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Help needed Marantz 140 Clipping fast not enough power ?

B

Bogdan1986

New Member
Hello dear audiophiles,
I own a marantz 140 power amp since few days.The amp has been repaired (minor problem) few cap's were changed on the relais board.The amp works good so far,doesn't get hot at all but there is a ,,mistery'' regarding the fact the this amp has no power and is clipping fast.
Important things i have to add : i do not own the original preamp which this power amp should have ( therefore maybe doesn't get enough signal ? im using a marantz 2226 as preamp )
Why i am thinking this amp doesn't seem to have power? I have 2 pairs of kef c220 speakers connected to another marantz 2235 and the 35 watt/channel this amp produce is really really loud in my livingroom.When i conneect these speakers to MARANTZ 140 at half volume when is already clipping the sound is not even half the 2235 poduce at let;s say 40 percent .What it can be ? wrong preamp,bias or dc offset?
Id really appreciate any help/advice .
Have a good one ,Raul

 
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Never seen one but on the schematic it appears to have input level controls. If those are turned down, the preamp might clip before the amp. Try turning them all the way up. Other than that, at 75 W/ch it shouldn't clip that easily. Maybe a problem with the protection circuits or some other internal issue. I'd think the 2226 would be up to the preamp job, but you should compare the output level of that, with the input sensitivity of the amp.
 
Conrad is correct.
A properly functioning 140 will have way more power than your 2235 and the 2226 will work fine as a preamp for your 140.
Try the 2235 as your preamp to positively rule out the 2226 as causing your issue.
The 140 is a nice amp once it is fully restored as it has a troublesome single dual filter cap that is getting tired amoung other things.

Bob
 
ConradH said:
Never seen one but on the schematic it appears to have input level controls. If those are turned down, the preamp might clip before the amp. Try turning them all the way up. Other than that, at 75 W/ch it shouldn't clip that easily. Maybe a problem with the protection circuits or some other internal issue. I'd think the 2226 would be up to the preamp job, but you should compare the output level of that, with the input sensitivity of the amp.
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Thank u very very much for your reply sir.By ,, clipping sound'' either if is at 50 percent vol or maximum volume the marantz 140 will sound exactly the same.at 50 percent also the vu/meters go fully to the right like is pushed to the limit -very strange to see that.So from your comments i have to measure the output level of the ,, preamp 2226'' .. if so the output needed by the 140 marantz would be 1.5 v as hifi engine says .Ill measure that as soon i finish my work :) .Otherwise ill hook up the 2235 as preamp and compare the resuts....if even that is not working, as sir wlhd1610 said,i should check the dual filter cap( if ill be able to identify this dula filter cap-hopefully )
I want to thank to everyone who post on this thread, i really appreciate your help guys.
 
Too low of signal isn't going to cause the amplifier to put out too much, as implied by the meter movement. Too much signal could do that, but that is simply a matter of using a lower setting of the preamp volume control.

1.5v is the amount needed for full rated output. For lower volumes much less is necessary.

By lowering the volume of the preamp does the amplifier behave normally or still no?
 
whoaru99 said:
Too low of signal isn't going to cause the amplifier to put out too much, as implied by the meter movement.

1.5v is the amount needed for full rated output.

By lowering the volume of the preamp does the amplifier behave normally or still no?
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The amp sounds clear, no distortion ,doesn't get hot.
At low vol the vu/merters run like they should but as soon i turn the volume round 12 o"clock doesn't happen anything volume is just slightly higher..i mean this amp is rated at 75 watt/channel at 50 percent vol should sound really really loud with these kef speakers,as a smaller amp rocks with the kef speakers.
 
I think you may have a little bit optimistic expectation.

Yes, 75 watts is more than 35 watts but the difference in sound volume will be only about 3dB more at maximum, which is only a small increase in the perception of volume.

It should not make less sound, but if you were expecting a big increase in sound level from 35 to 75 watts that will not be the case.

If you were thinking 75 watts should sound much louder because it is more than twice as much is incorrect. Twice the power is 3dB increase which sounds only a small bit louder. To sound twice as loud as 35 watts would require ten times more power (350 watts), all other things equal.
 
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whoaru99 said:
I think you may have a little bit optimistic expectation.

Yes, 75 watts is more than 35 watts but the difference in sound volume will be only about 3dB more at maximum, which is only a small increase.

It should not make less sound, but if you were expecting a big increase in sound level from 35 to 75 watts that will not be the case.
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Oh, that i did not knew :( . But one thing i can tell you: this amp sounds 3 times lower them the other marantz 2235b. Im being very very serious .That cocerns me.Sounds much much lower then even 2226.I also have one pioneer sx 737 ...This receiver has the loudest 35 watt i ever heared among with 2235 marantz.
 
Again, it should not be noticeably less loud (unless, perhaps, the other units were being driven to clipping, which can give the impression of being louder/more powerful) and this is now clean power.

Also, the volume control is not a reliable indicator of absolute output. In other words, setting the volume at 50% does not mean the unit is at "half power". The volume control (with a few exceptions) is only a relative indicator, inasmuch as 40% is more than 30%, for example.

I don't know if the unit is functioning normally or not. Only that I detected some expectations that perhaps needed clarification, and that may explain some of your observations.
 
Ok so basically at the "same SPEAKER volume" as the other stereos it distorts. And it did NOT do this prior to repair?

Did you rule out the preamp causing this?
Did you rule out the source causing this?
Did you rule out the speakers causing this? - I think you did already by using the other stereo at the "same volume".
Is this distortion the same of both channels or on one channel?
Was this there before you had the amp serviced?

Now the 140 has separate volume controls for each channel up front. Can you just use your amp and try using those as volume controls. And try that with at least two different sources like a CDP and or a tuner.
 
airtime said:
Ok so basically at the "same SPEAKER volume" as the other stereos it distorts. And it did NOT do this prior to repair?

Did you rule out the preamp causing this?
Did you rule out the source causing this?
Did you rule out the speakers causing this? - I think you did already by using the other stereo at the "same volume".
Is this distortion the same of both channels or on one channel?
Was this there before you had the amp serviced?

Now the 140 has separate volume controls for each channel up front. Can you just use your amp and try using those as volume controls. And try that with at least two different sources like a CDP and or a tuner.
Click to expand...
Hello sir, indeed before this amp was repaired, one channel was working good no distortion .Thwe other channel as soon i was turning the vol up was going into shortcut straight away.The shortcut has been found due to someone;s previous reparation at the input channel.A wire was touching the input channels with ground.Also another piece of wire hjas been found between some transistor's on power amp board.After the shortcut problem was sorted out,the bad channel started to work again.Some caps were changed on relais board.After i brought the amp home,i tested and found out that this amp basically has no power output.Today im gonna swap another preamp, and as you said ,i will test it with a cdplayer,vinyl,tuner. Another gentleman said me that could be the dual filter cap ? He means the 13 000 uf capacitor,as this capacitor gets tired after so many years of use.
 
Although it can't hurt replacing those anyway. I would recommend you replace all the capacitors on the power supply board anyway.

Are you doing the work or do you have a tech doing it and charging you?

Also you should test to see if the power supply board is putting out the proper voltages. Do you have a schematic? I'll dig one up as well.
 
Update regarding my ,,low output" of my marantz 140..ive considered changing another amplifier(2230) as preamp and indeed now i get the right power output.Ive also changed the dual cap with 2x 10 000 uf audio grade caps.Thanks everyone who posted on this thread,you've been very helpfull.All the best from me and keep up ur good work as community on this amazing site :)
 
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