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Audio Research SP11 question

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Posted on August 13, 2016 at 13:32:15
fredtr
Audiophile

Posts: 1987
Location: Phoenix
Joined: January 4, 2005
 Can someone tell me if Audio Research SP11 Mark II R62 (or maybe it is R82, hard to read on the schematic) should be 6 ohms, 10 ohms or 15 ohms? This is the FET bias resistor on the plate of V4 on page 3 of the schematic.

http://www.audioresearch.com/ContentsFiles/SP11%20MKII%20Schem.pdf

The schematic shows it as 6 ohms, but there is a hand written note on the schematic that points to it with the note 10 ohms || 15 ohms. It has 6 ohm resistor but it appears to be drawing too much current until V4 starts to conduct.

I e-mailed Audio Research but they aren't answering me.

Thank-you.

 

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RE: Audio Research SP11 question, posted on August 13, 2016 at 16:48:38
mondial
Audiophile

Posts: 891
Location: S.E. ASIA
Joined: January 14, 2007
 Hi

Call Kalvin at ARC Monday morning 8:30am . Im sure you'll be able to talk to him .

mondial

 

RE: Audio Research SP11 question, posted on August 13, 2016 at 17:22:38
fredtr
Audiophile

Posts: 1987
Location: Phoenix
Joined: January 4, 2005
 Thank-you Mondial, I will try that.

I remember from years ago there was a Leonard at ARC that was very helpful. Does that ring any bells?

 

I think Leonard retired... (I own a wonderful ARC SP-15) nt, posted on August 13, 2016 at 17:43:04
Smelly_Socks
 .

 

RE: Audio Research SP11 question, posted on August 13, 2016 at 19:18:55
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 10-ohms || 15-ohms means 10-ohms in parallel with 15-ohms, which equals 6-ohms. That's rather odd unless they couldn't find a 6-ohm resistor so they used a 10-ohm resistor in parallel with a 15-ohm resistor on some of their circuit boards.

Good luck,
John Elison

 

RE: Audio Research SP11 question, posted on August 14, 2016 at 06:30:06
AJ
Audiophile

Posts: 532
Joined: February 24, 2001
 I haven't looked at the schematic -if the value is correct what they were likely attempting is to get the correct power dissipation by paralleling multiple resistors. The single resistor may not be able to handle the current dissipation requirements.

 

RE: Audio Research SP11 question, posted on August 14, 2016 at 10:41:21
fredtr
Audiophile

Posts: 1987
Location: Phoenix
Joined: January 4, 2005
 AJ thank-you for responding. There is a single 6 ohm 1/2 watt resistor which sets the bias for the FET so negligible current.

 

RE: Audio Research SP11 question, posted on August 14, 2016 at 10:49:10
fredtr
Audiophile

Posts: 1987
Location: Phoenix
Joined: January 4, 2005
 Thanks John, I didn't think of that.

 

RE: Audio Research SP11 question, posted on August 14, 2016 at 20:34:20
mondial
Audiophile

Posts: 891
Location: S.E. ASIA
Joined: January 14, 2007
 Hi ,

Leonard Gustafson was the guy who was very knowledgeable of all the early ARC products. He was my tour guide when I had a ARC factory tour back in 2007. His retired already and Kalvin was the guy who took his placed.

Mondial

 

RE: Audio Research SP11 question, posted on August 15, 2016 at 17:52:05
fredtr
Audiophile

Posts: 1987
Location: Phoenix
Joined: January 4, 2005
 John, you are right. ARC shipped some units with 15 and 10 ohm resistors in parallel. Thanks again.

 

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