Pass Labs HPA-1 Headphone Amplifier

I have been in this hobby for a long time and I really enjoy great musical reproduction. When it’s done well it makes me smile a lot and I get lost in listening…well recently I had a purchase that makes this feeling and experience happen a lot!

I had 24 amps in house at one time last year and am down to 10 at the moment, and am selling a few so it will go down to 5 - 6. Being an electrical engineering type I have fallen in love with amplifiers and their design and performance. The most important thing with an amp is its ability to amplify without getting in the way of those analog audio signals.

There are many really great choices for headphone amplifiers out there from $99 to thousands of dollars. All pretty good, some more so than others for various reasons. Perform an honest blind AB controlled level set test and it’s amazing how well they all are in comparison.

But every once in a while, an am amp comes along that measures ok, is simple, but has that “magic” that cannot be explained alone via specifications or cost.

The Pass Labs HPA-1 is one of these “rare” amps.

My HPA-1

Pass is for sure a well-known name in the industry and Nelson Pass is a “giant” in this area. There are a few of these guys around that I really admire and Nelson, Paul Klipsch, Mike Moffat, Jason Stoddard, David Hafler, Wayne Colburn etc…a long list and some are not with us anymore. But their contribution lives on. I loved the favorite word Paul Klipsch often used “bull!”……when a claim that was made that he vehemently disagreed to.

The designer of the HPA-1 is not on this list. Yet. Jam Somasundram is the man primarily behind the HPA-1. There are tons of great reviews of the HPA-1 amp, and the history of Jam and how he got to Pass Labs and the design criteria of the HPA-1. This amp is not the nice new “shiny” thing, its old. 2016 to be exact. But it has stood the test of time.

Many folks have this particular amp on their TOTL or End Game list, Steven Guttenberg has used this amp as his reference amp for years.

This experience is about the HPA-1 with my “stuff” and not a comparison against many other really good amps and those nice new shiny things that come out each month from a myriad of vendors. So, if your reading this to find out if the HPA-1 is better than your “super” amp…you can stop reading now. As Jason Stoddard often states “We dont tell you how things sound”…but “I” will give you some clues!

Nothing is perfect in audio, but the illusion at times is really good and having the HPA-1 in house I got really close to being there many times. More so than a lot of other good amps.

My “chain” (as the younger folks use of the word)…comprises of mostly REDBOOK 16 bit / 44.1khz ripped CD’s, using DbPoweramp, JRiver or Foobar 2000 in bitperfect mode. I am not a firm believer of High Res, Over or Up sampling…just good ole Redbook please…give me the bits please, just the bits…my dac is a Schiit Bifrost 2 into one of the many amps, in this case is simple SE into one of the two SE inputs of the HPA-1.

Headphones used are Focal Clears. Hedd Headphones, and MEZE Emperyeans. I also used HD600’s.

Other amps I have recently had the pleasure of listening with are a Phonitor XE, Soundaware P1, Schiit Lyr 3, Schiit Asgard 3, Schiit Jotenheim OG and Jotenheim 2, Schiit Magni 3, Schiit Hersey, ECP Audio T4, BH Crack, BH Mainline, Hagerman TUBA, Whammy, yadda, yadda, yadda.

I read all the reviews and listen to what trusted friends say or think about amps and throw all the rest of the BS out the door. The final arbiter is me and my ears. Nothing else matters.

So how can an amp that retails for $3500 not having a balanced inputs or outputs be any good? It it really worth $3500. Being a penny pincher and a DIY guy its a lot of money. Maybe not as much as a stellar mountain bike, but still $3500 is $3500.

The amp weighs 14 pounds. It’s a heavy amp compared to many other headphone amps…it’s about $250 a pound! Billet aluminum. Simple, strong, elegant look and construction! Made in the USA! I like this. A lot.

It has a simple look to it. A “HUGE” volume knob connected to a genuine ALPS pot…buttery smooth and easy to adjust and no slop at all. It calls you to “turn it!”…lol.

There is a micro-controller in the amp, and when you first turn it on the Power light blinks for 20 seconds with that nice muted “Pass Blue” color. Pass recommends having the amp warm up for an hour before serious listening or leave it on all the time 24/7 and its ready when you are.

