Introducing the Matrix M-Stage HPA-3U and HPA-3B, review to follow!

[bunkbail]

@raoultrifan May I know what analyzer did you use?

 

[raoultrifan]

Really sorry for not mentioning this: PicoScope 2204A with built-in signal generator, but also audiocheck.net audio files.

P.S.: Just changed the 4 caps from 2.2uF/250V to 4.7uF/250V. 20Hz square-wave is kinda flat now, not that makes an audible difference, but it's good for me to know that I can rely on a perfectly flat amplifier.

 

[raoultrifan]

For the sake of modding only, I've replaced resistors R10, R1, R13, R14 of 10kOhms with 270ohms resistors for further decrease amplifier's noise. These resistors are placed directly in signal path in series with the 50 kOhms potentiometer and for an inside temperature of 50C their noise would be 1.88881 uV RMS, that would be -114.5 dBV, same as stated in Matrix's datasheet (calculated with http://www.daycounter.com/Calculators/Thermal-Noise-Calculator.phtml). However, when volume it to the maximum then potentiometer's thermal noise covers the 10 kOhms resistors noise anyway.

The 270 ohms resistor are having only 0.310363 uV RMS of noise, that means -130 dBV. Difference is audible indeed, as I only modified one channel first and in my headphones one channel was having less noise (checked with sensitive cans like Beats Solo2 and Superlux 16-ohms IEM).

 

[raoultrifan]

The 10kOhms resistors swap I was speaking about in my previous post (also, notice the 4 missing caps C29, C30, C31, C32 from the low-pass filter that f...ed up the trebles roll-off):


The 4.7uF/250V upgrade caps from signal path:


...and how square waves look like with these bigger 4.7uF caps compared with the 2.2uF caps, but also compared with original high-pass filter + 2.2uF caps and with wires instead of caps:


Original HPA-3B with 2.2uF input caps


Modified high-pass filter mod & 2.2uF caps


Modified high-pass filter mod with input 4.7uF caps


Audio signal applied after the input caps (or short-circuit input caps)

Oh, not to forget, 20Hz sine-wave looks perfect, of course:


Note: Blue is the input audio signal from the generator, Red is the output audio signal from the 6.3mm jack. Only one channel was tested, the other one should be identical. Perfection means Blue superimpose with Red and become one sine.

 

[mickerru]

Anyone compared the balanced 3b vs schiit SE valhalla 2 using hd800? Deciding between the 2 if the matrix 3b is more advisable.

 

[WhiskeyJacks]

I tried to read through this thread all the way but I just have as much time as I would like to read everything, and I was hoping someone could give me a comparison that if the 3B balanced amp from Matrix is on par or better than the Jotunheim, now I know it is preference and opinion as far as hearing goes but I am okay with that, just so I have an idea because I get the Jotunheim for 45 dollars more or go with the Matrix 3b with burson V5i opamps

 

[raoultrifan]

Jotunheim seems very well built with higher output power in/out plugs too, not mention the cards you can add inside (also upgradable over time with future versions). If there's a way for you to test both of them it would be perfect, but if not...perhaps https://www.head-fi.org/showcase/schiit-audio-jotunheim.21792/reviews could help. If not, then please check https://darko.audio/2017/03/schiits-jotunheim-entry-level-endgame-head-fi/ etc.

 

[raoultrifan]

Hello,

While testing some more square-shapes a couple of nights ago I somehow managed to short-circuit the output of the left channel (single-ended) and one resistor got black and another one got brown. They were measuring fine (10 ohms), but there was a smell I didn't liked and I decided to swap them both to get rid of that nasty smell. As I had bigger heatsinks glued with Arctic Silver Alumina on top of all 16 drivers transistor (4 on each channel), I needed to remove one such heatsink to be able to unsolder the black & brown resistors...and sh..t happens...the SMD transistors got taken apart from the PCB by my brute force applied.

So, it took me a couple of days to get some low-noise BC550/BC560 complementary transistors to replace the originals. Quite a hard work for me, especially I've used through-the-hole transistors and there are no holes drilled in the PCB.



