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An issue with vintage amplifiers

João Henrique Jr.

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Jun 2, 2020
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An issue occurs when I hear music from the CD player through my older amps (from the mid-70s). It's a kind of distortion on certain snatches (not the whole records), as if those passages are partially saturated with sound. (Sorry, it's not easy for me to describe it in English.) The same CDs sound allright when I play them on the notebook (connected to the same amps, of course). Since the notebook is of a younger generation than the CD player, my first guess is that its internal DAC is more refined. But I may be wrong.
I’ve just ordered an external DAC on Amazon, my first one. I'm still waiting for it to arrive, hoping it’ll correct the trouble.
Reading the article How to get the best sound from your CD player (K. Bharadia) yesterday, I've found this: "If you're using a vintage amp built before the CD age you may have some issues, but a simple modification will sort them out." Seems like the author is speaking about the above mentioned issue. So, does anybody have any suggestion about it? What could be that modification?

Best regards - João Henrique
 

12th Monkey

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Aug 31, 2015
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Does the problem happen during loud sections (is that what you mean by saturated)? The signal from the CDP is analogue by the time it reaches the amp, so I can't imagine that it's anything to do with it being from CD. It may be that the CD's output is too high for the amp's input, and that some attenuation (reduction of output voltage) might help - I would think this would be most apparent during louder sections of songs.

If this is the case, attenuators can be bought for comparatively little - search for Rothwell attenuator on Amazon.
 

João Henrique Jr.

Active member
Jun 2, 2020
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Thank you for answering, 12th Monkey. That's it, distortion occurs mostly on louder passages. I've noticed it first on some mellotron laden Moody Blues passages. The same problem doesn't happen on my more modern amps, less powerfull than the older ones, and with less input sensitivity. (But I don't know if this has anything to do with the matter).
Thanks for the suggestion, I've never heard about attenuators before. This DAC I've ordered has volume control, so if this won't solve the problem, I'll consider installing attenuators.
 

Gray

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Nov 27, 2015
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The same problem doesn't happen on my more modern amps, less powerfull than the older ones, and with less input sensitivity. (But I don't know if this has anything to do with the matter).
It's got everything to do with the matter João (y)
It's the high input sensitivity that makes the older amp susceptible to overload from the high output of the CDP.
 
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12th Monkey

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Aug 31, 2015
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Thank you for answering, 12th Monkey. That's it, distortion occurs mostly on louder passages. I've noticed it first on some mellotron laden Moody Blues passages. The same problem doesn't happen on my more modern amps, less powerfull than the older ones, and with less input sensitivity. (But I don't know if this has anything to do with the matter).
Thanks for the suggestion, I've never heard about attenuators before. This DAC I've ordered has volume control, so if this won't solve the problem, I'll consider installing attenuators.
If the DAC has a volume control, that should help - play the offending pieces and reduce progressively until the issue goes away.
 

João Henrique Jr.

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Jun 2, 2020
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Thanks everybody, it's been very instructive.
The CD player is a Sony M27 (1989! Not much used and still working).
If the DAC shouldn't eliminate all the noise, next step will be the attenuators. I'll discuss the matter with a friend who builds his own amps and pre-amps, and upgrades old ones.
 

Dom

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So what do I do with my day? Mostly skateboard, but also listen to music. Life is hard and I have been running away from it my whole life. I think communication is our greatest achievement. :love:
 
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gasolin

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The CD's output is too high for the amp's input is not a vintage thing, it also happpens with alot of amps fra the 80's ,90's 2000, 2010 and still occours in 2020 with many new amps and cd combos.

Theres hardly any problems with a turntable regarding output being too high
 
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TrevC

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Jun 12, 2013
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The CD's output is too high for the amp's input is not a vintage thing, it also happpens with alot of amps fra the 80's ,90's 2000, 2010 and still occours in 2020 with many new amps and cd combos.

Theres hardly any problems with a turntable regarding output being too high
The majority of modern amps have no amplification at line level before the volume control because modern semiconductors are vastly superior noise wise. That's why they don't overload.
 

DougK

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Dec 8, 2013
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The majority of modern amps have no amplification at line level before the volume control because modern semiconductors are vastly superior noise wise. That's why they don't overload.
? ? Explain gain/input sensitivity on an amp to me then please. Or do these have nothing to do with overloading?
 
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João Henrique Jr.

Active member
Jun 2, 2020
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The CD's output is too high for the amp's input is not a vintage thing, it also happpens with alot of amps fra the 80's ,90's 2000, 2010 and still occours in 2020 with many new amps and cd combos.
The majority of modern amps have no amplification at line level before the volume control because modern semiconductors are vastly superior noise wise. That's why they don't overload.
These I've discovered right here on the thread.
 

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