|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
174.90.222.34
In Reply to: RE: alternate circuit RE: Proposed schematic posted by pmaneri@samsontech.com on October 12, 2016 at 15:06:38
Have a second look at my circuit, the 8 ohm resistor is never connected to the same amplifier which is connected to the speakers, and just like the dpdt circuit there's never more than two contacts in series with the amplifier at once. (I deem necessary to prevent ground loops). I have a slight ulterior motivation for doing it this way - from time to time I like to experiment with speakers, and I want to have it set up so the switches can also eventually be used to switch two amplifiers between two sets of speakers rather than one set of speakers and one set of dummy loads.
I also have a fairly high beam power tube powered amp, so I want to keep a low enough load reaistor so that under no conditions does the output transformer primary see excessive voltage.
Follow Ups:
Max - I'm sorry, you are correct. I didn't study your drawing enough. BTW, I measured the switch contacts on the 10amp switches I've been using and with over ten years use, none measured more than 10 milliohms. Use a godd, heavy duty switch and you'll be fine. - Pete
"Max - I'm sorry, you are correct. I didn't study your drawing enough. BTW, I measured the switch contacts on the 10amp switches I've been using and with over ten years use, none measured more than 10 milliohms. Use a godd, heavy duty switch and you'll be fine. - Pete"
Hi Pete
That's fantastic, I appreciate the fact that you both measured it and shared the results. 10m ohms is maximum initial contact resistance spec which is given for quality panel mount toggle switches from quality brands.
It's also an insignificant amount of additional impedance versus the 16AWG speaker wire run I am currently using, so I don't anticipate any changes to the signal. At first I wanted to use relays to accomplish this task, to perform the switching automatically when the home theatre receiver is turned on, but finding one with a 10 m ohm contact resistance begins to get difficult and more or less not worth it. Standard "ice cube" type relays are in the 50 - 100 m ohm range. Two in series makes 0.2 ohms, which is way too high to be considered absolutely transparent.
I think the key to maintaining this spec is not usage, but avoiding any switching under load. If these switches were used to actually switch 10A repeatedly, I doubt that I suspect the Chinese switches I ordered are more or less knock offs of the usual Carling or other US made switches, but obviously at a small fraction of the cost. I think your RS switches are likely sourced from a similar Chinese vendor, like most of their recent parts.
Max,
There is a nice looking Carling DPDT switch on the Antique Electronic Supply site, P/N P-H523, $7.65 ea. Doesn't list the current rating though. You'd have to ask. Looks heavy duty enough, made in Mexico if that makes you feel better. I do.
My Radio Shack switches may have been made in Taiwan, which has much better quality manufacturing.
Pete
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: