Class A SS: Journey for a budget champion for LCD-X

@HeyWaj10 if you’re not totally set on Class A, maybe the Pietus would be an upgrade to the Lyr.

edit: Pietus might not gel with your BF2/64

 

Phase 2: DIY Nelson Pass ACP+ vs. Headamp Gilmore Lite Mk2

Over the past week, after quickly realizing that the Lyr 3 was no longer going to satisfy my taste for the sound that a Class A Solid State headphone amp is going to give me, I ordered the Headamp GLmk2 to try out. In my mind, I wanted to compare the two Class A amps together and see if I could answer the following questions:

1. Is there a Class A headphone amp priced similarly to the Lyr 3 (~$500) that can give me the sound I experienced with the ACP+?
2. Could a production-grade, plug and play, offering (i.e. GLmk2) make the likelihood of going down the DIY route unnecessary?
3. Should the plug and play option not match the performance level of the ACP+, could I live with it, knowing that (a) I can’t currently buy the ACP+ and (b) there will ultimately be performance left on the table that I just won’t quite achieve?

It really didn’t take long at all for me to realize that the GLmk2 was reeaaallly close (like 90%+) to the performance of the ACP+…BUT, it was readily apparent that the ACP+ was still better. I feel every bit that way now as I did within the first 10 minutes of comparing the two.

Areas that make up the 90% of equality:

• Dynamics (both macro and micro), impact, slam, speed and PRaT
• Image precision, definition, and location
• Midrange sweetness and naturalness (that Class A tube-like "ness")
• Treble clarity, timbral and tonal accuracy*
• Detail (both macro and micro)*

Areas that make up the ~10% where the GLmk2 comes up short:

• Noise floor / blackgound – this is the single biggest differentiator; the ACP+ still has the inkiest of blacks.
• Soundstage depth – again likely due to the blackgound; while they are very similar, you can hear notes decay deeper into the void with the ACP+ and easily follow that decay all the way back
• *Overall detail and timbre/tone of the treble response is close between them, but the deeper blackground of the ACP+ makes these areas shine and are more easily discernable

Other aspects that differ between them are the richness and “organic” tone of the midrange, as well as how the treble response is presented. With the midrange, the ACP+ just has a more tube-like vibe to it. Maybe that’s the distortion profile, and while a certain brand of audiophile might lose their lunch over that, to me it just sounds really freaking good. Whereas with the GLmk2, the midrange is played more straight forward and with a traditional SS sound. It’s not a bad thing, but just when comparing the two against each other, my ears really seem to prefer the ACP+ delivery.

In the treble response, the GLmk2 seems to have a more refined(?) overall presentation. That might not be the best way to describe it, but while the detail is very much there, things come across a bit more smoothed over and ever-so-slightly less delineated vs. the ACP+. The treble of the GLmk2 reminds of the Lyr 3’s presentation with the Psvane tube. So it’s possible that, because of the ACP+ deeper blackground, the treble just comes through a bit more vivid and shinier, but also a bit more “raw” (not to be read as harsh).



I have to come back to the noise floor/blackground, as in my mind, this is the X factor that gives the ACP+ a distinct advantage and is the sole reason I don’t want to let this thing go. To apply an analogy, I think the best way I can put it is:

• The GLmk2 = late 201X LED 4K TV
• ACP+ = newer generation OLED 8K TV

The ACP+ still has a rendering ability that allows you to mentally follow the notes much farther back into the void. And while you can hear most of that with the GLmk2, you have to focus more closely to hear that happen. With the ACP+, it’s just there, and it’s so much fun to listen to that effect. Likewise, the ever-so-slightly greyer soundstage and presentation of the GLmk2 makes things seem slightly more homogeneous and less 3-dimensional. It almost gives the sensation like the soundstage is pulled forward more into my nose/head – whereas with the ACP+, it’s a smidge beyond my nose, but seems farther back because of the defined edges and deeper background. We’re talking about single-digit percent differences here, but it makes enough of a difference to me that it’s just undeniable.



So once again I’m struck with the question of where does that leave me? The way I see it, I have 2 possible scenarios – both of which involve selling the Lyr 3 that I did love for more than two years:

1. If I manage to sell the Lyr 3 in the next couple weeks, I will likely just keep the Headamp Gilmore Lite Mk2, given the fact that I cannot purchase the ACP+ kit (and no known timeline for those kits to be back in stock)
   • Note: I did take an evening to see about sourcing the kit’s components myself – it was a daunting task, and I’m not sure if I got the right parts even figured. That said, key items are not available currently (i.e. the heat sinks), so it’s still a bit moot either way.
2. If I cannot sell the Lyr 3 within next couple weeks, I’ll have to return the GLmk2, hold onto the Lyr 3 and continue to try and sell it, and in the meantime play the waiting game for a possible re-stock of the ACP+ kits.

In either of those scenarios, I don’t have the complete sound of the ACP+, which is a bit of a bummer, honestly. It’s hard to hear that sound, know how affordable it is to achieve it, and yet not have a clear path to it! What a weird situation I’m in. I learned A LOT from these past couple of weeks, but I’m going to have to see how this plays out.

 

Have to say, your impression gave me some similar feeling to my impression of cap modded Liquid Platinum: everything feels more clear, more precise and more defined. Just like you mention, a OLED TV with sick resolution. I was super happy about the mod, but ended up selling the amp 6 months later.

I'm glad that you really liked the ACP+, I want to get the kits and build one myself now! But my experience was that this "super resolution and contrast" eventually gave me this non-human eerie kind of feeling. It can be similar to the feeling of lack micro-details, I just found things or feelings missing, but in a more severe or darker way, but I couldn't put my finger on. Hell, it's even like using black magic, deep down I just felt so more and more uncomfortable.

