Drop + THX AAA™ 789 Linear Amplifier Discussions | Drop

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Drop + THX AAA™ 789 Linear Amplifier

Audiophile

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OneOddPhoton

Mar 20, 2020

I have been using the THX for about 5 months now. Yes it is as good as everyone says, HOWEVER the switch mode power supply included with the unit just does not do the Amp justice. I replaced it with as 24V 2A Linear power supply and wow, what a difference. Much more weight, control and authority. The detailed presentation is still there, however it (subjectively) sounds like the amp has gained a couple more Watts (not literally of course). I am using the HD 580, HD 600 and the HD 6XX but most notably, the hardest to drive Headphone on the planet, the HiFiMan HE-6SE. It was on the latter I noticed the most difference. Of course, if you are using sensitive Headphones and/or IEMs then the stock PS will suffice.

(Edited)

Mar 20, 2020

Matthias1979

Mar 20, 2020

OneOddPhotonVery interesting what you are writing about. I'm using the 789 for 3 months now and I'm interested in trying out what you've tried with replacing the stock power supply. I have some questions to you later in the text but let me tell you first some other improvements I've noticed with the amp that you might also already experienced.

In the first hours/days of using the 789 ist sounded very great but also somehow flat. After a certain burn-in-period it got more depth and improved in cetrain aspects of the sound quality. In the first 50 hours the low-end improved further and also the high-end got a little smoother. After about 100 hours and more the high-end still improved.
I only use the single-endet output and my headphone is the Beyerdynamic DT 1990 PRO. In the first days I listended to music by using the mode gain-2. That happed also until and over the period where at first the 789 still sounded flat until a certrain burn-in period. By using gain-2 I had to turn up the volume to about 80 percent to listen to a certain loudness. After some time I just tried mode gain-3 (and of course I had to turn down the volume knob because the music got louder with gain-3) and noticed that the sound got more depth, more clarity and control, better channel separation, better instrument separation and a wider soundstage while listening to a similar volume-level while comparing sound quality between gain-2 and gain-3 settings. The highs turned from silky/glassy (with gain-2) to crystalline (with gain-3), which I liked.

Over the last months I invested money in more expensive RCA-cables and better headphone cables. Everything improved the sound quality noticeably to my sensitive audiophile ears. :-) Now I'm interested in further improvements to the sound. And that's why I read your posting about the power supply with joy. At first, I believe you when you say that the 789 with the stock power supply does not sound as good as it could be. I ask myself how you got the idea to exchange the stock power supply and what you had to look for specification-wise concerning the new adapter and also of course not to damage the 789 over a certain time with the new adapter and its specs. (I'm not an electrician and therefore only have basic knowledge). What do you mean with "more weight" to the sound now. Can it be described as more thickness ore more punch? In other words you maybe mean a warmer low-end and mid-range? How can you descibe "more weight" in other words? You did notice these improvements to the sound by changing the adapter also with your Sennheiser-Headphones but more prominently with the more expensive HiFiMan HE-6SE. Of course I ask myself, if my DT 1990 with an impedance of 250 ohms can benefit from a better power supply to the 789 which drives the amp in a better way. If I look on the stock power adapter there a different specifications: INPUT: 100-240 V, ~ 50/60 Hz, 1.5 A Max OUTPUT: 24V, 1.8 A So did I get it right that you simply looked for another power supply with only a differing specification to the OUTPUT-value in terms of ampere? You simply got a new power supply with a 0.2 higher output-level in the ampere-aspect? Is that correct? Do the other specifications (shown above) still have to be the same on the new power supply (also concerning INPUT-specs)? And also you use the words "linear power supply" concerning the new power supply. It the aspect of "linear" important here when I look for a new power supply here in Germany where I live? Is "linear" a synonym to "direct current" (DC) or does it mean something else? I'm really curious if a better power unit to the 789 would also improve my sound quality - still, after it already got improved in certrain ways by constantly using gain-3 now. Thank you very much for commenting my questions. EDIT: I would try to find an adapter on the German Amazon-Website. Would it be asked too much if you would watch out there fore me and send me a link to an adapter that would fit whats needed exactly. I fear to maybe buy something with wrong spec as there is so much to look out for in terms of electricity. And then there obviously is also the aspect of Watts where a mistake might be made. And there is no specification about Watts on the stock power supply of the 789. EDIT 2: I began to search for supplies on Amazon. There's a lot to find and with diferent specifications. Two new questions that arose are: Is a INPUT-power of more than 1.5 Ampere allowed on the power supply? On the other hand I found power supples with max. OUTPUT-powers of not only 2 but 3, 4, 5 or 6 Ampere. But am I allowed to only buy those with a max OUTPUT-power of 2.0 Ampere or is it allowed to have one with 3 Ampere for example while hopefully the 789 knows how much Ampere it will use to the maximum to not damage itself? So what about those INPUT- and OUTPUT-values? What is important to know or should not be exceeded to stay on the safe side in terms of not overpowering the 789, while still have a benefit like you have now with your power unit-update? EDIT 3: And what about in case of OUTPUT-voltage? There are 12 Vvolts available, 24 Volts oder 28 or 29 for different usages. I ask myself how/from which side these values (Voltage and Ampere) that are written onto power supplies can be understood in generel. One one hand they mean, what the power unit is capable to produce in generel in terms of OUTPUT-Voltage and Amperes. On the other hand I don't know if a more capable power-unit is able to easily damage a device that it is used with or if it is the case that an end-device sucks only the power out of a power supply what it needs to run properly. But if the latter would be the case you wouln't have been able to give the 789 a higher value of Amperes (0.2) to hear improvements to the 789's sound quality. EDIT 4: Okay, I'm partially finding out things myself actually (at least what the differences between a "SMPS" and a "Linear Supply" are). :-) Anybody esle is allowed to join this conversation of course to answer the amount of questions I have produced here when you feel that you definitely know some answers (without giving away wrong information of course). :-)

