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I have built the Aleph J using the same diyaudio.com boards shown in the thread photos. In fact, I built the Aleph J at the height of the pandemic, and I connected with a couple audio buddies via weekly Zoom calls to coordinate three simultaneous Aleph J build projects in 2020 across the country. It was a great project to build together while everyone stayed home to work. I used balanced connections from my Schiit Freya+ line stage, and when I run the Freya+ in tube mode, the sound quality is very good. My other Pass DIY amp uses Sony VFETs, and this amp sounds fantastic as well, but like henry4841 stated before, the single-ended Aleph J has a tube amp-like presentation. My build uses the Toshiba JFETs as the First Watt builds used, but the JFETs that are included in the diyAudio.com store kit are equally good.

Glad to hear you are pleased with your Denafrips Pontus II DAC. I love mine, and I really have not felt a need to invest in a DDC. Digital music is more enjoyable and convenient to access using my Raspberry Pi 4 running Volumio 3. I mainly listen to ripped CDs, but will use Tidal on occasion to listen to music I do not already own.

Nice system with the Schiit Freya + preamp. I switched from an Audio Research LS7 single ended tube preamp to a Schiit Freya + driving a Pass DIY Aleph J Class A amp I built. This is a very musical combination. Since purchasing a Denafrips Pontus II DAC and running balanced connections throughout my system, I rarely spin vinyl anymore. I have only listened to the Pontus II in NOS mode, but plan to try OS mode soon. I really need to take time to listen to gear for an extended time before I decide if I like it or not. Well, I love the Pontus II. It just reproduces digital in a way I never thought was possible. I am now a believer in the R-2R DAC technology, especially in the way that Denafrips has implemented it. The Pontus II is built like a tank. I can appreciate the many comments made on the use of a DDC. I have my eyes on a Denafrips Iris DDC. I will need to research the best I2S cable option. Right now, I use a Jenving Supra USB 2.0 cable between my Raspberry Pi 4 running Volumio 3 and the Pontus II, and I am astounded at what I hear. The Jenving USB 2.0 cable is USB-certified and has the 90 ohm impedance that digital audio guru Gordon Rankin claims is essential to proper digital music transfer via the USB bus. Jenving cables are manufactured in Sweden and are engineered for performance and measure well. Anyway, I appreciate what folks are posting on this forum thread and plan to purchase an Iris soon.

I recently purchased a Freya + as a B-stock item, and it arrived within a week of ordering the preamp. I just couldn't wait the long lead time for a new unit. Anyway, I can't find any blemishes on the chassis and it was packed like a brand new unit with what looks like a new quartet of JJ 6SN7 tubes. It must have been a return. Instead of using the stock JJ 6SN7's, I installed two matched OS GE gray plate side FAT D getter 6SN7GTB tubes in the differential voltage gain positions (right side) and two new production Tung Sol 6SN7 tubes in the output buffer positions (left side). I initially used octal socket savers from Eurotubes in Portland, OR to elevate the tubes above the chassis to keep the chassis from any additional heat radiating from the tubes. Later on, I took them out as most of the heat generated using the Freya + in tube mode radiates from the regulated power supply underneath the top cover. For connections, I wanted full balanced connections from my DAC to my power amplifier. I used two pairs of DIY Mogami 2549/Switchcraft XLR balanced cables to connect my SMSL SU-8 Version 2 DAC to the Freya +, and the Freya + to my Pass DIY Aleph J Class A power amp that drives my modified Klipsch Forte II speakers. I have a Raspberry Pi 4 running Volumio connected via USB to my SMSL SU-8 DAC. I started off with the Freya + running in the differential JFET buffer mode, and I really like the clarity and large, deep soundstage. the bass response is very good and I really appreciate the black background with the all-balanced connections. Operating the Freya + with the nice metal bodied remote is very straightforward. I am not sure why some people have complained about the clicking noise of the 128-step volume attenuator. I found that it works very well with excellent channel balance. Overall, the differential JFET buffer mode presents a musical presentation with great tonality, timing, and great detail. After running about two hours, I switched the Freya + into differential tube mode, and the sound was initially a little edgy in the upper midrange with some sibilance, but over the course of 30-60 minutes, the sound smoothed out significantly. The soundstage started to open up to extend beyond my speakers side-to-side and well beyond the back wall. The tone took on a creamier richness if I can call it that. As others have said, the Freya + in tube mode will get warm--literally. I could place my hand over the power supply area where most of the heat is emanating and keep it there, so it wasn't scorching hot, but definitely warm. But then, I also have a Pas DIY Aleph J with some hefty heat sinks radiating a lot of heat too. The combination of the Freya + driving my Pass DIY Aleph J sounds beautiful. I can play anything from blues to jazz, to rock to symphonic classical, and the music is so engaging and organic. I have listened to lots of vinyl playing on my Denon DJ VL12 Prime direct drive turntable connected to my Audio Research PH5 tube phono stage and the Freya +. It just gets better with an analog source. Separation between performers is excellent and the fine detail and tonality of the music comes through very clearly. I hate to say it, but music sounds better playing through the Freya + compared to my Audio Research LS7 tube line stage. With the balanced connections, I have a black background, and maybe this is what allows me to hear things in recordings I hadn't heard before. Maybe it's because the LS7 only has single-ended RCA connections. I also have a rebuilt McIntosh MC240 tube power amp to connect to the Freya + using RCA single ended interconnects. In my experience, the sound really settled in nice after 20+ hours of cumulative playing time. The jury is still out on long term reliability. For now, I have to say I am very impressed with the build quality, the Schiit aesthetics, and more importantly, what I am hearing from this $899 preamp.

