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Adcom-- which preamps are Nelson Pass?

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Posted on June 15, 2010 at 15:43:23
DaveD
Audiophile

Posts: 63
Location: So. Indiana
Joined: October 13, 2002
Adcom junkies-- I have read that the GFP-555 preamp was designed by Nelson Pass, and that he considered offering mods for it but has not done so.

Are the GFP-555II and GFP-565 also his designs? Has one of the three proven more reliable or better sounding in their senior years? I have seen in the owners manuals that the 555 bass control is centered at 40Hz, which would be just fine for my system. The 565 and 555II bass control is centered at 20Hz, which would be too low in my case.

I am considering one of these in the event that my Hafler 915 gives up the ghost, or as an upgrade if they would be better performers.

 

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RE: Adcom-- which preamps are Nelson Pass?, posted on June 15, 2010 at 16:07:06
djk
Manufacturer

Posts: 5682
Joined: June 17, 2000
Pass had design input on the GFA555, but as far as I know, no input on the preamps.

Having been a bit of a designer myself, you give a company a design a for a Corvette, the product they actually build more resembles an Edsel.

You can ask over at DIYaudio.com in the Pass section if you want specifics.


Not 2 Big 2 Jail

 

Short answer - zero, posted on June 15, 2010 at 17:00:02
E-Stat
Audiophile

Posts: 19981
Joined: May 12, 2000
Contributor
  Since:
April 5, 2002
Pass is a power amplifier designer and relies on Wayne Coburn today for the phono/line stage designs at Pass Labs.

rw

 

The GFP-750 preamplifier......, posted on June 15, 2010 at 17:52:08
kootenay
Audiophile

Posts: 5090
Location: Calgary, Alberta
Joined: October 16, 2007
Contributor
  Since:
April 6, 2008
According to Stereophile anyway....



If a thing's worth doing, it's worth doing well
(Proverb)

 

RE: The GFP-750 preamplifier......, posted on June 15, 2010 at 20:33:23
Bigromano
Audiophile

Posts: 935
Location: Manitoba
Joined: April 6, 2005
I've heard that somewhere as well. Everything I've heard about the GFP-750 has been positive. I would love to hear it one day.

 

RE: The GFP-750 preamplifier......, posted on June 15, 2010 at 21:13:10
Belgarchi
Audiophile

Posts: 390
Location: Texas
Joined: September 25, 2004
Not bad, but disappointing, actually...

Yves

 

"GPF-750 is a Nelson Pass design..variation on PassLabs Aleph P &Son of Bride of ZEN", posted on June 16, 2010 at 00:35:39
This header is from Adcom's official brocure for Adcom GFP-750 I have in my possesion. "The circuit couldn't be simpler says Pass...the circuit can run unbalanced, although the performance is best when it's run balanced" Another quote from Adcom flyer for product.
So I would say it IS a Pass product
I still own n Adcom GPF-750 thoughIt is just sitting waiting to get around to selling it someday.
My current preamp is a Bryston BP-26

 

I'd second that, posted on June 16, 2010 at 02:09:24
plantsman
Audiophile

Posts: 4790
Location: Maine
Joined: April 4, 2002
It is the best of the Adcom preamps but no more than mediocre in the greater scheme of things. It has a rather bloodless quality.
"There are political consequences to remembering things that never happened and forgetting things that did." Ariel Levy

 

I stand corrected, posted on June 16, 2010 at 10:22:12
E-Stat
Audiophile

Posts: 19981
Joined: May 12, 2000
Contributor
  Since:
April 5, 2002
Wayne Colburn joined Pass Labs in 1994, but his influence on the DIY designs apparently didn't begin until the Pearl phono preamp.

rw

 

I third that, posted on June 16, 2010 at 15:24:55
AbeCollins
Audiophile

Posts: 22473
Location: USA
Joined: June 22, 2001
Contributor
  Since:
February 2, 2002
Over hyped by Stereophile, the GFP-750 gained popularity for a while. I took the bait and bought one and wasn't too impressed.

Nelson Pass "design" doesn't mean Nelson Pass choice of high quality components for Adcom. Sure, the circuit is designed by Pass but the parts quality are dictated by Adcom.

 

RE: Adcom-- which preamps are Nelson Pass?, posted on June 17, 2010 at 10:03:27
mcgjohn@yahoo.com
Industry Professional

Posts: 331
Location: Midwest
Joined: February 5, 2008
Yes, I agree. The adcom GFP and GFA units do not use the best parts, have small power supplies and benefit greatly from any upgrades.

Many of the GFA amps used a chrome plated steel grounding buss. Don't forget that is in the signal path. replace with copper or brass buss bar stock, obtainable from sevral sources. The 555 Mk1 and Mk2 come to mind. Maybe that was done for flashy hood off display for marketing but it does nothing for sonics.

All of the GFP units need a bigger Xformer. OE units are on the order of 7 to 15 watters. Move up to a 400 watt if you want to hear what a GFP really sounds like

best

 

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