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Phono Preamp comparison (horror story)
fewtch
post May 28 2002, 20:33
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I received my new Denon turntable today, which has a built in phono preamp.

Since reviews state the Denon preamp isn't that good, I went and bought a separate (Techlink) preamp, which now it looks like I wasted $33 on this piece of crap.

Compare the two. Here first is the Techlink, which seems to be doing no RIAA equalization at all to my ears. Terrible over-emphasis on the highs:

http://home.attbi.com/~fewtchmon/techlink.mp3

Now compare the Denon, which sounds pretty good to my ears:

http://home.attbi.com/~fewtchmon/denon.mp3

Does everyone agree the Techlink sounds horrible? My god, everybody be sure to stay away from it (www.tracertek.com).


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Trelane
post May 28 2002, 20:39
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I prefer the sound of the Denon over the sound of the Techlink...
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fewtch
post May 28 2002, 20:50
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Ditto... there's something wrong with the Techlink's sound. Highs are too emphasized, midrange seems de-emphasized, bass sounds screwy... :rant:


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ancl
post May 28 2002, 21:14
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What kind of pickup (MM or MC) is the turntable using?
If the preamp is made for the wrong type you might have those kind of effects.
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fewtch
post May 28 2002, 21:29
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I don't know, it's a cheap preamp so I would assume MM (which would match correctly with my turntable). Sold for $59 at the website, at least I got a deal on it... maybe I could return it.

To tell the truth, this new Denon turntable has better detail & less rumble than what it's replacing (Sony PS-J11)... but I think the Sony has the better built-in preamp (frequencies are more balanced, bass is better). Maybe I'll have to save up for a better preamp, but I don't know what I would get.


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bryant
post May 29 2002, 03:11
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I had never heard of that Techlink preamp, but I can't imagine it sounding that bad unless it isn't working right. Maybe you could ask them if it's supposed to suck... wink.gif

The NAD is generally considered to be a good little phono preamp, and it sells on eBay for under $100:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewI...item=1355128981

BTW, I have never actually seen a turntable with a built-in preamp (although I know they exist), but how can you use an external preamp with such a turntable? Does it have two sets of outputs?
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JonPike
post May 29 2002, 06:00
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QUOTE
Originally posted by fewtch
To tell the truth, this new Denon turntable has better detail & less rumble than what it's replacing (Sony PS-J11)... but I think the Sony has the better built-in preamp (frequencies are more balanced, bass is better).  Maybe I'll have to save up for a better preamp, but I don't know what I would get.


Wow.. sorry to hear that Techlink is such a piece.. hope you can return it.

On the Sony vs Denon thing.. might it be possible to remove the Sony board, and replace the Denon's with it? Hell, it might just fit! ;-) If not, you could put it in a separate box, and make it an ouboard preamp.. and then (assuming the TT has direct and preamp'ed outputs) do A/B tests between them..

That would be probably the cheapest way to go, and you already have an idea of the quality.. Could be a good starting point, till you settle on something better.
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fewtch
post May 29 2002, 06:08
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QUOTE
Originally posted by bryant
I had never heard of that Techlink preamp, but I can't imagine it sounding that bad unless it isn't working right. Maybe you could ask them if it's supposed to suck...  wink.gif

The NAD is generally considered to be a good little phono preamp, and it sells on eBay for under 0:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewI...item=1355128981

It's an idea... the one built into the Denon seems adequate, if a bit lacking in bass.
QUOTE
BTW, I have never actually seen a turntable with a built-in preamp (although I know they exist), but how can you use an external preamp with such a turntable? Does it have two sets of outputs?

There's a simple switch that selects either regular "phono" or preamplified output.


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fewtch
post May 29 2002, 06:43
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P.S. I'm not gonna complain too loud, this turntable is head & shoulders above the one I had before (just made the nicest sounding vinyl recording to digital I've ever done). But the Techlink preamp was a total waste of money... oh well.


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macdaddy
post May 29 2002, 07:15
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new week, new thread, same usual suspects...

fewtch-I am sorry to hear about your preamp predicament. I'm glad the Denon worked out for you, though-it's probably a very solid turntable...

