SI Super-T and speaker AB switch to ONE speaker - diyAudio
Go Back   Home > Forums > Amplifiers > Class D

Class D Switching Power Amplifiers and Power D/A conversion

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 22nd March 2006, 03:45 AM   #1
diyAudio Member
 
Join Date: Apr 2005
Location: Bremerton, WA.
Default SI Super-T and speaker AB switch to ONE speaker

In short, I need a mono speaker signal. I need to combine the L and R speaker outs to one wire and then go through an AB switch to two speakers, but only one will be playing at a time.

These are single driver speakers (8 ohm) that I am prototyping, and I need to do fast AB switching between the two to test for different design parameters.

Can I safely do this, and what kind of switch would I need? I can solder well enough, but I need this to be absolutely safe for the amp and the speakers, and I don't know enough about electronics to feel confident doing this without advice.

Thanks for any advice you can give.

Doug
  Reply With Quote
Old 22nd March 2006, 04:06 AM   #2
DcibeL is offline DcibeL  Canada
diyAudio Member
 
DcibeL's Avatar
 
Join Date: May 2003
Location: Saskatchewan
Would it not make more sense to send the input signal into a SPDT switch and have each "throw" connected to either left or right input of the amp. As it doesn't seem to me that you are trying to increase power output in any way, I don't understand why you would want the switch on the output.

I tried drawing a picture. I should have been an artist . When switch is in position 1, the top speaker plays, when the swtich is in position 2, the bottom speaker plays. Very effective for A/B comparisons of speakers.
Attached Images
File Type: jpg hookup.jpg (14.3 KB, 201 views)
__________________
The power of Science compels you!
  Reply With Quote
Old 22nd March 2006, 05:10 AM   #3
diyAudio Member
 
Join Date: Apr 2005
Location: Bremerton, WA.
Thanks DcibeL,

I always thought it was bad to only have one channel of an amp "amplifying." That's why I was thinking via the speaker wires.

So you are saying to run both L and R input cables into a switch and then run one cable each to the L and R input of the amp? (I use RG6 for this setup). In other words, you are saying to combine the L and R input at the switch to make a mono output for the L and R inputs of the amp? Correct?

You are right, I'm not trying to increase power or anything. In fact, I want this as neutral and safe as possible for the equipment.

Thinking out loud here: The L and R input from source goes to the single pole of the switch. Switch setting A sends the combined L and R signal to the R channel input of the amp via one cable. Switch setting B sends the combined L and R signal to the L channel input of the amp via one cable. Correct?

QUESTION: So what type of SPDT switch do I get to switch a 75 ohm RG6 signal? Rotary? Toggle? Wall switch? (This is where I am totally ignorant) I will have to buy four RCA jacks (2 in, 2 out) and wire them to the switch, correct?

Am I making progress?

Thank again,

Doug
  Reply With Quote
Old 22nd March 2006, 12:46 PM   #4
DcibeL is offline DcibeL  Canada
diyAudio Member
 
DcibeL's Avatar
 
Join Date: May 2003
Location: Saskatchewan
Quote:
Originally posted by Taperwood
So you are saying to run both L and R input cables into a switch
That would be L or R signals into the switch, and connect all grounds together.

Quote:
Originally posted by Taperwood
QUESTION: So what type of SPDT switch do I get to switch a 75 ohm RG6 signal? Rotary? Toggle? Wall switch? (This is where I am totally ignorant) I will have to buy four RCA jacks (2 in, 2 out) and wire them to the switch, correct?
You can use which ever type of switch you like, I would try for a "make before break" type to reduce popping when the signal is switched. If you don't know what that is, your local electronics supply store will. If you were planning on making a switch box for this purpose, all you would need is 3 RCA's. 1 in, 2 out.
__________________
The power of Science compels you!
  Reply With Quote
Old 22nd March 2006, 03:35 PM   #5
diyAudio Member
 
Join Date: Apr 2005
Location: Bremerton, WA.
Quote:
Originally posted by DcibeL

That would be L or R signals into the switch, and connect all grounds together.
Keeping in mind that, above all, I want to protect the amp and drivers from damage, but I was thinking of taking the two center pins and the two grounds on the L and R inputs and combining each inside the switch since I will have to run wires from the RCA plug to the switch anyway. Would that be safe to do? Or would a RCA stereo to mono patch cord work better?

I really need the signal from both L and R for this to work. It would be hard to test speakers when all you can hear is half the stereo signal

I'm still wondering about having only one amp channel active at a time, though. You are saying this should not affect it at all?

