Just budging in to say this is the best thread by far, with all of the right names contributing.
The only thread i am forcing myself to shut-up, read and enjoy.
Just one question:
What speaks against placing relays in the PS rails for drivers and output devices, with the front end on separate rails.
I admit i am a relayholic.
The ones i have been using for a long time do not oxydise, have very low resistance through multiple contacts, take 160 amps peak with 2 in parallel, disconnect in only a few milliseconds.
Jan: i did not have the privilige of observing the home set of Jean Hiraga in France 20 years ago, modest and calm are the words to describe him though.
The only thread i am forcing myself to shut-up, read and enjoy.
Just one question:
What speaks against placing relays in the PS rails for drivers and output devices, with the front end on separate rails.
I admit i am a relayholic.
The ones i have been using for a long time do not oxydise, have very low resistance through multiple contacts, take 160 amps peak with 2 in parallel, disconnect in only a few milliseconds.
Jan: i did not have the privilige of observing the home set of Jean Hiraga in France 20 years ago, modest and calm are the words to describe him though.
jacco vermeulen said:
Jacco,
Which relays are those? I have been using the amplimo silver/wolfram contact relays for my protection circuits. 100A break capacity, don't know the switching speed. Used in the speaker line.
I think that using a couple of small signal transistors are adequate to protect the amp, even if relays are cheap and fast, they are mech devices and most designers are somewhat suspicious about them. It is also a philosophical thing, I can fully understand Lars' decision to use a relay for protection, it's just that I prefer a solid state circuit and accept the possible short audible action over the short complete interruption by a relay. I don't think one is "wrong" and the other "right", just different ideas.
On Hiraga: I once visited him at his offices in a Paris suburb in the building of his publishing company. Since the heydays of L'Audiophile, the successor is now only one of a range of magazines. So his audition room was in that building, this was 1998 or so. This was an audiophile's dream. Wall-to-wall horn speakers, all the famous Voice of the Theather Altecs were there, plus a lot I had never seen. Handwound xover coils looking like fire hose reels. And then these tiny, innocent-looking 1-tube amplifiers. But the sound, man, the sound! There was no need for comments. You just listenend. If I would use one word, it is AUTHORATIVE.
One thing I brought back was a list of records he uses for evaluating equipment. One artist was Mark Curry. Now, there is at this time also a singer called Mark Curry, but he is colored, and the one I mean is caucasian. He only made one CD, early 90'ies, and a couple of singles. He tried again in 1996 or so with the Ten pin trio, but that flopped. He's a kind of modern-day Donovan. The CD is called It's only time. I have scavenged the world and have everything from him now, last one was a demo EP I found somewhere in Australia. demo only, not for sale. Yeah.
This is very cleanly, directly and unprocessed recordings, a pleasure to listen.
If you're interested, mail me off-line.
Jan Didden
Attachments
janneman said:
No...as you noted, this is the province of a thermal latch...............
.....but it may be wise to design for the SOA at the steady state operating case temperature Tc of your transistor...
For instance, the nominal SOA of 200W for the MJL1302A/3281A is refered to Tc=25deg. C...
....while the true Tc during normal operation (viz: with chosen heatsink) is more like Tc~60deg. C.....equivalent roughly to a SOA of 140W....
So...it would be wise to have your protection locus approximate a constant 140W parabola, (linear-linear scale assumed), except of course, where the secondary breakdown parabola intrudes on your nominal ratings...
Lars Clausen said:
No...
Lars Clausen said:
Your scheme is deeply flawed for a number of reasons...:
1) It is infact a single-slope scheme with a single breakpoint....very inefficient!
2) The location of the locus in the SOA varies with the rails....Bad!
3) You're using one transistor to detect both polarities....which is a false economy of the most profound variety, as this will result in an inaccurate locus for both polarities at best, and even worse, may result in unnecesary invocation of protection....
Lars Clausen said:
...not even close....
The relays i was referring to are the former SDS S and ST types.
The S model withstands 400 amps for 1 mS on 4 parallel contacts.
Golden contacts, gasfilled and sealed.
With 4 contacts in parallel 20 amps continuous.
Turn-off within 5 mS.
Contact resistance below 10 mOhms.
The ST does even better but has only 2 parallel contacts.
Personally i like a bit of both, and have done so.
