I have an SWR LA15 that I want to add some switches to. I would like to have a switch to turn the speakers off completely (to avoid the big POP when powering on) and another switch to the tweeter for on/off operation. My questions are can these mods damage the amp? If I play through the amp with the speaker turned off by accident, would that screw up the amp? If I turn off the tweeter would I need to account for the smaller load on the amp, or will the tweeter not draw enough to worry about? If need be, I guess I could switch these to some resistors to simulate the load to a speaker. If so, could someone point me in the right direction for values to the resistors I would need? Thanks, Casey
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Need help with amp modifications
- Thread starter csm672
- Start date
Hi.
Cutting off the tweeter isn't too hard and the frequency it operates in doesn't require substitute load. Without knowing the circuit, I'd use a simple ON-OFF SPST switch.
For muting the output to avoid the pop, why not turn the VOL to zero?
Adding a switch can be a bit tricky even though SS amps usually don't mind as long as the load resistance is not below the minimum. IOW, open is all right so a similar SPST switch could be used as in the tweeter. With a DPDT You can cut both of the lines, but IMHO that doesn't serve any purpose.
Regards
Sam
Cutting off the tweeter isn't too hard and the frequency it operates in doesn't require substitute load. Without knowing the circuit, I'd use a simple ON-OFF SPST switch.
For muting the output to avoid the pop, why not turn the VOL to zero?
Adding a switch can be a bit tricky even though SS amps usually don't mind as long as the load resistance is not below the minimum. IOW, open is all right so a similar SPST switch could be used as in the tweeter. With a DPDT You can cut both of the lines, but IMHO that doesn't serve any purpose.
Regards
Sam
Another option is to get a tech to mod your amp with a turn on delay mute.
http://music-electronics-forum.com/t10525/
http://music-electronics-forum.com/t10525/
Hi.
Certainly possible, just as it is to take advantage of the chips mute function if it's not a discrete design like the WP series is.
My point was to keep the cost down. A $100+ mod for a $350 amp just to get rid of the pop seems a bit overkill. But that's just me.
Regards
Sam
Certainly possible, just as it is to take advantage of the chips mute function if it's not a discrete design like the WP series is.
My point was to keep the cost down. A $100+ mod for a $350 amp just to get rid of the pop seems a bit overkill. But that's just me.
Regards
Sam
Ya, that speaker mute function is a waste on an amp like that. Just turn the amp down. Tweeter mod sounds useful and easy, though.
Thanks everybody. I do turn the amp down to "0" before turning on but it still pops pretty loud. If I forget to turn it down it gets really loud. I think the amp sound ALOT better w/o the tweeter, but wasn't sure if I needed to account for the load or not. There is one song I play for my kids that the tweeter just sings, though, so I think the switch would be best. So would it be best to simulate a load for the speaker mute switch I am going to install, or will that just be overkill? Thanks!
Why not a potentiometer / Lpad so you can dial the tweet in [out]. I can see that being even more useful
Have you researched at all whether that pop is normal for the amp? I don't recall having any amps -- cheap or good -- that had such a pop that was so loud I thought I had to modify it. Maybe you have a problem that a tech could fix -- and that would be a far better solution (for the mute, anyway).
Simulating a load is more work than just putting a resistor in its place, though, AFAIK.
Good luck!
ltt
Simulating a load is more work than just putting a resistor in its place, though, AFAIK.
Good luck!
ltt
My Acoustic 360 had the loud thump/pop. So does my Workingman 300, but it has a speaker switch. It is normal for SWR to pop when turned on, but not if the volume is turned down. I'd have that checked.
My brother's amp guru said he had never worked on one of these that DIDN'T pop like this, though he did say that he hasn't had but 5 or 6 in his shop. SWR said it is normal and won't do any damage, but it is a little disconcerting. I was thinking maybe I could put a dpdt switch in, one leg on the hot side of the speaker and one on the hot side of the input, that way I wouldn't have to worry about playing the amp with no load. Thoughts?
Why not just plug the speaker into the amp after you power it up. Only do this at the amp end not the cabinet.
The pop is the amp settling into stability after power on. All SS amps do this though most have a power on delay that connects the speakers when the amp is stable.
Paul
The pop is the amp settling into stability after power on. All SS amps do this though most have a power on delay that connects the speakers when the amp is stable.
Paul
Yeah, that would be easy, but the speaker is connected internally and I would have to remove alot of screws to do that. I'm thinking the switch to the input and speaker would be the easiest and cheapest solution. If I knew more about circuit designs I would try to put a "soft start" in, but that is a little over my head right now!
I don't know...the pop never bothered me in the least when I had an SM-500, though it did have a speaker mute switch. I grew up on amps that did it and it never bothered me. Some people get really irritated by it, though. Guess you're one of them 
come to thing of it, if you're going to start mucking about, consider this:
put in two jacks, one from the amp, one to the speaker, then connect the two with a speaker cable. that should be nice and simple, you can put the jacks anywhere, and don't necessarily have to mangle the chassis. Then if you're in a high-volume situation, you can volume down, pull cable, turn off. But that would also let you power a different cab with this amp, or run a different amp to this amp's speaker...I did this with a beater Peavey TNT, and it turned out to a very practical mod.
Also, be sure you test a switch arrangement before physically mounting anything -- I wonder if there's a chance a switch would allow or cause a different kind of pop or shut down noise, even if all it does is break the positive wire to the speaker.
I'd still be concerned, though, if my amp made a disturbingly loud pop after I'd turned the volume down and then turned off the amp.
(Just for context, in the past I have gigged regularly with 3 different SWR amps, but no LA combos).
put in two jacks, one from the amp, one to the speaker, then connect the two with a speaker cable. that should be nice and simple, you can put the jacks anywhere, and don't necessarily have to mangle the chassis. Then if you're in a high-volume situation, you can volume down, pull cable, turn off. But that would also let you power a different cab with this amp, or run a different amp to this amp's speaker...I did this with a beater Peavey TNT, and it turned out to a very practical mod.
Also, be sure you test a switch arrangement before physically mounting anything -- I wonder if there's a chance a switch would allow or cause a different kind of pop or shut down noise, even if all it does is break the positive wire to the speaker.
I'd still be concerned, though, if my amp made a disturbingly loud pop after I'd turned the volume down and then turned off the amp.
(Just for context, in the past I have gigged regularly with 3 different SWR amps, but no LA combos).
Its a 50-50 deal, the manufacturer puts in little relays that close after a few second delay and you have the #1 failure point in your amplifier... The relays get dirty from the sparks and flash from closing...
Yes Boom and Bang is very irritating. My unfavorite is the farting death of improper shutdown...
The mods are just not worth the time and effort and Mr Resale time will hit you in the pocket a second time. Best upgrade and save the pain?
BOB
Yes Boom and Bang is very irritating. My unfavorite is the farting death of improper shutdown...
The mods are just not worth the time and effort and Mr Resale time will hit you in the pocket a second time. Best upgrade and save the pain?
BOB
Reading my mind. Unmodded amps usually sell better than modded amps, especially if you have to do drilling.
Hey, I know it's not a great amp. But it really doesn't sound that bad at practice levels and it was MADE IN USA (try finding another practice amp made in the U.S.! Carvin not withstanding!) Plus, I'm only into this for $75 and I like to tinker with things, so a few bucks for some toggle switches and drilling a couple holes is well worth it if I can switch the tweeter off and ditch the pop. I just really wanted to make sure I wouldn't screw it up electronically. Thanks everyone! Casey