What I do like now: background noise decreased even further. Basically, when the first 2 gains are used this amplifier is on pair with my Objective2 when tested with sensitive cans like Beats Solo2, AKG K550 and Superlux HD-381F (16 ohms IEM). There's virtually no noise at all in my headphones if volume's to the minim on the first 2 gains; however, when the high gain is used there's a barely audible background noise, but only with the sensitive cans from above, not with the others.

What I don't much like: it looks dirty and non-professional with those transistors over there (well, same applies for the previous mods I've done). Also, no heatsinks can be applied anymore, so temps are really high one those drivers transistors (>60C with case open).

 

[raoultrifan]

Original SMD transistors and some black/brown resistors vs. the new THT components:


The new BC550/560 transistors installed


However, I can't recommend this mod, because of its high complexity and the improvement in Signal-Noise Ratio is barely noticed (and only with the highest gain).

 

[Devangel]

I'd be happy if someone could summarize all the mods for hpa-3b and hpa-3u in a post because I'm a bit lost with all the pages being a beginner and I'd like to improve my hpa-3b. Thanks.

 

[raoultrifan]

• I can only recommend the following mods, because the sound gets improved and these mods are easy to be done: 1), 2) & 4).
• Also, some other improvements might be considered, though the sound don't get improved: 5), 6), 7)
• Despite the sound gets improved, I'll make the mods 8), 9) and 10) optional, because of the complexity and risks of damaging electronic components or the entire amplifier. An easier and maybe better solution would be to replace the default LME49860 with OPA1652 (these op-amps can be powered from +/-18V and the amplifier will benefit of a lower background noise).
• Mods from 11) to 16) are quite complicated and there's a high risk to damage the amplifier for good, so can't recommend these mods, unless you really know what you're doing and if you also have a multimeter and a scope around. If you don't have a scope and perhaps a frequencies generator you should probably not touch the low-pass and high-pass filters because you can't verify if the mods have been successfully or not.
• Mod 3) is really dangerous to DIY and electricity hazard might happen, so I don't recommend it! Instead, please use a power strip with common-mode filter inside or change the inside power outlet with one containing common-mode filter within. You can also get an isolation transformer with common-mode filter inside or outside, this way you'll also remove any possible ground loops you might have in your audio chain.

Per https://www.head-fi.org/threads/int...-review-to-follow.770610/page-4#post-12120336:
- 1) Installing G.O.S.S. (Grain Oriented Silicon Steel) to shield the toroidal transformer. This will remove a bit of existing hum from the right channel (which can only be heard with very sensitive cans and volume to the max. without input source connected).
- 2) Replacing 2.2uF WIMA MKS 4 (Metallized Polyster) with JB JFX Premium Film Cap (Polypropylene Film) or with 2.2uF Audyn Plus, preferable 4.7uF, per https://www.head-fi.org/threads/int...review-to-follow.770610/page-21#post-14121897.
- 3) Installing EMI/RFI noise suppression filter (one stage common-mode filter) to reduce any possible noise injection from mains into the audio chain.

Per https://www.head-fi.org/threads/int...-review-to-follow.770610/page-5#post-12157815:
- 4) Adding more decoupling caps at the backside of the PCB, between op-amp's V+ & GND and V- & GND.
- 5) Adding Arctic Silver MX-4 thermal paste (overkill, I know) to the output stage transistor's heatsink.

Per https://www.head-fi.org/threads/int...-review-to-follow.770610/page-5#post-12178996:
- 6) Adding 2 heatsinks above the 2 op-amps to better dissipate the heat.
- 7) Swapping the 4 existing heatsinks from above the 16 SMD transistors with bigger ones (I've used Arctic Alumina bi-compound, but I strongly recommend thermal dual-scotch tape instead of Alumina). Also, ignore the fan I've installed in there, I don't recommend it.

Per https://www.head-fi.org/threads/int...-review-to-follow.770610/page-7#post-12390513:
- 8) Swapping the original JRC7818/7918 power regulators with NJM7815/7915 to lower the voltage from 36V to 30V, so I can install more op-amps to roll. You will loose a bit of the output power, there's enough juice left in there.
- 8') Same from above, but with very low noise regulators from Sparko.
- 9) Installing BURSON SS V5 duals to increase the soundstage, clarity and depth. Also, case needs to fit well, so some adapters could be used, preferable originals from Burson if possible.