I took the top cover off by removing 4 allen head “bolts” and took a look inside. Yes there are many professional glamour shots online but having the amp here and being able to see it in person is really awesome for a EE guy…for sure! Great parts, a very well laid out design…the electrical flow is spot on…a robust toroidal transformer (with MU metal and faraday shield), good filtering (that’s BIG caps)…, BIG heatsinks, good soldering, great wire terminations…all those things I like to see in a really high end unit…care in the build, lots of billet aluminum. Seeing the transistors mounted up off the left and right channel signal area PCB is a treat for a guy like me…all lined up perfectly, straight and in line…like they are going on a parade! (Note: I asked Pass if I could open the amp up to look inside without voiding the warranty. The answer to me was “Yes” but unplug it first!”).

Published Specifications: Class A all the way.

Gain (dB) 8 db
Frequency Response 10hz – 100k -1 dB
Output Power into 20 ohms 3500 mW
THD + Noise < 0.005 at 1V out
Out Power into 300 ohms 200 mW
Input Impedance 50K Ohm
Output Impedance < 2 ohms
Power Consumption (Watts) 23
Unit Dimension (W x D x H) (In.) 11 x 13.5 x 4
Unit Weight (LBS) 14

This amp is circa 2016. Except for the older reviews there is not much out there that speaks to this amp in recent times. But if you take the time to go back and read thru them its clear that this amp is indeed special. Pass has an established name in the audio industry, from the First Watt and the F7 has left many audio folks impressed. Yet the amp is not a Nelson Pass or Wayne Colburn design, but the new kid on the block Jam Somasundaram’s. Jam was the director of engineering for Cary Audio. They have known each other for 35 years…so IMO they have had a long time to cross pollinate ideas, theories and technology.

One thing I gleaned in researching this amp is the way PASS designs, builds and tests their stuff. They listen. They listen “often”. They are into discrete Class A products, purely analog. They are not into the “frills” just robust no-frills enclosures with a great sound above all else. Designing, building listening…over and over and over for many months. Measuring at the end. Does the design listened to so often match the numbers at the end? Building something for the sound and voicing etc. and measurements last…I like this.

It’s not a shiny or delicate object. Its built to last. Billet aluminum enclosure, the front plate is 1/2 thick solid aluminum. Does this make it sound any better? No. But it’s really cool. LOL. The unit is in this heavy aluminum “box” bolted together with hex head “bolts”. It’s a classic Pass look. It’s an industrial in your face look that screams “USE ME!”…all the time 24/7. And that’s Pass’s recommendation in the manual… leave on 24/7. Why? Warm up, stability, best performance, ready when you are for the best usage. That said I asked Pass if its ok to turn it off when done listening. The answer was “yes”…it’s more of a convince thing to be ready for listening anytime. Still an hour or so of warm up is recommended before any serious listening.

It’s an “exceptional” solidly built box. Period.

The buttons on the front are three. Clicky. Input 1, Input 2, Preamp. A Power on led or diode is directly above the Input 1 Led. All “Pass” blue.
A 1/4 or 6.3mm Neutrik input jack is to the right of these with the “PASS” logo CNC milled into the front panel. No 4- pin XLR, 3 pin XLR, 3.5mm, Aux etc… nope…just that one solitary 1/4 hole. Must be telling us something? Wonder if we are listening?

Oh, by the way some have stated they don’t like the 1/4 jack…well it’s the same jack you find on Gibson’s Les Paul guitar…and technically there is a reason for this particular jack being used as well. Again, a small point of design that was not overlooked.

The rear is as simple. Less “Pass Glitzy”. ON/ OFF switch in an integrated IEC power assembly with a fuse, which is self-replaceable. One set of RCA outputs for the preamp, and lastly two RCA inputs. No balanced. Simple. The bottom has four aluminum feet with rubber washers. The whole box is anodized.

Why do I take the time to discuss the box? Its build? Because with a Pass HPA-1 you’re not just buying an amplifier, it’s a structure. A very well-built structure that is well above many other boxes out there…and yes you’re paying for this, a lot. You’re paying for a year of design and test. You’re paying for excellence, all over. It’s like a family heirloom. And oh, by the way the best part of this “structure” is inside!! A great home for a great amplifier circuit.

I am a purist. I like simple well-built and well performing stuff, especially in audio. For me this amp was always there on the radar. It fits my audio goals.
Totally analogue, nothing attached to the digital world. (there is a micro-controller but not in the audio chain). The goal was to operate all the time reliably. To sound as good as possible. To basically drive any headphone load across a broad range of loads. Voltage. Current.

