Puzzling problem with 6SN7 adapter

[adamct]

OK, someone help me out. In January I bought one of those 6SN7 --> 12AU7 adapters on eBay. I got the one that appeared to be high-quality, with a nice ceramic socket and gold-plated pin holes. I think several others here have the same adapter. I made sure I got the 6.3V version. When it arrived, I tried it out with a couple of 6SN7s, but they all seemed noisy, although they were quiet in other amps. I chalked it up to some sort of bad "synergy" between the tubes and the Crack (w/ Speedball). I put the adapter to the side for a few months, until I got a couple more 6SN7s. Again, I pulled the adapter out and tried them with the Crack. Still noisy. Then I decided it must be the adapter. I contacted the seller, and although I was outside the complaint period, they gracefully sent me a new one at no charge (fast shipping from China, too, which is unusual). Tonight I try out the new adapter and...same problem.

Here is the exact situation: the noise is stronger in the left channel than the right. Much stronger. At low volume levels, the noise changes with the volume pot, but quickly hits maximum noise levels and stays constant after that. The tube plays music just fine - no cracking or popping or anything, just noise when I hit pause. My Crack is literally DEAD SILENT when I use it with my other input tubes, without an adapter. The noise doesn't change when I jiggle the RCA inputs. There shouldn't be any interference from other devices, as there aren't any nearby, and (again) the amp is quiet with other tubes. And the noise is the same no matter which 6SN7 tubes I use.

Anyone else have a similar experience? If so, how did you solve it? I know some people like 6SN7s with the Crack, but I can't imagine anyone would find this level of noise acceptable, so what I have must not be normal. Suggestions? What could be causing these problems?

Best regards,
Adam

P.S. I have heard from at least two other people who have had a similar problem, and were also unable to solve it. Is the 6SN7 just not suitable for the Crack? Is the adapter design somehow defective? Is anyone using 6SN7s via adapter without any noise?

[Paul Birkeland]

The 6SN7 works well in the Crack, I have used them plenty of times.  Ultimately, it may be easiest to rewire the Crack to use the 6CG7/7AU7, or perhaps to try a simple 6.3V DC wall wart to power the heaters on the Crack to see if the AC that heats the tube is radiating to other parts of the tube in the adapter.

-PB

[adamct]

Thanks, Paul. I might wind up trying an adapter from another vendor... 

[Aeolus Kratos]

Hi Adam,

I assume you ordered this adapter, right? http://www.ebay.com/itm/1x-6SN7-to-12AU7-Vacuum-tube-adapter-socket-converter-/300943315564?pt=Vintage_Electronics_R2&hash=item46119e926c

Try this one : http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=320659633166&ssPageName=STRK:MEWAX:IT#ht_1080wt_793

It looks cheaper and not as 'well-made' as the one you ordered, but it works well

Best regards,
Kratos.

[adamct]

Dadgummit, Kratos, where were you 30 minutes ago?!?  . I just bought one of these.    And you are right about the two that I currently have. I'll try the new one, and if that still doesn't work, I'll go for yours. Fourth time is the charm, right?

[dubiousmike]

Adam - I assume you may have already seen my posts in the other 6sn7 adapter thread?  I first bought the adapter Kratos linked - which had exactly the same issue you describe in your OP (bad noise in one channel that increases with the pot). Then I bought the lowtherclub version you just ordered. It is the lesser of the two evils but still has a bit of noise in both channels.

Personally I'm throwing in the towel and will stick to buying more 12au7s and 12BH7s in the future - which all run dead quiet in my crack.  Hope your second roll of the dice on an adapter goes better than mine did.

[adamct]

Thanks, Mike. I'm inclined to agree with you...

[Aeolus Kratos]

Dadgummit, Kratos, where were you 30 minutes ago?!?  . I just bought one of these.    And you are right about the two that I currently have. I'll try the new one, and if that still doesn't work, I'll go for yours. Fourth time is the charm, right?

Haha, yeah, you're right. I have not tried any tube adapter that you ordered, but I hope that you won't need to go for the fourth tube adapter to enjoy the fantastic sound of the 6SN7s on the Crack

Best regards,
Kratos.

[adamct]

The best part of all this is that I have no idea why I'm doing it, other than boredom. I love my Crack with 12AU7s / 12BH7s, tube rolling is not fun for me, and I don't really want to get into the morass of 6SN7s...

LOL --- we'll see. Maybe I'll be singing a different tube if I finally get an adapter that works...

[Aeolus Kratos]

The best part of all this is that I have no idea why I'm doing it, other than boredom. I love my Crack with 12AU7s / 12BH7s, tube rolling is not fun for me, and I don't really want to get into the morass of 6SN7s...

LOL --- we'll see. Maybe I'll be singing a different tube if I finally get an adapter that works...

Tube rolling is one of the most fun and additive things in my audio passion, I enjoyed this as much as 'rolling' headphones or DACs :p

Good luck with your coming tube adapter!
Kratos.

[adamct]

Maybe I'll be singing a different tube if I finally get an adapter that works...

That was not intentional, but it is one of the funniest Freudian slips I've seen...

[2wo]

It may not be a problem with the adapter per say, but the fact that it adds extra wire, connections, stray capacitance and just more stuff to pick up noise...John

[adamct]

If that's the case, then I wouldn't expect anyone to be able to run 6SN7s via adapter without picking up plenty of noise. I've heard people say they were using adapters and had zero noise. Frankly, "zero" can me something very different depending on who you talk to, but the noise I've experieed with two adapters so far wouldn't fit into anyone's definition of zero noise...

[adamct]

The 6SN7 works well in the Crack, I have used them plenty of times.  Ultimately, it may be easiest to rewire the Crack to use the 6CG7/7AU7, or perhaps to try a simple 6.3V DC wall wart to power the heaters on the Crack to see if the AC that heats the tube is radiating to other parts of the tube in the adapter.

-PB

So, my Lowther Club adapter arrived yesterday. It is a considerable improvement over my other two adapters. I was able to listen to one of my 6SN7s that I have been eager to hear in my Crack and actually here the 6SN7 / music, instead of just hearing static / noise. What I heard was very promising. Maybe even enough to make me eat crow and admit that tube rolling makes more of a difference than it has with the other XX tubes I've tried. But ultimately, there is still noise at an unacceptable level. During moderate to loud music passages, it isn't noticeable, but on quiet passage it intrudes. I have gotten used to my Crack being dead quiet and can't go back. So I either need to buy yet another adapter and knock on wood, or try your suggestion, PB.

What would I have to do to make this work? Will any 6.3V DC power supply work? Does it have to be exactly 6.3V or will 6V or 6.5V also work? Does it have to be linear? Regulated? Current rating? Where do I attach the leads, and what wires do I need to cut / desolder?

[adamct]

Also, what did you mean by wire the Crack to use 6CG7/7AU7?

Thanks in advance,
Adam