Per https://www.head-fi.org/threads/int...review-to-follow.770610/page-19#post-13830489:
- 10) Installing BURSON SS V6 duals to increase the soundstage, clarity and depth. Also, case needs to fit well, so you could use some adapters (preferable originals from Burson if possible) or loose the warranty and remove op-amps shells to lower their height enough to close the case.

Per https://www.head-fi.org/threads/int...review-to-follow.770610/page-20#post-14100120:
- 11) Cutting backside PCB traces from the XLR plugs to the input caps, then further to the ALPS 4-gang potentiometer and getting the audio signal through good quality copper shielded wires. This way hiss and noise decreased a little bit; after all, I'm speaking of more than 20 cm of PCB traces (on expensive amplifiers input potentiometer is positioned nearby the XLR plugs and a metallic extender from the volume knob is used to adjust the volume).
- 12) Swapped 2 x BURSON V6 Classic opamps with 2 x OPA1652 installed on DIY SOIC-DIP8 adapters to further decrease background noise (some noise was audible only when using high sensitivity cans combined with highest gain setting of +20 dB). It's not much of a difference the 2 opamps, but there's a slight barely audible improvement (it's easier do check when swapping only 1 opamp only, then left headphone will have a different hiss/noise vs. the right one).
- 13) Increased treble roll-off frequency from 20 kHz to about infinite by completely removing the Low-Pass filter. Not quite recommended because some input sources might oscillate and deliver ultrasonic sounds, but in my case I'm safe...I know what DACs I got at home.
- 14) Decreased bass roll-off frequency a little bit by replacing the 50 kOhms input XLR resistors with 150 kOhms resistors (there's a high pass filter created by resistors and input caps). Ideally would be not to touch these resistors, instead to swap the input 2.2 uF caps, but I couldn't insert bigger caps inside the HPA-3B case...maybe some other time will do that too.
- 15) There was a slight channel imbalance no matter the gain I used, so I had also resolved this from the gain stage from nearby the 2 opamps. Basically, there are 4 x resistors (around 5.4 kOhms each) that are connected between pins 2/6 and GND for each opamp, so decreasing a little bit these resistors will increase amplifier's gain. I did that by adding in parallel 4 more resistors (48 kOhms each) on the back of the PCB.

Per https://www.head-fi.org/threads/int...review-to-follow.770610/page-21#post-14121815:
- 16) Replacing resistors R10, R1, R13, R14 of 10kOhms with 270ohms resistors for further decrease amplifier's noise (this might increase the existing channel imbalance, so take this mod with a grain of salt).

Per https://www.head-fi.org/threads/int...review-to-follow.770610/page-21#post-14127810:
- 17) Replacing SMD transistors with TTH BC550/BC560 lower just a little bit the background noise of the amplifier.

 

[omegaorgun]

Anybody experience with the 2C Classic? I ordered up a Burson opamp based on the fact earlier revisions could work with them.

There is an OPA2134 in ti right now, slapped an NE5532 in it and it sounds less harsh to me, less top end grain so excited for the burson v6.

 

[loserica]

- 2) Replacing 2.2uF WIMA MKS 4 (Metallized Polyster) with JB JFX Premium Film Cap (Polypropylene Film) or with 2.2uF Audyn Plus, preferable 4.7uF, per https://www.head-fi.org/threads/int...review-to-follow.770610/page-21#post-14121897.

I took into account in the future the replace of input capacitors (Audyn Plus) with Jupiter Cooper Foil Paper&Wax!! I think Jupiter will sound great in this amplifier.
Sennheiser HD600 sounds great with Matrix, undoubtedly over Beyer DT880 (it bring a great transparency, a lot of details and superior musicality & refinement).

 

[maxxevv]

• An easier and maybe better solution would be to replace the default LME49860 with OPA1652 (these op-amps can be powered from +/-18V and the amplifier will benefit of a lower background noise).
• .

This was from months back, was wondering if you have tried using a pair(s) of LT1128 with appropriate dual channel adaptor to replace the LME49860 ? It takes 18V rails and I have tried it on my portable amp, it works stable. And based on it specs sheet, has probably the lowest noise ratings of any op-amp that's commonly available.

 

[raoultrifan]

No, but it might be a good idea. I’ll see when I’ll have some time to purchase these, thank you for the hint.