Loud hum in Beepre

[Jeroen]

Hello Paul,

Without the tubes I measure 172,7 v on the left side and 175,2 v on the richt side.

Best Regards,

Jeroen

[Jeroen]

Ignore my last post, those were the OA voltages.

(it's getting late here in Holland and I'm getting sleepy)

The IA voltages are; 177,7 v on the right side, 177,8 on the left side.

Cheers,

Jeroen

[Doc B.]

There is a fundamental issue here that does not seem to have been addressed. From the photos we can see that this preamp is not stock. It looks like the pot or pots and the jacks have all been changed from stock. Every one of those parts has a connection to ground. Anywhere that a ground has been incorrectly connected there is the possibility of a hum issue. Without us being able to know how the non stock parts have been connected it is not really possible to offer a solution based upon our experience.

My suggestion is to reconfigure the preamp into its stock configuration. You may find that the hum issue will be solved. From there you can methodically change one thing at a time to be sure your changes are not adversely affecting the performance of the circuit.

[Jeroen]

Hello Doc,

Thank you for your response and advice.

The hum problem has likely been solved.

It wasn't a ground hum, so the problem wasn't in the little ajustments I did nor in the ground wiring.

The amp was getting not enough AC voltage sometimes. The AC voltages at our home are varying between 223 and 225 volt. With 225 volt the amp works fine without hum, but as soon as the AC voltage drops the amp produces a loud hum. The filament regulator boards were getting not enough power to regulate the current propperly.

I will wire a power transformator (between AC outlet and amp imput) to raise the imput voltage with 12 volt.
Hopefully that will do the job.

Keep you updated!

[Jeroen]

A couple of months ago I finished the Beepre amp, wow what a great amp! Incredible soundstage and a lovely smooth sound, I love it!

Before I could play music with the amp I had to raise the AC voltage to let the regulator work properly. (see previous posts).

By the time I finished the amp the AC voltage at our home was somewhere between 223 and 225 volt. I raised the voltage going to the amp by 12 volt, to get 235, 237 volt. This way the amp works well, although the amp is getting hot.

Lately the AC voltage at out home sometimes drops to 218 volt. When this happens the amp starts to hum very loud. I'm thinking of raising the voltage by 20 volt to tackele this problem. But when the AC voltage at our home is 225 again the amp will get 245 volt.

Could I hurt the Beepre with 245 volt?

Best Regards,

Jeroen

[Grainger49]

There are what is called a constant voltage transformer.  It includes a tuned circuit, lots of reactance that keeps the voltage at the specified voltage. 

You could get one of those or a power regenerator and set it to 240V.  Either way the voltage to your stereo will not vary.

Sorry, but neither answer is inexpensive.  Well, not to me.

[Paul Birkeland]

245V is not an issue on the 240V transformer.

-PB

[Jeroen]

Hi Paul and Grainger,

Thanks you for you response.

I'm a bit reserved using a constantant voltage transformator. I tried a isolating transformer on the Beepre to filter out trash coming with the AC current. It made the sound completely dead.

Glad to hear I can use 245 volt. Could you give an indicating how much power the Beepre is using? It helps me picking a suitable transfomer.

Thanks in advance.

Best Regards,

Jeroen

[Paul Birkeland]

I suspect that the BeePre is somewhere around 60VA, as always, leave a bit of headroom (so maybe 70-100VA).

-PB

[Jeroen]

Dear Paul,

Thank you for your response. I've just found a transformer that will do the job.

I will post some pictures of the finished Beepre soon.


Regards,

Jeroen