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
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
Member
Joined 2003
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.
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.
Attachments
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
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
Member
Joined 2003
That would be L or R signals into the switch, and connect all grounds together.Taperwood said:
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.Taperwood said:
DcibeL said:
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
Yes, that's fine
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.
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
(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
Member
Joined 2003
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.Taperwood said:
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.
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.
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.
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
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
Am I missing something? As far as I can see, he can parallel L & R signals, and feed to both inputs via a c/o switch perfectly well.
panomaniac said:
Thank you. (By the way, I appreciate your work on your website) Okay, I got it, combining speaker outs is bad.
I never dreamed it could be this complicated 🙂 The reason I don't want to plug and unplug is that after about five seconds, the brain forgets what it just heard. I need to switch more quickly, while the same passage of music is playing. The differences are sometimes very subtle between the speakers.
I hope by now I have explained the why. I need both left and right channels to play through each speaker.
Regarding the input then: I can't connect a single end to the source as there are two outs, left and right. At some point, I have to combine the L and R channels into one so that each speaker gets the full signal on the recording. I know they make stereo to mono 3mm plugs because I used to have one. So why couldn't I just use either a Y cable or tie the L and R inside the switch, unless this is unsafe for the equipment?
For a template to this whole discussion: If an amp had a mono switch, how would that be wired?
Doug
dnsey said:
dnsey,
Yes, that's exactly what I see the solution to be based on what everyone has told me. Everyone is confident this is safe for the amp, right?
I apologize for not making my own drawing first and saving everyone the time, but I honestly came in here thinking I could do this via the speaker outs. Thanks everyone for setting me straight on that.
Doug
xplod,
Your schematic in Post #15 makes the most sense to me (from my limited wiring ability). This, combined with dsney's original schematic, is something I feel I could accomplish.
Panomaniac's version would work too, if I used xplod's stereo>mono solution. I would then just need to put in a switch, but that adds a lot more connections that I could screw up 🙂.
So does everyone reading this thread agree that the plan in Post #15 would work without blowing up anything? It is my current understanding that the Super-T amp is not bothered by only one input receiving a signal at a time.
Doug
Your schematic in Post #15 makes the most sense to me (from my limited wiring ability). This, combined with dsney's original schematic, is something I feel I could accomplish.
Panomaniac's version would work too, if I used xplod's stereo>mono solution. I would then just need to put in a switch, but that adds a lot more connections that I could screw up 🙂.
So does everyone reading this thread agree that the plan in Post #15 would work without blowing up anything? It is my current understanding that the Super-T amp is not bothered by only one input receiving a signal at a time.
Doug
The schematic in 15 will work. But you might lose some bass. It means that you have a high impendance source which could cause some loss of bass or "drive". You would certainly have the same signal, though. It's easy enough to try.
Are you sure that you need left and right? Why? Can't you just use one channel, always the same one?
Are you sure that you need left and right? Why? Can't you just use one channel, always the same one?
Member
Joined 2003
That should work okay, since there will be 20kOhm between each source output it won't load them down. But like panomaniac stated, it will create a 10kOhm source.xplod1236 said:
panomaniac said:
The drivers I'm prototyping right now are Fostex FE 108 E Sigmas. There is no bass below 60Hz🙂 Very good drivers otherwise. The bass is handled by a sub, but that's not even turned on when testing. Given that, do you think the resistor circuit would be okay?
As for using one channel, if I could find some audiophile-quality mono recordings, that would be fine, but conventional stereo is the sum of two channels. Sometimes an instrument is boosted in one channel over the other; sometimes background vocals are only in one channel. There is no way to hear the full audio spectrum without both channels.
As an extreme example, listen to an early Beatle's stereo recording to see what I am talking about. Often, a guitar will be in one channel and the drums in another, etc. With vocals, it's expecially critical. If the soprano is in the left channel and the tenor in the right, which one do you choose? They are at entirely different frequencies. Makes it tough to evaluate one speaker at a time when the only difference between the two might be 3 ounces of stuffing, which might only affect 1 - 2Khz in the midrange, for example, and suppose that information was simply missing from the channel you chose.
Doug
- Status
- Not open for further replies.