Hi everybody,

First of all, I'm Dutch. English isn't my arterial language, so if I screw up a sentence or two it's not because I'm stupid or dyslectic, it's just because I'm Dutch .

I'll first give a little background story about this old Rotel amplifier. If you don't care about it, you can just skip all of the following text and start reading again below the dotted line...

In the early 70's, right after my parents got married, my dad decided he wanted to have a good stereo setup, to fully enjoy his classical music.
So he bought the Rotel RA-611 amplifier, together with the matching Rotel tuner, a Dual 1219 turntable and a pair of Sonab Carlsson OA-5 TypeII speakers. A few years later he added an Akai GXC-715D cassette deck.
When CD's came into the mainstream market he bought a CD-player and a new amplifier, a digital tuner, and a double cassette deck. Since then, the Rotel amplifier and tuner and Akai cassettedeck have had several owners, but they always stayed in the family. About 10 years ago they got into my possession. A few years later I also got the Sonab Carlsson speakers.
I lend the Rotel tuner to one of my brothers, because I have no use for it, and he uses it every day, to this day. The Akai cassette deck was in frequent use, up until three months ago, when the left channel suddenly stopped working. I stopped using the Sonab speakers about four years ago, because they have aged very badly and started to sound dreadful. My dad still owns and uses the Dual 1219 turntable.
The Rotel amplifier has spend the last eight years in storage up in the attic, wrapped in plastic, until I recently 'discovered' it again. Since I was looking for a radio to use in my kitchen, I though: "Hmm, why don't I put that old Rotel to some good use?"
So, I hooked it up, plugged it in, and it worked brilliantly.

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However, I noticed there are two slight problems with it. Aside from it's poor cosmetic condition (all the writing around the rotary-switches have faded it away, so I had to look up pictures on the internet to find out what each of the three switches do) it has quite a strong hiss and it makes a very loud 'plop' noise over the speakers when you turn it off.
Now, the hiss is quite hard, but when listening to music isn't really noticeable. It's only evident during quite moments. The hiss is constant, it doesn't react to the volume knob. However, when I press the high fil switch the hiss almost disappears. Same happens when I slide the treble-switches all the way down. But then again, the hiss isn't that bad, and if I remember correctly, the hiss was one of the reasons my dad decided to retire the amplifier in the early '90's to begin with. So that's no biggie.

The thing that worries me the most is the very loud 'plop' sound it makes when you turn it off. When I look at my speakers, the woofers can be seen moving very violently when they make that 'plop' sound. I'm concerned it might damage them in the long run. So, I currently turn the speakers switch to 'off', before I shut down the amp, but I sometimes forget, and when I do the sound makes me jump in the air, because it's so loud and sudden.

So, my question is: Does anyone know what causes that loud plopping-noise when I turn the amplifier off, and is there an easy fix for it? I'm not a real hero with a soldering iron, but I'm willing to give it a try.

Oh, and here's a pic of the amp & tuner:

Those in the picture aren't mine, although my tuner has got the exact same bulb burned out. My amp looks a lot worse. And for some reason my amp doesn't say "ROTEL" on the front, but "REC".

Does the 'pop' occur a few moments (a second or so) after switch off? If so, it could be something to do with the mains transformer(s) discharging (if that's the right word). I think it's the transformers in my phono stage that make a sort of popping sound as they power-down.
If there's any validity in that theory, I have no idea if the pop is avoidable.

DF

P.S. "arterial language" - excellent turn of phrase. Language coarsing through our veins.

Thanks for your reply, DocFoster.

The plop occurs at the exact moment I press and release the on/off button.

Since you are thinking it might be unavoidable, I was wondering: Would it also have made that 'plop' when it was new? Is this 'normal' for a vintage amp?

P.S. Suddenly felt the urge to pump Alice Cooper's "Poison" through the old Rotel.

Don't ask me how, but the Rotel is working fine again. It still makes a 'plop' when you turn it off, but it's very soft now. After the 'plop' the sound slowly fades away.

Maybe it's because it hasn't been used in years, and it's now powered on almost all the time that it suddenly decided to work a little better?

The hiss is still there though, but I don't care about that.

DF

It's been a while, and I know it's not polite to be kicking up such an old topic, but I just wanted to say:

Wow!!

The Rotel is still very much alive and kicking. I just hooked it up to my headphones for the first time, as I'm working on my laptop in the kitchen now and it's night. I'm completely baffled at the clear sound it's giving!
In the kichen I have it hooked up to two pairs of very cheap speakers, and the sound isn't that great (good enough to listen to while cooking or as background music while working, but that's about it).
But now, blasting through my headphones this is truly amazing! And I'm using my laptop with it's crappy soundcard as the source, and it already sounds way clearer and better then the Sony STR-DE425 amp I have in my livingroom.

I might hook this old Rotel up to the JBL-speakers in the livingroom, to see how THAT would sound! I think this antique Rotel will kick my Sony's ass!

I have experianced the same beautiful clear sound from a secondhand Rotel RX-603 interestingly this also has the hiss that disapears when the high filter is switched on. A friend of mine(electrical engineering student) says that this is a result of not having a turntable pluged into the phone input but seeing as I don't own a turntable i have never tested this

@Ajarb
Honestly, I think that our amps are at the moment nowhere as good as they once were. They're almost 40 years old, and I think the capacitors and other stuff have aged. That's probably where the hiss comes from. As I will never throw this Rotel away, I'm seriously considering to letting it getting restored to it's original condition and running on full specifications again. The Rotel deserves that. If it sounds this good while being worn, just imagine what it would sound like when restored!

I've got another amp to use in my kitchen. It's a Denon PMA-860 Optical Class-A amplifier. Sounds pretty awesome.
The Rotel has claimed it's rightfull place in my livingroom as my headphone amp.
No speakers attached to it, speakerswitch on off. Looped through my Sony amp, by using the Sony's rec-out into the Rotels' aux-in.
For movies and surround sound I use the Sony. For my headphone listening I use the old Rotel.
Might consider switching the Sony for the Denon in my kitchen, but the Denon is lacking a remote control, which I find pretty annoying in my livingroom.
Tried the Rotel, but it misses the power to drive the four JBL-speakers. It lacks the 'oomph', that both the Sony and Denon have got.
Still though, that Sony has to go. The old Denon and antique Rotel are kicking it's ass!