FM-Stereo-Tuner: Currently vs Vintage Version - e.g. Accuphase T-1200 (DDS) vs. Sequerra Model No. 1

[tiefbassuebertr]

I was recently amazed when I discovered this 5-year-old (pretty new) FM tuner model T-1200 (T1200) from Accuphase:
https://www.accuphase.com/cat/t-1200_e.pdf
https://www.accuphase.com/model/t-1200.html
https://www.accuphase.fr/t1200.htm (good pictures)
https://revolutionturntable.com.au/shop/products/electronics/accuphase-t-1200-fm-stereo-tuner/
https://soundline.co.nz/products/accuphase-t-1200-fm-tuner#mz-expanded-view-698524628483
https://www.stereonet.com/forums/topic/281090-accuphase-t-1200-tuner/
https://www.analog.com/media/en/technical-documentation/data-sheets/ad9864.pdf
It is astonishing to me that FM radio is to be switched off or has already been shut down in some countries (replace by DAB/DAB+)
Interesting to know for me is, what was the motivation on Accuphase to create such a top class FM tuner with DSP technology so as the difference in sound performance compare to old fashion top class device for FM stereo reception like e. g. this unit:

Sequerra Model No. 1
https://sb015eafc300824f1.jimconten... - FM-1 - FM Stereo Tuner (user's manual).pdf
https://skyfiaudio.com/products/the...uner-top-3-ever-made-complete-your-collection
https://www.fidelity-online.de/der-sequerra-fm-1-von-herrn-f-aus-o/

or to similar top class vintage units like K&H FM2002 or Revox B760.

 

[MarcelvdG]

I don't know anything about these specific tuners, but for car radios, the main advantage of digital IF processing is that you can apply more fancy weak signal processing tricks than with an analogue design. For example, phased-array techniques that automatically use the best weighted sum of the signals of two aerials to get rid of multipath interference. Variable IF bandwidths were already used in completely analogue designs. Of course FIR IF filters can have a better phase response than analogue IF filters, which presumably leads to less distortion. You can also make really nice FM demodulators digitally, but a product detector using a coaxial cable for conversion from frequency to phase difference as used in the Studer A726 also works very well (but is too large and too heavy for car radio).

The main disadvantage of digital IF is the interference that you get from all the digital circuitry, and that you somehow have to keep out of the tuned channel.

 

[BFNY]

What M said ^^ + the ability to switch modes based on the signal quality automatically, and deliver the best sound quality possible, based on the signal available. The ability to make sharp cutoff narrow (<150 kHz ) low group delay filters is essential in many crowded markets. This is cake for DSP at audio frequencies. The added benefit is using an outboard DAC for the S/PDIF FM output.

Silicon L:abs was huge in developing low cost DSP based FM circuits, where the IF is filtered, then under sampled with a relatively slow A/D, then processed.
These are mostly for portable and car audio use, but specs are poor compared to the referenced tuners above, and most top line FM tuners after 1974.
The chip based DSP processing has limits, and the math precision used limits dynamic range, distortion, separation, etc.

Accuphase is one of the few to do this FM DSP in house, and do it right. No precision limits, with world class specs, and supposedly, sound too.

FM is very much alive in the USA, not really any current plans to ever go all digital. Analog FM, on both transmit and receive, is much cheaper.

 

[MarcelvdG]

NXP has some pretty good car radio chips with digital IF processing. Sensitivity, dynamic selectivity, IP3 and large signal handling are all very good. They normally use oversampled ADCs, sigma-delta ADCs in fact, so the analogue IF filtering is only meant to prevent aliasing. Channel filtering is done digitally.

 

[limono]

Here is my "stack" Digital Accu T1000 and aligned analog Tandberg TPT3001a .
You can see which one is in use 🙂. Accuphase is very good actually. I also played it with Abbas tube dac but I prefer 3001a for its vitality connected to old Naim amps. It's way better than Nat03 . Maybe Nat01 would stand a chance. Having said that I'm selling Tandberg since I can't afford to keep bought at the moment and it's almost impossible to find North American version of T1000 and I'm in a " gold" period of hifi . Tandbergs are fairly easily accessible just expensive to service. A top tuner. Both came from biggest collection of radios I saw. Probably all best FM tuners ever made. Sansuit TUX1 ,Squerra Ref.Marantz 10B
Top Burmester Restek FM3003 Wieschoff, and mamy many others. If I had money I'd buy top 10 of them. FM is the best audio format ever conceived..I can listen everyday, all day. Any other " perfect source" ? 2 hours max

 

[adason]

I am very fond of fm tuners. Had many including top of the line kenwood and technics. FM tuner is constantly on unless i listen to lp's or cd's. Since i discovered how quiet sony st-s555es is, i sold all. Now i have 5 sony 555es tuners one for each system. (I still keep one magnum dynalab for sentimental reasons)

 

[limono]

Yeah , I fall asleep with FM radio ON. "Classical days and Jazzy nights" with no debilitating commercials every 15 minutes. Blessed Public Radio!

