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Sherwood 7100 receiver

75.56.50.236

Posted on July 10, 2011 at 20:07:21
Tadlo
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Posts: 1925
Location: midwest
Joined: March 8, 2003
I picked up a Sherwood 7100 at a garage sale Saturday. I used to own a 7100A. What exactly is the difference between the 2 models?

 

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RE: Sherwood 7100 receiver, posted on July 11, 2011 at 13:26:38
Bold Eagle
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Posts: 6936
Location: America's Heartland
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Don't hold me to this, it has been a looong time; but didn't the A denote a Dynaquad connection?

Jerry

 

OK OK I found the references, posted on July 11, 2011 at 15:41:29
DavidLD
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Joined: May 29, 2002
The original 7100 had output transformers whereas the 7100A was a direct coupled design Reference : http://www.head-fi.org/forum/thread/56962/71-sherwood-s-7100a-as-an-amp-for-hd600s

I vaguely recall a discussion we had on that subject here on Vintage years ago

Output power also went up. The number I am seeing tossed around for the original 7100 on the Internet is about 18 wpc rms both channels driven. I have no independent verification of that but I think that is close. My trusty Stereo Review directory from 1974 lists the rms power for the 7100A at 22 wpc at 1 Hz RMS for each channel with both channels driven. I think the 17 wpc number in the reference above is wrong or perhaps over a wider frequency range. My 1974 directory indicates all Sherwood receivers from that year were direct coupled.

David

 

Interstage not output transformer, posted on July 12, 2011 at 02:45:46
DIY John
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RE: "The original 7100 had output transformers"

I think if you study the schematic, you will find that the original 7100 had interstage transformers to split the phase and the output transistors were directly connected to the speakers. The 7100A had no interstage transformer.

 

RE: Interstage not output transformer, posted on July 12, 2011 at 05:01:27
DavidLD
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I knew you engineering guys/schematic readers would be able to fill in the details as to the differences in the 7100 vs 7100A once prodded. IIRC a conversation that took place here years ago claimed that the 7100 and 7100 A were quite different beasts not only with respect to cosmetics (ie the switch types mentioned in the linked post) but also elements of the basic internal design, and one consequence of the changes was that the 7100A produced more power than the 7100 did.

It appears to me that Sherwood first introduced the direct coupled design in the US-made S-7900 and S-8900 models. This was then followed with the introduction of lower powered versions with the Japanese-made S-7300 being next, the S-7200, and then the S-7100A which replaced a non-direct coupled S-7100. My 1974 directory even lists an inexpensive (under $200) direct coupled S-7050 model rated at only 10 wpc rms.

Sherwood always was very conservative with their power ratings, and in many instances you could add 5 or even 10 wpc to the advertized power rating to get a comparable figure from many of the other manufacturers. All the Sherwoods, even the low-end models, had excellent, very sensitive FM tuners. That there are as many as there out there still functioning is a tribute to their solid engineering and basic build quality whethere made here or in Japan. All in all a great vintage brand even if not quite as popular among vintage addicts today as Marantz or Pioneer of the same period.

 

RE: Interstage not output transformer, posted on July 12, 2011 at 05:20:12
Tadlo
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Posts: 1925
Location: midwest
Joined: March 8, 2003
I had a 7100A until about a year ago when I gave it away. The 7100 that I picked up last week is cosmetically indistinguishable from the 7100A (except for the lack of the 'A' on the nameplate). When I tried it out the sound seemed much warmer and less transparent and crisp than I remember the 7100A being, and I suspected that it might not be direct coupled.

 

RE: Interstage not output transformer, posted on July 12, 2011 at 16:37:36
Palustris
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Location: Cape Cod
Joined: September 12, 2008
That makes more sense.

 

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