I wrote and published this in the Shootouts 2.0 section in the site
www.fmtunerinfo.com where I am both a contributor and moderator………
……………………………………………………………………………………………
"I've spent the last several months extensively comparing a modded Denon TU-800 vs. a modded Yamaha T-85 vs. a stock, unmodded Sony ST-S333ESXII (the export version of Sony's ST-S730ES tuner) vs. my McIntosh MR 74 that Terry DeWick updated. The results were surprising to me.
"The Denon TU-800 was gone through and modded by Bill Ammons and the Yamaha T-85 was gone through and updated by Mike Williams. I believe both Bill and Mike did superlative work on the respective tuners, and the audible differences boil down to what can you achieve when you max out two well-regarded tuners. I believe the Denon and the Yamaha are performing at their maximum capability, and I attribute the differences I hear to the design and engineering differences between the two tuners.
Tim made some comments on our writeup on the Denon TU-800. Don Scott and our panelist Bob had both observed that the TU-800's MPX filter does not seem to do anything, and Tim said, "The MPX button is wasted space on the TU-800's front panel." Our panelist Ray's TU-800 finished fourth in a DXing shootout that you can read about in our Technics ST-S8 writeup, and Tim said, "My experience was somewhat similar to Ray's experience, which I shall get into below." Tim also noted that all of the features described in Denon's sales brochure on the TU-800 "seemed to work well except for the MPX-NR switch. However, I am not an engineer so when Denon talks about the technical wizardry of these features I don't know if what they're claiming is fact or fiction."
Tim sent his TU-800 to Bill Ammons, whose comments follow:
"Tim, I have done an incoming test on the TU-800. Here are the numbers that I took (this was before anything was done to the tuner):
Distortion @ 1 kHz
Wide 0.15%, Narrow 0.7%, Super Narrow 2.8%
Stereo Separation @ 1 kHz
Wide 37 dB, Narrow 26 dB, Super Narrow 23 dB
65 dBf RF input quieting (no weighting)
Mono -75 dB, Stereo -70 dB
50 dB quieting points (unweighted)
Mono 0.7 µV, Stereo 23 µV
I can get the distortion down in the narrow IF mode by using some 220 kHz low GDT filters. That should keep the selectivity good, and increase the stereo separation. The 800 uses a good MPX chip, however the way the stereo separation control is done, stereo separation can only be optimized for one IF band. I might be able to add a second separation control for the narrow IF band.
As far as audio mods go, the output IC can be replaced with an OPA2134AP. There are only a few capacitors in the audio circuit.
Now for the Super Narrow IF band. I think adding an IF Filter Adder PCB and experimenting with a mix of 220 kHz low GDT and some standard 150 kHz filters to get the distortion down would be the best way to go. That would increase the filter count to 5 and should give you excellent 200 kHz selectivity.
As for power supply mods, other than recapping there is little to nothing that can be done to improve a small linear power supply. With a -75 dB noise floor and no AC contribution showing up on the analyzer, it is doing its job well.
I think this tuner will do an excellent job in weak-signal locations. I have not hooked it up to the antenna yet. I am 5 miles away from the transmitter farm and often very sensitive tuners get RF overload.
I can replace the power supply caps with new 105C rated parts. I am not sure what audio op-amp(s) are in the unit, but I can replace them with adapter PCBs if they are SIP parts. I use OPA134 and OPA 2134 (dual channel). With this age of tuner there are probably only one or two caps in the audio path, which also could be replaced.
I was hoping to add a stereo control PCB to increase separation. However, the way Denon configured the audio path, this idea will not work. The distortion in the Wide mode is very low. I did add an IF Filter Adder PCB in the Super Narrow path. The IF gain stages in that path are not that strong,so I had to back off to a lower loss filter. In the Super Narrow IF mode I have no problem getting a 90.5 from 100 miles away next to a local on 90.3.
I replaced the two op-amps in the stereo/audio path with bi-FET parts. The stereo (or composite) driver IC is now a TLO-72CP. The output amp is a OPA2134. The 0.47 µF output caps have been replaced by 47 µF parts, so the bass should be much fuller. I got a little more stereo separation by replacing the composite/stereo coupling capacitor with a 100 µF part bypassed by a 0.082 µF poly.