Been really busy and unable to keep up with all the audio forums. I very much enjoy the Aiyima A04 TI TPA3251 Class D amp. Mine is not stock as I have installed Burson V5is op amps, CoilCraft toroidal inductors, and some short lengths of Duelund DCA16GA Tinned Copper wire. I use this as a power amp connected to my Pass DIY B1 Korg NuTube preamp. The Aiyima drives a pair of KEF LS50’s nicely. I am not familiar with the Aiyima TPA3255 amp. Is this the newer A07 amplifier?

If you don’t win either lottery, your best bet is to purchase some roughly matched NOS Tokin THF-51S SITs (VFETs) from eBay seller watanabetomoaki. Nelson Pass will have a design out that will use these SITs in a similar manner as his new single ended SIT amp using Sony 2SJ28 N-channel VFETs. Nelson Pass has mentioned that the Tokin SITs might be more capable of higher power output, but I am not clear how much more over the 8-10 watt capable Sony VFETs.

I also have this DAC. It is not MQA-compatible, but it is a very fine DAC nonetheless, especially at its reasonable price. In trying different filter settings and sound settings, I’ve found a combination that works very well in producing a very natural sound through my system. I’ve tried balanced (XLR) and single ended (RCA) outputs and both are great with the balanced outputs sounding best. I am very pleased with the construction of this DAC with its robust power supply and quality components. The chassis is a weighty machined Aluminum enclosure. For streaming, I use a Raspberry Pi 4 in a silent fan-cooled Vilros die-cast Aluminum enclosure running Volumio with a Tidal subscription, and my personal music collection on a LaCie USB 3.0 hard drive.

I recently completed a Pass DIY clone of the Aleph J amplifier. I’ve been comparing it to my Dynakit Stereo 35 with Enhanced Fixed Bias (EFB), Pass DIY Sony VFET, and rebuilt McIntosh MC240 amplifier. To my ears and one of my audio buddy’s ears, the Aleph J is a very special amp with my Klipsch Forte II speakers. It is most similar to the Pass DIY Sony VFET amp, but has something special that puts it in the running with my favorite, the McIntosh MC240 tube amp. The soundstage is huge like the Sony VFET and MC240 amp, but the level of detail, natural tonality, and excellent separation combined with the pace and timing are something to behold. I’ve only had the amp running for over a week now. We’ll see how I feel about this a month or two from now. I suspect I will continue to enjoy this amp. My friend who heard it wants me to build one for him with a dual mono configuration in a larger chassis with larger heat sinks to set the output bias even higher. This amp gets warm, but Fall weather is settling in now, so the heat radiating from the amp’s heat sinks is not a problem.

The OPA627AU op amps are shown in the top photo. The OPA1622 op amps are shown in the bottom photo. I have not tried the LME49720 op amps yet.