Maybe I'm just a dynamic headphones + tube amp guy, and I just found HD800 + Vali 2+ with RCA 6BQ7 sounded really good as they just sounded full. Maybe it's the black background that got me?

My suggestion is to try to play with the ACP+ for a bit longer, and see if it really suits you.

 

What I would recommend is to do not settle if you want the ACP+. Have you tried posting wanted ads on HF or USAM? You never know and could get lucky that someone has a built kit just sitting around. Otherwise this is always going to be in the back of your mind.

Also, I would definitely return the GLMK2. Otherwise if you keep, it and then try to sell it later, you will surely lose value on them. Even recently I saw a GLMK2+GRPS for 400 total on audiogon. The Lyr 3 has consistantly and conservatively sold for 300-350ish, and better IMO to keep your Lyr until you can get the ACP+.

If you can source the materials, even better. The Heat Sinks, are available from digikey btw. Im sure you can find them somewhere. (https://www.digikey.com/en/products...sion-of-boyd-corporation/551002B00000G/240980)

It is kind of a mood killer when you're listening to something, and you know you are missing that X factor, the characteristic that you cannot unhear. Try not to settle.

 

This ^

You can’t undo your first crush.

You might try the GL with the GRPS which might give you better blackground but that’ll increase your cost. As mentioned, a used set might be your budget ticket, but I think you already know what you want.

 

Here's how you get an ACP+:

Step 1. Go to the DIY Audio store and click the "notify me when available" button. Their kits usually get restocked within a couple of months of running out.

Step 2. Go to the diyaudio.com thread about the ACP+ and ask for help sourcing parts. The people there are awesome and will take care of you.

 

The BOM is in the FW article here: https://www.firstwatt.com/pdf/art_acp.pdf

You DO want to get the board and jfets from the store (available now). The jfets and accompanying resistors are matched by NP and delivered to the kit that way.

EDIT - it's just the boards available. You want those jfets so it probably makes sense to wait for the full kit.

 

It's really wild, I have not heard this total package of sound under $1000 before. The transparency of the ACP+ is just top notch, and it knocks the engagement factor out of the park.

 

I'm definitely leaning towards this. I haven't posted any wanted ads, didn't really think to do that, but it may be worthwhile to try!

Makes complete sense - the worst case would be keeping the GLmk2 and then end up getting the ACP+ kit and building it, which would render the GLmk2 obsolete, in my mind, and be much harder to sell - for a loss or otherwise.

I must have searched the wrong thing or place, as I could have sworn I saw those heat sinks were unavailable. But this is great to see, and puts me back on track for possibly sourcing all the materials for a complete package.

Agree - this thing would be in my mind constantly with whatever amp I had that was not the ACP+. I've never been this excited about a headphone amp before.

 

I did do Step 1, but ran into a blocking issue with Step 2 (might be because of my work computer's VPN, I got flagged as spam). But I intend to share my compiled Excel sheet of sourced materials based on the PDF's BOM. I'm close to having it complete, but definitely have several questions that I am sure the community there can help answer.

Great points - it's likely I'm duplicating efforts, but it was still good for me to go through that process myself to learn. Hell, it took me a while to realize that R1, R2, R3, etc. was simply a sequential ordering, and had nothing to do with the actual resistor value!

And yes, I think part of what's making this ACP+ I've had sound so awesome in the blackground is the added SMPS that the owner implemented. I'll definitely look into the the Noise Nuke as an option as well!

 

What about a chungus-khan trafo followed by a bridge, CRC-filtering... And a buck converter!

P.S. I generally agree - the main power source dictates the linear/switching moniker. Linear means you spend the rest of the circuit fighting radiated and diode-switching AC noise, switch-mode means wrestling with RF hash blared inside the amp and back into mains.

 

The JFETs are definitely the biggest head scratcher for me at the moment. While the kits are out of stock, there is a dedicated ordering page for the matched JFETs here: https://diyaudiostore.com/products/matched-jfets?_pos=1&_psq=matched+jfet&_ss=e&_v=1.0

However, I don't have the first clue as to which would be the appropriate selection for the ACP+. That is one of the key questions I'll have for the DIY Audio community once I can join in there.

 

Yeah, fair point. I meant that both amps share the natural and sweet overall presentation of Class A, wherein it doesn't come across as dry or comparably artificial as other designs can. The ACP+ just has a bit more "wetness" to the midrange, whereas comparatively the GLmk2 presents a more straightforward and drier sound.

 

On that one page, scroll down. P channel quad is given for the ACP+.

Then go to this page and look up the IDSS of the jfets. https://diyaudiostore.com/pages/idss-choice

What you end up with is this:



The boards are available for purchase right now. There you go, you got boards and fets. The other stuff can be sourced from mouser or digikey. If anything is currently not available, ask the diy audio guys for substitute suggestions. There are plenty of parts that can be used so fret not - you can have this thing playing in a month.

 

I'm still learning how to associate the right adjectives to describe what I hear - plenty of room for improvement (and comparatively much less component experience than most of the folks here). Power hasn't been a major concern for me, as I have the LCD-X and Grado SR-80e. With the LCD-X, there is way more power than I could even think of using. 12:00 is about as high as I need to go.

And from what I'm experiencing, the ACP+ is even more resolving and revealing of microdetail. I definitely prefer the highs of the ACP+ as well. While I do imagine the GRPS would help improve things further, I'm not willing to shell out another $300 to find out how much. Even then, I have doubts, and at that stage you're talking about an $800 investment vs. $200 ($300 if considering a nice chassis to put it in).