As for station-grabbing power, this tuner would do better in a lower signal environment than in an urban setting. What is odd is this tuner can pick up a distant 99.5 that is usually not able to be picked up due to RF overloading the front end. The TU-800 picks this one up perfectly while the Kenwood 600T just spits out intermod.
The stereo noise filter is simply a small value capacitor that is switched in circuit between the left and right channels. It narrows the soundfield of the difference (stereo) signal above 2 kHz or so, masking out some background noise.
I will take some final numbers late today and it will be ready to go."
And here's Bill's follow-up report:
"The TU-800 is done. The test numbers in the Wide mode are excellent. In both the Narrow and Super Narrow mode I have been able to get very good distortion numbers. The Narrow mode does not have as much stereo separation as Wide, but still sounds excellent on the distant 90.5 classical station I use. Here are the test numbers I got:
Distortion @ 1 kHz - 100% modulation
Wide IF 0.065%, Narrow 0.10%, Super Narrow 0.13%
Stereo Separation @ 1 kHz - 100% modulation
Wide IF 60 dB, Narrow 35 dB, Super Narrow 30 dB
65 dBf RF input quieting (unweighted)
Mono -77 dB, Stereo -71 dB
50 dB quieting points (unweighted)
Mono 0.3 µV, Stereo 13 µV
I have been switching back and forth with a Sansui TU-919 that was just rebuilt and the Denon. The TU-800 sounds better and can pick up more out-of-market stations."
Here are Tim's preliminary comments to the T-85. In our main writeup on the tuner, our contributor Ryan noted that it is an underrated audiophile tuner: "Yamaha used a true analog multiplier in the multiplex. The technical description of the multiplex is complex, but suffice to say this is one of the very best ways to decode a stereo signal, but because it costs more than using just one simple chip, it wasn't done frequently." Tim said, "I wonder if this is why I greatly preferred the sound of my modded T-85 over the other tuners in my test. Perhaps someone with more technical knowledge than me can chime in here." Ryan said, "Even in stock form, the T-85 is very good, and I suspect that with carefully matched filters and a few component changes almost nothing could touch it," and Tim agreed with Ryan on this.
In our main T-85 writeup, our contributor Charles said, "One thing I don't like about the T-85's 'auto-mode' IF band selection is that it always seems to go to a narrower bandwidth than I would select. Also, once it goes down to a narrower bandwidth (say, if there's some temporary interference), it never bothers to go back up again, so there's an annoying 'downward ratcheting' effect. On my favorite presets, I defeat the auto-bandwidth." Tim said, "Charles is correct about this peculiarity. I suspect it was a deliberate decision so a 'quieter' signal would be heard."
Our main writeup also quotes our contributor Eli: "The T-85 is one of my favorite tuners, maybe even my all-around #1, all things considered. But I just don't want people to go out and buy one expecting super selectivity in stock form." Tim said, "The mods made to my T-85 put it on an almost equal footing with my Mike Williams 'modded to the max' Sony HD tuner when the T-85 is in its Super Narrow IF mode. However, I have not yet done a long-term comparison on weak stations between my maxed-out T-85 and my maxed-out Sony HD tuner." Eli also praised the T-85's AM performance, and Tim concurred: "I believe the T-85 is equal in AM performance to my beloved McIntosh MR 74 and the MR 75 AM tuner residing in my McIntosh MX 117. The Sony HD's AM section also does quite well, but we're so far off the grid there are no AM stations broadcasting in HD that I can get."
Tim also noted that all of the T-85's features "seem to work well. However, I am not an engineer, so when Yamaha talks about the technical wizardry of these features I don't know if what they're claiming is fact or fiction." Tim specifically points out that the T-85's "digital fine-tuning control works quite well when the station you are trying to catch has strong stations on either side of it."
