New Adcom 555ms with SDA-2B

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rhythm
rhythm Posts: 60
in Vintage Speakers
Hello, I see a lot of positive comments here for the classic Adcom 555 with vintage SDA speakers. I think most of the posts I've seen have been about the classic 555, and I'm wondering about the latest Adcom offerings.

I'm wondering specifically if the Adcom GFA-555ms would work well with my 2B's. It's rated at 125W/200W for 8/4 ohms, and is labeled as a high current amplifier. Any experience with this amp with vintage Polks? Would this model do the 2B's the justice they deserve?

Thank you,
Greg
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  • Unknown
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  • VR3
    VR3 Posts: 29,752
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    To me, a name for a brand doesn't mean much.

    They are owned by a Taiwan based company now... As to performance is hard to know without hearing them
    - Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit.
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  • rhythm
    rhythm Posts: 60
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    A couple of reviews I've read refer to this as "the Nelson Pass-designed GFA-555ms amplifier", so it sounds like it's quite related to the classic 555, but I'm figuring this must be a newer 'version' in one way or another. And being that it's new (as of late 2023 I believe), I was hoping perhaps someone on this forum had tried one of these and could share their experience with it, and whether or not it's got the power that these speakers like to have. Specs are one thing, but real experience is another, so if anyone has tried it...


    Thanks,
    Greg
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  • VR3
    VR3 Posts: 29,752
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    Possibly could be similar...

    original series II
    plxsawya41w1.jpeg

    new version
    23hwyazdllxp.jpg

    - Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit.
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  • rhythm
    rhythm Posts: 60
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    Definitely a more modernized implementation at the least...

    Main thing of course is: how does it sound and perform? Hopefully someone here has checked the new model(s) out (GFA-555se or GFA-555ms) and can report what they think.
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  • VR3
    VR3 Posts: 29,752
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    Just in my brief online searching, I noticed the new version goes for about the same as the old version used, fwiw
    - Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit.
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  • Unknown
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  • invalid
    invalid Posts: 1,559
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    pitdogg2 wrote: »
    Only the original Adcom 555 was a Nelson Pass design IIRC. The 2 and later versions used a Darlington configuration, which strayed away from Nelson's design.

    I thought both versions used a Darlington configuration, but the mk2 used a triple Darlington and the 555 used a Darlington pair.
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  • Unknown
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    edited May 2025
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  • michaeljhsda2
    michaeljhsda2 Posts: 2,216
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    Where's the large capacitors in the new version?
    SDA SRS 2.3TL's
    Silk Audio MS-90-BT integrated tube amp
    Yaqin MS-20L integrated tube amp
    SDA 2B TL's
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  • Unknown
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    edited May 2025
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  • VR3
    VR3 Posts: 29,752
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    They went to not so large capacitors if I had to guess 😁
    - Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit.
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  • JayMX
    JayMX Posts: 464
    edited May 2025
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    I have reworked a 555se for a friend and have been into a few original 555’s and 555ii’s. Not familiar with the “ms” version. As I understand it, the original 555 is the only “true” Pass design. But the later versions still use the same (essentially) physical layout, transformer, rails, final stages and main caps. Rectifiers moved up on top the caps in ii and later. To answer the question above, the big caps are still there, the newer versions just have pcb’s that mount on top of them vs the “free air” configuration of the original 555. Worthy of note, up to se, there are no speaker protection relays. Chris Hoppe offers a really nice kit to add protection and a 12v trigger as well. I plan on building a couple of those this winter…

    The units I’ve had (and still have) are absolute tanks. The driver board is a completely different schematic when going from 555 to ii and se is the exact same schematic as the ii. The se has nicer heat sinks (less sharp edges, beefier) and felt a little more “mass market” than previous revisions. Original 555’s definitely have more of a homebrew feel when it comes to build quality, if that makes sense. Every one of them has had heat issues in the early stages. I’ve rebuilt several using Chris Hoppe’s replacement kits which beef up the board, all of the components and adds heat sinks to most of the semiconductors in the gain stages.