I have had a chance to roll op amps in this little, yet powerful, amp: Texas Instruments OPA1622 Burr-Brown OPA627AU In comparison to the stock Texas Instruments NE5532 dual op amps, both significantly improved the sound quality in terms of creating a larger, deeper soundstage, better frequency response at the extremes, and improved detail. Both sets of op amps required 2-3 hours to really settle in. Since both types were mounted on DIP8 adapters, they were very easy to plug into the DIP8 sockets. On the other hand, removing the stock TI NE5532 op amps with their soft metal legs was more challenging and I ended up mangling the legs of one of them that would not come out of the socket easily. After much listening, I prefer the Burr-Brown OPA627AU op amps. The presentation is tonally rich and the bass energy was equal to my Pass DIY Sony VFET Class A SS amp and rebuilt McIntosh MC240 tube amp. The soundstage is life-size with really good separation of performers. The midrange and treble are very smooth with no brightness sometimes associated with Class D amps. In all, a very high quality amp, power supply, and optional op amps can be had for less than $100 to power Klipsch speakers.

Yes. There is an output pot on the Mean Well to make that adjustment.

For your setup with the balanced connections to the Pono Player, you are set with the best solution in the Texas Instruments TPA-32xx Class D amplification. I prefer the Aiyima for its compact simplicity and the very dead silent background. It has a built-in protection against the thumps/pops on power-up and power-down. I no longer have to be concerned with using the reset switch on the TI TPA3255EVM to mute and unmute the amp. I also wanted to roll op amps to see the effects on sound quality. The amp as-is is a keeper, at less than $50 sans power supply, it is quite a bargain for an amp capable of powering low-medium to high sensitivity speakers.

Hey All, I wanted to purchase an Aiyima TPA3255 2.0 amp through eBay, but the seller in China could not ship the amp due to the COVID-19 virus outbreak. They were great about it and promptly refunded my payment. That left me with the choice to purchase the Aiyima TPA3251 2.0 amp through Amazon.com who had some inventory of these amps in the US. I had to purchase a Mean Well LRS-200-36 switching power supply to power this amp since it does not come with a power supply. I had to dial down the power supply's output to 30VDC since the power rail capacitors on the Aiyima amp are rated at 35V. I've had great results with a Mean Well LRS-350-48 switching power supply powering my Texas Instruments TPA3255EVM Class D amplifier. I connected this amp to my main system using my Audio Research LS7 tube line stage preamp and modified Klipsch Forte II speakers. This is where I started my critical music listening and discovered that the right and left channels are reversed, so I switched my right and left hand RCA interconnect connections. My reference power amplifiers are a rebuilt McIntosh MC240 vacuum tube amp and Pass DIY Sony VFET Class A solid state amp I built with the diyAudio.com store kit offered several years ago. Both of my reference amps are excellent and I am quite pleased with the low distortion and highly musical performances of both amps in my system. I connected the Aiyima Class D amp to the Audio Research preamp and my speakers, and I have to say this little amp is impressive. First of all, it is very quiet with no music playing through it. I held my ear close to my efficient Klipsch speakers and didn't hear any hiss or other noise. Unlike the Texas Instruments TPA3255EVM amplifier, this amp only supports the use of single ended inputs. I'm sure the amp could be modified to accept balanced inputs, but XLR and TRS balanced connectors are too large to fit inside the compact enclosure. All that said, I like this Aiyima amp so much, I am now considering selling my Texas Instruments TPA3255EVM amp.

The Pass Labs and First Watt amplifiers are built with different design philosophies. Pass Labs amps are built to work with a wide range of high end audio speaker systems—some which represent very difficult loads, while most First Watt amplifiers are designed for high sensitivity speaker systems like horns and full range single driver systems with minimal crossovers. Not sure if meaningful apples-to-apples comparisons can be made since they are designed for different purposes. Having attended several Burning Amplifier Festivals in San Francisco including the last one a month ago, I can tell you that Nelson Pass’ passions are with the First Watt and Pass DIY crowds.

When I lived in the San Francisco Bay Area, I used to attend the San Francisco Tube Users Group meetings at the small auditorium in the Randall Museum. We used a pair of Klipsch Chorus speakers that were re-capped by one of the members. I hope the group still gets together, because I met some really great people in that group, had the opportunity to learn from others, and hear some great gear. The class should be very educational and the hands-on building experience is priceless. It’s a great way to get into DIY audio.