Snap, crackle & pop @ turn on

[JimJ]

Like I said on SIN, the only "issue" I'm having with the SV811-10 monos is a crackle and static when first turning one monoblock on. It does it even with the volume turned all the way down on the preamp, and it's a consistent volume. Only does it when the amp's been sitting for a while unused - when I quickly cycle the power, it doesn't crackle.

It's a minor annoyance, but it's something I'd like to fix if it's possible...Mike, any ideas about how I could go about solving this? I'm thinking it's a cap problem of some kind...but I'm apprehensive about changing caps in this thing, they're huge.

Thanks in advance.

[JimJ]

Nevermind, figured out what was going on...noisy power tube in the left channel. Swapped it out and the other one was popping and crackling...bingo.

Just glad it's not something in the amps themselves.

[JimJ]

And of course, Parts Express is backordered on SV811's until 5/18. Wonderful...guess I can start work on the wooden bases for them in the meantime.

[MikeS]

Tell Parts Express that one of those SV-811's has a wanked cathode/filament structure and it's basically fried. See if they will replace it......they should if it's still under warranty.

I bought a NOS Sylvania 5930/2A3W from a online site for 80 bucks.
Worked great for about a month until the warranty was void.
Then the 5930 did the same thing you described, static noise with mild pops, comes and goes, and then stays......lame.....and I had to eat it....

Bought a pair of Sovtek 2A3's for a little over 60 bucks and they still work fine.

[JimJ]

Well, they seem to be in stock with singles, so I might as well just order two individuals. Matching isn't as important with the power tubes as it would be with the driver tubes anyway...I can live without perfectly matched outputs.

[MikeS]

Well, they seem to be in stock with singles, so I might as well just order two individuals. Matching isn't as important with the power tubes as it would be with the driver tubes anyway...I can live without perfectly matched outputs.


Considering the amps are monoblocks, I would think you would be hard pressed to hear a 5% emission difference between each output tube in each amp.

Maybe 10 or 20%.......but then you would have to question how parts express is testing the damn things. Like what's the limit of transconductance they are letting slide by.

I don't think Sovtek makes the SV-811 (there were 2 types) anymore.
Parts Express musta picked up a shitload of 'em, because they are pretty much it.
Sometimes they pop up on eBay, or on other online sites for they same price or more. They were 40 bucks a pop, but I think they jacked up the price.

If they were a little cheaper, I'd jump on a pair. 8, 10 watts of directly heated thoriated tungsten triode should sound rather nice.

I have re-register on SIN, but I did see the pics of your SV-811 amps.

I see the 10,000 mic, 16 volt capacitors.......those must for the SV-811 filament. Appears to be a SS rectified HT supply by the lack of a rectifier tube.
The driver tube looks like a disimiliar octal triode or something, 6EM7/6EA7?
(Have I seen a SV-811 amplifier schematic driven by a 6EM7/6EA7 on the net somewhere?........)
Rather beefy output transformers, looks like Hammond.

So what's the bass like on those amps? I guessing you listened to at least one with the good tube on your Klipsch.

I haven't had a tube amp yet that was SS rectified or DC heated, they all are AC heated with rectifier tubes.

But I have a pair of 7.5 volt RCA 801A's with thoriated tungsten filaments I wanna use......I need to sit down and build a well-filtered DC supply for the filaments.
Plate voltage is only 400-500 volts, I'll swing that with a tube rectifier, or a pair of half-wave damper tubes.
3.8 watts per side would be plenty in this pad, and the light bulb effect would be novel.....

Nice amps.

[JimJ]

I've heard various things on USENET, as of 2004 they seem to have been manufacturing them, but not distributing under the SED name with the rest of their tubes. Would make sense why PE and another plcae that sells the low mu version (http://www.audioelectronicsupply.com/) can restock them. Just seems to have completely gone under the radar, though...

I know they don't make 6EA7's anymore new, but there are approximately eleventy billion and one available on the used market for the price of a good burger, so I'm not worried about the availability of those.

[MikeS]

I've heard various things on USENET, as of 2004 they seem to have been manufacturing them, but not distributing under the SED name with the rest of their tubes. Would make sense why PE and another plcae that sells the low mu version (http://www.audioelectronicsupply.com/) can restock them. Just seems to have completely gone under the radar, though...

I know they don't make 6EA7's anymore new, but there are approximately eleventy billion and one available on the used market for the price of a good burger, so I'm not worried about the availability of those.

Interesting about the availibility of the SV-811. Maybe I should by a pair when I'm more flush. Either that or follow through on the Aikido 6SN7 linestage project....but then I kinda like the sound of the 12B4A as a linestage....thermionic brain damage.......

Yup, the 6EA7 was a television tube and there is quite a few around still, but tube audio dorks do know about them.
They are a very linear tube with low distortion, I don't think there is euro version. Never heard 6EM7.....
How many disimiliar triode tubes can drive itself?

Where can you get a 6EA7 for the price of a good burger? I need a spare pair for my 2A3 amp.....RCA 6EA7 would be prefered.

[JimJ]

Not sure about RCA, but Ebay has quite a few...NOS GE's mostly I think.