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Is the de-emphasis time constant that important anymore?

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If you want to hear what was intended then you need the proper de-emphasis. If you are ok with dialing until is sounds "ok", then have tone controls and give it a try.

I think he's confused about the role of an audio processor and it's effect. Just because the transmitted chain may have advanced and complicated dynamic processing engaged, doesn't necessarily mean it is being used to change the equalization curve.

EV3
 
A tuner made for the U.S with 75 µS deemphasis used in Europe (50 µS preemphasis) will sound dull (limited top end). The 75/50 µS is a standard still in use, you should use a tuner with the correct deemphasis whatever it is tube or not, or whatever audio processing (Optimod,...) is used by the broadcaster. The 75/50µS conversion is a very simple task any tech could do, only consisting in changing the value of a single cap (or resistor) in the audio filtering circuit after the MPX decoder. Then why not use the correct deemphasis ? You wouldn't listen to RIAA equalized records with old AES or COL phono equalization...
 
I see from the schematic that the Yamaha CT-7000 has an internal switch for just this purpose. I'm not seeing anything similar on the schematics for the MR 74 or MR77.

When you say "any tech," I dare you to find such a tuner-capable person in Abu Dhabi or Dubai!
 
FauxHall said:
I see from the schematic that the Yamaha CT-7000 has an internal switch for just this purpose. I'm not seeing anything similar on the schematics for the MR 74 or MR77.

When you say "any tech," I dare you to find such a tuner-capable person in Abu Dhabi or Dubai!
Click to expand...

Well... when I said "any tech" I was maybe a little too optimistic: I should have said any GOOD tech with some understanding of basic analog circuits and experience in fixing audio equipment. I understand there aren't many in Dubai... But if you could be more specific about the tuner you intend to buy and convert (is it a MR74 or MR 77 ?) maybe I could help by telling you which part (and value) must be changed to convert from 75 to 50µS. Then (allmost ?) ANY local tech should do the job for you.
 
Right now, I'm hot on an MR77 from a shop in upstate New York. I asked them for shipping and changing the de-emphasis so they can have it complete when delivered.
 
This post just caught my eye. Yes, the wrong de-emphasis will make an audible difference - in your case a dull or "muffled" balance. The schematics for most tuners can be found, so even those without a switch, or links for this purpose could easily be changed. (Just ask on here!)
Interestingly, the Lexus/Pioneer tuners (on the LS400 at least) would seem to be shipped to Europe with 75uS de-emphasis. Despite all the attention to detail, it looks like they missed that one. (I've also seen portable radios with 62.5uS as a compromise. Shameless!)
 
In the MR77 the deemphasis network is just ahead the SCA stereo filter, made of R406/C406 (R408/C407, right chan.) on the output amplifier board. For 50µS deemphasis change the value of C406/C407 from 1n5 (1500 pF) to 1nF (1000 pF, 5% or better tolerance). Ideally it should be checked experimentally with an audio generator but 1 nF should be fairly close.
 
FauxHall said:
Right now, I'm hot on an MR77 from a shop in upstate New York. I asked them for shipping and changing the de-emphasis so they can have it complete when delivered.
Click to expand...

I have the same issue here in New Zealand, we are 50µS. It does make quite a noticeable difference, you really need to change it.
Most McIntosh tuners do not have a switch, it is a case on changing a couple of caps in the unit. That you need the service manual for.
I see you've asked them, hopefully they can do it for you...
 
Looks like the MR77 deal I was chasing fell through so I'm onto a Sony ST-5000FW from the UK.

It has the multi-voltage switch so I'm good on the power side but the multi-language owners manual from HiFIEngine has no mention of de-emphasis switch. The UK seller claims it's from the US originally but that it sounds fine on UK broadcasts. I wonder Sony has an auto-selector circuit for de-emphasis.

Anyone with a clue?
 
The Sony ST-5000FW doesn't have a user selectable deemphasis switch, nor does it have a "auto-deemphasis selector circuit" (a feature I haven't seen on any tuner).
In the ST-5000FW the deemphasis network parts are enclosed in a proprietary LPF filter module unit which makes any conversion problematic. Also, the ST-5000FW doesn't play in the same league as the McIntosh MR77. I would pass on this one...
 
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