Tim sent his T-85 to Mike Williams, whose comments follow:
"Got your tuner unpacked and checked out the T-85 yesterday. As is, she is pretty poor, the alignment (CLS) is way off and having issues tuning to the signal generator. Also it is clipping the negative portion of the sine wave. Got a bad amp or power supply. [Tim notes that this was an eBay purchase that the seller described as 'working fine,' but he wasn't upset that its performance was bad because it was a 9/10 cosmetically, he paid only $75 for it, and he had planned to send it off for mods, anyway.] After inspection and refreshing myself with the manual, here are my [Mike's] recommendations:
Recap the power supply and repair if needed; super tuned with 5 matched filters, 280 kHz x 3 Wide and Super Narrow, 150 kHz x 2 for Narrow; Black Gate output coupling caps. There are three amplifiers in the audio circuit. I recommend adapter boards and modern audiophile type op-amps. For the best sound quality I would recommend all three amps upgraded."
And here is a list of what Mike actually did:
"Initial check out found it would not tune, alignment needed. Also clipping negative portion of signal. Rebuilt power supply. Troubleshot clipping to leaking muting transistors, replaced all four muting transistors. Super alignment/sockets/matched filters, 280 kHz x 3, 150 kHZ x 2. Black Gate output coupling caps 006% THD. Upgraded three audio op-amps, with adapter board, LME 49860NA."
On the Sony ST-S333ESXII, Tim said, "I really, really like the ergonomics of this Sony. I think all tuners should have a tuning knob like the Sony, but alas, most digital tuners do not." Read more of Tim's comments on this tuner in our main writeup on the Sony page. And on the McIntosh MR 74, he said, "There is not much I can add here. My MR 74 has been, until now, my best-sounding tuner." Read more of Tim's comments on the MR 74 in our main writeup on the tuner.
So, FINALLY, here are the results of Tim's shootout!
"A few years back, I shared with the FMtuners group some issues I had with a Yamaha CT-1010 that the dealer I bought it from could not resolve. In retrospect, I guess I had one that was built on a Monday, and in retrospect, my issues with the CT-1010 were atypical. I loved the looks of the CT-1010, and when it was working, I thought it sounded slightly better than the Marantz 125 it replaced. So it was a leap of faith for me to buy another Yamaha and then invest $$$ to update it and mod it, but the sow's ear I got on eBay was transformed into a silk purse and the queen of the ball. Please note this is not a comparison between Bill Ammons and Mike Williams; rather it is a comparison of the original design and engineering expertise between the Denon and the Yamaha.
The Yamaha has gently nudged aside my MR 74 as my best-sounding tuner. The modded T-85 is more selective and it is quieter than the MR 74, and it actually sounds a bit better. The acid test for me is classical music (particularly piano) on WDAV (Davidson College) and live studio broadcasts on WETS (East Tennessee State University). The sound of piano music is more dynamic and live-sounding than on the other tuners. The modded TU-800, the ST-S333ESXII, and the MR 74 are excellent, mind you, but the modded T-85 surpasses them by a not-inconsiderable margin. I have to agree with Ryan's comments that the T-85 is very good, and I suspect with carefully matched filters and a few component changes that almost nothing could touch it. Another strength of the modded T-85 is its ability to present a natural soundstage with excellent depth and width (the MR 74 comes close, but it is bettered by the modded T-85). And the modded T-85 possesses phenomenal bass response that is simply unmatched by the other three tuners. Organ music sometimes shakes the house, which I have never experienced with any other tuner in my system.
So what about the other tuners? Well after countless hours comparing the modded Denon TU-800 and the stock Sony ST-S333ESXII, I was unable to discern ANY difference in performance or sound quality between them. Classical music and piano in particular did not sound quite as good as the modded Yamaha T-85. The 'attack' of piano music on the modded TU-800 and the ST-S333ESXII was slightly less dynamic, and there was a slight 'edge' or 'glare' that I did not hear on the T-85 (the MR 74 was slightly better here than the modded TU-800 and the ST-S333ESXII, but not quite as good as the modded T-85).
As for sensitivity, the modded T-85 is slightly more quiet on weak signals in the Super Narrow IF mode than the modded Denon TU-800, stock Sony ST-S333ESXII and modded McIntosh MR 74. My modded Sony HD tuner is slightly more selective, but it doesn't sound as good as the modded T-85.
So, I really, really like the modded Yamaha T-85 for both its sound quality and sensitivity. Now I'm wondering if I will see any significant improvement in the stock Sony ST-S333ESXII if I send it off to be updated and modded? As always, YMMV."
……………………………………………………………………………
Cheers
