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JohnJ

Understanding THD in tube amplifiers

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Ski Bum    308

Probably a simple ground loop, due to adding the new piece of kit to your rig, rather than the hum coming from the processor itself.  Check that first.  

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JohnJ    411

Always check ground before doing anything with something with current! Yea the ground wire from the phono had no place to connect on the new iTube 2. It's substantial aluminum to act as a heat sink for the tube. Never a place on the amp or anywhere, I've been cheating and screwing it onto the chassis of my C-300 cassette deck for a long time. That kept me from having any issues when using the phono internal preamp. Incoming unit has a post for the phono ground! Hope this one works, two strikes already!

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seti    224

I've tried amplifiers that by the specs and extremely low THD should have sounded amazing only to rip them out after a few days of listening. Among a few I tried were NAD and Tripath but I couldn't do it for long.  Tripath was just terrible. There is indeed more going on than specs suggest.

 

 

 

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JohnJ    411

Found the issue and I've decided how to remedy it for now. My turntable that I read about at an audiophile site that "Someone at Audio Technica" told him "totally removed the internal preamp from the signal path in this AT-LP5 as opposed to the previous AT-LP120" DOES NOT function that way. 

After Plan C produced a much worse humming / buzzing I called Audio Technica here. The tech gave me that info. The Pro-Ject Tube Box DS produced a massive increase in S/N ratio set at the middle of three choices compared to the first two. That increase accounts for hearing more of the issue I suppose.

Sometime in the future I might replace the whole tt setup but right now I will return an iTube2 to the signal path. The hum/buzz it created I did have to turn it up more to distinguish. In a year I might try to part with the analog side of things here unless someone makes me an offer! :rolleyes:

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HDBRbuilder    576

Does your amp have a wall plug that can be inserted either way (i.e., both spades on it are the same size???)  If so, then just try the old-school simple fix:  unplug it and plug it back in with spades in opposite wall receptacles holes.

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JohnJ    411

Good thought but no, all this equipment except the dinosaur cassette have the new type plugs. We outfitted the house with those kind of sockets a decade ago. Stereo is on one of the three pronged outlets that are actually prevalent here. 

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seti    224
On 9/21/2017 at 12:37 PM, JohnJ said:

Found the issue and I've decided how to remedy it for now. My turntable that I read about at an audiophile site that "Someone at Audio Technica" told him "totally removed the internal preamp from the signal path in this AT-LP5 as opposed to the previous AT-LP120" DOES NOT function that way. 

After Plan C produced a much worse humming / buzzing I called Audio Technica here. The tech gave me that info. The Pro-Ject Tube Box DS produced a massive increase in S/N ratio set at the middle of three choices compared to the first two. That increase accounts for hearing more of the issue I suppose.

Sometime in the future I might replace the whole tt setup but right now I will return an iTube2 to the signal path. The hum/buzz it created I did have to turn it up more to distinguish. In a year I might try to part with the analog side of things here unless someone makes me an offer! :rolleyes:

 

Very nice. Good research. Troubleshooting can sometimes make me crazy... crazier...

 

 

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JohnJ    411
10 hours ago, seti said:

 

Very nice. Good research. Troubleshooting can sometimes make me crazy... crazier...

 

 

Yep, and it's always nice to get to the root of the issue!

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