For anyone who might be interested: Nelson Pass-designed ACA amplifier kit "back in stock" :)

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Comments

  • stretchlstretchl Posts: 1,029
    edited July 5
    Anyone reckon the Pass amp would work well with a pair of 705’s? Or perhaps as monoblocks, which apparently is a build option? Thanks.
    “Anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge.'
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  • EndersShadowEndersShadow Posts: 15,870
    stretchl wrote: »
    Anyone reckon the Pass amp would work well with a pair of 705’s? Or perhaps as monoblocks, which apparently is a build option? Thanks.

    Ehhh.... I'd pass...... the 705's need a decent amount of wattage and current, and the pass aren't built to do either of those to the scale you'd need.
    "....not everything that can be counted counts, and not everything that counts can be counted." William Bruce Cameron, Informal Sociology: A Casual Introduction to Sociological Thinking (1963)
  • ZLTFULZLTFUL Posts: 4,573
    The ACAs need some decently high sensitivity speakers. Otherwise, you are going to miss a LOT on the low end and things are going to sound sloppy.

    "Some people find it easier to be conceited rather than correct."

    "Unwad those panties and have a good time man. We're all here to help each other, no matter how it might appear." DSkip
  • mhardy6647mhardy6647 Posts: 18,760
    Performance-wise, the original morph of the ACA isn't all that dissimilar to a single-ended 2A3 amplifier -- albeit a bit more powerful and probably wider flat response compared to any even marginally affordable 2A3 stereo amp.

    So... think SET/fleapower friendly loudspeakers.

    Vintage Altec, JBL or (shudder) Klipsch fills the bill nicely (e.g.).
    "It's like watching a roomful of people who couldn't get through college algebra discussing the flaws of quantum physics theory. I guess it could be fun, but it's ultimately a waste of time." -- seen on audiokarma

    "Some amps run on self bias, some amps run on fixed bias. But his amps run on confirmation bias." -- seen on audioasylum

    "Writing about hifi is like dancing about architecture" -- paraphrasing some wag (possibly Frank Zappa)
  • mpitogompitogo Posts: 277
    Music-2.0 Raidho D-3.1 | Audio Research Ref 40 | Jeff Roland 925 | Esoteric Grandioso K1 | Transparent Reference, IC, Speaker and Power | HRS SXR Rack
  • leftwinger57leftwinger57 Posts: 2,883
    So 'Doc' I can't believe no one has asked you about this after all these years. Why didn't you paint or ,stain those speakers. They stand out like very sor thumbs and need some beautification. Being an old Yankee you must have some Marine varnish up there so throw some coats on. and counter sink those screws. Chemistry and radionics are your strong suit but not to much on the the aesthetic. Look who's the critic now ....lol
    2chl- Adcom GFA- 555-Onkyo P-3150v pre/amp- JVC-QL-A200 tt- Denon 1940 ci cdp- Adcom GFS-6 -Modded '87 SDA 2Bs - Dynamat Ext.- BH-5- X-Overs VR-3, RDO-194 tweeters, Larry's Rings, Speakon/Neutrik I/C- Cherry stain tops Advent Maestros,Ohm model E

    H/T- Toshiba au40" flat- Yamaha RX- V665 avr- YSD-11 Dock- I-Pod- Klipsch #400HD Speaker set-

    Bdrm- Nikko 6065 receiver- JBL -G-200s--Pioneer 305 headphones--Sony CE375-5 disc
  • EndersShadowEndersShadow Posts: 15,870
    He's a "form" over function kinda guy DUH!

    Also with as much as he's tweaked them over the years at times (adding in super tweeters, other horns, etc) at the top of them it wouldnt make sense IMHO to finish them.
    "....not everything that can be counted counts, and not everything that counts can be counted." William Bruce Cameron, Informal Sociology: A Casual Introduction to Sociological Thinking (1963)
  • mhardy6647mhardy6647 Posts: 18,760
    The answer is supremely simple. I could only make them look worse if I tried to finish them.
    "It's like watching a roomful of people who couldn't get through college algebra discussing the flaws of quantum physics theory. I guess it could be fun, but it's ultimately a waste of time." -- seen on audiokarma

    "Some amps run on self bias, some amps run on fixed bias. But his amps run on confirmation bias." -- seen on audioasylum

    "Writing about hifi is like dancing about architecture" -- paraphrasing some wag (possibly Frank Zappa)
  • mpitogompitogo Posts: 277
    edited August 5
    The kits came in yesterday, spent Sunday building. The monoblocks are now breaking in... er heating the room. Measured 126F at the heatsinks. The entire chassis is hot.

    uofr2z64959b.jpeg
    je1bx322muhy.jpeg

    Music-2.0 Raidho D-3.1 | Audio Research Ref 40 | Jeff Roland 925 | Esoteric Grandioso K1 | Transparent Reference, IC, Speaker and Power | HRS SXR Rack
  • msgmsg Posts: 4,265
    Looking good!
    Can't wait to hear the listening impressions.
    What will be the rest of the setup?
  • mhardy6647mhardy6647 Posts: 18,760
    edited August 6
    They look excellent. Nice work.

