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Old 23rd October 2007, 11:40 PM   #1
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Default 4 channel conversion to mono 1 channel

Hi all, just a quickie!

Would it be possible to take a 4 channel amp and convert it to a 1 channel amp? Don't get me wrong, I'm not looking for more power. I have a Maystar 4 channel jobby. I've had it for years and its never failed even though its had a bit of Pepsi spilt down the fan vent,OOPSit didn't die , and I'm running 2 of the channels in bridge mode for my sub. I can't afford to go and buy a new amp, but, am I not wasting unused amperes in the switch mode, because the other 2 channels aren't being used, plus maybe it would sound better if I just had a pair of transistors driving my woofer?
Or maybe a parallel pair?

With reference to
Simple AMP DIY
post no3, djQUAN has a psu, in which he says he drew a line across the board and cut it, (obviously in the right place). I've looked at the board and at first glance, there's more than just +/- and Gnd tracks, djQUAN if you read this, how the heck did you decide what/where to cut?
It says 4 x 100 watts on the sticker , but by time you realise this, its probably BS, what sort of sensible power could I expect if I could pull it off? I'm only driving a 10inch in a wedge 50 quid special. So maybe 75wr.m.s. overall. I could do with something meaty to do, for the winter months. What do you think?

Cheers

iUSERTLO72p
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Old 24th October 2007, 12:05 AM   #2
ppia600 is offline ppia600  United States
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Just buy one dual voice coil (4 ohm per coil) subwoofer. Bridge two channels on one woofer coil, and bridge the other two channels on the other woofer coil. No wasted power
Just be sure to adjust both gains and crossover frequencies exactly the same or it won't be as efficient. Someone here can surely tell you how to match the gains. I'm not going to wear my fingers out explaining how to, someone else will surely have a better way anyway.
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Old 24th October 2007, 09:27 AM   #3
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Default Yes, thats one way but...

Quote:
I can't afford to go and buy a new
This suggests that I'm broke , also the idea is to maybe use one of Rod Elliotts projects, and maybe learn something. Okay some people might not go for having quality bass in there motor, but I like it.
Cheers for the response, If I had the readies, I'd go that route. Although my amp has 2 filters, 2 channels on high pass and 2 on lowpass. Or all 4 flat.

Cheers

iUSERTLO72p
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Old 24th October 2007, 01:07 PM   #4
djQUAN is offline djQUAN  Philippines
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Default Re: 4 channel conversion to mono 1 channel

Quote:
Originally posted by iUSERTLO72p djQUAN has a psu, in which he says he drew a line across the board and cut it, (obviously in the right place). I've looked at the board and at first glance, there's more than just +/- and Gnd tracks, djQUAN if you read this, how the heck did you decide what/where to cut? [/B]

there are actually two V+, two V- and one gnd tracks because it is a dual supply amp. both V+ and V-'s have the same output voltages but are independent of each other because they have separate power transformers, rectifiers and output caps.

just look around the circuit and trace the copper running from the output to the rectifiers, inductors and output capacitors and see where you can cut a nearly straight line. just make sure if the powersupply has some feedback path for regulation, don't cut that part.

cutting was done using a dremel type tool and a cutting disc attachment.


you can use only two channels on a 4 channel amp and if it has a single supply (most likely it does but I'm not sure) then using only two channels rather than four is not wasting any power but even better for the PSU since it has extra juice from the unused channels that can be used by the other two.
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Old 24th October 2007, 01:25 PM   #5
ppia600 is offline ppia600  United States
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Default Re: Yes, thats one way but...

Quote:
Originally posted by iUSERTLO72p


This suggests that I'm broke , also the idea is to maybe use one of Rod Elliotts projects, and maybe learn something. Okay some people might not go for having quality bass in there motor, but I like it.
Cheers for the response, If I had the readies, I'd go that route. Although my amp has 2 filters, 2 channels on high pass and 2 on lowpass. Or all 4 flat.

Cheers

iUSERTLO72p
Even if you run all four channels into one mono channel, you're not going to gain any more power output (assuming you keep the same woofer). The current capability of the amp could theretically go up, but since the amp will still be running the same voltage in the power supply, and the woofer impedance is staying the same (because you can't buy a new one, and I'm assuming its a single 4 ohm version since you haven't stated to the contrary) you will be using pretty much the same wattage. The damping will change slightly but the amp's voltage maximum will be the same. That is why I suggested changing the woofer type to require more current from the amp.

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Old 24th October 2007, 02:37 PM   #6
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Default Hi!

That is true, but P = U x I (20V x 4 x 5A ).

This situation is good for Low impedance speaker<2Ohm.

BTW for vhich car you want to use this amp.

Regards zeoN_Rider
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Old 24th October 2007, 02:51 PM   #7
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Default Hello gain

Quote:
Don't get me wrong, I'm not looking for more power
Hello, I just wanted to improve the amp. I assume that using 1x 4 ohm driver, sorry should have said , that I could build a better quality amp. I don't know how the power rating would change. I just wondered if the powersupply could just run one set of transistors/or parallel another pair, to give the same power as 2 channels bridged. I was thinking that the crossover distortion created by the bridge be removed and maybe THD/Damping or whatever goes into making an amp stage perform well.

I don't fancy trying to build a SMPS, seems too complicated. But a new amp stage would be nice.

Many thanks for replying. I was looking at attaching this or similar
http://sound.westhost.com/project3a.htm
What do you think djQUAN?

Cheers

iUSERTLO72p
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Old 24th October 2007, 02:52 PM   #8
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Default zeonrider

Vauxhall/Opel Corsa

A small hatch
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Old 24th October 2007, 03:27 PM   #9
djQUAN is offline djQUAN  Philippines
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what amp is that? can you post pictures of the insides and outside?
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Old 24th October 2007, 03:34 PM   #10
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Default Have a look

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