Review: TRL Audio Mirror D1 Signature DA converter

Category: Digital

TRL Audio Mirror D1 Signature
Modifications by Tube Research Labs
Cost $1100 (Price of stock Audio Mirror D1 Signature plus TRL modification fee).


Spendor 1/2e (AlphaCore Goertz MI-2 Veracity cables and jumpers).
Cary V12i (12 x Siemens EL-34, 2 x Sovtek EL-84, 2 x Siemens 7308).
Joule Electra LA-100 MkIII (Sylvania 5751, Raytheon 6350, 2 x Raytheon 6EM7, 2 x Raytheon 0A2).
TRL Alesis ML9600
TRL Audio Mirror D1 Signature DAC
Interconnects: Cable Research Labs Silver (preamp>amp, transport>DAC), Nordost Red Dawn (DAC>preamp).
Power Cords: Wireworld Silver Electra 5 (amp), Cable Research Labs Silver (preamp, transport), VH Audio Flavor 4 (DAC).
Line Conditioner: Running Springs Audio Haley.
CD treatment: Shine-Ola


As an analog junkie, I have been quite content spinning LPs and listening to 2-track masters (live concert recordings on DAT, reel, and cassette). A digital set-up has never been a priority for me. About 10 years ago I bought a Quad-77 CDP and was quite content with it until I made some recent upgrades to my system which really exposed the Quad as a weak link. In my search for a digital front-end component I first started out looking at one box solutions. After having auditioned many fine tube and solid state players, I ran across a review on the TRL Sony 595, and subsequently a number of threads on Audiogon discussing TRL modified equipment. So I took the plunge and emailed Paul Weitzel, President of TRL to discuss my needs. After several quick and informative emails I ended up with the TRL modified Alesis ML9600 CDP and HD recorder. However, as recommended by Paul Weitzel, the ML9600 would best serve me as a transport so now I had to go and find a DAC to pair with it.

Enter the up/over sampling versus non-up/over sampling dilemma. Being pretty much a digital neophyte it took me awhile to get up to speed on all things new in the digital world. Things sure came a long way in 10 years. I auditioned many fine units, but alas, I was bitten by the non-os filterless design bug after researching Audio Note and Sakura Systems components. My ears told me that I much preferred this design as it came very close to analog reproduction. Now I just had to decide on the right non-os filterless DAC. An ad on Audiogon caught my attention for the Audio Mirror D1 Signature. The price was right ($500) and the trial offer was a perfect way to hear the unit. So in comes the D1 Signature and it never left. In fact, after letting it break in I got the idea of getting a second one and sending it to TRL to be modified, then doing a comparison of the two. Well the second D1 Signature was acquired, TRL completed the modifications, the unit has gone through a 500 burn-in, and some A/B tests were run. I am now comfortable in making my observations so read on for more details.


Before getting into the results of my listening tests I think I need to make a couple points. First off, this is the first review I have ever written. I apologize in advance for my shortcomings in my writing style or presentation of the information. I will say that if you’re expecting a very sophisticated review you may want to stop reading now. I am only capable of writing what my ears hear from the music reproduction. I will probably misuse audiophile terminology in my effort to convey to you observations from various musical pieces that I am very familiar with. That being said if all that doesn’t bother you or you’re just a curious type read on.

Secondly, those of you looking for specifics on what types of modifications were done to the stock D1 Signature should also stop reading now. I can’t tell you what I don’t know although I will make assumptions based on some physical observations (which may or may not be correct). TRL modifications are proprietary and not disclosed. The standard protocol is a black box approach with a fee of $550 per unit. Those who have a need to know everything that was done to modify their equipment including a parts inventory may not find themselves compatible with this approach. However, TRL is a company with extensive audio engineering and recording experience as demonstrated by their tube and solid state designs, recording labels, and their extensive modifications to many well known pieces of audio equipment. In addition, the engineers at TRL are also involved in the medical industry and no doubt some of their experience in that field working on sophisticated medical equipment has allowed them to take that knowledge and apply it to the audio side of the house (being in the healthcare/medical field myself this makes sense as medical equipment needs to be very quiet and accurate).

As for what I do know about the modifications I can tell you that some structural changes were made to the DAC. Audio Mirror D1 Signature owners know all too well that the digital RCA output is “strategically” placed under the IEC receptacle. I have found that using an upgraded power cord results in the weight of the female end placing some downward stress on the digital cable end and therefore stress on the digital RCA output as well. TRL performed a structural modification that resulted in swapping the position of the digital RCA output with the coaxial/optical switch on the rear panel of the D1 Signature. They also upgraded the stock RCA jack to a Cardas RCA jack. One annoying problem solved.

