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Demo model NAD T753 vs current NAD T750 and is that humming issue sorted?

 

New member
Username: Usernamex

LondonEngland

Post Number: 1
Registered: Oct-05
I've been reading with interest the old posts on the NAD T753 (and rest of the range) humming issues. I've summarised the points (I think), but I wouldn't mind running it past someone : )

Here goes!
- Many owners have had humming problems, often with several units being tried
- Many haven't had any problems
- NAD have said
* the problem is related to "the Cirrus Logic Processor ...radiated power supply contamination and other environmental contributors..."
* "affect a small minority of the T753's" - or maybe more?
* "...has upgraded in production all current T 753's to include a power supply cap"
- The other "environmental contributors" are other analogue inputs in the owners setup
* Unplugging the other piece of kit and turning the amp off and back on gets rid of the hum and hides the problem until its reconnected?
* The problem has died down on the forums as people have had their amps fixed, or have bought the upgraded models?
- Overall, the problem has been more or less been fixed?

As hinted at in the title, I'm considering upgrading my prologic T750 with a demo model T753 (and therefore probably early production). I'd like to understand the risk of getting a dodgy amp and to know whether I can get it properly fixed if I'm unlucky. Also, how bad is it really, would it annoy "us" and leave most average people (girlfriends, wives, mad uncle ted) wondering what all the fuss was about, or is it really appalling?

Also, how much of an upgrade do you think this will be? (considering my speakers, cd player and amp). And, any idea how much the prologic T750 would be worth, best to sell it with my dvd with DD / DTS decoder?

Oh yeah, almost forgot
NAD T750
NAD 521BEE
Sony DVP-S735D
Monitor Audio Silver S2's, s1'S and centre

Thanks!
Mike
 

New member
Username: Usernamex

LondonEngland

Post Number: 2
Registered: Oct-05
Damn, I must be asking stupid questions

Maybe if I had "Panny" in the post title at least Edster may have looked?
 

Anonymous
 
Yup, you're daft as a brush no-one is interested!
 

New member
Username: Usernamex

LondonEngland

Post Number: 3
Registered: Oct-05
Damn shame that
 

Anonymous
 
Not really mate, why don't you take your nads and play elsewhere eh?
 

New member
Username: Usernamex

LondonEngland

Post Number: 4
Registered: Oct-05
Well, while I do admit to being an accomplished bollock scratcher, don't you think thats a little harsh?

I am genuinely interested in what people here might say!
 

Anonymous
 
is that why you're posting anonymous messages to yourself? a sneaky way to attract attention! You rougue and cheat!...
 

New member
Username: Usernamex

LondonEngland

Post Number: 5
Registered: Oct-05
Could be, could be!

probably won't work!
 

Anonymous
 
seems a bit insane, defintely random behaviour. Stop it right now!!!!
 

Gold Member
Username: Artk

Albany, Oregon USA

Post Number: 2134
Registered: Feb-05
I would not again buy an NAD AVR. The hum/issue is an issue that many folks (spouses etc) may not notice but that is appalling to many audiophiles. Good luck.
 

Silver Member
Username: Eramsey

South carolina United States

Post Number: 343
Registered: Feb-05
A background AC buzzing or a hum that is not due to a ground loop is completely unacceptable in a receiver especially one of that caliber. My HK AVR 335 is completely silent, meaning no background noise or sound can be heard through the speakers other than source material. Sometimes a very faint "hiss", can be heard with ear pressed against speaker, will be heard with some brands especially very inexpensive receivers- $250 or less. This is generally acceptable and not cause for concearn. How much can you expect from a $200 receiver anyway? But you should hear any "buzzing" through the speakers or a hum, provided a ground loop is not present.
 

New member
Username: Usernamex

LondonEngland

Post Number: 6
Registered: Oct-05
"How much can you expect from a $200 receiver anyway?"

Woah are they that cheap elsewhere (or just sound it)? The T753 RRP of £599 and I can get an ex demo for £299... if thats maybe a grand $US and $500 for the demo?

So I was thinking the T753 is a bargin at £299, as I'd been very happy with the T750 I'd be lazy and just get it without a demo... as I type it, it does sound dumb!

Anyway, I've spent a couple years living in the UK, with my Hifi gear in NZ. When I recently went home to NZ, I planned what I should have done in the first place, take what I can to England and sell the rest.

Some now I've got my T750 and DVD here, and my infinities deltas on sale in NZ. I bought a proper cd player and some reasonable monitor audio S2 speakers. Then it seemed very daft not to have the matching centre and rears. I've since been making sideways glances at the NAD T750... I'm thinking my new speakers probably deserve better, and i't would probably be bad manners not to upgrade it too.

At the time I bought the T750, it was the most AV musical amp I could get in my price range (that I heard!). I used it for 2.5 years, left in a cupboard for the next 2.5 years. Should have sold it at the time!

Now what should I do with that £300 / $500+ budget I wonder?
 

