2. tech-talk
  3. 1350609378

DId lightening strike twice? Amp s problem

OK, so I'm pretty frustrated 'cause I'm not sure I believe that two amps can apparently fail (same symptoms) minutes apart. Just got a pair of Hornings from Trelja and they sound great, but I had a bit of a low hum that was just barely audible at the listening position w/o any music playing. Amp is a VAC Ren 30/30 MKIII. I check cabling, try lifting ground on the amp, plug it into my Dodd power conditioner, then direct to the wall, swap out power cords, no help. So I sez to myself, we'll see how the Hornings sound w a little EL-34 magic, so I swap in my Doshi-modified Lectron JH-50. As soon as the start-up relay closes, I get a very loud buzz!! Not a hum but a loud buzz, increasing in volume for a few seconds after the relay closes until I get to the power switch. Figuring that maybe something happened while the amp has been sitting idle for about a year, I swallow about 6 advil, disconnect the pre and the source components, shut down all of the computers, sacrifice a goat and swap the VAC back in (man, I thought that the iron on the Lectron was heavy; the VAC should come w a crane!) Hook it back up, power up and SAME F'N BUZZ. W the VAC it's a little different; you begin to hear it at very low volume while the start-up sequence is finishing, gradually ramping up until the relay closes and then WHAM. Same in both channels. The VAC has variable feedback via a rotary switch on the rear apron and if I increase the feedback, the volume of the buzz does come down a bit, but its still so loud you could never listen to music and I'm afraid it will damage the speakers. I've tried running an extension from another outlet, I've tried running each amp from the conditioner and from the wall. I disconnected the cable box from the power and the cable (TV in same room, but not interconnected to main rig). I've swapped out i/cs. I've tried it w and w/o ics connected to the amp's input(yes w speakers hooked up...I made that mistake once, years ago and learned my lesson!). Same thing. HELP!!!!!!!!!!!!!!
128x128swampwalker
hifitime
715 posts
 
Unless I'm missing it, I don't see any reference made to your swapping the interconnects with something different. They're made of silver, and break easily. I see a reference made to speaker cables (Jade Audio Vermeil), same brand, but not the Jade Audio interconnects.
swampwalker's avatar
swampwalker OP
5,138 posts
 
Hifitime- Yes, I have a full loom of Jade Vermeil. Good deduction and good idea. When swapped in the ss amp, I used the i/c that was already connected to it. I will change the i/c and report back.
swampwalker's avatar
swampwalker OP
5,138 posts
 
Changed 1/cs but as far as I can tell, that is not the issue. What seems to make the difference is changing the position on the ground switch on the Doshi Alazap pre-amp when paired w the VAC. The switch is not labeled, but toggled one way, loud buzz, toggled the other way just back to the moderate hummmm this whole episode started with. Maybe I'll swap my Lightspeed passive back in and what that does. I certainly don't need any pre-amp gain w the 96 dB Hornings.
hifitime
715 posts
 
Oh well, sorry. I was hoping that this may have been that simple item that got overlooked.
zd542
5,339 posts
 
I have the same VAC amp that your have. It's a very quiet and well made product. The only time I have ever had any noise issues is with cables that are not made well. If you can, I would try some different IC's. Right now, I have some Tara cables on my VAC (The 2). They're fine and give no problems, but I do feel the newer Audioquest products are the best shielded and most reliable of all the cables I have owned and tried, so far. I'm not saying that your cables are the issue; only that it may be a good idea to try some others and rule them out as an issue.
More to discover