When I received the D1 Signature back from TRL I couldn’t resist opening up the unit to see whether or not I could tell what had been done to it. I had my stock unit opened up as well to compare. From what I could tell, and again these are assumptions, there was some work done on the power supply, some rewiring (the type of wire used by TRL results in the long burn-in process), and the DAC chips appeared to be dampened. I know that is not much to go on, but I can say from further conversations with Paul Weitzel, the noise level of the DAC dropped 20db as noted in his bench test of the unit. That is significant and will help explain some things I refer to in the testing section. TRL testing also revealed the stock D1 Signature would distort in the mid-range at around 1k to1200hz when very dynamic musical passages would hit it hard. As a result of the modifications another problem was solved as the distortion no longer occurs according to the follow-up testing conducted by TRL.

Those existing Audio Mirror owners curious as to TRL’s opinion regarding the stock D1 Signature will be interested to know that they felt in its stock form the DAC was a very nice sounding unit. TRL mentioned that as a result of the modifications I should expect an increase in micro and macro dynamics, while also experiencing expanded depth, presence and soundstage. As for the last comment, I’m sure some reading this will comment that this is what all mod shops say about their work, and they are right, but the proof is in the pudding and that is what I hope to be able to convey in the next section.


Testing and observations were made using the following music sources:

Rob Wasserman – Trios
Miles Davis – Amandla
Diana Krall – Love Scenes
Steve Kimock Band – Live at the Gothic Theater 2/22/02 (digital master)
Steve Kimock Band – Live at Cervantes Ballroom 4/27/03 (digital master)
Phillip Glass – The Low Symphonies
Frank Zappa – London Symphony Orchestra Vol. I & II

My process for conducting the testing was very simple. I decided to run through some tracks on each recording where I was familiar with certain elements of the sound that I wanted to hear reproduced on the stock and TRL D1 Signature. Obviously, I need to also account for my listening room which presents some challenges due to its size (8’ x 11’, 10’ ceiling). For the run through I played specific tracks on each recording and noted some general observations. The stock D1 Signature presented the music quite well and as I have come to expect after 6 months of use. Vocals were nicely centered and full bodied, although placed behind the speakers; the soundstage was deep and tall, and from a horizontal perspective inched towards the outer edge of the speakers, but not beyond that. The background was black and instruments were readily identifiable with very good placement, which made the two classical pieces especially enjoyable.

As for tonal qualities, the stock D1 Signature has exceptional bass, not to mention very good reproduction in the mid-range, aside from the aforementioned distortion. I have always found the highs on digital equipment somewhat harsh (easily exposing bad recordings or weaknesses in the digital equipment itself), and the stock D1 Signature is no exception (especially with horns and cymbals), but in comparison to other DACs, especially those that upsample, the highs are smoother and like the overall tonal quality, more analog sounding. Overall the stock D1 Signature is non-fatiguing and I found that I could listen to digital playback (even bad recordings are tolerable) for hours.

Switching to the TRL D1 Signature, if I had to sum up the differences in music reproduction in one word that word would be “detail”. You just hear more of the music and you hear it with more accuracy. Not only were the vocals nicely centered and full bodied (Diana Krall’s voice sounded very liquid), the placement was much closer and at times appearing as if they were at the speakers, the soundstage depth increased and from a vertical perspective seemed to go from floor to ceiling. From a horizontal perspective the soundstage extended beyond the outer edges of the speakers. The background was blacker and like the stock D1 Signature instruments were readily identifiable with very good placement. However, this time around the two classical pieces (especially the complex Zappa recording) really showed the differentiation between the two units as I could much more easily hear the string sweeps and pinpoint placement of the various orchestral sections. Not to mention, in some passages the music jumped out at you and instruments that could be faintly heard with the stock D1 Signature were now more clearly heard as a result of greatly improved presence.

Rather than make note for note comparisons on the tonal quality, I thought what I would do here is make some notes on the differences in the sound I heard based on observations from specific passages of the music. Bass improvement in the TRL D1 Signature resulted in tightening of the bass, but still retaining the bloom, much like tube sound, but without the tradeoff of the noise. This was very evident on the bass duet between Rob Wasserman and Willie Dixon on the Trios recording. Both were playing fretless upright electric bass guitars and the finger movement was much more noticeable and notes much more accurate and pronounced (it sounded as if they were plucking the strings in the room with me). When Willie Dixon yells “slap it” to Rob Wasserman that is exactly what you hear next, the slapping of the strings which on the stock D1 sounded more like they were being rubbed or grazed instead of struck.

