Teerawit
Headphoneus Supremus
- Joined
- Mar 21, 2005
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No fair 98venom, you got a pre-machined case!
Originally Posted by Teerawit No fair 98venom, you got a pre-machined case! |
Originally Posted by rickcr42 Seems to me there was a HUGE deal made by a couple of members here who spent 2 months trying to design a simple A/B switch for three channel headphone amps yet here is a simple dual pole switch on the output of the amp recommended by the amp designer ? What gives ? Either switched grounds ARE or they ARE NOT important for this topology since the attack on Ray Samuels A/B switch was solely based on it as was the assault on anyone who even hinted at using a two pole switch on the output and that includes simple muting relays which also took on a voodoo aspect here. it seems the answer is not only inconsistant but all over the map and it would be nice to have clarity.A definitive answer for future reference |
guess I'm saying that, if in doubt, just switch the grounds because its only a little mor expensive for the 2 pole rotary and extra wiring, plus you'll eliminate any chance to develope hum (at least due to the pre-amp), correct? |
Rick, I would hope that you look at the diagram more closely before attacking my post. |
They are not to be used interchangeably. It is also assumed that the preamp out will be connected to a high-impedance input stage of a power amplifier which is a very light load with very little return current, therefore there will be virtually no signal ground pollution. Headphones on the other hand (especially low-Z ones) cause much higher ground return currents, and are thus handled by the active output ground channel |
This input selector switch is the non-shorting type. Does this mean that it "disconnects, then reconnects" and would cause a pop if the grounds were switched |
Also, My original question was weither I should switch the grounds of the input sources and then just feed 2 ground wires (1 per channel) to a common ground with the ground channel of the M3. |
I mean, is the ground channel of the M3 meant to JUST drive the common ground of the heaphone and not the power amp? |
Originally Posted by rickcr42 non shorting means "BreakBefore Make" or in simple terms no contact between switching so could cause "pops" though to be honest not having a 3-CH headphone amp am waiting for the definitive answer before saying this is an absolute. Usually the answer would be use a shorting switch like the very inexpensive Lorlin.one of the few commonly available shorting rotary switches. I personally would go with simple there and use the normal type 2-pole rotary switch to select the left and right channel signals while leaving the ground alone. There are lucid arguments for both ways but the alternative usually means adding extra resistors across every single switch contact to avoid switching transients and that to me is ovecomplicating the simple to cure a problem not usually there it is an "active" ground rather than the typical passive-wire ground buss style ground connection and can be looked at as any other active circuit. That is with a hi-Z input impedance and lo-Z output impedance (typical of active stages) so the input requirements WAY easier to accomodate than the output which can be loaded down in extreme cases like any amp could be. I would not stress the input but treat it as any amp while paying attention to the output in the attempt to avoid any potential problems before they actually become a problem and thus requireing a fix. DIY means you have the option to plan your attack and get it right before building the actual "thing" under consideration with the forum allowing options from various sources to make your life digfficult |
One thing, though, why would I need to wire resistors to every switch tab? I know you said to avoid switching transcients, but what does that mean specifically? |
For now I'll bet on the shorting type switch, but I'll wait for the definite answer, as you are. And I'll just switch the + and wire grounds together. |