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In Reply to: RE: ALT. 1. posted by cpotl on January 11, 2015 at 09:26:46
Interesting.... try putting a 5K resistor across the current source.
dave
Follow Ups:
"Interesting.... try putting a 5K resistor across the current source."
I think maybe that damps the ringing down just a little. But it's a fairly marginal difference, I think. Another thing I've just tried is adding a 100 ohm resistor in series, immediately after the silicon rectifiers, as maybe a slightly closer approximation to a vacuum tube rectifier. The resonant frequency seems to shift up a tiny bit, and the amplitude of the modulation on the power supply increases somewhat, of course. Here's a simulation with the 100 ohm series resistor and the 5K shunting the current source also.
Chris
(I'm not sure why some of the wires in the schematic aren't showing up in this jpg file, but they really are there! I don't seem to be able to find a way of directly saving the LTSpice window as a jpg or whatever, so I've been resorting to taking a screenshot and then cropping it. There must be a better way?)
..
Nice. Seems to confirm that tube rectifier or SS doesn't make a big difference.
Now...do we have a way to estimate what effect this would have on the sound?
Chris
using the same Triad parts posted back then. He indicated his 2A3 amp seemed to roll off the bass below 80hz. After less than an hour of listening he went back to the conventional supply. This was two years ago so maybe Jeff made some improvements since then?
This has been a lot of fun doing these sims.Inspired by the sims posted by cpotl and deafbykhorns, I did a little playing around with some power supplies.
It's cool to have a little more insight beyond PSUD.
It is also reassuring to see how well adding capacitance to the supply really stiffens things up with a "regular choke." It's pretty easy to make that squiggle disappear to a negligible amount ~1V with 300uF
I will also note that my power supplies did not exhibit any ringing, so I will pat myself on the back there too. lol.
My models could use more refinements to suit my specific needs but overall it is very insightful.
Cheers.
Edits: 01/11/15
but will usually require some tweaking when bread boarding. It will at least get you close and give you a visual indication of any potential problems. It's a great little tool and fun to build the amplifier in Spice before spending hundreds of dollars on parts. If anyone is interested in some sim files, shoot me an email and I'll send you some files to get started.
This is interesting stuff that you're all doing-- I suggest you involve Dave Slagle as much as you can.I have a suggestion for you-- perhaps more a question: what happens when your simmed power supply is connected thru an output transformer (inductance, resistance and reactance) to a tube's plate, and also, what happens to the supply when it is tapped and shunt-loaded after the tap-- to also run a driver stage?
What does the power supply do under the conditions of running distributed loading and filtering in the amplifier-- beyond the simple simmed power supply?
I humbly submit that the entire amplifier-- ALL of it-- is the power supply, and its overall performance must be considered as a whole power supply system operating under changing and mixing pulsing conditions.
The question therefore becomes: "how can this possibly be simmed or evaluated if you only consider the main power transformer, the rectifier, the chokes and two capacitors?". Those are but a few of the parts in the power supply!
---Dennis---
Edits: 01/12/15 01/12/15 01/12/15
we can't SIM a complex musical signal......
Wait a minute, has anyone injected several different freq. signals into a SIM yet?
sure you can. Just instruct your voltage source to play a .wav file. You can even save the output as a .wav and listen to how your circuit sounds.
dave
Wow, I'm going to try this one! If I can figure it out
Yes, some guitar amp guys play through spice to simulate various effects before they build stuff.
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instead of incessant condescending philosophical BS....tell us about your new methods that your cheerleader says are 50% better then anyone else could possibly think of or apply...or just start with how you deal with the inherent distortion ( you admitted to when questioned by Tre). later in the design of your amp... throw the little people a few crumbs...
Dennis HAS shared with us all up here, over the years. Its been posted. Maybe I need to try to do a compilation of his posts, in chronological order, without the rebuttal type posts included.
I would be qualified to do that, because I know him for 30 years, and generally how he thinks. THAT would be a big project. But, I have done this for John Hasquin's supply posts, and Bill Swenson's supply posts....sweet stuff to read. Ask me and ye shall receive, anyone !!
You need to read Hasquin and Swenson first, to get a decent background that makes sense, cause they have done it, heard it, know from their direct personal experience.
Jeff Medwin
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Love it! If it gives you good music, Dig it!
---Dennis---
BTW, the values you are simming are strictly "mine" as it applies to the Joppa filter, and it is NOT what DF and JM use for themselves exactly !!
Jeff Medwin
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