Massdrop x THX AAA™ 789 Linear Amplifier - Impressions Thread
Oct 9, 2019 at 10:45 AM Post #1,816 of 2,613
Price point of the Qutest aside...ground loops can be resolved fairly easily. While I run balanced *everything* as a matter of choice, unbalanced signals are perfectly acceptable for short runs.

A few minor housekeeping steps will make for a happy listening experience:

1. Plug everything into the same outlet if at all possible. This keeps everything on a level playing field from the 'source power' side of things.

2. Try a different outlet. If everything is plugged into the same outlet, but that outlet creates buzz and another one does not.....the outlet needs to be checked.

3. If the outlet looks good (ground wise) but there is still hum... perhaps your circuit is getting interference from HVAC or another large appliance. Try again moving to another outlet NOT on the same circuit.

4. If none of this works or you cannot move your setup or afford an electrician to sort it.....buy an isolation transformer. Tripp Lite sells one on Amazon for around 120 bucks.

This will solve 99% of all ground issues. FWIW I have never had to resort to buying an isolation transformer. Dirty power is an issue that should be addressed regardless of if you are an audiophile or not. :wink:

Best of luck.

... or I can just get a product that has XLR jacks. The Grace SDAC is balanced and only $150. The SMSL SU-8 V2 DAC is only $219. Both tested well and seem to get the job done. In terms of similar price as the Qutest, there's the Benchmark DAC3-B, Matrix Audio X-SABRE Pro, and the Violectric V850. Also if the measurements on Audio Science Review are to be trusted, the Qutest has four filters, but two of them do absolutely nothing different from the other two and are redundant. That + lacking balanced connections = a no-go for me.

I live in an old building with bad wiring and all sorts of interference issues from power lines and WIFI and generators, etc. So balanced is a must.
 
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Oct 12, 2019 at 3:42 AM Post #1,817 of 2,613
I understand where you are coming from...and using XLR connections seems like an easy fix; but if the power conditions in your building are as bad as you describe, I would give a strong recommendation for you to consider investing in a voltage regulator AND an isolation transformer - regardless of if you plan to use a balanced signal path or not.

Old, degraded, or compromised wiring is susceptible to a myriad of additional unwanted artifacts....everything from sagging power to the interference you describe. Audio equipment - ALL audio equipment - regardless of the pedigree of design or connection standard, are vulnerable to power variances like these. It would be unfortunate to spend this amount of money only to be disappointed in the end. After all, what we are really pursuing is the enjoyment of sound right?

Pursuant to that, while I think Amir is really doing an admirable job over at Audio Science Review, I would support the old adage of listening with your ears and not your eyes. Measurements are great for general categorization, but do not tell the whole story. There are plenty of examples of equipment designs that measure poorly but sound amazing...and vice versa.

From the original list you offered, it appears you have a nice budget to work with WRT your proposed setup. Since price is not the most limiting factor in your purchase decision, maybe focus on what YOU think sounds good and works best (synergy-wise) within your listening environment. Find a dealer that will support your journey by letting you return anything that doesn't get your blood pumping...and enjoy the process!
 
Oct 12, 2019 at 6:35 PM Post #1,818 of 2,613
I have balance cables coming for my SDAC connected to my 789. Right now it's just connected via the SE output of the SDAC into the amp. Also I'm using the balance headphone out for my 6XX and 58X. If I'm spending the money on this amp I may as well use it to it's full potential. In any case I have question. So I have seen in Zeos reviews that he has placed some sort of arrow indicator on the volume knob of this amp as some others as well. Does anyone know what he uses or where I could buy them? Without listening I cannot tell how high the volume is. Or perhaps I could colour in the indent on the volume knob with a white marker.
 
Oct 12, 2019 at 6:51 PM Post #1,819 of 2,613
I have balance cables coming for my SDAC connected to my 789. Right now it's just connected via the SE output of the SDAC into the amp. Also I'm using the balance headphone out for my 6XX and 58X. If I'm spending the money on this amp I may as well use it to it's full potential. In any case I have question. So I have seen in Zeos reviews that he has placed some sort of arrow indicator on the volume knob of this amp as some others as well. Does anyone know what he uses or where I could buy them? Without listening I cannot tell how high the volume is. Or perhaps I could colour in the indent on the volume knob with a white marker.

I think he cuts it out of a post-it note.
 
Oct 13, 2019 at 10:45 AM Post #1,820 of 2,613
I think he cuts it out of a post-it note.

So I just use the sticky part of a post-it note?? Kind of a waste of paper. The volume knob has an indent in it to indicate volume level. Perhaps its possible to colour it in with a white marker.
 
Oct 13, 2019 at 11:44 AM Post #1,822 of 2,613
Oct 14, 2019 at 1:44 AM Post #1,823 of 2,613
Hi All,

I'm new to the hobby and have the following two chains in mind:

1. Modi Multi Bit > Loki > Vali 2 > (unbalanced) THX 789
2. SDAC > (balanced) THX 789

Is it possible to link the Vali 2 to the THX 789? Was interested in this combination to incl. some warmth to my music when I feel like it. If there are other suggested chains with a similar price value also interested to hear.