 

[hbtaudio]

I love FM radio, at the moment I'm listening with my old ReVox A76. Not only amplifiers are interesting, tuners are also really fascinating, even if you build them yourself. Unfortunately, the program in Germany has been eroding for decades, it's downright lacking in quality. In September, DAB is being pushed regularly. The compression is also extremely annoying. Live broadcasts from concert halls are still great. I love FM.

HBt.

 

[Chris Hornbeck]

That's sad to hear. How strange, that America, facing internal threats from political idealogues, still has a vibrant Nation Public Radio, and other places that Americans might see as being more civic-minded, are stressed. It's a tough world, and we can only hope to pass it to our children's children half as well as we were given it.

All good fortune,
Chris

 

[hbtaudio]

Thank you very much Chris.

 

[doug s.]

Here is my "stack" Digital Accu T1000 and aligned analog Tandberg TPT3001a .
You can see which one is in use 🙂. Accuphase is very good actually. I also played it with Abbas tube dac but I prefer 3001a for its vitality connected to old Naim amps. It's way better than Nat03 . Maybe Nat01 would stand a chance. Having said that I'm selling Tandberg since I can't afford to keep bought at the moment and it's almost impossible to find North American version of T1000 and I'm in a " gold" period of hifi . Tandbergs are fairly easily accessible just expensive to service. A top tuner. Both came from biggest collection of radios I saw. Probably all best FM tuners ever made. Sansuit TUX1 ,Squerra Ref.Marantz 10B
Top Burmester Restek FM3003 Wieschoff, and mamy many others. If I had money I'd buy top 10 of them. FM is the best audio format ever conceived..I can listen everyday, all day. Any other " perfect source" ? 2 hours max

older thread i know, but i found it, searching for an accuphase t-1200 service manual. i have a few comments about the better tuners, and an interesting story about my accuphase t-1000, which is why i'm curious to find a service manual for their latest tuner.

i've had two tandberg 3001a's, one never serviced, the other serviced by heinz preiss, an excellent tech who worked on tandberg and electrocompaniet, among others. (he retired quite a few years ago, not sure if he's still amongst the living - i'm an old fart, and he was quite a bit older than i am.) anyway, tho very nice tuners, my stock onix bwd-1 w/soap-2 power supply was better sounding and just as reception-capable. my refurb'd modded hk citation 18 was better than both of them. the hk 18 was better than a refurb'd modded accuphase t109, only because the accuphase had noticeably foreshortened soundstaging height. other than that, they were neck-and-neck; the accuphase had a wee bit wider soundstage, but it didn't make up for the feeling that you were looking down at the music. so i'd rate the onix as the best of the "2nd tier" tuners i've had. tuners i'd consider 1st tier for sonics are the accuphase t-1000, sansui tu-x1 with mild mods, sansui tu-9900 w/full blown mods, sony st-a6b w/full blown mods, rotel rht10 w/full blown mods, any mono or stereo sherwood, s3000iii or later; mono units used w/quality (relatively) modern s/s mpx decoders (sonics, not reception, tho the sherwoods are still ok for all but the worst reception situations), audiolab 8000t. there's a few others that are up there, but i have never been able to do blind a/b w/them to be sure exactly where they stand. revox b760, b261, b260, aiwa at9700, philips ah673/6731, denon tu850 and tu900. the revoxes are supremely accurate and detailed, perhaps lacking the tiniest bit in warmth, and benefit from a tube buffer stage.

