Normally ADA compliance is required for commercial spaces only. Churches and residential are exempted. But AHJ often doesn't really know the fine points of the rules. Now California did require me to add home improvement qualifications to my contractor's liscense as they figured anyone who does sound systems must do residential work.
Brad 700 boxes! If I ever have to move my shop I hate to think of what that will take. It is as I put it "Not that big only half an acre, but it is heated and air conditioned."
Brad 700 boxes! If I ever have to move my shop I hate to think of what that will take. It is as I put it "Not that big only half an acre, but it is heated and air conditioned."
Just for the record, I will give some input to relays.
Walt Jung, Dick Marsh and I have all looked into this, especially regarding contact materials. Holm is our 'bible' in this subject.
Personally I have found: Normal gold on gold sealed relays are adequate for everything but the very best audio playback.
Again, NO RELAY is better than any relay, and if you don't need one, don't add it in. IF you MUST have selector switching, then Shallco silver on silver switches are better, like the CTC Blowtorch uses. But they are darn inconvenient to use, because they cannot be easily remote controlled.
Generally, the low level or 'dry' contact relays or switches are preferred for preamps. With each relay, there are choices of contact material. Go for the lowest operating level switch most of the time. While I have designed with quality relays for the last 46 years, I don't have ANY in the CTC Blowtorch or the Vendetta Research Phono stage. That should tell you what I really think about relays. However, I can still get A ratings on my preamps even while using relays in the circuit path. They DO add convenience and versatility to a design. I am personally suspicious of reed relays, mercury contact relays, solid state relays, and open relays.
Walt Jung, Dick Marsh and I have all looked into this, especially regarding contact materials. Holm is our 'bible' in this subject.
Personally I have found: Normal gold on gold sealed relays are adequate for everything but the very best audio playback.
Again, NO RELAY is better than any relay, and if you don't need one, don't add it in. IF you MUST have selector switching, then Shallco silver on silver switches are better, like the CTC Blowtorch uses. But they are darn inconvenient to use, because they cannot be easily remote controlled.
Generally, the low level or 'dry' contact relays or switches are preferred for preamps. With each relay, there are choices of contact material. Go for the lowest operating level switch most of the time. While I have designed with quality relays for the last 46 years, I don't have ANY in the CTC Blowtorch or the Vendetta Research Phono stage. That should tell you what I really think about relays. However, I can still get A ratings on my preamps even while using relays in the circuit path. They DO add convenience and versatility to a design. I am personally suspicious of reed relays, mercury contact relays, solid state relays, and open relays.
One of my earliest "discoveries" was that anything which just relied on one piece of metal resting on another was bad news - so the first round of tweaking is to rip out, bypass or in some way "harden" the circuit everywhere this occurs. This always markedly improves the sound - goodbye edgy, irky, uncomfortable qualities; hello rounded, pleasant, harmonically rich tones ...
I assume you meant "stuffed" there - simple answer, hardwire the lot. Yes, means a bit of physical hacking of the gear but I couldn't live with the sound with connections, etc, done normally. It's been my way for 3 decades now, and every time I hear expensive audio systems with those lovely "overtones" of dirtiness in the sound from crappy connections, I'm mighty pleased that I've done it my way ...
I use small signal relays extensively in my designs. Hermetically sealed with gold contacts. I have never experienced 'harsh, edgy sound' and never once (not once) had a small signal relay go funny on me.
Separately, I deployed thousands in some of my industrial instrumentation days on Mux cards where they were switching mV signals at exceeding low currents (few uA). So, I have practical experience across the deployment of thousands of relays, and the AP tells me (and Doug Self) that across a closed pair of contacts, distortion is below the Sysd-272 noise floor - so at least -114dB.
What are we relay monkeys doing wrong here?
Separately, I deployed thousands in some of my industrial instrumentation days on Mux cards where they were switching mV signals at exceeding low currents (few uA). So, I have practical experience across the deployment of thousands of relays, and the AP tells me (and Doug Self) that across a closed pair of contacts, distortion is below the Sysd-272 noise floor - so at least -114dB.
What are we relay monkeys doing wrong here?
I am willing to bet if you measured the distortion of your connections they would be Zero Frank.if it says zero on the AP it means you cannot hear it.
Trouble is, there's a time factor involved ... yes, if the contacts have just been switched, the contact surfaces wiped then the contact resistance has good properties, and I'm quite sure no residual distortions could be picked in measuring gear, by any means. However, the contact areas don't stay pristine - if left undisturbed then some chemical, materials behaviour occurs and an audible degradation starts to build up, slowly. Nearly 30 years ago I went crazy trying to sort this out, I spent weeks, months, trying to work out a definitive, long term solution - in the end I thought, I've had this! - pull out the soldering iron, make every connection gas tight - ahh, peace at last !!
Brad, explaining is not an option, too complicated, but do visit http://www.hifiengine.com, it's a site full of service schematics and it's free, but you do have to join. Go to the library, select Harman Kardon, and download the service manual for model 680 integrated amplifier. It's all there. File size about 8 MB.
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On my side, it use sealed (DIP) relays for low level signals. Works fine.
For high levels, like in my protection board, i found the best solution was to use both static (MOS) and mechanical relays in parallel. As big relays are slower than little mosfet ones, i use mosfet switch to cut the signal at the input of the amp in the same time. This ensure that the big relay will not have to cut big amp signals, so don't sparkle during normal cut off operations.
During power on, the mechanical relay will be slower than the mos fet, so don't have to suffer from any sparkle due to rebound.
During normal operation, the mechanical relay (two contacts) in parallel with the mosfet just eliminate the issues with changes of RDSON with curent.
On a practical use, this seems to works during decades satisfactorily without deteriorating the sound quality.
The problem with hardwired connections to cables is they are only reliable in a completely static assembly, that means the cables fixed to some mechanical support and not allowed to flex freely. For most multi component home set-ups hard wiring is not the most practical solution or the best IMO. But if you are going to do it here's a guide
http://snebulos.mit.edu/projects/reference/NASA-Generic/NASA-STD-8739-4.pdf
Of course you could always use 38999 or similar type connectors and hypertcs for interboard wiring.
Yes, I agree that mechanical stabilisation is crucial for long term reliability, I have had many instances of a solder joint failing, over the years, because of my fiddling with things. But I accept this in the context of my experiments, I'm looking for solutions that prove a point, that demonstrate the viability of my approach.
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