I ordered the hagtech bugle over the weekend (the developer said it would ship today sometime). I won't know about quality until I build and test-I bought the half kit, so I'm going to have to mess around with getting more parts from somewhere, and I won't know precisely what I will need until the kit arrives. I will then have to construct the thing. BUT it could quite possibly be comparable in cost to the piece you are attempting to return, so if you get your refund, you might want to go down the same road (misery loves company)...

JonPike-warning: you might be getting a pm from me in the very near future (and thanks, in advance)...
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fewtch
post May 29 2002, 18:04
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Listening to the samples from the Techlink preamp again, it seems to me that the sound follows the so-called "V" equalization curve (rather than flat like it should be). Bass and treble are overemphasized, and there's almost no midrange.

I wonder if this is by design in the Techlink, in order to make cheap speakers sound better? I got an Email back from a rep at the company, stating they've sold over 1000, customers have been very happy, and "it should work with any cartridge." *sigh*... rolleyes.gif

P.S. Macdaddy... I'd be interested to hear your experiences with the Bugle (the kit aspect sounds like fun too). After quite a successful transfer to digital yesterday, I'm thinking the preamp built into my turntable is adequate enough to preclude spending yet more $$ on a new one.


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JonPike
post May 30 2002, 07:44
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Macdaddy.. I'll be looking.. good that one of us took the plunge.. I might join you in a bit.. I'll be more than happy to show you sources for parts and help you pick some good ones..

fewtch... I'd try harder to get 'em to take it back.. they probably WISH they sold 1000's.. you might try the "I'm a regular on a audio forums that have a readership of 1000's.. you don't want THAT much bad publicity, do you" approach on them. wink.gif it might even work.

Sounds almost like (though I'll have to check) a MC optimized pre, as opposed to the Moving Magnet type.. At least I remember the sound as much brighter (high treble), I don't recall if the bass went up too.... I have a switch on the one built in the Yamaha amp, and tried it back when I was first setting things up.

Think these guys know the difference between a MC or MM cartridge?? "it should work with any cartridge." my ass! It's gotta be designed for one or the other, or switch between.. the wrong type is completly inappropriate..

Ask them which it's designed for.. if they act like there is no difference, DEMAND your money back, and call Consumer Affairs.. they either don't know what they're talking about, (but are promising they do) or are conciously misleading people about it..

Worse case... we could turn the TNT-Audio guys on them. They'd likely buy one, (or we send them yours) do a reaming review as an example and warning of people trying to rip off unsuspecting customers... They like that kind of thing.. biggrin.gif And what would these guys do, sue 'em? Sorry, wrong country! (most TNT guys are in Italy)

Let me know if you have problems.. I know who to talk to over there.. :diabolic:
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fewtch
post May 30 2002, 07:51
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Actually, they said they would take it back. Thing is, I have to find the packaging (if indeed I saved it), get an RMA number, plus it's gonna cost another 5 bux postage to mail it (at least), not to mention packing & all that... then waiting for them to credit my Paypal account... on a $29.00 item I'm not sure if I want to expend the time & energy for all this.

I might stick it in the closet to re-sell it some other time on ebay (insert evil grin), give it to someone else who doesn't care much about sound quality but needs a phono preamp, or just use it for parts or something instead. Dunno yet. Minus the main electronics, it could make a nifty "basic switchbox."


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2Bdecided
post May 30 2002, 09:49
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I wouldn't swear to the accuracy of this, but from your audio sample it's possible to make a rough frequency response measurement of both units. And looking at that, it seems that the HF RIAA equalisation is completely absent from the Techlink. In other words, they don't know how to design a phono pre-amp!

This is what the approximate frequency response looks like:

Dennon: http://privatewww.essex.ac.uk/~djmrob/mp3board/denon.gif

Techlink: http://privatewww.essex.ac.uk/~djmrob/mp3board/techlink.gif

If you apply an approximation to the HF part of the RIAA equalisation to the techlink signal, you get this:

http://privatewww.essex.ac.uk/~djmrob/mp3b...techlink_eq.gif


Like I said, it's not exactly scientific, but I think it implies a design fault in the RIAA equalisation.