It’s the first Pass headphone product. It’s also the lowest cost Pass amp! An added benefit for some is a world class pre-amp, that is not an afterthought or simple tap off etc…I don’t use this part of the unit. Maybe someday.

Ok so attach the power cord. It’s a huge power cable. Gosh really nothing wimpy about this unit. Big and stiff cord. Attach inputs. Turn on. The amp starts in a mute state. Blue power light blinks on and off for approx. 20 seconds. Press one of the INPUT buttons or Pre-amp. Plug in cans, press play, turn that BIG knob…and “Smile”.

So what’s the design all about. Well it’s a fully discrete design. Using discrete transistors, resistors, capacitors etc…look at the pictures. You will see one op-amp in the unit but it’s a DC servo. This is a direct coupled amp. Low feedback. The power transformer is a beast. It took a few tries to get this the way they wanted it to be, low noise, toroidal with care for keeping the AC isolated from the other circuits, with MU metal and a faraday cage. 40,000 uf in filtering caps on to discrete voltage regulators. All on their BIG individual heat sinks. The choice of “type” of components in this amp was very well thought out. To someone that likes circuits and is not just an “appliance” operator this is special and important to me. Toshiba J-Fets in the input stage. This is the “voltage” gain part. Fairchilds Mosfets in the “direct” coupled Class A output stage. This is the “current” drive part. A real ALPS pot. A large pcb with all the stuff soldered well to it. Clean layout. Labeled very well.

Ok let’s talk sound and performance.

One thing I found using this amplifier is that it made every headphone I plugged into it “work” better. It has the uncanny ability to bring out the very best of any transducer you use with it. Its worthy of any TOTL headphone. Many reviewers have used Focal Utopias, LCD4’s, Abyss etc… with spectacular success. With my Focal Clears, Hedds, and Meze Empyreans it was nothing but stellar each and every listening session. The Hedds were the hardest to drive “spec” wise, but the HPA-1 easily drove them very well.

It makes listening a totally new experience. Slam, fast transients…no audible distortion…bass that is excellent, extremely well controlled. It draws one into the performances and nothing is left unheard. Good or bad. There is this sense of personal connection with the music. It’s addictive, and I found myself wanting to just listen and not wanting to stop!

The sound, the ambience in recordings, the reverberations in a concert hall, or recording studio are readily apparent. Excellent resolution, exquisite details. The ability to really hear what the recording was originally all about with good headphones is there in spades. Dead silent background. Thunderous bass, with body and soul. Fat juicy musical notes just jump out at you… often quite shocking how well they are displayed in your “ears” and brain!

Many amps are good, some really good, and others are above and beyond. With the HPA-1 you’re in the above and beyond category all the time. It’s easy to have your expectations dashed with great claims when that new shiny object lets you down. You sell it and move on. The HPA-1 is one of those rare audio devices that really lives up to the hype. And really there wasn’t a lot of hype around it. It was just the first foray into a headphone amp by a company that likes simple clean discrete designs… that often lead to excellence. This amp is excellence.

I got this from Desmond at Pass: “We like simple clean designs and they tend to work better.” Indeed.

There is a fluidity of sound that flows from good recordings…makes you feel like the presentation is above the ordinary… it’s very clean, very accurate, very precise, but so musical…a SS kind of euphony…Sound that comes out from a inky black silent background…just wonderful.

Many reviewers have just simply stated “Spoiler Alert - this is among the best heaphone amps I’ve ever encountered”. And I totally concur. It’s that good.

Even though this amp was not directly designed by Pass himself it meets all the Pass design criteria, build goals, simplicity and this amp did not get out the door without “poppa pass’s” blessing. After all its his name that is machined into that front panel!

Some interesting quotes from the designer Jam Somasundram:

“The HP-1 was designed more like a small power amplifier than a traditional headphone amplifier. It will drive headphones that have impedance ranging from 15 to 600 ohms (which is a conflicting set of requirements for a good design). To overcome this, we had to use relatively high supply rails as well as a high bias. (Note the rails are 24 volts).

The amplifier uses a complementary topology with a cascoded J-Fet input stage and a Mosfet output stage. The design is fully discreet and uses very small amount of feedback and has a wide bandwidth.

The output stage is biased into Class A for more linear operation and improved distortion characteristics.

