amp up, I assumed the LEDs (CR12, 13, 14 and 15) were Vee and Vdd indicators, as I used to see neon lamps used as B+ supply indicators on some old tube equipment. Looking at the schematic, they are driven by Q8 and Q9 which I *think* are part of the servo circuit. But I'm not sure...anyone know what their function is?
Thanks in advance
Thanks. analog_sa, why would LEDs be used in a biasing circuit? Why not just use zeners if regulation was desired?
Thanks llwhtt, can you elaborate? I'm used to (very old school) lamps acting photoresistors as part of a distortion meter, but I don't see these LEDs acting on anything else as is true of other comparator or bridge circuits I've seen
Using a distortion analyzer you adjust the 2K trimmer for least amount of distortion at a certain frequency and power level. I had to figure this out when repairing an Andromeda II many years ago. This was confirmed by Jason Stoddard who worked at SUMO way back when. I don't remember what frequency or power level I used.
The Standard test frequency is 1KHz , wattage depends on what kind of volume you normally like to listen to music at --taking into consideration the actual designed "full power " wattage which advertisers like to "manipulate " but if its a DIY build you are going to con yourself .
Load would be Standard 8 ohms making sure its a very large wattage resistor with little inductance or a water cooled type and the bias adjusted into class A or AB or as is usual about 5 or 6 watts in class A then AB which D.Self hates as he made great play of the changeover being bad.
All the while watching the oscilloscope connected after the analyzer--make sure you differentiate between distortion and power supply injected noise its a good test for a power supply big sharp waves are not good as you increase the bias and you want an analyzer for solid state that can go down to 0.001 % distortion , obviously tubes are a different matter.
Load would be Standard 8 ohms making sure its a very large wattage resistor with little inductance or a water cooled type and the bias adjusted into class A or AB or as is usual about 5 or 6 watts in class A then AB which D.Self hates as he made great play of the changeover being bad.
All the while watching the oscilloscope connected after the analyzer--make sure you differentiate between distortion and power supply injected noise its a good test for a power supply big sharp waves are not good as you increase the bias and you want an analyzer for solid state that can go down to 0.001 % distortion , obviously tubes are a different matter.