[ecod123]

Belated thanks to everyone above for the inputs and suggestions. It took a little longer than expected to trouble-shoot as I tried every suggestions, except for opening up the amp as I am a little hesitant with my technical skills.

Think I may have solved the RF problem. Here's the truncated chronology of my troubleshooting path:

1. Tried swapping the tubes first. No change.
2. Bought a power conditioner. No change.
3. Bought a couple of cheater plugs and tried it but no change. And now less hairs on my head.
4. Finally gave in and rearranged the setup, moving my components from the right of the right speaker to a location right smack in between the speakers. But this also blocked the fireplace! Hopefully I can add more tube components later to provide the heat.

#4 allowed me to introduced shorter speaker cable runs. I had ordered a pair of RF shielded speaker cables and those arrived in time. And the RF noises disappeared!!! I was in blissful audio nirvana that day until night rolled in and then the radio station signal reappeared.

At that point, I was ready to throw my laptop at the components! Didn't do it because I realized it would be an expensive lesson and the ministry of finance would not have approve.

Then I noticed the lights on the wall behind the audio components - energy saving CFL bulbs. The power outlet I used was above the fireplace and right in the middle of 2 separate wall lamps with CFL. And I turned those on, as well as others in the rooms when it got dark a while ago. I turned those off and the the RF interferences were gone!!

So, I think the shorter cable length helped. The CFL probably exacerbated the problem at night - no wonder I had noticed initially that the RF noise got louder at night.

And out of curiosity, I took the tube amp to my friend place and there wasn't a RF problem even with longer run speaker cables. Something wrong with my house?? Not in the scary sense, I hope.

But at least now I can enjoy my music without subconsciously trying to listen out for the radio noise in the lulls between songs. Now that's blissful! So nice I am already thinking of upgrading to tube pre-amp and more powerful tube amp.

Yes, blissful indeed. Which would not be possible without the invaluable inputs from everyone. Thanks again!

[woofersus]

Glad it all worked out.  I've had flourescent light wreak havoc on wireless mics before, so it may be the lights themselves and not the circuit.

Those SP3's (built by Melody for Onix) were serious little overachievers, and even more so at current used prices, so it's a great entry into tubes.  Have fun!


Tim Evans
East Street Audio
Onix, Melody, & ACA

[raindance]

This was a really strange troubleshooting process. I would have looked at the speaker cables last as the input stage is high impedance and subject to noise pickup, which includes radio stations. The speaker outs are low impedance and not usually a source of noise. In your case, it may be due to coupling in the negative feedback loop, but I've not heard of a problem due to speaker cables before.

The most common source of these issues is unshielded interconnects that some folks insist on using for unbalanced audio.

Also, in order for an amp to detect a radio signal, there has to be a diode or something acting as a diode somewhere to make it happen. So I'd suggest there might be a dry joint in the feedback circuit. Do the channels have equal volume and frequency extension?

[ecod123]

This was a really strange troubleshooting process. I would have looked at the speaker cables last as the input stage is high impedance and subject to noise pickup, which includes radio stations. The speaker outs are low impedance and not usually a source of noise. In your case, it may be due to coupling in the negative feedback loop, but I've not heard of a problem due to speaker cables before.

The most common source of these issues is unshielded interconnects that some folks insist on using for unbalanced audio.

Also, in order for an amp to detect a radio signal, there has to be a diode or something acting as a diode somewhere to make it happen. So I'd suggest there might be a dry joint in the feedback circuit. Do the channels have equal volume and frequency extension?

Thanks for helping out a fellow member. Actually the troubleshooting process briefly outlined in post #21 was in response to many helpful suggestions from fellow AC members and was a follow-up to the troubleshooting outlined in post#1.

The very first thing I inititally did was to swap power cords and ICs. The ICs used included Monster, Onix, Audioquest, Cobalt, Purity Lab and lastly, Zu's Mission cable. Many of those ICs were shielded and one was touted to be designed to minimize RF interference.

I did also try all the other suggestions except for opening up the amp to find a cold joint as I was a little hesitant of my technical skills.

Based on JohnR's helpful link of the gut of the amp, I will, when time permits, investigate the the dry joint angle to determine if that's may have contributed to original problem.

 

[rivieraranch]

Remember radio signals travel farther at night. Stations have to turn down their power after dark because of this phenomenon. Also, CFL bulbs are stupid. They don't work. The ones I had in my kitchen took 10-15 minutes to come to full power - so out they went. I have some outside and in the garage and a few other places, but for a kitchen or bathroom where you need reliable light, I will take incandescent bulbs any day over these fake looking, cheesy, malfunctioning bulbs. Unlike CFL's, incandescents work.  I am hoarding them.

[Mark Korda]

Hi Ecod123,here's what happened to me.I built a Dyna -35 amp.I tore it down and started from scratch replacing every thing circuit boards,electrolytic cap,ect.I bought it on e-bay and the tubes came with it.They all seemed to light up.I did my best,trying to be as precise as possible.When I plugged it in Pat Boone was singing April Love and it hummed too.Funny thing was I had nothing hooked up to it yet,cd,tuner ect..I live in Portland Me. and knew only 1 radio station that would play that in their format,73 AM.I was pissed,so I sent it to Frank VanAlStine for fixing.Her's what he found.The new gold plated input jacks I installed,I forgot to ground,Dynas originals were grounded with out wires to the chassis.Heres another thing.I assumed the tubes that came with it were the right ones,I could not read the markings.Oh! contraire!Frank found out they were the wrong output tubes and set me up with the correct ones and my amp is been singing like a lark ever since.Nothing against Pat Boone.I hope this gives you a clue...good luck...Mark Korda

[Wayner]

Extra long speaker wires can also act as antenna elements and if the station is local, an unwelcome invitation to RFI mischief. There has been a few debates concerning lengths of interconnects versus speaker cables, provided your installation has the option to move the amp, and I'm not sure who is always the winner. It may help to go with longer interconnects and shorter speaker cables if possible.

No other ideas for you right now.

Wayner