now, w/my accuphase t-1000 story; this just happened recently. i picked up one, plus some cash, in trade for my tu-x1 a year ago. i've tried a few of the older analog t101's and t100's, as well as the t109, and always wanted to try one of the newer models. yes, i really like it, and it's in rotation in my system. (and the tu-x1 is a massive beast that i didn't use very much.) a recent electrical storm turned the accuphase t1000 into a japan-spec tuner!?! suddenly, it was tuning from 76-90 mhz! as it turns out, it was originally a euro-spec tuner, as it said "230v" on its label; i'd never checked it before. so, accuphase being accuphase, i knew i'd have trouble getting this issue resolved. sure enough, even tho this tuner has been out of production for almost 15 years, accuphase usa refuses to touch it, as the company forbids it. the distributor did "unofficially" recommend two unaffiliated service centers that they said they know do quality work on accuphase gear. one is local to me, so i reached out to them. they said they'd had one customer that experienced a similar problem, and i'd be looking at ~$300 to fix it.

so, i searched the web for info about this type of issue, and found a 10 year old post on an aussie audio forum. a guy there mentioned that he'd changed de-emphasis and voltage on a used t1000 he'd bought from japan, that tuned to 110mhz when he got it, (not sure how a japan-spec tuner would tune to 110mhz?); then changed voltage/deemphasis again, when he sold it to an american buyer. so, i pm'd him, on the chance he could provide assistance. lo and behold, he responded, sending me a t1000 service manual - in japanese and english!

with the service manual, it took me less than 5 minutes to re-set the de-emphasis, voltage and tuning band, which i suspect were all changed by the power outage we experienced in a recent storm. if anyone wants a copy, pm me; i'm reluctant to post it; i don't want to subject this forum to unwanted legal attention.

while i can understand accuphase wanting to protect its distributors and dealers from less expensive gray market goods, accuphase is certainly not winning any friends with its outdated service policies. it should limit its "no service" policy to current production goods only, imo.

doug s.

 

[Groove T]

How ever, i had the Sequerra, latest version, sounded better than any other for me , but thermal drift was always shitty due power supply drift.
After 6 hours it became stable when i went bed for sleeping.
Sold it, now still using Micromega Tuner with 32 Khz Output on my digital system, everything fine.

 

[newvirus2008]

The main disadvantage of digital IF is the interference that you get from all the digital circuitry, and that you somehow have to keep out of the tuned channel.

Today's inexpensive DSP radios address this issue by using a lower IF frequency <100kHz (vs. 10.7MHz), with the DSP doing everything other than the also mixer stage. There're also some others that do not need an MCU like RDA7088. I tried one and it had excellent stereo reception with an 80cm quarter-wave antenna. but anything shorter didn't work very well (not sure why as the input stage was still analogue).

 

[MarcelvdG]

There are lots of practical reasons for using a low IF, but I don't see how it would help against clock harmonics or data-related sidebands around clock harmonics entering the RF input and mixing with the LO or some harmonic of the LO. A flexible IF does help to some extent, as does a harmonic reject mixer. If you can change the sign of the IF (switch between high and low injection), that's a very simple way to at least get some flexibility into the IF.

 

[newvirus2008]

The way I understand it, the harmonic power in the DSP clock fades away much better when its frequency is lowered (with lowering of IF). Besides, the index of any angle modulation present in the signal also gets multiplied with harmonic order (e.g. 90th harmonic has 90 times deviation), significantly reducing the power spectral density of the interference when compared to that of the FM station / local oscillator (only slightly lower freq due to low IF).

 

[MarcelvdG]

The high-performance radios I worked on usually had a main DSP clock frequency well above the FM band, but not at an integer multiple of the FM frequencies. The clock frequency itself cannot cause interference then, but its harmonics still can when they mix with LO harmonics. Digital interfaces were another source of trouble, as interface standards then often limited the choices for clock frequencies. It could always be made to work well with good frequency planning and good shielding.

 

[newvirus2008]

I haven't worked on such radios but I think it is very likely that inexpensive DSPs are adhoc (vs. SDR) and the filters, pilot PLL, demodulation / dematrixing have dedicated hardware modules.

 

[Noir69]

Quite old, but interesting suject ! Looking at characteristics of Accuphase tuners (as given by the manufacturer), I'am wondering why the minimal assumed performances are identical for several successive models (i.e T108, T109, T109v, T1000...). A noticable break-through happens for the most recent (T1200 with a rather different technology) with substantial improvements regarding S/N ratio and channels separation ... But, my question is, "is it usefull", I mean, theese performance improvement can they - or not - be heared by the listenner ? As the T1200 is sold almost 6000€, is it decent ?