The transformer has been custom designed for the HPA-1. It is a toroid that is rated at over three times of what is required for the circuit and has a Faraday shield built in as well as magnetic shielding around the circumference of the unit, to reduce noise. We had to go through several prototypes before we came up with one that met our requirements. Contrary to popular belief, transformers can make a huge difference.

The importance of the power supply cannot be ignored in a good design and to this end, the regulator is composed of discreet components and is a very low noise design with over 40,000 uF of capacitance with local decoupling for each channel.

Switching and mute functions are controlled by a custom programmed micro-controller.

We have left out any unnecessary features that we deemed would compromise the sonic performance of the unit; less can sometimes be more.”

“The unit is designed to stay on at all times. The power switch is located in the rear.

When the power is turned on the unit goes into a mute state for twenty seconds. This is done to allow the circuitry to stabilize. During this period, no functions are available, and the power led will flash. When the unit goes out of mute into operate mode the power led will stop flashing and stay on.

The amp has two inputs that can be selected from the front panel.

The unit also has a pre-amp function, which is selected from the button on the front panel. When the pre-amp function is engaged, the headphone output is disconnected — only one output (either headphone or pre-amp) is available at any one time. This is done as a safety feature.

The unit gets to optimum performance about one hour after turn on. In the event of a power loss, the unit shuts off, and upon restoration of power the unit will go through the mute cycle and return to the state it was in prior to the loss of power. It will remember the last input and function and will return to that setting. This is also true when the unit is switched off with the power switch.

Finally I suggest you try the unit as a pre-amp, we believe it will hold its own against products which cost much more.”

Q: Is there any area about the HPA-1 which you feel could have been improved if cost was no object? It’s already quite expensive as headphone amps go but is there anything that was “held back” for any reason?

A: If cost were no object I suppose we could improve the power supply further, or use a dual mono version, all of which I have tried with minimum improvement. Sometimes added complexity can work against you. If you look at the price/performance curve, I think we are in a pretty good spot.

Q: Similar to question 1, is there any design aspect or parts implementation that would have been used if there wasn’t any regard for realistic manufacturing processes etc? I know the DIY community does some crazy stuff that wouldn’t be tenable for a company to build even in modest numbers.

A: I actually tried some crazy stuff (ideas) in the design but only used them if they worked. Parts were chosen for the best performance, and we found that some audiophile (boutique) rated components actually hurt the sound. We tested the amplifier with a wide variety of headphones to check that we were not missing anything. Also, reliability plays a key role in a product like ours, and you do not want to skirt too close to the edge.

Q: Are there any similarities to any of the existing Pass models? I’m not referring to general similarities like low feedback but rather specifics…. was anything borrowed or inspired heavily from any portion of another Pass product? I guess I’m trying to clarify if this is a complete “ground up” design.

A: The design is quite different from existing Pass models, primarily because of the requirements of a headphone amplifier as I mentioned in my other e-mail. This is a totally ground up design, we might use similar parts but the topology is completely different.

Q: I like your comment on voicing. Can you explain in your words the difference between “design” and “voicing”?

A: I would say design is the basic topology/circuit used in the product that works and meets your basic objectives. Voicing is the tricky part which includes for example your choice of components, amount of feedback, and biasing, among others. In my opinion voicing can make the difference between a good or acceptable product and a great one. On the other hand, voicing is not going to help a bad design.

Q: Also related to the above question: as you know, some of the more objectivist designers’ frown on the term voicing… I suspect you understand their point of view but simply disagree, so where do you think they go wrong?

A: A long time ago I thought that specifications were everything, but quickly learned that there are some things in audio that can’t be easily quantified, or qualified for that matter. Specifications should be used as a guide, and if higher distortion means a better sound then you have to make a choice…. Of course, some sort of balance has to be struck.

For example, if distortion was the main criteria for the quality of an amplifier, no one would own tube amplifiers. Things like Yamaha receivers would rule the day. In my opinion the technical aspect of a design is only part of the equation, and the rest is an art form. I am not stuck in any design camp, which I find can be counterproductive. For example, the no-feedback idea — you have to use elements that work for your design, otherwise you can paint yourself into a corner with the end result being a handicapped product.

We at Pass Labs listen extensively to everything we manufacture and the process is quite lengthy. Our main ideal is that no product should be released before it’s time.”

So for me in conclusion this is the “best” amp I have ever used or heard for that almost perfect goal of a “realistic” audio performance with great headphones. Its indeed a TOTL or End Game amp for many and especially for me.

I bought this amp and have no intentions of selling it!

If you can get ahold of one, give it a try. You might like it. A lot.


Final Pix:
All the Pass has to offer to date for Headphone addicts…HPA-1 and the Wayne Colburn Whammy!
Made in the USA by Pass and “Me”.


I have a story to share and some stories need to be put in writing so that the actions of exceptional people are memorialized and passed on.

One such exceptional individual is Kent English of Pass labs. Kent is a real professional who absolutely knows his stuff and puts the faith of his products and the customer first!

I emailed Pass looking for service help, I told Kent what my problem was in the best detail I could muster while trying not to come off like the dummy I know I am🤪

Kent was brutal in his answer letting me know that he has yet to see an actual broken HPA-1 and then clearly walked me through what the suspect issue was, (rare but possible loose connection) and WHAM! Spot on baby! He even had a local to me, service technician and shop looped into his email response on the small tiny chance that I may have had a real issue or needed a helping hand. He was clear in stating that shipping the amp back to him across the country would not be needed and most certainly not encouraged since he had every confidence I could make the correction myself and be operational lickety-split!
Damn if Kent was not 100% spot on!

So a heartfelt thank you to Mr. Kent English at Pass Laboratory, his wisdom, experience and knowledge along with his approach to customer service and his products are so many levels above and beyond the mass corporate bullshit we get nowadays. I am a rabid fanboy for life.

PS. The PASS HPA-1 is built like a tank and not even the angry disgruntled gorillas that work for USPS were able to take one out :muscle: :muscle:

She is as beautiful inside as on the outside😍



Awesome, glad u got it sorted out.
Its worth every penny I paid for it.

And its indeed a “real” Classy Class A amp all the way…

Going to become a family heirloom!

The actual layout was designed for easy troubleshooting …


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All these topless pics are getting me hot.


Class A amps indeed can get a tad warm!!!


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Many amps have come and gone since the HPA-1 landed here on my desktop listening area…its still here running 24/7. Tested recently against iFi Signature iCAN Pro amp…it holds its own here…

Not all the bells and whistles as the iFi ICAN Signature…no tubes, just a CLASS A amp that is voiced for exceptional musicality and open and airness…

Final Audio 8000 Pros and recently a new set of ADX 5000’s its my gold standard as to how an amp should “sound” or “not sound”…

Acutally thinking of parting with the new iFI stuff…just not that better all around. Yes the iFi has Xbass, Crosstalk, 3 and 4 pin XLR, 4.4mm Pentacom balanced, 1/4 SE and more…but why?? Hmmm.
Oh and tubes. Ok. Fine.

The PassLabs is like the best in SS with a slight musical tube touch…sweet…very sweet…

Just a lovely amp…


Comparing a $149 amp with a $3500 amp…LOL

I’m sorry, as much as I love good audio gear, I’m lookin at this amp and I see no reason why this thing should cost what it does. I’m sure it’s a great amp, yada-yada-yada. I’d like to see the BoM that shows just how much it costs them to make this thing. Then maybe I can understand it. Hell, I’d like to just be able to listen to one so I can actually hear what the difference would be. But it will probably never happen, so it doesn’t matter. And I think that is the big disconnect here. But whatever. Enjoy.

Totally understand your feelings on this amp…same can be said on many other high dollar audio devices. I do have first hand knowledge of the cost of another high dollar amp. I will not divluge the name but I will tell you that this item retails for $2300, then dealer cost is about 1/2 this amount *the middle man), so the cost to make it would be less for the manufacturer.

This amp in particular has been cloned by a person and it took this person 100 hours to do this…this included the figuring out and guessing the circuit, schematic, board layout, marching parts etc…It also included this person machining and milling out the case…so it was and is a really close look alike.

Its simple to look at this expensive amp and state it costs way too much for you. Fine I respect your opinion and there are other lesser costly options that will perform as well.

This is NOT a mass produced headphone amp. Labor is often thought to be “free”…in this case PassLabs building one is less labor intensive for PassLabs than the person that went thru the hundred plus hours to make one…

This amp is not made in China with who knows what parts etc…That IMO is worth some bucks…but
hey I dont be-little anyone that wants a $99 amp or a $5,000 amp…disconnect for some sure for others not so much…

I love cheap Schiit stuff…as well…sans the picture…its all good. And as Schiit states if you dont like it dont buy it…no one is breaking your arm to buy this amp. There are many other great choices out there.


Note: That ole thing about driving a Cadillac vs a VW etc…both get u there…etc

Actually the difference between this amp and many others is really very close…sonically.
The big difference IMO is the voicing…soundsage…very musical and airy sound…
So that begs the question why do I have this?
Answer: Because I can.


The Pass stuff is expensive because it’s way overbuilt and all parts are hand selected and matched. Other than the capacitors which have ~20 year life span (there are no capacitor that will do better) but are easily replaceable, the amp will work and sound the same as day 1, long after you’re in the ground :grin:

Unlike 99% of products these days, you get what you pay for.

If you’d like the BOM, the amp’s been reverse engineered over on DIY audio and you can build your own for approximately 50% savings. And the actual real designer of the amp is there to help you and give you hints. Not all shall be revealed though because the design is Pass IP. So get ready to do some homework and also, scrounge the world for high quality but no longer produced output devices and hope you don’t end up with fakes.

Yeah its been reversed engineered…but most folks dont have the skills to fabricate that tanks built like case…that guy is 1 out of a 1000 to do this from scratch…amazing for sure…

Pass might hire him!! lol.

Do you mean a kit? That would be kinda awesome! If not there would be no point. Heck, I would have no time to build the kit if there was one, let alone go chasing around for parts. Come on, now! :laughing:

No, I would want the real one. I am quite sure this amp is amazing. But I’m just not feelin the overall package. I am still not convinced I am lookin at nearly 4 grand, either. But hey, that’s just me. It still comes down to I would have to actually listen to one and go from there. And I think that is fair.

No kit, it’s called “DIY” for a reason :wink:

Just milling out the case and parts would cost a LOT of bucks…my guess at least $500 + for the case easily with the bevels and 1/2 thick aluminum from panel…

Like @A_Jedi says its not a kit for sure…

I asked Pass if I could take the covers off to take a look without having the warranty violated and they said ok to me.

Quality Control and test sign-offs:


In the design process of having a amp work with a wide set of impedance’s with NO gain switching having 3.5 watts on the low end…a good amount of engineering was done down to picking out the “specially” wound transformer, several prototypes were excluded. The layout is such that left and right circuits are laid out for ease of troubleshooting etc…Soldering is exemplary.
(Soldering inside to me means ALOT, no flux on the boards, clean, well done, no failure points).

I have said this before the amp has a beautiful “voicing” for a SS Class A amp…very what I call “musical”. This AM I am gong back and forth between the iFi iCAN SIgnature amp and the HPA-1.
The HPA-1 has an immediate more open soundstage both of these amps are touted as very good amps and cost the farm out west.!

The volume “pot” on the HPA-1 is buttery smoooooth…and with most cans regardless of impedance the pot is always off the “bottom” of the pot travel, unlike the iFi and its gain settings at unity…its vol pot doesnt get over 10 o’clock and thats very LOUD here.

Then there is that 'Schiit" thing of being made and built here in the USA. Yes I have no bones about this. I like it, alot. And yes I have other not made in the USA stuff as well…its not a bang on overseas stuff my subjective preference. Semper Fi here.

Happy Thanksgiving to all! Enjoy the Turkey!


Yeah I figured as much! :grinning_face_with_smiling_eyes: Oh well. @lost33 Thank you for the audio porn! It truly is a thing of beauty. The innards, that is.

Happy Thanksgiving to you, Sir. And to all. Enjoy the day.

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Versus a recent chi-fi made amp: Cold joints, flux residue all over the place…just poor shoddy workmenship by folks that dont care as much for quality vs speed …get it out the door etc…

That is some tech-gore right there!
Almost a miracle they are soldered in at all at this poit.

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This is from an amp with “Spectacular” measurements! Mine is not the only unit that I have seen this shoddy workmanship. To be fair on the other side all the small components are well soldered…wave soldered it looks like.

Just all the bigger parts, like electrolytics, switches caps, RCA phono jacks, power jack etc…all seem to be hand soldered by some folks that have no clue how to solder and the flux which in itself is ugly offers no real immediate problems, but over time it could…

You really get what you pay for…if your into DIY u can avoid this, but not all the stuff out there is DIY.

I sent this unit back for a refund.

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