Marantz MA500, only 50Hz output? - Page 2 - diyAudio
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Old 20th June 2007, 12:12 AM   #11
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Hi! I have a pair of MA500s as well and am planning on upgrading the caps. Kaspro could you post a list of all the caps you replaced along with their values if possible? Burnedfingers any other tips - better components etc? Thanks

Leon
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CD63KI (let the mods begin!!), MA500 monoblocks & home built stepped attenuator passive preamp. Lots of other lesser junk.
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Old 20th June 2007, 01:20 AM   #12
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Take a look at posts #4 & #6 and they will give you the part and the value. Nothing sonically to gain by using a more expensive part. I suggest that you replace ALL parts listed in one shot so you aren't bothered taking it apart again. Be sure to do both of the amps.
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Old 22nd September 2008, 08:32 PM   #13
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I have purchased a set of these for driving a JBL 400 watt 4 Ohm subwoofer.

After reading this, I guess I should rebuild them. I cannot email as yet, so I am asking Burnedfingers to contact me.
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Old 22nd September 2008, 10:08 PM   #14
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You purchased a pair to run mono bridged to drive the JBL 4) ohm subwoofer?

If so you cannot run a load lower than 4 ohm with this amplifier in mono bridge or it will go up in a puff of smoke.

This amplifier will drive a 8 ohm or more load in mono bridge.
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Old 23rd September 2008, 12:48 AM   #15
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I purchased 3 of them.

So, they cannot drive a 4 ohm speaker? Why are they advertised as being a 4 ohm speaker?

Good lord.

Could I ask you to send me the schematic you mentioned above?
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Old 23rd September 2008, 01:22 AM   #16
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They are advertised to run a 4 ohm speaker per mono block.

When you mono bridge them you use two of them. One drives the positive waveform of the signal and the other the negative.

Just because a amplifier is advertised to drive a 4 ohm load doesn't guarantee it will do it in bridge mode. In all reality I believe that each channel is actually driving a 4 ohm load in bridge mono. Please correct me here if I am mistaken.

According to Marantz the impedance needed when in mono bridge is 8 ohms. My experience with these amplifiers has proven that low impedance loads will result in the magic smoke being let loose.

Typically the impedance of that driver will dip even lower than the 4 ohm nominal impedance and cause the amplifier even more stress.

Don't get caught up in the numbers game. Under ideal conditions if an amplifier (stereo) or two mono blocks are designed correctly one might expect power to increase by a factor of 4 in mono bridge. In all reality it is usually around 3 times. If you have an amplifier that puts out 200 watts per channel and everything was perfect you would get around 800 watts in mono bridge. Now the difference in level between 200 watts and 800 watts would be 6db.

You need to ask yourself if the extra strain on everything is worth this little difference in level. I would suggest selling that JBL driver and purchasing a professional sound model which would more than likely be 8 ohms and of higher sensitivity. It sounds like that JBL subwoofer is of the car vintage.

Drop me an email and I will give you a copy of the Marantz service manual for the MA500.
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Old 23rd September 2008, 02:48 PM   #17
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Burnedfingers-

The speaker is the S120p whose specs are that it has "nominal impedance of 8 ohms". But when I put it on a meter, i get a reading of 12 ohms which quickly drops to 5.4 ohms. So I was guessing that it would need an amp that could handle 4 ohms because it will most likely drop down to 4 ohms. What do you think about that?

Robert
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Old 23rd September 2008, 02:48 PM   #18
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Also-

I am under moderation at the moment, so I cannot email you as yet.
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Old 23rd September 2008, 05:06 PM   #19
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by burnedfingers

Just because a amplifier is advertised to drive a 4 ohm load doesn't
guarantee it will do it in bridge mode. In all reality I believe that
each channel is actually driving a 4 ohm load in bridge mono.
Please correct me here if I am mistaken.
Hi,

Bridged each channel driving an 8 ohm load sees a 4 ohm load.

A 4ohm capable amplifier = an 8 ohm bridged capable amplifier.

To bridge into 4 ohms you need 2 ohm capability per channel.

/sreten.
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Old 23rd September 2008, 06:27 PM   #20
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Quote:
Originally posted by sreten


Hi,

Bridged each channel driving an 8 ohm load sees a 4 ohm load.

A 4ohm capable amplifier = an 8 ohm bridged capable amplifier.

To bridge into 4 ohms you need 2 ohm capability per channel.

/sreten.
Okay, I understand that now. So, how does that effect driving a speaker whose nominal impedance is 8 ohms but whose impedeance drops to 5.4 ohms on a meter?

This is the same impedance for the woofers in JBL's L890/L880 towers that I own. The question here is whether the Marantz mono blocks will drive such a speaker when bridged.
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