|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
104.129.198.106
In Reply to: RE: Standby switch...pros and cons? posted by DAK on August 18, 2016 at 13:52:01
Then you can have a low voltage switch to turn on the high voltage. Or better yet a timer circuit and no switch to worry about. Since the MOSFET or SCR is hard on, you don't need much heatsinking either as you would in a series pass regulator.
Don't get caught up in the "sand sound" debate. The MOSFET will have 3 ohms or less on resistance. How is that an issue at 300v+ ? Likewise an SCR will drop 0.7 volts - not an issue either. And this is not a series pass regulator application where the output impedance varies. A solid state B+ switch will impart "no sonic signature" or other audiophile ills.
One caveat with an SCR, you can't turn the HV back off with the "HV switch" once it's turned on. Ypu must power down the amp to break the current flow through the SCR to turn it off - basic SCR theory.
Another plus of the SCR is you could use a momentary switch. Once latched, the SCR stays on. That was you can;t accidentally leave the B+ switch on when the whole amp is turned off.
Follow Ups:
Hi Gus, thank you for the suggestion. Unfortunately, i don't have any of the devices you are referring to. While i am always open to trying new things, it seems that adding a switch and a cap is far easier and i have them in stock. I am also looking to gain more B+ would your implementation do that? regards.
Any device in series with the B+ will drop voltage. Like I said, a solid state junction is less than a volt drop and in a tube B+ circuit that's hardly significant.
To get more B+ you need more secondary voltage or explore capacitive voltage doubler options.
If it's a small b+ increase you need you can cheat a little by pushing the transformer AC input voltage up with a buck/boost transformer. Remember the step up ratio is in your favor here. But be careful of over heating, I would not go beyond 130 volts AC input.
Mosfets are a lot like vacuum tubes in that they are voltage operated and and a higher input impedance.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
With a LCLC filter if add some capacitance before L1 that will bump up the B+. I am pretty sure that adding 5uf will give me an additional 30 to 50 volts. I am going to take the ps to the shop today and put the additional capacitor in the circuit and see what i get. cheers
But if adding more first C increases your B+, that tells me there was not enough first C to begin with. I know it's a common trick to adjust the B+ by varying the first C but I don't personally like that approach.
He means going from a LCLC filter to a cLCLC filter.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I don't see how that would be a significant difference being either too low or too high.
model it both ways in PSUD. Remember that a CLC is going to differ in terms of what it can deliver vs. an LC supply. (higher B+, lower current)
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: