Little amp help please....

speekergeek · 30th June 2004, 01:45 AM

Hi all! I made a kooky mistake and didn't read before i bought a sub amp. it was this one.. http://www.allelectronics.com/cgi-bi...A-6&type=store
I thought i was getting a good deal and i may have if only i could get a little help. The amp has speaker level inputs, and i was going to use my line out from my reciever to power some bass shakers in my couch. well dumb me didn't read carefully as the amp has no line in. I am somewhat electronics competent but surely no engineer. I was told to look for a resistor dividor and try to bypass it, there were several pairs of resistors of varying ohmage. so here is what i did, i took a cheap speaker and hooked it up to the output of the amp, then i ran my line level (sub) to two wires. (I measured the output of the reciever and it is in the area of .03 volts during semi-loud passages) I took those two wires and started poking around the bottom of the first circuit board (the small one with the level knob and the xover freq pot) well after many loud pops I found 2 spots that work...... one of them makes the actual subwoofer go quiet while all juice is diverted to the crappy speaker, and the other spot sure gets good reception of some AM radio station. plleeaaaassee help me, ask any questions of me about this that i may not have said clearly. If i had a schematic i could have done this in 5 minutes, as it is i spent 3 hours poking around in spots after the initial resistors in the circuit. thanks much.

Mike

I also forgot to mention that in the spot where the radio station came in, the speaker would not go as loud as in the other sub killing position.

getafix · 30th June 2004, 04:51 AM

aren't the speaker level inputs the "line-in" of the amp? and one of the wires at the back is connected to the speakers/bass shakers?

speekergeek · 30th June 2004, 05:18 AM

I guess they are the "line-in" but the line in is at speaker level, which is however many watts it can take. It uses a resistor dividor (i believe) to scale down the voltage and it sends that signal to another amplifier. wierd me thinks. but the subwoofer line level voltage out of my reciever is .03 volts'ish. and the output of the amplifier is connected to a speaker so i can hear if the circuit is working. so far i have found 2 spots after the divider that work, but one gives me an AM radio station as well as the bass signal, and the other spot steals the signal from my main subwoofer. it is strange. I need help from a whiz kid here...... why would it recieve am radio? why does it steal the signal? those are my Q's

Mike

sreten · 30th June 2004, 03:20 PM

Probably the easiest thing to do is take a feed from your
subwoofers bass driver / amplifier output and feed this
into the shaker amplifiers high level inputs.

I'd fit a 100R series resistor to this feed, if the frequency
control on the shakers amplifier does not go low enough
fit a capacitor across the shaker amplifiers inputs (after
the 100R series resistor) for further bass shaping.

Its also possible the shaker amplifier will accept a line
level input directly to the volume control on the board,
here you need to disconnect the attenuator network
feeding the volume control (if the circuit is arranged
this way, it may be, it may not be).

sreten.

Davide82 · 30th June 2004, 07:46 PM

Wouldn't it be easier to amplify the line level you want to use?
If you build a very small-easy circuit with a cheap IC (e.g. LM386 from National) you can get what you want without touching your amp.

planet10 · 30th June 2004, 09:19 PM

If you start at the speaker level inputs and trace the circuit from there, it should be pretty easy to figure out where to install a set of input jacks. There should be a cap between those and any satelitte outs... following the other path there should be a series R for each channel, then they should sum togther... that is the 1st spot to consider. There may be a little more passive circuitry before you get to the 1st active stage, some will be needed, some may not.

dave

DIAR · 1st July 2004, 05:56 AM

I have a passive preamp with 10 kohm DACT stepped attenuator.
http://kotiweb.kotiportti.fi/audiovideo/DIY/preamp1

Is it ok to use passive preamp with Gainclone or should I expect some problems? I'm going to use TDA7294 DIY kit:
http://www.tricomp.fi/tuote2.php?id=...nrakennussarja

