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What should I watch out for with a custom SS pre + DHT (2A3/45) SET?

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Posted on August 12, 2012 at 05:35:04
Frihed89
Audiophile

Posts: 13073
Location: Copenhagen
Joined: March 21, 2005
 Is high gain, very low impedance going to present any problems to my Fi 2A3/45 monos + 94dB 2-way speakers? I have a prototype SS (opmap output) pre that sounds very good with this amp and speakers, but I didn't want to pour money into improving it, if there were problems.

Also, is there a harmonics issue?

Observe, before you think. Think before you open your yap. Act on the basis of experience.

 

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Is high gain... prototype SS (opmap output) pre WITH 2A3., posted on August 12, 2012 at 08:42:08
Chris O
 What you are going to be facing is a lot of white noise and a hyper sensitive volume control on your pre. Too much gain is bad. Your Pre is just a buffered attenuator 99.9% of the time, all the gain is wasted.

 

RE: Is high gain... prototype SS (opmap output) pre WITH 2A3., posted on August 12, 2012 at 10:38:40
tube wrangler
Manufacturer

Posts: 1362
Location: USA
Joined: January 29, 2007

That's true-- and is one of the reasons to use a passive pre of 10-15 Kilohms..

An additional issue MIGHT crop-up, that would be hum added at the amp's inputs-- from the Pre ground side-- it sometimes gets applied to the amp's ground side and ALSO makes it into the amp's "hot" input..

This COULD occur if the S/S pre has very low output impedance-to-the ground side. This connects (thru the low output impedance of the Pre) any trash that is on the pre's ground side-- although somewhat attenuated-- right into the "hot" side-- to a degree-- of the amp.

This isn't TOTAL--but it IS increased ground side distortion being applied to the SET's input.

Don't let all this theory bug you-- try it. Every system has different distortion-injection points and different possible ground loops-- you just have to "try" around..... there is probably a hookup sequence that will work.

If it performs well for you-- quit worrying.

---Dennis---

 

Thanks, posted on August 13, 2012 at 00:08:53
Frihed89
Audiophile

Posts: 13073
Location: Copenhagen
Joined: March 21, 2005
 So many possibilities to track down ground-induced hum when you have 4 pieces of gear in series.


Observe, before you think. Think before you open your yap. Act on the basis of experience.

 

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