    I have found that I prefer the ii’s with Chris’s kit installed. The top end is better, imaging is better, and the background is quieter. I also like how robust the kit is. I sold my original pair of 555’s. I never disliked them, I just didn’t need six of them… 😎

    Chris offers a lot of good info and is quite responsive to questions. An odd, mad genius kind of individual, but super nice. Chris knows lots of lore about the 555. Definitely a guru. Here’s the website: https://hoppesbrain.com/

    And yes, the 555, ii, and se are all common ground.

    You can’t go wrong, just get some good healthy feed circuits, speakers that love the juice, and enjoy! 🤘🏻🤘🏻



    Current Collection: Monitor 4a (Peerless), Modified Monitor 7b (Peerless), RTA15TL (SL3000), Full mod SDA CRS 4.1TL (198’s), SDA SRS 2.3TL (198’s), R100's, R200’s, R300 🤩
    Pairs that have passed through: Monitor 4b (Peerless), Monitor 5a (Peerless), Monitor 5B (Peerless), Monitor 5b (SL1000), Monitor 5b (SL2000) (4x pair), Monitor 7b (Peerless), Modified Monitor 7c’s (194’s), Monitor 10a (Peerless), Monitor 10b (5x pair), RTA8, RTA8TL, RTA 11T, RTA12c (194's), SDA1(mod to “a” & SL1000 Wuhan mod), SDA CRS, SDA 2 (2x pair), SDA 2a, SDA 2b, SDA 1b, SDA 1c, SDA SRS 2 (2x pair), SDA SRS 3.1TL (198’s) (2x pair)...and more to come, it’s a sickness.
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  • michaeljhsda2
    michaeljhsda2 Posts: 2,216
    edited May 2025
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    ...
    SDA SRS 2.3TL's
    Silk Audio MS-90-BT integrated tube amp
    Yaqin MS-20L integrated tube amp
    SDA 2B TL's
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  • JayMX
    JayMX Posts: 464
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    Original 555:
    amy2uayzembm.jpeg

    555ii with Hoppes board installed:
    7ik2yuque1vr.jpeg



    Current Collection: Monitor 4a (Peerless), Modified Monitor 7b (Peerless), RTA15TL (SL3000), Full mod SDA CRS 4.1TL (198’s), SDA SRS 2.3TL (198’s), R100's, R200’s, R300 🤩
    Pairs that have passed through: Monitor 4b (Peerless), Monitor 5a (Peerless), Monitor 5B (Peerless), Monitor 5b (SL1000), Monitor 5b (SL2000) (4x pair), Monitor 7b (Peerless), Modified Monitor 7c’s (194’s), Monitor 10a (Peerless), Monitor 10b (5x pair), RTA8, RTA8TL, RTA 11T, RTA12c (194's), SDA1(mod to “a” & SL1000 Wuhan mod), SDA CRS, SDA 2 (2x pair), SDA 2a, SDA 2b, SDA 1b, SDA 1c, SDA SRS 2 (2x pair), SDA SRS 3.1TL (198’s) (2x pair)...and more to come, it’s a sickness.
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  • Unknown
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  • invalid
    invalid Posts: 1,559
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    Doesn't Hoppe have a soft start board for the adcom 555? My 555 went though power switches pretty regularly, but it hasn't in several years due to the fact it let out the magic white smoke. I don't think it's worth putting money into.
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  • rhythm
    rhythm Posts: 60
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    Lots of good and interesting information on this thread about the Adcoms. I was looking for a good amp for my SDA-2B's under 2K, and I got curious about these newer Adcoms. They have a few in the current lineup: GFA-555se, GFA-555ms, and GFA-565se which are at 2K or less, but there doesn't seem to be much info on them, other then the specs that Adcom shows. On the fence about taking a shot with one of them.
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  • audioluvr
    audioluvr Posts: 6,079
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    Stick around for a while. Get up to 100 posts and advertise in our wanted section. There's probably some really good used stuff here members would part with. Where do you hail?

    Welcome to Club Polk.
    Gustard X26 Pro DAC
    Belles 21A Pre Upgraded with Mundorf Supremes
    B&K M200 Sonata monoblocks refreshed and upgraded
    Polk SDA 1C's modded / 1000Va Dreadnaught
    Wireworld Silver Eclipse IC's and speaker cables
    Harman Kardon T65C w/Grado Gold. (Don't laugh. It sounds great!)

