Hello!
I just bought this 1978 Rotel RA-1412. Its my first vintage amp and am pretty excited. So far so good aside from a couple things. I noticed while listening through one of the headphone ports im hearing a slight hiss and some crackle pops but its not consistent... only seems to happen once and awhile for a few minutes. I dont hear it when I source isnt playing but it could be by chance.
The way im getting the source is like this: hi-res audio from Windows PC> out through an optical cable> into a newer Rotel RA12 > Pre-Out > to RA-1412 Aux in.
Any place I should look to improve the noise?
The buttons on the right side of the unit (which picks the source) are also kind of finnicky and stick. The bottom button pops completely off if I push it in all the way and I push another button above in. Anyone know where I can find the parts to replace the switch?
Thanks again for everyone's time!
I just bought this 1978 Rotel RA-1412. Its my first vintage amp and am pretty excited. So far so good aside from a couple things. I noticed while listening through one of the headphone ports im hearing a slight hiss and some crackle pops but its not consistent... only seems to happen once and awhile for a few minutes. I dont hear it when I source isnt playing but it could be by chance.
The way im getting the source is like this: hi-res audio from Windows PC> out through an optical cable> into a newer Rotel RA12 > Pre-Out > to RA-1412 Aux in.
Any place I should look to improve the noise?
The buttons on the right side of the unit (which picks the source) are also kind of finnicky and stick. The bottom button pops completely off if I push it in all the way and I push another button above in. Anyone know where I can find the parts to replace the switch?
Thanks again for everyone's time!
Usual procedure is to troubleshoot/diagnose vintage equipment due to aging components.
Cleaning controls/switches, and using test equipment to observe any issues - with - a service manual.
Loose button caps can be secured with a dab of plain white glue.
You wouldn't buy a 1978 automobile 'as-is' and expect it to perform properly and/or safely, would you?
Cleaning controls/switches, and using test equipment to observe any issues - with - a service manual.
Loose button caps can be secured with a dab of plain white glue.
You wouldn't buy a 1978 automobile 'as-is' and expect it to perform properly and/or safely, would you?
Nope definitely not 🙂 Which is why im excited to make some improvements. I also bought the matching tape deck but it has some issues with fwd and rwd and the eject mechanism but im looking forward to fixing that too.
Call me crazy, but after some observations last night I noticed whenever im moving my wireless mouse, or using the scroll wheel, that's when I hear the hissing noise in my headphones. Seems to be some kind of interference!
It IS interference.
Audio systems are prone to having strange interference problems because when they were made, there was NOT the kind of 'wireless' devices that are in use today.
Also, you are connecting that audio device to a computer - which adds to the problems. - incompatability.
It wasn't made to be connected to a computer, or even near such a thing.
Mixing modern digital with vintage audio will have such results.
If your computer has a decent analog output, I would just use that, and skip running the signal thru the RA12. I've been doing this for years without issue into an old Pioneer receiver.
As far as the noise goes, you'll really need to have the amp restored. Lots of old noisy transistors and leaky out of spec caps in there. Cool looking amp though. 👍
jeff
Hi Jeff unfortunately the PC doesn’t have analog out. I’m going to try to pick up a usb dac with analog output and see if it helps. Turns is coming from the newer Rotel as well - so something is up. Still digging.
Try going from the RA12 into the main in of the RA-1412, ie, use tone and volume control
on the RA12. If noise still present then suspect RA-1412 power amp stage. If nose disappears
then RA-1412 preamp.
Didn't see any of the usual bad actors/transistors in the amp though 2SA750 is coming under
greater scrunity (after 40 odd years!)
Noise in one? or both channels, psu issue?
You could buy a can of freeze spray if you are into diy...
on the RA12. If noise still present then suspect RA-1412 power amp stage. If nose disappears
then RA-1412 preamp.
Didn't see any of the usual bad actors/transistors in the amp though 2SA750 is coming under
greater scrunity (after 40 odd years!)
Noise in one? or both channels, psu issue?
You could buy a can of freeze spray if you are into diy...
Many recent PCs dont'have any analog outputs anymore, the headphone jack will soon be fitted only on niche/premium models. People use wireless headphones anyway, and most A/V content has moved to streaming services so analog interfaces are a issue for DRM - the PC manufacturer may be forced to pay extra royalities to fit them.
If the noise is related to mouse activity or screen refresh on the monitor, there is a good probability that the computer power supply is leaking radio frequency interference trough the ground connection, and this noise is finding its way to the input section of the vintage amplifier because it predates the EMC directive for conducted immunity that has been put in place to prevent this issue exactly. I've experienced this interference several times with tube amplifiers from the '50 and '60. It will disappear either installing a USB insulator chip between the external dac and the computer (this is already fitted inside many good quality USB DACs), or replacing the stock 19V power supply of the portable computer with another one without ground connection.
If the noise is related to mouse activity or screen refresh on the monitor, there is a good probability that the computer power supply is leaking radio frequency interference trough the ground connection, and this noise is finding its way to the input section of the vintage amplifier because it predates the EMC directive for conducted immunity that has been put in place to prevent this issue exactly. I've experienced this interference several times with tube amplifiers from the '50 and '60. It will disappear either installing a USB insulator chip between the external dac and the computer (this is already fitted inside many good quality USB DACs), or replacing the stock 19V power supply of the portable computer with another one without ground connection.
Ah, more cost-cutting, more manipulation of the population.
I heard something the other day about Apple's USB connection changeover. - another 'forced' cost on the consumer.
And I was annoyed that TV sets stopped using RCA jacks too.
My 2014 Panasonic Viera has a few, but NO audio line output - only Optical.
So...... more cost to me..... to buy an Optical to RCA converter, so I could feed audio to my stereo receiver.