AmpCamp Amp

Discussion in 'Power Amps' started by Puma Cat, Jul 20, 2020.

  1. Puma Cat

    Puma Cat Almost "Made"

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    I'm building up a pair of the Amp Camp amps (ACA), which are a full Class A amplifier designed by Nelson Pass. These come as a kit for $327, including all parts, the heat sinks and chassis, and can be used as a stereo amp or bridged or paralleled monoblocks. I bought two and will be configuring them to run as bridged monoblocks. They will put out about 15 W of Class A power into 8 ohms in bridged mode. I completed all the boards this weekend and have started putting the chassis and connectors together.

    Here are some pics of my ACA 18 "Premium" Parts build. This is subsituting some of the stock components with more premium parts and changing a few resistor values. This my first build since I built my Hafler DH-101 more years ago than I care to remember...[​IMG]

    Photos from my wondrous little Fujifilm X100F, shot with available light and/or TTL fill. Even the base kit uses really nice parts, e.g., Vishay metal film resistors and Elna capacitors, but I've upgraded some of the caps with a Nichicon Gold Tune cap at C1 and the aluminum organic polymer Nichicon caps at C2 and C4 that comprise part of the premium parts build.

    The boards for each channel or "half", depending on the configuration.

    [​IMG]
    [​IMG]

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    Close-up of one fo the boards; here R4 is run parallel with another resistor to lower the resistance in this part of the circuit to optimize current to the transistors.

    [​IMG]

    The rear panel with information on how to make connections and setting to run in different output configurations. One can use the amp in stereo or as a monoblock simply by using the switch at the top of the rear panel.
    [​IMG]

    [​IMG]

    I'll post more pics of the amps as I progress with finishing the build.

    The speakers I am planning on using these will are the X-LS Encores designed by Danny Richie of GR-Research in Texas. These are also sold as a DIY kit for a whopping $249 for the base configuration.

    The X-LS Encores are 87 dB/1W-m sensitivity which should be fine as I typically listen at levels 68-72 dB when sitting 7 ft in front of the speakers in my small listening space. They have a nominal impedance of 8 ohms.

    [​IMG]

    My cabinets were built up by one of Danny's employees, who is also a woodworker. He's veneered them for me and stained and oiled the cabinets.

    Here's a pic of my cabinets...
    [​IMG]

    Once I receive the cabinets and speaker components, I'll wire up the crossover, connect and mount the drivers, and assemble the parts into a finished loudspeaker.

    More pics to follow on this project, so stay tuned...
     
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    Last edited: Jul 20, 2020
  2. Puma Cat

    Puma Cat Almost "Made"

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    Tonight I mocked up the chassis and boards assembled to determine the length of the hookup wires required from the boards and switches to the rear panel. Becuse the boards are "asymmetric" with respect to their positions on each heat sink, I wanted the wire lengths for the respective connections to the boards and each amp to be identical, so this was the best way to do it.

    [​IMG]
     
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  3. JoshMorr

    JoshMorr Friend

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    Looking good. I have had one of these hooked up to some Klipsch Chorus for years in my garage. Fun amp.

    Which power supply are you using?
     
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  4. Puma Cat

    Puma Cat Almost "Made"

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    Hi Josh,
    The ACAs come with a 24V, 5A 120 W Meanwell SMPS "laptop" style power supply. Not crazy about using an SMPS, but it will be fine as this is just a fun project. I'll probably use my Michell TT, SME V, and Koetsu (go ahead, twist my arm) for this system to avoid SMPS nasties on the digital streaming front end.

    If I really like the amps and will be using them a lot, I'll look into having a proper external LPS made up for me; I'm thinking Keces might be able to do it.
     
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  5. Puma Cat

    Puma Cat Almost "Made"

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    Okay, so I finished up the first amp with premium parts and the resistor changes....here it is, all completed.

    [​IMG]

    [​IMG]

    in the rack, making music as I write this...;):)
    [​IMG]
     
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  6. Puma Cat

    Puma Cat Almost "Made"

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    So, one of the little things that potential owners of this sweet little amp should be mindful about when connecting the cables is to not accidentally flip the switch on the top of the rear panel. When making connections last night with the amp in the rack, I must have accidentally hit this switch, and put the ACA from Stereo into Bridged mono mode. As both speakers were connected and I was hearing music from both speakers, I didn't notice anything until Kenny Burrell, on his Midnight Blue album, was playing the track, Saturday Night Blues. Kenny is hard-miked on the left on this cut, and I noticed I could hardly hear him during his solo. A quick check of the back panel indicated I had inadverantly switch the amp to Bridged Mono mode. It sounds notably better when configured as a stereo amp and the music for each channel is going to the proper speakers...doh!
     
  7. Metro

    Metro Friend

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    Not many Guttenberg followers on SBAF, but this one is very interesting.