    There is about a 5% genetic difference between apes and men …but that difference is the difference between throwing your own poo when you are annoyed …and Einstein, Shakespeare and Miss January. by Dr. Sardonicus
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  • rhythm
    rhythm Posts: 60
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    audioluvr wrote: »
    Where do you hail?
    Southern California
    audioluvr wrote: »
    Welcome to Club Polk.
    Thank you!
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  • BlueBirdMusic
    BlueBirdMusic Posts: 3,132
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    FYI, saw this on FBM this morning:
    ADCOM Pro PowerAmp $800 $1,100
    Listed 2 weeks ago in Stone Mountain, GA

    8l3sjt3s6adk.png

    https://www.facebook.com/share/1FkU2LpJro/
    "Sometimes you have to look to the past to understand where you are going in the future"
    Harry / Marietta GA
    m9iutt1ly1yd.png
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  • boston1450
    boston1450 Posts: 7,759
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    IIRC the 5802 is not common ground
    Randy-Maine
    2ch-RTA15tl crossover upgrade
    by David WMG
    Yamaha cr1000 cr2040
    HT-Yamaha Parasound Acurus
    MIT BJC Cs1000p Polk Rotation
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  • boston1450
    boston1450 Posts: 7,759
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    Have you put any thoughts on other brands ? I use a Parasound 2250 (bought here CP) & I've used Acurus 200/3 (now my CC & rears) . I was using Adcom 555 w/565pre & to me it was a upgrade. Mind you I didn't upgrade the 555 as you can improve it... On my 2b's I used a Yamaha CR2040 & they stayed together for 2 years before I gifted the 2b's to my oldest & she still rocks them today. Don't hesitate to research other options
    Randy-Maine
    2ch-RTA15tl crossover upgrade
    by David WMG
    Yamaha cr1000 cr2040
    HT-Yamaha Parasound Acurus
    MIT BJC Cs1000p Polk Rotation
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  • skipshot12
    skipshot12 Posts: 2,156
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    No good for SDA speakers but, that seems like a very nice price for a 300w amp?
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  • rhythm
    rhythm Posts: 60
    edited June 2025
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    Hi boston1450,

    I'm definitely open to any other brand. I just happened to notice that Adcom had these newer versions of their amps available at an affordable price so I was curious if anyone here had any experience with them. But I'm open to whatever will do a good job giving the SDA 2B's what they need to sound their best.

    Just to make sure I understood correctly, are you saying that you feel the Parasound 2250 was an upgrade compared to the Adcom 555?
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  • boston1450
    boston1450 Posts: 7,759
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    rhythm wrote: »
    Hi boston1450,

    I'm definitely open to any other brand. I just happened to notice that Adcom had these newer versions of their amps available at an affordable price so I was curious if anyone here had any experience with them. But I'm open to whatever will do a good job giving the SDA 2B's what they need to sound their best.

    Just to make sure I understood correctly, are you saying that you feel the Parasound 2250 was an upgrade compared to the Adcom 555?

    To me at that time it was. I had to make a choice as the Adcom was in need to be refreshed & possibly upgraded. So I choose to get the Parasound. I listened to it when I got it & stored the Adcom 555 which worked fine but at the time was overdue. I ended up selling it off. I enjoyed the Adcom & it sounded great on SDA's & I knew if I spent the $$$ it would have been awesome. i have heard the newer 555ii & it sounded very nice. The newer ones I have not
    Randy-Maine
    2ch-RTA15tl crossover upgrade
    by David WMG
    Yamaha cr1000 cr2040
    HT-Yamaha Parasound Acurus
    MIT BJC Cs1000p Polk Rotation
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  • Sitka
    Sitka Posts: 77
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    Hi Rhythm, I power my 2B's with a Yamaha A-S2200 and for me it was look no further. I listen mostly to acoustic instruments and ambient electronic in hi-def, and the definition, attack, imaging and soundstage are amazing (with Dreadnaught). So good it even fools my cat who will start looking for the little bird in the center of the soundstage. Great piece of kit for the price, no digital anything. If you want to rock the house, there are better options, but if you want lifelike sound, worth a look.
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