Nelson Pass "Amp Camp Amp" (via the Polk Forum's ALL212 & others) and classic monkey coffins

mhardy6647

So, some of you may know that - in an obscure and awfully karmic way -- a unique variant of Nelson Pass's (First Watt's) Amp Camp amplifier (aka ACA) built by the forum's redoubtable ALL212 has wended its way to my doorstep. The critical roles played by the forum's wagnerRC and daboyz in this gambit will be disclosed at some later, appropriate time.

http://www.firstwatt.com/pdf/art_amp_camp_1.pdf

http://forum.polkaudio.com/discussion/174610/nelson-pass-amp-camp-amp-dual-mono-custom-built
http://forum.polkaudio.com/discussion/175957/ok-youse-guyses-are-gonna-roll-your-eyes
http://forum.polkaudio.com/discussion/comment/2291768#Comment_2291768

This is a fascinating and impressively good sounding solid state amplifier informed by Pass's belief (shared by many of us) that The First Watt is the Most Important (an aphorism attributed to Dick Olsher). The ACA is a single-ended, Class A biased amplifier (yes that's redundant -- but of course not all Class A amplifiers are SE). The ACA boasts specs that are reminiscent of a single-ended 2A3 amplifier (low power, relatively high output impedance, less than sterling harmonic distortion stats). Does it sound like one?

I tried it out with the Duplexes and it acquitted itself well -- its got that breathy intimacy and "there-ness" of a good SE direct-heated triode amplifier. I did find that the real thing (in my case, a slight variant of Joseph Esmilia's "simple 2A3" amp design) does, however, get the edge (heh-heh-heh) in terms of midrange palpableness

But, I hear you ask, what about pairing the ACA with something you'd never hook an SE 2A3 amplifier to, Marky? What happens then?

Marky looked around and noticed a pair of KLH 5s that have been visiting for a few months.
This particular pair, belonging to AK's LexDM3, is cosmetically beautiful and in good but unrestored condition electronically (i.e., original capacitors on the XOs). I'd tried them on an hk770 amplifier and been kind of underwhelmed -- so, why not just hook it to a 5 watt (@ ca. 10% THD) single-ended solid state amplifier with a damping factor of "about 3"?

DSC_7011 (2) by Mark Hardy, on Flickr

Any resemblance of Henry Kloss's 1960s KLH 5 three-way sealed-box "monkey coffin" loudspeaker with Matthew Polk's 1970s Polk Audio Monitor Series Model 10 two-way passive-radiator loaded monkey coffin is strictly coincidental. That's not a PR in the KLHs

The acoustic suspension KLH5s are inefficient -- almost notoriously so (though not in the same league as, say, the Dahlquist DQ-10 or any Magneplanar). They have all cone drivers (although the HF dispersion of the tweeter is enhanced by a hemispherical dust cap) and run that woofer in a very damped alignment. Not exactly a recipe for success -- but the combination (ACA and KLH 5s) sounds good. Darned good. Darned good.

mrbiron

I must say, your choice in words..........unparalleled.

I just don't know where "darned good" fits in the spectrum of satisfaction. My guess is between great and ok?

mhardy6647

ahh, you turn my head --
but you are too kind.
I should, of course, have written "palpability" instead of "palpableness".



Seriously, though, the ACA sounds good.

Darned good is a family forum-friendly way of saying "effing good".

mrbiron

mhardy6647 wrote: »

Darned good is a family forum-friendly way of saying "effing good".

Then cut to the chase and say "effing good"......damnit!

Jim Shearer

Hey Mark,

I took a look at the photos in ALL212's sale thread. It appears to me that he did the mod (adding R15, 2.21K) which Pappa Pass added after going over the prototype. This reduced distortion and increased the output to 6 watts! Yes, you have 20% more power than you thought!

The deal just gets better...

Cheers, Jim

mhardy6647

Whoa, six watts -- no wonder it takes the KLH 5s in stride...

mhardy6647

I am listening to (don't laugh, now!) Let it Be -- Naked on the ACA & 5s. The vocal quality is noteworthy. And I am used to (ahem) superb vocal reproduction via the Duplexes.

mhardy6647

I am now auditioning a pair of Tannoy Devons on the ACA. The low DF of the amp is not altogether to their liking (bass is whoompfy) but otherwise the pairing is very clean & sweet sounding.

The Jennys are currently Wailin as I type this, thereupon.

Photo tomorrow -- ambient light in here is not great for nighttime shots.

txcoastal1

"whoompfy"....tell me please that my tax money didn't pay for that one

Please elaborate

ken brydson

txcoastal1 wrote: »

"whoompfy"....tell me please that my tax money didn't pay for that one

Please elaborate

WAAAAAA

mhardy6647

txcoastal1 wrote: »

"whoompfy"....tell me please that my tax money didn't pay for that one

Please elaborate

subcritical damping. Qtc >1.0

Think: Cerwin-Vega

naah, no problem for the taxpayers on whoompfy -- just an onomatopoeic neologism for "soft bass".

EDIT: You'd only have gotten ripped off if you were payin' taxes when Jimmy Earl Carter was president...

txcoastal1

mhardy6647 wrote: »

txcoastal1 wrote: »

"whoompfy"....tell me please that my tax money didn't pay for that one

Please elaborate

subcritical damping. Qtc >1.0

Think: Cerwin-Vega

naah, no problem for the taxpayers on whoompfy -- just an onomatopoeic neologism for "soft bass".

Now that cost us some nickels