    126 ain't bad (assuming that's Fahrenheit kind of degrees, and not those Commie Celsius degrees ;) ). "Hot" is about 150 (relative to my sense of touch)! :)
    "It's like watching a roomful of people who couldn't get through college algebra discussing the flaws of quantum physics theory. I guess it could be fun, but it's ultimately a waste of time." -- seen on audiokarma

    "Some amps run on self bias, some amps run on fixed bias. But his amps run on confirmation bias." -- seen on audioasylum

    "Writing about hifi is like dancing about architecture" -- paraphrasing some wag (possibly Frank Zappa)
  • mpitogompitogo Posts: 277
    So I've played them for a little bit but two things.

    1) Polk T15 are not the best speakers. I also have a pair of ML Motion 40's sitting around but these are 4ohms and the bridged mono's look to only be rated for 8 ohms or higher.

    2) I need to redo the bias. I had followed the v1.5 build guide, these kits came with 19v supplies and bias is set at 10v. The new v1.6 kits come with 24v 5a supplies and should be biased at 12v per diyaudio.com members.
    Music-2.0 Raidho D-3.1 | Audio Research Ref 40 | Jeff Roland 925 | Esoteric Grandioso K1 | Transparent Reference, IC, Speaker and Power | HRS SXR Rack
  • mhardy6647mhardy6647 Posts: 18,760
    Time for high sensitivity, baby! :)

    27138816799_d247e72652_b.jpgDSC_9976 (3) by Mark Hardy, on Flickr
    "It's like watching a roomful of people who couldn't get through college algebra discussing the flaws of quantum physics theory. I guess it could be fun, but it's ultimately a waste of time." -- seen on audiokarma

    "Some amps run on self bias, some amps run on fixed bias. But his amps run on confirmation bias." -- seen on audioasylum

    "Writing about hifi is like dancing about architecture" -- paraphrasing some wag (possibly Frank Zappa)
  • ClipdatClipdat Posts: 4,528
    Does it run hotter with no load connected to it because of it's class A topology? Or will it run at that same temp when it's in use?
    Got Dayens?
  • heiney9heiney9 Posts: 23,833
    I really wanted to pick one of these up, but I have 3 other projects and I have no current use for this little wonder amp.
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
  • vcwatkinsvcwatkins Posts: 1,677
    Have regrettably been away for quite a while but thought I'd check in re: the ACA.
    This thing sounds FANTASTIC!

    Meridian Exporer II Test
    The day after it was finished I brought it in and hooked it up to a simple little computer rig to get some hours on it. The rig was:

    PC (Roon Remote) > Jitterbug > Wireworld Starlight Red A/MiniB > Meridian Explorer II dac > AQ headphone-RCA adapter > MIT S3 interconnects > Amp Camp Amp > MIT S3 speaker cables > Hartley Reference Mini-Towers

    I believe the speakers are 95db but am not certain. The room is about 12'x12' with an 8ft opening centered on the back wall. Using Roon's software volume control, I needed to set it 80ish% for most music; but, at 90% it provided plenty of gain for any music I played.

    Amazing clarity and detail, excellent soundstage with instruments spread evenly from ~5 degrees outside the speakers. Fantastic, detailed bass. Not sure how to describe this, but it has an addictive purity of tone; detailed but not brittle; lush but not overly sweet - it just sounded right and true. The best sound I've ever had in this location. Instantly fell in love with it. I was ecstatic, especially given this is not, what I assume to be, an optimal rig.

    Audio Research LS-3
    I ordered a Schiit Saga to try out. While waiting for it to arrive, I tried the ACA with my usual sources in the study and an AR solid state pre:

    Roon > ethernet > Bryston BDP-1 > Bryston BNC > Bryston BDA-1 > MIT S3 > ARC LS-3 > MIT S3 > Amp Camp Amp > Hartley Ref MiniTower

    Way more gain - too much in both passive and active - and the sound suffered and was no longer magical. Reverted to the Meridian-direct source while waiting a little longer for the Saga.

    Schiit Saga
    Saga arrived a few days ago, so I slotted into the Bryston source rig. Sounds noticeably better than the Meridian-direct (or is it the Bryston's?, likely a combo of both). But, a bit surprising to me, the Saga does not add any gain - in fact, it seems to be less. In passive, I have to turn it to 3:00 to listen to most things at a realistic volume. Still fantastically detailed, but I do worry about distortion at that level (or higher when I'm feeling my oats). Switching to the tube adds the slightest amount of gain (I think) but is barely perceptible. I like the little Schiit enough to keep and try with other gear. I'll also try to slot in the Joule pre for fun, even though they won't likely be paired for any length of time.

    I have yet to build Frugel-horn cabinets or similar (hope to do that this month), and am considering used Zu Omens or new Tekton Double Impacts. But for now, I'm happy as a clam listening to this lovely little amp with stuff that I have on hand.

    I HIGHLY recommend this amp if you get the opportunity to buy a kit or an assembled one. Many thanks to @mhardy6647 for the heads-up on availability.