If I had to pick one area that resulted in the most improvement it would be in the reproduction of the highs. The highs on the TRL D1 Signature are very detailed without the harshness I have found to be consistently present in digital equipment. As Paul Weitzel might say, the “digititis” in the stock D1 Signature has been removed. On Miles Davis’ Amandla, throughout the song Jaco, the drummer is ever so lightly rattling a cymbal which on the stock D1 Signature sounds more like a drone in comparison to how the TRL D1 Signature reproduced the sound with clarity and detail. The live digital masters of the Steve Kimock Band show the TRL D1 Signature reproducing the cymbals on Rodney Holmes’ drum kit and treble on Steve Kimocks’ guitar effortlessly and accurately. Having been to both of these live performances and recording one of them with an onstage microphone set-up (the other is a 16 bit digital soundboard), the TRL D1 Signature makes me feel that I was once again in the audience. In contrast, the stock D1 Signature provided excellent reproduction, but there was some slight distortion in the highs and the sound lacked some of the ambience of the live recording (it came closer on the digital sound board versus the miked recording). The decay of the cymbals, as well as other notes in the TRL D1 Signature was also extremely natural.

Final Thoughts:

The stock D1 Signature is an exceptional DAC and an exceptional value at its price point. Those of you who have read my posts on this DAC know that I feel it bests some DACs at 3 or 4 times the D1 Signature’s price (currently $550). However, the TRL D1 Signature is at another level altogether and I would not hesitate to say that it could compete very well with the higher end Audio Note non-os DACs (I know it will blow away the 47 Labs Shigaraki because the stock D1 Signature accomplished that feat), as well as some of the upsampler DACs such as Northstar, AudioLogic, and Audiomeca. I’d even venture to say you would be hard pressed to justify the cost difference of the TRL D1 Signature with that of the Dodson, EMM and DCS rigs when you compare the sound. The increased detail now lets me hear the music as it was meant to be reproduced and has given my analog rig a run for the money. Before, with the stock D1 Signature I could sit for hours at a time in listening sessions, but now I feel I could sit for days on end. Coming from an analog junkie like me that is saying a lot.
Nice review Tony. Thanks for taking the time.
Second the nice review & the time to write it.
I'll be checking into one of these Dacs, they sure look nice !!
I'd like to compare one (modded too) to my tubed Audio Logic Dac & a friend's upcoming Museatex Bitstream (to be modded) this will be *very interesting*
Thanks for the review. I would find it hard for this DAC to better an Audio Logic DAC (depending on model and tubes installed). I have had a least 12 DACs in and out of my system and only a few bettered the AL DAC with stock tubes. But I also didn't pay list price for any of these DACs so retail pricing does not come into play for me as fara as overall value comparisons.

I also don't see where anyone compared them in a review.

Happy Listening.
Very good review,not often do you read a review of a piece that has been modded and the reviewer has an unmodded sample handy to directly compare,,ill be sending mine off soon,,,,very informative review ,thanks Tony

Talk to Paul Weitzel at TRL about the AudioLogic they modified for another Audiogon member. I think you will find the conversation quite enlightening. I would love to hear the comparison to the modded Museatex. There is something gravitating me to that DAC. However, I can have only so many toys at one time.

I never had a chance to listen to an AudioLogic although at one time it was on my list. After I decided to go the non-os filterless route I lost interest in it. You could be right that the TRL Audio Mirror may not beat the AudioLogic, but I think it would compete very well against it at the very least. Of course system dependencies will have an impact on any comparison. Only one way to find out. It appears you like to experiment with DACs, you could get an Audio Mirror and have it modified and get back to us with the results. I for one would be interested in hearing the results of such a comparison.
Excellent review. I too had the audio mirror dac (unmodified) and found it to be exactly as you described. I think it one of the most analog sounding units I have heard. The bass is correct and deep, the midrange is solid and detailed. What I found to be the only area it didn't excel in was in upper end clarity. I have a Museatex IDAT that I compared it too and found it more enjoyable. Could I have lived with the Audio Mirror? Absolutely. I can't comment on the modified version. Excellent value.
Will somebody please tell me what TRL stands for?
Will somebody please tell me what TRL stands for?
In some circles, it stands for Total Request Live . But you probably want Tube Research Labs .