(Edited)

Mar 20, 2020

Usehername

107

Mar 21, 2020

OneOddPhotonDo you have a link to the linear power supply?

Mar 21, 2020

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Charminbaer

Mar 29, 2020

Matthias1979You basically have to use the exact same voltage, that is the most important aspect! If the voltage is too low, your unit wont work properly because it is designed for exactly 24V DC. And if you use more than 24V DC you will probably kill your amp, so don´t ever do that ;) As for ampere rating, it is only necessary to get at least as much as the original powersupply has. More does not hurt and is actually better sometimes. In regards to soundquality it is important to get a powersupply that has very low ripple and noise specs. Unfortunately those are not always specified by manufacturers. Rule of thumb is that linear supplys have less of both because of how they convert AC to DC. SMPS generally have more of the 2 before mentioned (there are exceptions with very well engineered ones) and additionally have a lot of high frequency switching artifacts (kilohertz to megahertz range). Since the THX789 uses a SMPS I guess DROP specifically tuned its powerfiltering stage to cancel out the switching artifacts of this exact SMPS model they are using. So using another different SMPS could lead to worse soundquality. Using a good linear powersupply though is almost always the better option in terms of soundquality. The only downside is that it consumes considerably more power (~40-50% worse efficiency than SMPS). The real question though is whether it is worth it. Good linear power supplys cost over 100€. More like 200€ That´s half the price of the THX. I myself would rather invest in a good source (High quality Audioplayer) and DAC, because the amp is only as good as what those two feed into it. But that is something everyone has to decide for themselves. ;)

(Edited)

Mar 29, 2020

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Matthias1979

Apr 1, 2020

CharminbaerHello "CharminBaer", thank you very much for joining this conversation and answering questions to my post – and also answering "around the corner". I hoped I could at least try to get a SMPS with 2.0 Amperes of output. But for the reason you mentioned (concerning very low ripple and noise specs) I now will step away from that idea, because I don't want to go a step back in sound quality if a new SMPS would cause switching artifacts. I also think that Drop already optimized the stock SMPS on the basis of your mentionings. I already saw that linear power supplies are not cheap and the fact that they are consuming considerably more energy this is also a point where I also want to step back from that solution. Like I wrote in my posting in the past year I already invested in certain hardware aspects to optimize the sound quality here and there. But as soon as one calls himself an audiophile then the longing for making the sound better and better even if it already sounds amazing is there. And of course when you read that you can optimize at a certain point where you didn't think of before an optimization can be made at all (power supply) then... :-) There one more side question i'm thinking about: As I checked those linear power supplies I saw that they all have the same "electric ports" (where those cables of electiricians can be put in for testing purposes). With the endings of those cables one would not be able to put those on the power-port of the 789. So there must be some kind of adapters or specific cables. I don't know how that works but as this linear power supply-option is consuming too much energy I step away from that and therefore the answer on the cables is not needed. But if you know the answer, than tell me how that works anyway if you like. :-)

(Edited)

Apr 1, 2020

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