How could I employ an old subwoofer amp that expects speaker cables from the amplifier as input? I want to use the subwoofer pre-amp outputs instead.
Is it possible to drive this subwoofer amp with my subwoofer outs from the pre-amp? It is set up to use the speaker cables directly out of the amplifier .
Could this be done with a transformer or some sort of line buffer?
I am not sure I understand the issues and would appreciate some direction or clarification of the issues.
Thanks
Is it possible to drive this subwoofer amp with my subwoofer outs from the pre-amp? It is set up to use the speaker cables directly out of the amplifier .
Could this be done with a transformer or some sort of line buffer?
I am not sure I understand the issues and would appreciate some direction or clarification of the issues.
Thanks
Brand and model please?
It *might* have low impedance inputs, as low as 1k and even lower since it will bedriven by a speaker out, hence 4/8/16 ohm range.
Your preamp out won´t be happy driving that, if at all.
By the same token, it might expect, say, 5 to 20V RMS signal, doubt your preamp can put thgat out.
But we are only guessing, so please enlighten us.
It *might* have low impedance inputs, as low as 1k and even lower since it will bedriven by a speaker out, hence 4/8/16 ohm range.
Your preamp out won´t be happy driving that, if at all.
By the same token, it might expect, say, 5 to 20V RMS signal, doubt your preamp can put thgat out.
But we are only guessing, so please enlighten us.
I’m sorry to be in the dark myself on this. I don’t know how these things work but assume it’s like a plate amp on older subwoofers without RCA preamp input.
Maybe someone can shed light on how those work?
Maybe someone can shed light on how those work?
Not sure I would bother - your amplifier isn't going to be contributing much in way of noise or distortion for what seems to be a relatively low end subwoofer.
Two issues:
1. Can the amp operate on the signal from the pre-amp? Good chance the amp's output will be in the ball-park, with the pre-amp's volume control rotated pretty high.
2. Is the pre-amp happy with the load it sees when connected to the amp? Likely there is a large mis-match between what the pre-amp is designed to drive (at least 10kOhms) and the load which the amp presents to it (possibly a load meant to imitate a speaker).
Purely guessing, I'd say it would do no harm to a properly designed solid-state pre-amp to try it and it might work OK. But if the pre-amp is unhappy with the match, chance you could remove the imitation load in the amp input. But otherwise, prolly challenging to make it work by simple external changes.
B.
1. Can the amp operate on the signal from the pre-amp? Good chance the amp's output will be in the ball-park, with the pre-amp's volume control rotated pretty high.
2. Is the pre-amp happy with the load it sees when connected to the amp? Likely there is a large mis-match between what the pre-amp is designed to drive (at least 10kOhms) and the load which the amp presents to it (possibly a load meant to imitate a speaker).
Purely guessing, I'd say it would do no harm to a properly designed solid-state pre-amp to try it and it might work OK. But if the pre-amp is unhappy with the match, chance you could remove the imitation load in the amp input. But otherwise, prolly challenging to make it work by simple external changes.
B.
Thank y'all for entertaining this question. I figure I can always use a small chip-amp as the interface to this venerable old iron SAE high current subwoofer amplifier.
As I think about it I was mostly interested in the design of these subwoofer amplifiers. They were an early 80's kinda design that persists on lots of plate amps that have both an RCA and a speaker-line input. Curious as to how that works.
As I think about it I was mostly interested in the design of these subwoofer amplifiers. They were an early 80's kinda design that persists on lots of plate amps that have both an RCA and a speaker-line input. Curious as to how that works.
While I can solder and follow instructions I have a Neanderthal understanding of electronics.
What is a voltage divider? My guess it that it reduces the current coming from the amplifier but dunno.
What part of that circuit is the divider? The resistors?
What is a voltage divider? My guess it that it reduces the current coming from the amplifier but dunno.
What part of that circuit is the divider? The resistors?
Last edited:
That’s helpful. From this link I have leaned what a voltage divider is and that:
If learning Ohm's law was like being introduced to the ABC's, learning about voltage dividers would be like learning how to spell cat.
LOL
Many thanks
If learning Ohm's law was like being introduced to the ABC's, learning about voltage dividers would be like learning how to spell cat.
LOL
Many thanks
If I read it right, the speaker-cable input has a load resistor of 100 Ohms. Some pre-amps might play OK into that load albeit with a low voltage signal but doesn't sound really acceptable.
But the speaker-cable input is reduced to 10% (compared to the pre-amp jack) before continuing on its path in the amp. Which may mean that your amp (which expects a speaker-cable signal) is expecting a signal 10X what a pre-amp would typically supply. Again, might work OK even with that head-wind, but doesn't sound really sensible.
Sticking with the schematic, if you open the amp, you might find something like that 100kOhm resister or some voltage divider being used to cut down the speaker-cable input before the first amplification stage. A simple matter to disable the voltage division.
You are also using a coax output from your pre-amp into unshielded in the amp. For most pre-amps, it shouldn't introduce too much noise. But take care about ground connections.
BTW, "10X" is like 20dB voltage increase which is like what the amp portion of an amplifier would typically provide. So it makes sense to see that inside the pictured schematic.
B.
Last edited:
Fair to say, depending on the exact design of your particular subwoofer amp, you may be able to change a few components and adapt it for your intended use, but it's unlikely to work well without modification.
May be an interesting challenge if you want to figure out how this all works [emoji3]
May be an interesting challenge if you want to figure out how this all works [emoji3]