I am going to build an amplifier with a number of output devices i have been cherishing a great number of years.
I can not afford to use them for ChateauBriand as they are irreplaceable.
Every protection option mentioned on this thread will be what i intend to use, even Michael's triple slope, i am very gratefull he sent me the article(ordered the 4 pound softcopy too, jan)
I do see the downside of relays on the output though,i wondered if i could move the relays from the output to the rails.
In my goldy locks years my veggie girlfriend and i went long weekends to Paris 2, 3 times a year.
She desired Beaubourg.
Me, La Maison du L'Audiophile, long talks with Monsieur Walther, and café at the bar/café on the corner of La Rue de la Bastille afterwards.
Every year i attended the listening sessions in the backroom.
On one ocassion i had the fortune to be able to write myself on a list for an evening of demonstrations and talk, Jean Hiraga being one of the speakers.
Here is a scrible of a famous French audio person, with a nice sense of humor, on one of my 80s magazines.
The S model withstands 400 amps for 1 mS on 4 parallel contacts.
Golden contacts, gasfilled and sealed.
With 4 contacts in parallel 20 amps continuous.
Turn-off within 5 mS.
Contact resistance below 10 mOhms.
The ST does even better but has only 2 parallel contacts.
Personally i like a bit of both, and have done so.
I am going to build an amplifier with a number of output devices i have been cherishing a great number of years.
I can not afford to use them for ChateauBriand as they are irreplaceable.
Every protection option mentioned on this thread will be what i intend to use, even Michael's triple slope, i am very gratefull he sent me the article(ordered the 4 pound softcopy too, jan)
I do see the downside of relays on the output though,i wondered if i could move the relays from the output to the rails.
In my goldy locks years my veggie girlfriend and i went long weekends to Paris 2, 3 times a year.
She desired Beaubourg.
Me, La Maison du L'Audiophile, long talks with Monsieur Walther, and café at the bar/café on the corner of La Rue de la Bastille afterwards.
Every year i attended the listening sessions in the backroom.
On one ocassion i had the fortune to be able to write myself on a list for an evening of demonstrations and talk, Jean Hiraga being one of the speakers.
Here is a scrible of a famous French audio person, with a nice sense of humor, on one of my 80s magazines.
Attachments
jacco vermeulen said:
...actually contrary to intuition, wiring relay contact in parallel does nothing to increase service life i am afraid....see pg 62 here:
http://relays.tycoelectronics.com/schrack/pdf/C0_v4bg_4.pdf
More stuff:
http://relays.tycoelectronics.com/schrack/techn/relbook.stm
http://relays.tycoelectronics.com/schrack/pdf/definitions.pdf
http://relays.tycoelectronics.com/schrack/pdf/relay_basics.pdf
http://relays.tycoelectronics.com/application.asp
Mikeks: I´d say lets take your amp and my amp, crank them up to full power and short the outputs. Then let's see which one last longer 
I gather you have given a lot of thought to this issue, but as i see it there is one particular reason that close SOA monitoring on the reactive load side is simply unnecessary, and a waste of time. But on the other hand you don't seem too open towards other people's suggestions, so i'll just let you work this one out yourself ....
At least i can say that any circuit that limits the current in the output stage - like the one that limits the current in the output stages, according to the SOA slopes - will always influence the sound quality. Enough for me to not even consider it.
It limits the current, but you don't accept that people call it a current limiter ???
Have a nice weekend
I gather you have given a lot of thought to this issue, but as i see it there is one particular reason that close SOA monitoring on the reactive load side is simply unnecessary, and a waste of time. But on the other hand you don't seem too open towards other people's suggestions, so i'll just let you work this one out yourself ....
At least i can say that any circuit that limits the current in the output stage - like the one that limits the current in the output stages, according to the SOA slopes - will always influence the sound quality. Enough for me to not even consider it.
It limits the current, but you don't accept that people call it a current limiter ???
Have a nice weekend
Lars Clausen said:
You are absolutely correct....no question..!!
A SOA limiter must of neccesity...and by definition have an effect (and a profound one at that!!) on the 'sound quality' as soon as it's invoked....
But it must not, and cannot, (if properly designed), have ANY audible effect if such invocation is not required by your output devices...
http://www.diyaudio.com/forums/showthread.php?postid=636909#post636909
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