The Variac is a monster, bought used on ebay, for $20, and some friends of mine wrapped it in some nice shiny sheet metal... have to paint it one of these days. Solder station is not as old, but was basically retired, and I did not want to see it go in the dumpster... most of the parts for my VSSA chassis prototype came from the scrap barrel at a machine shop... did I mention I like to recycle? 😀
Not quite, but I like to listen to it anyway, and I plan to upgrade its current home to the new chassis when I get a chance.
I am planning to build a new (to me anyway) capacitance multiplier supply for VSSA, and put some of my pet theories to the test. Want to help? 😉
Which of the amps mentioned, would have a turn on / turn off thump so low
(or none at all), to make them usable in an active setup, driving a tweeter
without a DC protection capacitor ?
(or none at all), to make them usable in an active setup, driving a tweeter
without a DC protection capacitor ?
Member
Joined 2009
Paid Member
I'll pop my head into the VSSA thread to see what you are up to -
If you trust the feedback from owners of the amps, all them in the first list. But why - a series capacitor of good quality does nothing to degrade the audio at tweeter frequencies - chosen correctly (large enough value - i.e. not used as a cross-over component, assumes cross-over is at line-level) there won't be any ac across the capacitor to give rise to any 'so called' capacitor distortion.
Yes, agreed, especially because it would save the tweeter in the event of amplifier failure.
But to answer the "why":
It needs to be large enough and high quality (Polypropylene), so it will be bulky and expensive.
Omitting it if possible is the more elegant solution.
I have a schematic of a Tannoy System 800A active speaker (It doesn't employ a cap in front of the tweeter) and own the passive version (System 800).
Sometimes (in the far future) I might try the active network, that´s why I asked.
But to answer the "why":
It needs to be large enough and high quality (Polypropylene), so it will be bulky and expensive.
Omitting it if possible is the more elegant solution.
I have a schematic of a Tannoy System 800A active speaker (It doesn't employ a cap in front of the tweeter) and own the passive version (System 800).
Sometimes (in the far future) I might try the active network, that´s why I asked.
Very interesting thread for documentation purpose, it would also be of great importance if the topology used could also be specified. (e.g. P3A-CFP, Leach-Symmetrical...and so on.) 😉
I may be wrong, but I think the fully balanced is a good choice if you want to avoid switch on thump.
The supply rails should come up quite slowly, and its important that the front end, which really controls the DC and low frequency behavior of the amplifier, is in control during the power up (or down) event.
By the way, the worst amp I heard recently for power on thump was a Misical Fidelity A20 (IIRC the model number correctly) which I repaired for a friend. It has a good sound, but power up and down -wow - terrible thump.
The supply rails should come up quite slowly, and its important that the front end, which really controls the DC and low frequency behavior of the amplifier, is in control during the power up (or down) event.
By the way, the worst amp I heard recently for power on thump was a Misical Fidelity A20 (IIRC the model number correctly) which I repaired for a friend. It has a good sound, but power up and down -wow - terrible thump.
Member
Joined 2009
Paid Member
I think you are right, it seems a good starting place for avoiding turn-on and turn-off noises.
Concerning P3A and other circuits by Rod Elliott. His site is so big that it is not easy to read all of it, but nice turn on and off behavior in his amps is due to the sink for the input pair, quote:
"I elected to use a current sink here to ensure that the amp would stabilise quickly upon application (and removal) of power, to eliminate the dreaded turn on thump"
I can't remember who or where, but recently a builder explained that the input stages of the amplifier must "turn on" in the correct order for the output offset to be stable during the LONG turn on period. That Long period could be 10ms to 100ms. In speaker transient terms that is very Loooong.
Member
Joined 2009
Paid Member
That makes sense if the idea is to have the feedback loop active before the output gets too excited but it seems to me that the feedback loop has to wait until the feedback shut cap has charged up and the VAS has to charge up the bootstrap cap too ...
Member
Joined 2009
Paid Member
Hi Col - Although there are schematics posted this is really a commercial Class D type module, without pcb layout it's likely not a practical DIY option. Glad to hear you are enjoying the maps.
Hi Bigun,
how about SR50, SR100, or SR200 Studio Reference Amplifier by Apexaudio?
I guess it is free thumps 🙂
how about SR50, SR100, or SR200 Studio Reference Amplifier by Apexaudio?
I guess it is free thumps 🙂
Gainclones have no turn on/of thumb.
I am using them several years to my active speakers and i trust them for my tweeters without a protection cap.
I am using them several years to my active speakers and i trust them for my tweeters without a protection cap.
Datasheet for LM3886 quote:
"Supply under-voltage protection, not allowing internal biasing to occur when Vee + Vcc <=12V, thus eliminating turn on and turn off transients"
- Status
- Not open for further replies.