jkeny said:
Keep in mind that I don't have much more experience than you do. So then:
On total cap vs. rate of change: Yes, I think so, at least as compared to something like a plate load CCS.
I don't think your application really complicates it much (but I don't know if I understand the application, cause it seems odd that a pwm amp would use input voltage to control volume -that's what pulse width is for, no?). The calculations I showed are for a 2V Vds. Vds will be lowest at the highest output setting. You could increase the bias string current at least 5x what I used as an example. You can find better FETs for the application.
You've got a bit it heat to shed, so good radiating area will be important.
Sheldon
The way this particular dig amp works is that for the first 30dB vol is controlled digitally, then it uses voltage adjustment on the output stage from 10 to 40V, then it's back to dig control.
It seems like Panasonic gave some thought to the sonic effect of digital control and opted for voltage /volume regulation in the main range of listening! Just a pity they used SMPS to do this as the sound with 12V battery is so much better! Hence the search for a high quality regulated variable PS.
P.S. - I believe John Swenson has taken the BDT preamp to VSAC this weekend - will be interested to hear feedback from anybody who heard it!
It seems like Panasonic gave some thought to the sonic effect of digital control and opted for voltage /volume regulation in the main range of listening! Just a pity they used SMPS to do this as the sound with 12V battery is so much better! Hence the search for a high quality regulated variable PS.
P.S. - I believe John Swenson has taken the BDT preamp to VSAC this weekend - will be interested to hear feedback from anybody who heard it!
Being intrigued by the regulator circuit John came up with I built one up and proceeded to test, measure, and blow it up many times in the interest of learning more about the circuit.
Performance is very good the way John has it set up but there are improvements that can be made both for performance and reliability.
I changed a couple of capacitor values, one for improved stability, the other for better performance. I also added some protection circuitry and a current limit circuit.
I'm planning on building several of these into a multiple output bench supply to replace my old Tektronix Engineering power supply. The Tek supply works pretty well but is noisy, both electrically and acoustically. It also has a tendency to blow up at inopportune times as it does not have good current limiting, instead, relying on 2 watt CC resistors on the SS rectifier diodes. It let loose again today during testing of the Swenson regulator. Had to open all the windows to get that wonderful burnt CC smell out of the house. Maggie was not very impressed with the smell but enjoyed the show... It was interesting to see the meters on the power supply back lit by orange flame
Anyway, take a look at me website for the info.Gary P's DIY page
Performance is very good the way John has it set up but there are improvements that can be made both for performance and reliability.
I changed a couple of capacitor values, one for improved stability, the other for better performance. I also added some protection circuitry and a current limit circuit.
I'm planning on building several of these into a multiple output bench supply to replace my old Tektronix Engineering power supply. The Tek supply works pretty well but is noisy, both electrically and acoustically. It also has a tendency to blow up at inopportune times as it does not have good current limiting, instead, relying on 2 watt CC resistors on the SS rectifier diodes. It let loose again today during testing of the Swenson regulator. Had to open all the windows to get that wonderful burnt CC smell out of the house. Maggie was not very impressed with the smell but enjoyed the show... It was interesting to see the meters on the power supply back lit by orange flame
Anyway, take a look at me website for the info.Gary P's DIY page
I'm in the final stages of building a BDT preamp & while I'm waiting for Dave Slagle's trafos to arrive by post from US to Ireland (4 - 6 weeks from experience), I thought od trying these Nuvotem toroid PS trafos 3.2VA 115-0-115:22-0-22. I would have gone for 1.6VA but not in stock until end June - the higher inductance of the smaller trafo is what is needed in this case
I know nothing about this stuff so I'm relying on others to get me through this.
Do you think this trafo will work OK - it's cheap to try anyway, €20 for pair?
Has anybody built this new BDT preamp?
I will be trying the GP mods to the VR & hope all will be finished at the end of next week. WIll report back
I know nothing about this stuff so I'm relying on others to get me through this.
Do you think this trafo will work OK - it's cheap to try anyway, €20 for pair?
Has anybody built this new BDT preamp?
I will be trying the GP mods to the VR & hope all will be finished at the end of next week. WIll report back
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