My attempt at fixing the NAD 2700THX

[killdozzer]

HEEEYY!!! I'm almost half as happy as I was when I fixed my speaker.


This time it was "luck favors the brave". Funny thing, I use to think the knobs move slowly and hard in order to leave the impression of a solid build quality like in some units where it's done deliberately, but when this "wonder-spray" did its thing, the knobs fly like crazy and nowhere throughout the path of the potentiometer do I have one crack or break in the channel.

 

[killdozzer]

I did some testing:

BUT THAT'S NOT ALL!! And the best is yet to come. The NAD power amp has two sets of main ins, You use one for audio and that one is equipped with the subsonic filter (in fact in NAD it is both infra- and ultra- sonic filter). The other 'main in' input to which you can also connect a pre/pro is meant for the movies and you don't have the filters as it's suppose to go as deep as possible.

My mistake was that I though my pre-amp has the filters built in as well, but the filters are just in the power amp. When I tested the TT with the NAD power amp the cones stopped pulsating. Hey!! A PURE BONUS.

I could get them going, if you wonder, but that would mean turning the master volume to two thirds or 3/4. I did that for a short period of time just to be sure. At that level the speakers start making some dreadful noise; screeching and buzzing and humming at the same time and I guess that was the feedback closed between the speakers and the TT. I turned it down right away. But this only happen with needle down on the empty part of the LP, record spinning and me sending like 80-100w to the speakers. Which means this is not likely going to be a problem I'll encounter in my everyday listening. Playing a record at very high levels through the NAD didn't result in any cone pulsating.

 

[killdozzer]

Now, my next plan, before I make some changes to my system, is to use the NAD for the LP's.

Is it possible to have two amps connected to the speakers at the same time so you can switch between them?

Would two sets of wires going to the speakers be a problem of any sort?

 

[<eargiant]

Now, my next plan, before I make some changes to my system, is to use the NAD for the LP's.

Is it possible to have two amps connected to the speakers at the same time so you can switch between them?

Would two sets of wires going to the speakers be a problem of any sort?

That's a NO-NO. You need an amp switcher box.

 

[slipperybidness]

Moving on with the cleaning today. Few shops I visited don't have a wrench that would go into such a narrow deep hole to unscrew a hex nut. Change of plans, I'll try to clean them your way first.

I need some reassurance; Is it really completely safe to clean them this way? Is it really safe to turn them 50 times and more from side to side to make the slider do all the cleaning on the inside and scrape the dirt? Won't this affect them? Isn't that too much scraping?

That is the normal routine.

Likely a socket would work better than a wrench.

 

[killdozzer]

That is the normal routine.

Likely a socket would work better than a wrench.

I call them all wrench just because that's the word I know. I looked up socket, we call it gedora in my parts.

Anyway, the amp works perfectly now.

 

[killdozzer]

I did some more testing today. I'm just so happy I got this beast back in working order, I can't tell you.

I was assembling some "IKEA-esque" flat box and it had a lot of Styrofoam inside. It is the old kind made out of granulae, where you can see them being mold together in a desired shape. I was very surprised to feel it conducts music almost too easy. Holding a bigger peace in air while my speakers played loud made me feel through my fingertips all of the music; the melody, the rhythm , everything. I thought it would isolate, I was going to use it under some equipment (well not anymore).

The other type, foam-like, the one inside the box my LS50's came in didn't conduct anything. It was one of the best decoupling mat for my speakers so far.

Which brings me to the subject; I've noticed very few spikes beneath the turntables. Mostly it's one type of rubber or another. How come? Aren't spikes good for TT's? I did see that those plinths and shelves have spikes, but rarely on the TT itself.

 

[lovinthehd]

Why would a spike be useful compared to something that can absorb vibration?

 

[killdozzer]

Why would a spike be useful compared to something that can absorb vibration?

I thought if spikes are good for decoupling, the same reason you put it under the speakers, maybe you could decouple the TT with them... As I said, I saw plinths for TT's having spikes, but not the TT's themselves. I was wondering why?

Although, what I have in mind is the reverse; stopping the vibrations from the furniture to cross over to the TT.

 

[lovinthehd]

AFAIC only use for spikes is to anchor your speakers thru carpet. The whole plinth/spiky thing I've always viewed more as an aesthetic choice rather than anything I've needed or wanted...kinda like tt clamps, LOL. You just want to isolate the tt from physical vibration. Sorbothane might be something to consider.

ps the stock feet on my SL1200mk2 are pretty dang good, wonder if they might be available to you? (assuming same threading)

 

[killdozzer]

AFAIC only use for spikes is to anchor your speakers thru carpet. The whole plinth/spiky thing I've always viewed more as an aesthetic choice rather than anything I've needed or wanted...kinda like tt clamps, LOL. You just want to isolate the tt from physical vibration. Sorbothane might be something to consider.

Yes, it's almost always sorbothane. But I don't think spikes are for the thru carpet thingy. Otherwise you wouldn't have this:

to accommodate the spike, you can't put this under your carpet, it would bulge. I think spikes are the "cancellation" principle; as it narrows, the frequency it conducts is higher and higher until it's too high and irrelevant as it won't make the furniture it sits upon resonate.

ps the stock feet on my SL1200mk2 are pretty dang good, wonder if they might be available to you? (assuming same threading)

I doubt it, this is what I have beneath:

A spring, a foot and a rubber bell to go over the spring.

