Help needed!

hjali

Novice Member
Hello all!
Please bear with me as I'm pretty much a beginner to all this.
After years and years of thinking about it, I've only recently taken my first real (albeit very, very shoestring budgeted!) plunge into the world of hi-fi.

I've picked up a very old, and seemingly equally used setup that consists of a Technics SU-V90D amplifier along with Technics SL-P770 CD player. The accompanying speakers I picked up from the same gentleman are a pair of Mission 731's.

Please correct me if I'm wrong but is this what would be referred to as a thoroughly mismatched setup? :suicide:

Anyhow, my question (for now 😅) is, if anyone could maybe help or guide me towards a straightforward yet conclusive way/method of testing out my amp (and speakers?). The problem I'm facing is that the amp and speakers sound pretty okay, until they don't! I feel like there are some distortions somewhere that I can't so easily identify. Then there are outright crackles at times that are unmissable. At other times there seem to be dropouts in one channel that come and go. Then there's the fact that I still don't know just how in order the speakers are either.

So, if you see my predicament, could anyone please guide me as to how I can further investigate and get to know this system, and try and identify exactly where the problems lie. I'm happy to DIY as I'm taking this purchase as more of a learning experience and first foray into both analogue & digital high(ish!?) end audio.

Here's how I'm listening at the moment: I'm primarily only listening through the amplifier's optical in, with output either coming from the CD player's optical, or through my TV's optical out. The TV is connected via HDMI to a Playstation 4 running spotify. Furthermore, last night I also attached another pair of speakers; a pair of Kenwood S-1M's. First on their own to compare with the 731's, and then along with them, the S-1M's being wired to the amp's "Main" channel, and the 731's attached to the "Remote" channel. Again, all playing simultaneously, they sound pretty okay until they don't.

How can I identify exactly what & where the problem(s) lie?
 
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ShanePJ

Well-known Member
AVForums Sponsor
If the crackling is happening via both the CD and TV devices, It sounds like it could be an amp issue as it seems you have tried another pair of speakers. Did you notice if it was the same channel or both channels that created the crackling sound. The obvious bits are to check the cables again, but I suspect you have already do that with you trying another pair of speakers

On another note, you should really be connecting the CD player with RCA Phono Cables and not optical. With the TV, you have used the right connection, just make sure the TV is set to Stereo/PCM so it doesn't try to output a signal the stereo amp doesn't understand
 
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hjali

Novice Member
If the crackling is happening via both the CD and TV devices, It sounds like it could be an amp issue as it seems you have tried another pair of speakers. Did you notice if it was the same channel or both channels that created the crackling sound. The obvious bits are to check the cables again, but I suspect you have already do that with you trying another pair of speakers

On another note, you should really be connecting the CD player with RCA Phono Cables and not optical. With the TV, you have used the right connection, just make sure the TV is set to Stereo/PCM so it doesn't try to output a signal the stereo amp doesn't understand
ShanePJ, thanks so much for your reply. It was both channels that would, what seemed to me, at random emit the crackling sounds. I think you may be right in that there is some possible amp issue. Could dust inside the amp be a possible cause for something like this?

Having said that, the seller has since brought me another pair of speakers. Sony bookshelves this time, I can't remember the exact model, but the result seems to be that there is now far, far less distortions/crackling sounds, if any. So, I can only assume that whilst there still remains some possible issue with the amp, the speakers definitely had some sort of problem going on.

Aside from that, thank you for letting me know about sticking with RCA cables for the CD player. Out of curiosity, why do you say that though? I ask since the CD player offers both outputs, and I assumed that the quality/resolution (probably not using the right word here) would be higher when using the optical cable. Am I wrong in thinking so?
 
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ShanePJ

Well-known Member
AVForums Sponsor
It could be that the replacement speakers are easier to drive than the first pair, but as you are saying "far less distortions/crackling sounds, if any." it sounds like it will be the amp. Its an old amp and I suspect it will not be worth repairing as it could be an obsolete component or a dry joint which requires some work

Regarding the RCA from the CD player to the Amp, usually the CD player has a better DAC built into it than an amplifier which is where the magic happens with converting that digital CD signals into an analogue signal for your amplifier

If you use the optical which is a digital signal, then this will bypass the built-in DAC inside the CD player and use the one inside the amplifier (which I mentions usually have inferior versions) and what you are trying to achieve is the best signal path to deliver the best signal to your speakers

I hope that helps
 
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