     
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  8. EmDub

    EmDub Rando

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    This amp looks really interesting. Looks like you finished it over the summer. What are your impressions now that you've been able to live with and listen to the amp for a while? Can you please talk about your setup and how the amp sounds? Thanks!
     
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  9. dBel84

    dBel84 Friend

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    Not sure how I missed your post. Very clean build. Be curious of your extended thoughts too. (now that the "proud dad" and new toy factor have eased a little)
     
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  10. SpeedSmith

    SpeedSmith Rando

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    Getting ready to build a pair of these. I'm very excited about the v1.8 updates, especially the 3-position switch. The ability to easily connect as bridged monoblocks with XLRs for balanced sources or use them with SE sources bridged or parallel mono is wonderful.

    I have the boards and power supplies. Just waiting on the cases from Italy. I plan to at least stuff the boards next week that way I'm ready to wire.

    I have a pair of Schiit Aegir and a Crown CDI1000 on hand to compare them against. I'll post some thoughts once they are done and run in. Wish me luck!
     
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  11. Pancakes

    Pancakes Friend

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    I'm super interested in this. Been vacillating between ACA and Aegir forever.
     
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  12. dBel84

    dBel84 Friend

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    F4 = just incredible.
    EDIT - I should have clarified. Dropped this into the system (which replaced the Aegir temporarily) = this is what I expected from the Aegir
    Not much more skill needed.
    [​IMG]
    perhaps a teensy bit bigger
     
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  13. SpeedSmith

    SpeedSmith Rando

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    I will keep you posted. ;)
     
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  14. SpeedSmith

    SpeedSmith Rando

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    Just a little bit bigger. Ha! The F4 is on my list. I'm using the ACA to enhance my soldering skills. To date I've only built a Bottlehead Crack and an ICEPower Class D unit. Luckily they both worked well. Fingers crossed.
     
  15. Philimon

    Philimon Friend

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    Im going to build as my first solder lesson. Parts have arrived but I missed first fedex delivery attempt to sign for chassis. Kind of feel bad about that since it was 110degrees out.

    Would like to try with headphones.

    ASR’s review and measurements: Not recommended, too low power, too much distortion.

    Archamigo’s review and measurements: kinder perspective, recommended for intended usage (beginner diy and tube sounding ss amp).
     
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  16. Puma Cat

    Puma Cat Almost "Made"

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    Chr*st, not ASR again. I thought we got past all this 40 years ago when folks who actually listened realized the testing that Hirsch-Houck Labs did in Stereo Review had nothing to do with how a component actually sounded when reproducing music. Further, ASR's "listening tests" do not reflect how the ACA 1.8s actually sound.

    Furthermore, they are not as smart as Nelson Pass when it comes to amplifier design.

    I've been listening to my ACAs as a pair of bridged monoblocks a lot lately (with my GR-Research XLS Encores), and really getting some hours on them and they have gotten better and better and better. They need a minimum of 100 hours or so of burn-in, I'd say to fully come on-song, but once they get there, they are very impressive. They are very quiet, transparent, resolving, with excellent soundstage and imaging, and very musical with excellent dynamics, tonal balance and sophistication in resolving instrumental timbres. Moreover, with running as bridged monos, I was listening at levels of 72-85 dB with speakers of 87dB/1W efficiency and they played plenty loud enough, and can provide dynamic slam and immediacy when required by swings in the musical content. Most importantly, they create quite an engaging and involving listening experience. Amir's comments in his "listening impressions" are completely inaccurate, in my experience.
     
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    Last edited: Jul 1, 2021
  17. Philimon

    Philimon Friend

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  18. dBel84

    dBel84 Friend

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    Looking good

    Not sure about either of those adapters

    HiFiMan makes one - https://www.hifiman.com/products/detail/84 , but maintains balanced configuration.

    The key to using this with the ACA is to make sure that you pull off the active signal for the channels and use the common signal for shorting together for ground.

    The ACA is wired such that the red tab is common and shorted while the black tab is active ( this is to invert polarity for the amp output ) - thus you need to be a little more cautious with wiring up an off the shelf adapter.
     
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  19. Puma Cat

    Puma Cat Almost "Made"

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    Looking good, Phil. Coupla notes: it can be somewhat time-consuming to bias the power transistors, so be patient and wait for any changes to the bias pots "settle" as it takes some seconds for any changes to stabiliize.

    I've found that it takes about 100 hours for the amp to fully run-in to the point where it will really start to sound it's best.

    Also, if possible...try it with some speakers. I used mine as bridged monos mostly with the GR-Research X-LS Encores, and even those are 87dB/1 Watt effiicient, the ACAs could drive easily drive them to levels I usually listen to, which is around 70-74dB, on average with peaks to 80-82 dB. The ACAs will sound more open and extended and spacious as the amp runs in.
     
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  20. Armaegis

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