 

[lovinthehd]

Yes, it's almost always sorbothane. But I don't think spikes are for the thru carpet thingy. Otherwise you wouldn't have this:
View attachment 29558
to accommodate the spike, you can't put this under your carpet, it would bulge. I think spikes are the "cancellation" principle; as it narrows, the frequency it conducts is higher and higher until it's too high and irrelevant as it won't make the furniture it sits upon resonate.


I doubt it, this is what I have beneath:
View attachment 29559
A spring, a foot and a rubber bell to go over the spring.

No one has convinced me that the spikes cups are anything but a way to use your spikes improperly. Audiophiles will buy a lot of stuff they don't really need, tho. On my speakers/subs are rubber feet, work just fine on hard surfaces, even on carpet (I don't particularly need the anchoring thing let alone any further isolation). YMMV.

As far as the pics go, can't enlarge them to where I can see any details of the feet. Description of construction sounds a bit different altho probably not a lot but don't want to take mine apart (can't see the whole mechanism without doing so). Like these https://www.ebay.com/sch/i.html?LH_CAds=&_ex_kw=&_fpos=&_fspt=1&_mPrRngCbx=1&_nkw=technics+1200+foot&_sacat=&_sadis=&_sop=12&_udhi=&_udlo=&_fosrp=1

 

[killdozzer]

As far as the pics go, can't enlarge them to where I can see any details of the feet.

It's a thumbnail, just click on the image.

 

[lovinthehd]

It's a thumbnail, just click on the image.

Now I can expand them, might not have given enough time for the photos to fully load the first time....slow internet has made me see many a video as only a still....

Looks to be a different type.

 

[highfigh]

No one has convinced me that the spikes cups are anything but a way to use your spikes improperly. Audiophiles will buy a lot of stuff they don't really need, tho. On my speakers/subs are rubber feet, work just fine on hard surfaces, even on carpet (I don't particularly need the anchoring thing let alone any further isolation). YMMV.

As far as the pics go, can't enlarge them to where I can see any details of the feet. Description of construction sounds a bit different altho probably not a lot but don't want to take mine apart (can't see the whole mechanism without doing so). Like these https://www.ebay.com/sch/i.html?LH_CAds=&_ex_kw=&_fpos=&_fspt=1&_mPrRngCbx=1&_nkw=technics+1200+foot&_sacat=&_sadis=&_sop=12&_udhi=&_udlo=&_fosrp=1

The cups for spikes are used to prevent chewing up the floor.

 

[killdozzer]

No one has convinced me that the spikes cups are anything but a way to use your spikes improperly. Audiophiles will buy a lot of stuff they don't really need, tho. On my speakers/subs are rubber feet, work just fine on hard surfaces, even on carpet (I don't particularly need the anchoring thing let alone any further isolation). YMMV.

Sometimes I really enjoy when it ends up like this; it seems we were both right, but speaking of different spikes. Sharp spikes underneath the speaker stands and underneath SW are meant to anchor the speaker. But then, there's this type, which I was talking about;

 

[slipperybidness]

No one has convinced me that the spikes cups are anything but a way to use your spikes improperly. Audiophiles will buy a lot of stuff they don't really need, tho. On my speakers/subs are rubber feet, work just fine on hard surfaces, even on carpet (I don't particularly need the anchoring thing let alone any further isolation). YMMV.

As far as the pics go, can't enlarge them to where I can see any details of the feet. Description of construction sounds a bit different altho probably not a lot but don't want to take mine apart (can't see the whole mechanism without doing so). Like these https://www.ebay.com/sch/i.html?LH_CAds=&_ex_kw=&_fpos=&_fspt=1&_mPrRngCbx=1&_nkw=technics+1200+foot&_sacat=&_sadis=&_sop=12&_udhi=&_udlo=&_fosrp=1

I used to own a set of spikes and the cups. Ordered them from PE as part of a larger order.

I never even took them out of the box, ended up selling them brand new for about what I paid for them.

They "seemed" like a good idea when I bought them. But then just the hassle and logistics of trying to put my TT on them, I abandoned that idea.

Should be obvious, but planned to put them on my ProJect. I agree on the SL1200, it's already a tank!

 

[killdozzer]

Then again, I found this paper that says measurements disprove the whole theory!!

 

[lovinthehd]

The cups for spikes are used to prevent chewing up the floor.

Just seems silly to take up your carpeting to slide a puck underneath....

 

[lovinthehd]

I used to own a set of spikes and the cups. Ordered them from PE as part of a larger order.

I never even took them out of the box, ended up selling them brand new for about what I paid for them.

They "seemed" like a good idea when I bought them. But then just the hassle and logistics of trying to put my TT on them, I abandoned that idea.

Should be obvious, but planned to put them on my ProJect. I agree on the SL1200, it's already a tank!

I've got all the spikes that came with various speakers. Might figure out something to do with them one of these days....

The SL1200s are indeed tanks.