New member
Username: Rdperry12

Post Number: 2
Registered: Oct-05
I have a nad 752 and think it sounds great. I have no hum or hiss, The only problem I have had is my preamp jumper plug came lose and i lost sound in my right channel. Pushed the jumper back in and have had no problems since. I am upgrading my receiver to a Denon 3805 for video upconversion and powered rear surrounds.I know it can be a hard decision when upgrading so I thought I throw in my two cents to try and help. If this 753 has been used as a demo it probebly doesn't have any hum issues.
 

Anonymous
 
Good news on my front. I have a NAD T 743, had the hum problem and resolved it 100%.

I purchased a new NAD T 743 a couple of weeks ago. It had the same hum problem described in the archive -- https://www.ecoustics.com/electronics/forum/home-audio/113762.html.

I tried everything to get rid of this. Many days/hours of troubleshooting. After describing to the dealer the problem and what I had done to troubleshoot, they said to return it and exchange it since it was only two weeks old. I chose not to simply because of the effort to disconnect it and return it. I chose to research the web and test to see if it was some other issue. Good that I did.

To my impression it was a ground loop problem and this is what I focused on. However, it would hum even when only the NAD was hooked up, with no other devices connected to the NAD. I tested this by using the FM tuner in surround mode. Turned the volume all the way down to -75 DB, and it hummed quite loud in all surround modes. In stereo mode it was fine. All of the hum was from the center channel and surrounds. After reconnecting my DVD player, DVD-recorder, CD changer, and HI-DEF cable box, the hum was still loud regardless of which device was being used.

As long as it was in a surround mode it hummed/buzzed. Not a speaker hiss, so don't confuse the two. The solution? I put some rubber couch casters under the NAD equipment mounts, isolating the unit further from the rack it was installed in. This is a particle board rack, not metal. I did this due to a comment a fellow made on site that discussed the theory behind ground loops. He corrected a past ground loop issue by putting plastic pieces between his devices and his metal equipment rack. Although my rack is particle board and not metal, I decided to give this a try, and was not expecting much as I had pretty much exhausted everything else.

As soon as I placed the first caster under one of the feet and lowered the unit, the hum was completely eliminated! Like turning a switch off. I have tested all devices now using every surround mode. I am very surprised that this did the trick, but extremely happy. Will it work for everyone? I dont' know but for a couple of bucks worth a shot. Some might have a ground loop problem that might require other treatment, such as a ground loop isolator or such between the NAD and the offending device. Is this a problem with the NAD? I would say yes, in the sense that some internal component (or just poor case grounding) may cause it to be overly sensitive to ground loops. Or maybe not.

My previous receiver (Technics SA-DA10) installed in the same rack with the same equipment and cables did not have any hum issues. After reading the archived threads on the NAD issue, and considering that many NAD owners did not have the problem, and some still had the problem even with replacement units, it may be due to the fact that their environment did create a ground loop that the others did not suffer from. So putting a new unit into the same environment would not correct the issue. I would recommend anyone with any brand of device and a ground loop hum try this.

BTW, I used 4 very small casters that have black rubber inside, and a slippery gray outside plastic type of coating that allows them to be used to slide furniture over tile/wood/carpeted floors. Any home hardware store carries these.

One more point. I am very happy with the NAD sound. I am an "entry level" audiophile, with about $6500 invested in my 5 B&W speakers, and the equipment listed above. The NAD really does have a great musical ability to it that sets it apart from the Yamaha's, Denon's, Pioneer's, etc. Those are great for movies and such, but the NAD does that well also, and is much more musical in 2 channel. My old receiver was 100W by 5 channel. The NAD T 743 is only 50W by 5 channel, and really drives the speakers louder and clearer than my old receiver ever could. This is installed in room that is 25 ft x 12 ft by 10 ft (high). Pretty impressive considering the NAD power specs are so much lower than the Technics. There are lots of positive user reviews about the Technics SA-DA10 on audioreview.com where it's musical ability is touted, but I have both now and the Technics does not hold a candle to the NAD in terms of musicality. Good luck to anyone with a ground loop hum out there.
 

Gold Member
Username: Artk

Albany, Oregon USA

Post Number: 2141
Registered: Feb-05
Many of us who returned our NAD's did not have a ground loop issue. Those of us with experience isolated that first. NAD is replacing the analog boards in these receivers which seems an admission that something is wrong. BTW the NAD fix doesn't work either.
 

Silver Member
Username: Danman

QUEBEC CANADA

Post Number: 580
Registered: Apr-04
I have never been a fan of AV equipment and I will tell you that it is not ONLY NAD that has these problems! My dealer told me that Rotel and Arcam have been returned at the same rate as the NAD's but for some reason only NAD has received the bad rap!

If I was going to invest in this tyoe of listening (however I doubt it), I would buy a surround pre processor and seperate power amps. There is just TOO much crap in one box for me! Audio should be simple in order to be reliable. I know my method is quite expensive and elaborate but I would at least have peace of mind.
 

Gold Member
Username: Artk

Albany, Oregon USA

Post Number: 2153
Registered: Feb-05
As a former Rotel AVR owner I can can confirm that it had the same issue. It was the Rotel RSX965, notorious for having QC issues. I returned it several times for repair.

Until I can afford high end multichannel gear my Yamaha RX-V657 will do just fine. The 2 channel part of my system is more important to me.
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