30th June 2004, 01:45 AM	#1
speekergeek diyAudio Member Join Date: Oct 2003 Location: santa rosa	Little amp help please.... Hi all! I made a kooky mistake and didn't read before i bought a sub amp. it was this one.. http://www.allelectronics.com/cgi-bi...A-6&type=store I thought i was getting a good deal and i may have if only i could get a little help. The amp has speaker level inputs, and i was going to use my line out from my reciever to power some bass shakers in my couch. well dumb me didn't read carefully as the amp has no line in. I am somewhat electronics competent but surely no engineer. I was told to look for a resistor dividor and try to bypass it, there were several pairs of resistors of varying ohmage. so here is what i did, i took a cheap speaker and hooked it up to the output of the amp, then i ran my line level (sub) to two wires. (I measured the output of the reciever and it is in the area of .03 volts during semi-loud passages) I took those two wires and started poking around the bottom of the first circuit board (the small one with the level knob and the xover freq pot) well after many loud pops I found 2 spots that work...... one of them makes the actual subwoofer go quiet while all juice is diverted to the crappy speaker, and the other spot sure gets good reception of some AM radio station. plleeaaaassee help me, ask any questions of me about this that i may not have said clearly. If i had a schematic i could have done this in 5 minutes, as it is i spent 3 hours poking around in spots after the initial resistors in the circuit. thanks much. Mike I also forgot to mention that in the spot where the radio station came in, the speaker would not go as loud as in the other sub killing position.

30th June 2004, 04:51 AM	#2
getafix diyAudio Member Join Date: Jun 2003 Location: somewhere in Mandaluyong	aren't the speaker level inputs the "line-in" of the amp? and one of the wires at the back is connected to the speakers/bass shakers? __________________ forever dreaming of a better set-up...

30th June 2004, 09:19 PM	#6
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	If you start at the speaker level inputs and trace the circuit from there, it should be pretty easy to figure out where to install a set of input jacks. There should be a cap between those and any satelitte outs... following the other path there should be a series R for each channel, then they should sum togther... that is the 1st spot to consider. There may be a little more passive circuitry before you get to the 1st active stage, some will be needed, some may not. dave __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

1st July 2004, 05:56 AM	#7
DIAR diyAudio Member Join Date: Jun 2004 Location: Capital City Area	Passive preamp+Gainclone ? I have a passive preamp with 10 kohm DACT stepped attenuator. http://kotiweb.kotiportti.fi/audiovideo/DIY/preamp1 Is it ok to use passive preamp with Gainclone or should I expect some problems? I'm going to use TDA7294 DIY kit: http://www.tricomp.fi/tuote2.php?id=...nrakennussarja

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30th June 2004, 05:18 AM	#3
speekergeek diyAudio Member Join Date: Oct 2003 Location: santa rosa	I guess they are the "line-in" but the line in is at speaker level, which is however many watts it can take. It uses a resistor dividor (i believe) to scale down the voltage and it sends that signal to another amplifier. wierd me thinks. but the subwoofer line level voltage out of my reciever is .03 volts'ish. and the output of the amplifier is connected to a speaker so i can hear if the circuit is working. so far i have found 2 spots after the divider that work, but one gives me an AM radio station as well as the bass signal, and the other spot steals the signal from my main subwoofer. it is strange. I need help from a whiz kid here...... why would it recieve am radio? why does it steal the signal? those are my Q's Mike

30th June 2004, 03:20 PM	#4
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Probably the easiest thing to do is take a feed from your subwoofers bass driver / amplifier output and feed this into the shaker amplifiers high level inputs. I'd fit a 100R series resistor to this feed, if the frequency control on the shakers amplifier does not go low enough fit a capacitor across the shaker amplifiers inputs (after the 100R series resistor) for further bass shaping. Its also possible the shaker amplifier will accept a line level input directly to the volume control on the board, here you need to disconnect the attenuator network feeding the volume control (if the circuit is arranged this way, it may be, it may not be). sreten.

30th June 2004, 07:46 PM	#5
Davide82 diyAudio Member Join Date: Dec 2003 Location: xxxxx	Wouldn't it be easier to amplify the line level you want to use? If you build a very small-easy circuit with a cheap IC (e.g. LM386 from National) you can get what you want without touching your amp.

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