Doug
  Reply With Quote
Old 22nd March 2006, 04:22 PM   #6
dnsey is offline dnsey  United Kingdom
diyAudio Member
 
Join Date: Mar 2004
Location: Shropshire, England
Quote:
I was thinking of taking the two center pins and the two grounds on the L and R inputs and combining each inside the switch since I will have to run wires from the RCA plug to the switch anyway. Would that be safe to do?
Yes, that's fine
Quote:
I'm still wondering about having only one amp channel active at a time, though. You are saying this should not affect it at all?
No, no problem whatsoever - as far as the amp's concerned, each channel is independent anyway. It would be just the same as a stereo signal panned hard L or R.
  Reply With Quote
Old 22nd March 2006, 05:29 PM   #7
diyAudio Member
 
Join Date: Apr 2005
Location: Bremerton, WA.
Wonderful. Thank you DcibeL and dnsey. I will get the parts and make the attempt. If I have another question, I will ask.

(I do have an old throwaway chip amp setup (from computer speakers) that I can test this on first. I think that would be a good idea, given my comprehension of electronics).

Thanks again,

Doug
  Reply With Quote
Old 22nd March 2006, 05:37 PM   #8
DcibeL is offline DcibeL  Canada
diyAudio Member
 
DcibeL's Avatar
 
Join Date: May 2003
Location: Saskatchewan
Quote:
Originally posted by Taperwood
Keeping in mind that, above all, I want to protect the amp and drivers from damage, but I was thinking of taking the two center pins and the two grounds on the L and R inputs and combining each inside the switch since I will have to run wires from the RCA plug to the switch anyway. Would that be safe to do? Or would a RCA stereo to mono patch cord work better?
I'm not sure I quite understand what you are trying to explain here but here it goes. The grounds do not need to be switched. Just connect them together at some point. Don't use a Y-cable to try and mix Left and Right channels together. This will effectively connect the left output of your source to the right output of your source, and the result will be unsatisfactory. This is not the proper use of a Y-cable. Proper use of a Y-cable would be to plug one (either left or right) output from your source into both inputs on the amp. In this case both channels play the exact same thing, but without a switch to turn each side on and off.

I don't understand why you need to mix both left and right channels together. For testing purposes, this shouldn't matter. What would matter is that the same signal is tested on both speakers for an A/B comparison. The only "easy" way to mix both left and right channels together into a mono track that I can think of off the top of my head would be with the use of a computer.
__________________
The power of Science compels you!
  Reply With Quote
Old 22nd March 2006, 07:45 PM   #9
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
Going back to the top post.
You certainly DON'T want to combine the outputs in any way, the Super-T will not function like that.

If I understand what you are trying to do, the simplest solution woul d be:

Connnect one speaker to left, one to right. Use an RCA Y-cable on the input. Connect the single end of the Y to your source, the split end to the amp. That way you are driving left and right with an identical signal. (As seen in DecibeL's drawing).

Now just plug or unplug the Y-cable to left or right on the amp. If you want to be fancy, you could put a switch in there, but you don't really need it.
__________________
Take the Speaker Voltage Test!
  Reply With Quote
Old 22nd March 2006, 08:12 PM   #10
diyAudio Member
 
Join Date: Apr 2005
Location: Bremerton, WA.
Thanks, I understand that the ground does not go through the switch. However, I've also read in threads on modding some of these amps in this forum (excuse my ignorance) "never tie the grounds together on the (power something?)" Does this come into play here, or is it strictly related to the power supply?

The reason you need the full stereo signal is becasue of the mixing between the two channels. For instance, the recording engineer might have boosted the drums by 6db over the vocals in the left channel (or something like that). So if you were using the left channel only to AB test, you would not hear what you were supposed to hear. You couldn't properly evaluate the sound of the speaker because the drums would be dominating everything else. You need the signal from both channels to get the proper mix level.

Doug
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
speaker project super TAD mcmahon48 Multi-Way 0 5th February 2009 06:09 AM
Speaker switch smithy666 Solid State 12 8th August 2008 08:02 PM
Timer controlled speaker switch... JRace Everything Else 10 20th July 2007 03:39 PM
Speaker A/B switch Mikerobe Car Audio 4 6th January 2007 07:33 PM
speaker selector switch blbarth Multi-Way 4 22nd January 2006 01:07 AM


New To Site? Need Help?

All times are GMT. The time now is 06:00 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2