I'm planning to use this with Argon MK3 Mod headphone and Andromeda S IEM.
 
Oct 14, 2019 at 2:19 AM Post #1,824 of 2,613
Is it possible to link the Vali 2 to the THX 789? Was interested in this combination to incl. some warmth to my music when I feel like it. If there are other suggested chains with a similar price value also interested to hear.
Yes, the Vali 2 has a preamp output according to Schitt (see below). Basically, hook up an RCA cable to Vali's preamp output and then hook that into the SE input of the THX 789. On the THX AAA 789, switch between the SDAC-B and Vali 2 inputs using the input selector switch.

Serious Power, Gain Switching, Preamp Outputs
Vali delivers 1W into 32 ohms for hard-to-drive headphones—and, at the same time, offers a low gain mode for low-noise performance with sensitive headphones. You can also use the preamp outputs to add a tube preamp to your power amp or powered monitors.
 
Oct 14, 2019 at 2:28 AM Post #1,825 of 2,613
Yes, the Vali 2 has a preamp output according to Schitt (see below). Basically, hook up an RCA cable to Vali's preamp output and then hook that into the SE input of the THX 789. On the THX AAA 789, switch between the SDAC-B and Vali 2 inputs using the input selector switch.

Thanks! I see that your home setup is is SDAC-B > THX 789 / DarKVoice. Did you ever put a tube between the SDAC and the THX? just wondering if the Vali 2 is worth it. Any recommendations are welcome.
 
Oct 14, 2019 at 3:28 AM Post #1,826 of 2,613
Thanks! I see that your home setup is is SDAC-B > THX 789 / DarKVoice. Did you ever put a tube between the SDAC and the THX? just wondering if the Vali 2 is worth it. Any recommendations are welcome.
I recently tried that on my THX AAA 789 with my Darkvoice 336SE (RCA grey glass 6F8G + Tung-Sol 7236) as a preamp (fed by the SDAC-B SE output) and the sound was very, very close when volume matched (as best as I can) with the SDAC-B balanced input. This was done while listening to my HE-500 on the THX AAA 789's balanced output.
 
Oct 14, 2019 at 1:17 PM Post #1,827 of 2,613
I recently tried that on my THX AAA 789 with my Darkvoice 336SE (RCA grey glass 6F8G + Tung-Sol 7236) as a preamp (fed by the SDAC-B SE output) and the sound was very, very close when volume matched (as best as I can) with the SDAC-B balanced input. This was done while listening to my HE-500 on the THX AAA 789's balanced output.

If the difference isn't that big I'll just go for the Modi MB and Loki. Thanks!
 
Oct 14, 2019 at 2:41 PM Post #1,828 of 2,613
If the difference isn't that big I'll just go for the Modi MB and Loki. Thanks!
Oh, I forgot to tell you earlier that my Darkvoice is modded (Fitz mod). Anyways, I just tried switching power tubes (Tung-Sol 7236 for a 1950's RCA 6AS7G coke bottle, 20min warmup) while listening to my HD6XX and there really isn't any significant audible difference between the DV's preamp to the 789 (RCA) and SDAC-B to 789 (balanced) (volume matched by hand) with my HD6XX connected to the 789 balanced or TRS single-ended. The theme largely continues when I listen to my HD6XX directly through the Darkvoice's headphone output and comparing that to the HD6XX through the 789's balanced output. However, there is a difference between the HD6XX via the Darkvoice and the 789's TRS single-ended output, the latter of which sounds a bit more closed in.

Keep in mind though that the RCA 6F8G (+ adapter) plus either the Tung-Sol 7236 or the '50s RCA 6AS7G I used are far better than the OEM tubes that come with the Darkvoice. Then again, low impedance dynamics (e.g. Grado HF-3's) and planars (e.g. HE500 and LCD-2) sound like ass on the Darkvoice and an un-modded Darkvoice can exhibit buzzing with new/newish tubes that haven't been burned in. So, the Darkvoice essentially can only pair with high impedance headphones like the HD6XX (300ohms) in my collection. Still, the Darkvoice+HD6XX (with my preferred tube pairing) being imperceptible (to my ears) to the HD6XX balanced from the THX AAA 789 is pretty cool in of itself.
 
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Oct 14, 2019 at 4:52 PM Post #1,829 of 2,613
I'd like to share my opinion about using Gain 2 on THX. I never use it anymore as I have found it to be detrimental to the sound quality in my terms. Now, I use only Gain 1 mode as it provides much more fidelity and clarity to the sound, imho. Tried it with Verum 1, HE4 and Final Carbon (custom made headphone from Ukraine).
 
Oct 23, 2019 at 5:22 AM Post #1,830 of 2,613
I'd like to share my opinion about using Gain 2 on THX. I never use it anymore as I have found it to be detrimental to the sound quality in my terms. Now, I use only Gain 1 mode as it provides much more fidelity and clarity to the sound, imho. Tried it with Verum 1, HE4 and Final Carbon (custom made headphone from Ukraine).
Interesting because I changed to Gain 2 after listening with Gain 1 first. Are you using balanced or single ended headphone cable?
 

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