Hi John, all,
Marantz used to use a nifty relay that had sacrificial contacts to take the actual make and break for speakers. The the two smaller contacts had there arms bent a touch towards the N.O. contacts. A very simple solution to the problem.
Personally, I wish these were still available. I'd use them. They were available in DPDT and DPST configurations. Possibly others too, but these were the only ones I saw.
-Chris
Marantz used to use a nifty relay that had sacrificial contacts to take the actual make and break for speakers. The the two smaller contacts had there arms bent a touch towards the N.O. contacts. A very simple solution to the problem.
Personally, I wish these were still available. I'd use them. They were available in DPDT and DPST configurations. Possibly others too, but these were the only ones I saw.
-Chris
john curl said:
Yes, but for how long (for how many operations)?
It's the old debate of quality versus price.
Hi Joshua,
Now, look at things a different way. A speaker relay is much less expensive than a woofer and possibly crossover. Heaven forbid the grill covering should burn as well. I have received many amplifiers over the years that were responsible for fires.
I view a relay as cheap insurance. If you are worried that they won't last, just replace them every so often. Some people spend more on wires (I.C.s for the tweakers out there) than you could ever spend on replacement relays.
-Chris
Enough so that the power switch has normally died long before the relay. That is unless the amplifier is being driven as the relay opens or closes. I always turn to volume down before turning the set on or off. My relays are fine after many years.
Now, look at things a different way. A speaker relay is much less expensive than a woofer and possibly crossover. Heaven forbid the grill covering should burn as well. I have received many amplifiers over the years that were responsible for fires.
I view a relay as cheap insurance. If you are worried that they won't last, just replace them every so often. Some people spend more on wires (I.C.s for the tweakers out there) than you could ever spend on replacement relays.
-Chris
anatech said:
This is true, all of it.
My question concerned the quality versus the price of different relays.
Automotive relays have high rated current and they are cheap. My question is whether they are good for Power Amp output?
Yet, I may be worried over trivia.
Joshua_G said:
Hello Joshua_G
Firstly most relays are not good at breaking a DC fault condition that can occure on the output of a power amp. Secondly for reliability the contact material needs to be made of gold so that a non conductive oxide film does not develop over time which can stop low level audio signals getting through .
So if you are going to use an automtive relay you have to make sure it can break 63V DC into 4ohms ( 63V DC will be found in most 150W/8R amps).
Ask John what relay he uses , I suspect its a secret. Amplimo make a relay but I cannot find it on their website ( they have just upgraded it).
Good luck
Regards
Arthur
I can't say exactly what relay we use, because I did not specify it. A Taiwanese engineer designs the protection and housekeeping circuits. However, is is probably made in the far East, automotive in intention, and maybe with silver oxide or similar contacts. It seems to work and I can't complain, except that less is always best, so for a lower power, extremely high quality design, I would not use an output relay, on general principles.
I do know something about relays, as I have studied them closely over the years. Ragnar Holm's book 'Electric Contacts' (or something like that) is one of the best I have ever read on the subject. Unfortunately, I lost it in the firestorm of '91. Walt Jung still has a copy, however.
I do know something about relays, as I have studied them closely over the years. Ragnar Holm's book 'Electric Contacts' (or something like that) is one of the best I have ever read on the subject. Unfortunately, I lost it in the firestorm of '91. Walt Jung still has a copy, however.
john curl said:
It's available on Amazone:
http://www.amazon.com/Electric-Contacts-Application-Ragnar-Holm/dp/3540038752
Joshua_G said:
Probably not worrying about trivia. I researched relays recenltly and the striking thing about all those listed as Automotive is the high contact on resistance. A bit like adding a couple of hundred metres of speaker cable.
janneman said:
Sorry, yes, I was stating "high" by comparison to the average relay I found.
They varied from 1-3 milliOhms for mercury wetted through around 10-30 for those called "power" relays and 50-70 for "automotive".
I got most data from the farnell catalogue and other info from manufacturers data sheets on various web sites.
That's equivalent to about a 10-15 foot (4 meters) two conductor speaker cable made from 12 gauge copper. Eight feet of 10 gauge.
Imho, I'd never use a single contact when it was possible to use more in parallel... ymmv.
Alan, I have to ask, have you ever heard anything at all that made an audible difference to you, except for things that anyone would consider obvious and gross?? I am sincerely interested, since everyone's experience is different, and we are in a thread speaking about a preamp (have we forgotten?) that was designed and built with the premise that small details in parts and construction are audible and make a difference.
_-_-bear
PS. there already is/was a "relay thread"... and
PPS. John, is there a relay anywhere in the Blowtorch??
Alan, I have to ask, have you ever heard anything at all that made an audible difference to you, except for things that anyone would consider obvious and gross?? I am sincerely interested, since everyone's experience is different, and we are in a thread speaking about a preamp (have we forgotten?) that was designed and built with the premise that small details in parts and construction are audible and make a difference.
_-_-bear
PS. there already is/was a "relay thread"... and
PPS. John, is there a relay anywhere in the Blowtorch??
The ENTIRE output impedance of the JC-1 is .045 ohm, as measured by 'Stereophile', so we must use a pretty good relay.
alansawyer said:
I had an unverified feeling that it may be so.
john curl said:
Indeed, expansive, however I ordered it.
john curl said:
It definitely looks so, that it's pretty good one. It means that not all "automotive relays" are equal. (What else is new?).
Looking at some 'automotive' type relays, they all seem to have a 100 milli-ohm spec. That may be a car industry, minimum spec. However, think this through. Let us say you have a 30A rated relay, and the worst case spec is 0.1 ohms? At 30A how much voltage drop? How much power dissipation. THEN, it just doesn't make any sense.
Well, specs for typical automotive relays is 0.1 Ohm contact resistance, while JC-1 is total output resistance of 0.045 Ohm, which means they used good relays, better than the typical automotive ones.
Putting 0.1 Ohm at the output of a power amp makes no sense.
Did we mention that quality cost money?
Putting 0.1 Ohm at the output of a power amp makes no sense.
Did we mention that quality cost money?
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