    Craig
    Den: Rega RP6 (mods) * AT33PTGII * Jolida jd9 (mods) * Roon (Sonic Transporter) * PS Audio DirectStream Jr. * Joule-Electra LA-100 iii * Sunfire Sig II * PSAudio p3 * MIT S3 * Polk SRS 1.2 (full mods)
    Office: Roon * Meridian Explorer2 * Pass Amp Camp Amp * PSA Dectet * MIT s3 * Hartley Reference Mini-Tower
    Beach: Music Hall MMF5.1se * Speed Box II * DL103r * Parks Budgie SUT * Belles Phono 20a * Sonos * Schiit Yggdrasil * Belles 20a * First Watt F5 Clone/Pass Aleph 30 * PSAudio Dectet * MIT s3 * Polk SRS 2.3tl (full mods)
  • heiney9heiney9 Posts: 23,833
    Dang it! After your review, I think I want one again

    SOLD out again..............I'm on the waiting list, AGAIN...lol

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
  • mhardy6647mhardy6647 Posts: 18,760
    edited August 6
    The only "problem" with the ACA relative to SE DHT(2A3) amplifier (in my hands, that is) is that it doesn't quite have the midrange realness of the 2A3 amp. It is just a bit drier sounding (but there's probably a certain amount of expectation bias goin' on, too!). You all probably recall the one that is on a long-term visit (maybe it's a hostage?!) here; it's a little tricked up relative to the stock (first generation, I think) ACA configuration.

    Otherwise, it is at least in the running with a decent quality SE 2A3 amplifier. Bass may be a little better (not necessarily easy to tell with my loudspeakers). Certainly cheaper than SE 2A3 :) and its hottest parts don't run as hot as a pair of 2A3 output tubes in Class A :) I suspect (but haven't checked) that power consumption of the ACA (the one here, it may be recalled, is physically configured as a stereo amp with a "Bottlehead" like footprint) and the 2A3 amp are comparable.
    "It's like watching a roomful of people who couldn't get through college algebra discussing the flaws of quantum physics theory. I guess it could be fun, but it's ultimately a waste of time." -- seen on audiokarma

    "Some amps run on self bias, some amps run on fixed bias. But his amps run on confirmation bias." -- seen on audioasylum

    "Writing about hifi is like dancing about architecture" -- paraphrasing some wag (possibly Frank Zappa)
  • mpitogompitogo Posts: 277
    @Clipdat same temp load or no load.
    Music-2.0 Raidho D-3.1 | Audio Research Ref 40 | Jeff Roland 925 | Esoteric Grandioso K1 | Transparent Reference, IC, Speaker and Power | HRS SXR Rack
  • leftwinger57leftwinger57 Posts: 2,883

    Another question for the DOC here. You went fairly in depth in soldering and how to get the right heat and flow. What you did not specify is the type of instrument you personally use. Is it a tried and true Weller, the portable butane type, old school pencil type w/ holder, and a very old and large enough to weld a Liberty ship called the Cummings.
    Lew.....

    ]
    2chl- Adcom GFA- 555-Onkyo P-3150v pre/amp- JVC-QL-A200 tt- Denon 1940 ci cdp- Adcom GFS-6 -Modded '87 SDA 2Bs - Dynamat Ext.- BH-5- X-Overs VR-3, RDO-194 tweeters, Larry's Rings, Speakon/Neutrik I/C- Cherry stain tops Advent Maestros,Ohm model E

    H/T- Toshiba au40" flat- Yamaha RX- V665 avr- YSD-11 Dock- I-Pod- Klipsch #400HD Speaker set-

    Bdrm- Nikko 6065 receiver- JBL -G-200s--Pioneer 305 headphones--Sony CE375-5 disc
  • mhardy6647mhardy6647 Posts: 18,760
    I am seriously not an expert on modering soldering stations.
    I (still) like the Weller controlled heat stations... but there may well be better; I dunno.
    "It's like watching a roomful of people who couldn't get through college algebra discussing the flaws of quantum physics theory. I guess it could be fun, but it's ultimately a waste of time." -- seen on audiokarma

    "Some amps run on self bias, some amps run on fixed bias. But his amps run on confirmation bias." -- seen on audioasylum

    "Writing about hifi is like dancing about architecture" -- paraphrasing some wag (possibly Frank Zappa)
  • lightman1lightman1 Posts: 9,803
    Sketchy Craig is back!
  • vcwatkinsvcwatkins Posts: 1,677
    Dayum right.
    Den: Rega RP6 (mods) * AT33PTGII * Jolida jd9 (mods) * Roon (Sonic Transporter) * PS Audio DirectStream Jr. * Joule-Electra LA-100 iii * Sunfire Sig II * PSAudio p3 * MIT S3 * Polk SRS 1.2 (full mods)
    Office: Roon * Meridian Explorer2 * Pass Amp Camp Amp * PSA Dectet * MIT s3 * Hartley Reference Mini-Tower
    Beach: Music Hall MMF5.1se * Speed Box II * DL103r * Parks Budgie SUT * Belles Phono 20a * Sonos * Schiit Yggdrasil * Belles 20a * First Watt F5 Clone/Pass Aleph 30 * PSAudio Dectet * MIT s3 * Polk SRS 2.3tl (full mods)
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