Beomaster 8000 PHONO Noisey

Hi all,

I noticed that on my Beomaster 8000, when you are on the PHONO input (no record playing), you can hear FM transmissions leaking through and at max volume you can hear loud white noise and the FM transmissions are obviously louder. On the other inputs (TP1 etc) it's pretty much dead quiet. Only on PHONO do you get this added noise leaking in. I have had someone else test their 8000 and they have confirmed that theirs does this also. 

Is this a common issue? Any way of re-engineering this/improve on the design to eliminate this?

Its quite annoying, especially listening to quiet passages on vinyl at loud volume levels and hearing the news being broadcast in the background!! I pull the aerial out of the Beomaster, but the internal receiver is so good, I still get FM reception with no aerial even attached!! 

Any help?

I tried mine today and I don't have that problem. In my test scenario I have a Beomaster 8000 with connections from a Beogram 8002, Beocord 9000 (TP1) and an ipod (TP2). Using headphones plugged into the Beomaster, I started PH and paused it, then I cranked up the volume on the Beomaster and I couldn't hear any FM radio crosstalk at all. I also tested that my FM tuner was pulling in a station and it is working fine there.

-sonavor

Here is a link to a previous Beomaster 8000 repair on the forum where a similar problem was occurring. In your case I would probably suspect the IC202 (AD 10/278) analog switch. I'm not sure how easy it will be to find a substitute though.

-sonavor

What is your FM signal strngth meter reading on the station before you switch to PHONO? Is it high? 

I only get the FM crosstalk if a high signal strength FM station was previously selected on the radio.  If i switch to a low FM reading station, remove the aerial and then press PHONO, I don't hear the transmission. But i do get alot of white noise if turn the volume all the way up.

TP! and TP2 is silent with volume turned all the way up.

Do you get white noise as well when PHONO is selected and volume is turned up all the way?

 

Thanks

FM signal strength is irrelevant.

And yes, hiss on the phono input when volume is turned right up is normal. What you hear is the noise produced by the op-amps and resistors on a high gain stage. Line stages won't produce audible noise levels.

I don't have your issue on my two Beomaster 8000 receivers.

Are you sure what you hear is FM, and not AM?

It could be AM, I'm not sure. All I know is that I can hear some sort of transmission coming through and its usually talking, so quite possibly AM.

Does yours pickup AM? Is this normal?

It is very annoying.

My FM reception is about halfway in the strength meter. At that strength I can start hearing sound from the tuner (with the preset selected) at 0.1 on the volume dial. Decent listening level is somewhere around 2.5. If I switch to phono (PH) I don't hear any FM sound at all. Yes, there is some white noise if I crank up the volume above 5.  The same is true for the Beomaster 6000.  PH, FM and TP2 all share the same analog switch (IC202) that multiplexes the selected source through OP Amp IC5 to the second analog switch, IC4, where TP1 can be switched in. I would still suspect a problem in the analog switch. Whichever station you left on the FM tuner is going to be what is trying to go through the multiplexer switch. The strength of that source will affect the problem with the leakage through the analog switch. However, the white noise I believe is coming from the RIAA preamp circuit. You might experiment with the source volume preset pots and see how they affect the problem. It would be interesting if someone finds and tries out a substitute switch for the PH, TP2, FM source selection.

-sonavor

Thanks for that info Sonavor, very insightfull. 

I had a bit more of a muck around and it is definatly FM transmission that I am getting and it is the station I last listened to. So I have pre programmed a station that has no radio reception and press that before I press PHONO to ensure no FM crosstalk comes through.

This is only a bandaid fix though. I would like to fix this permanently. Do you have any idea where a new 21st century switch can be sourced from? Perhaps one that is even higher/better quality?

Cooker:

It could be AM, I'm not sure. All I know is that I can hear some sort of transmission coming through and its usually talking, so quite possibly AM.

Does yours pickup AM? Is this normal?

It is very annoying.

If you live not too far from a powerful transmitter it is quite possible. It also depends on the weather conditions.

Does this happen when the Beogram is not plugged to the Beomaster?

 

 

Cooker:

This is only a bandaid fix though. I would like to fix this permanently. Do you have any idea where a new 21st century switch can be sourced from? Perhaps one that is even higher/better quality?

I have done some searching for a replacement before and thought about possible replacements. A problem I have run into is it is difficult to find a 14 pin analog switch these days. There are 4-to-1, 16 pin multiplexers out there so maybe one of those types would have to be used. The solution may be to create a small board that takes a new device (probably a surface mount type of IC) and maps the pins to the pin outs on the Beomaster for the IC202. That is how Beolover made his replacement relays for the Beogram 400x turntables here.

-sonavor

Yes, definatly seems like a Beolover to the rescue situation

In my experience all this is pretty normal. When a strong station is tuned in the phono input gets some stray signal from the tuner input in the preamp section. The issue is that the tuner stays on when phono is selected. I simply program one of the presets to a 'white noise station' and select that before playing records. 

The white noise in the output at high volumes is also normal since phono has a 40dBV (100x) higher amplification than the other inputs. In combination with the high Johnson noise that comes from the cartridge and the 47k input resistor there is not much one can do. Also the surface noise from the record is much higher than the amplifier white noise, i.e. it is not an issue, really...that is just part of enjoying analog audio...;-)

Rudy