This page explains equalisation for gramophone records, and the reason it is necesary for all records:

http://www.rfwilmut.clara.net/repro78/repro.html#eq


Cheers,
David.
http://www.David.Robinson.org/

EDIT: typo
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fewtch
post May 30 2002, 10:47
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QUOTE
Originally posted by 2Bdecided
I wouldn't swear to the accuracy of this, but from your audio sample it's possible to make a rough frequency response measurement of both units. And looking at that, it seems that the HF RIAA equalisation is completely absent from the Techlink. In other words, they don't know how to design a phono pre-amp!

I figured it was something like that (I know a little something about preemphasis and the need for RIAA equalization, and that's just what the problem sounded like).

And this is what the specs for the Techlink say:

"Frequency response: According to RIAA standard"

:wtf:


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JonPike
post May 30 2002, 11:01
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Very cool.. I should have thought of running the sound thru the spectral analysis part of some software I have.. (Cool Edit, for one) Which program is that you're using?

And, you've confirmed our suspicions.. these idiots blew it when they designed the EQ!!
Looks like they made a try at the bass enhancement, but even that isn't right... it peaks up somewhat at about 1Khz, then sharply rolls off.. rather than ramping up and staying at the proscribed increase of gain down the spectrum.

These guys must be betting on most of their customers having no experience in listening to LP's... they'll just think they're supposed to sound like that!

"Welcome to the Tracer Technologies Web site. Tracer publishes, manufactures, and distributes some of the world's best audio products."

Maybe so.. but this sure as hell isn't one of them..

Heh.. I like this line in the specs. Isn't really saying anything isn't it? I guess it needs an addendum:

"Specs:
Frequency response: According to RIAA standard" (we fu*ked up)

People like this really piss me off.. I say, more should know the truth about this thing..
fewtch, willing to donate yours to the TNT-Audio review cause?? :diabolic:
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macdaddy
post May 30 2002, 15:58
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Fewtch, you should at least send a link to this thread to the company-David has exposed them pretty clearly. Tell ebay about it, too. These guys are flooding the auction site with these pieces of sh*t, and I'm sure that there are plenty of consumers who have bought the thing. I don't think ebay is down with crap merchandise, I could be wrong. But they should at least know about it...

JonPike-I will know exactly what is needed when the kit arrives. I'll be in touch when I have the instructions and parts list. Thanks again for offering to help.
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bryant
post May 30 2002, 17:51
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You guys are having so much fun ripping this company apart that I almost hate to make this post, but I really don't believe that they could be selling a phono preamp that does not follow the RIAA curve. Nobody could listen to that and a reasonable stab at the RIAA eq can be done with a few passive components (so they're not trying to save money). The only reasonable explanation is that fewtch got a bad one (or, there might even be something wrong with the Denon's output in "no preamp" mode).

I've never seen a moving coil cartridge for less than $200 (and most are over $500), so when they say that a sub-$50 preamp works with all cartridges, what they really mean is that it works with any cartridge that anyone in their right mind would hook up to it. biggrin.gif

Just my $0.02...
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fewtch
post May 30 2002, 19:55
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I agree with bryant, in that it can't be proven based on experience with one preamp / turntable.

I do think the company is rather shady (dumping these preamps on Ebay at $29, while still selling on the website at $59.00 is a good indication). And I doubt anything is wrong either with the preamp or the Denon turntable, but can't prove it.

If somebody else does care enough to order one though, and write a review on it, I would be watching with interest. Another thing to point out is I don't think it would be a fair review unless it came straight from the company (not through a third party).

There's still one available on Ebay, btw:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewI...item=1356838482

Another idea would be to contact the company and request one to review. My guess is they would refuse though... biggrin.gif If interested, here's some contact information:

"curtis crowe" <curtisc@tracertek.com>
"Denise" <denisem@tracertek.com>

Tracer Technologies, Inc.
3600 Board Road
York, PA 17402
(717) 764-9240 Voice
(717) 764-9254 (Fax)


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JonPike
post May 31 2002, 03:45
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Heh.. well, I guess I agree with you guys as well.. Thinking about it in the cold light of day, (it was late the other night) I've calmed down a bit. We should probably give them A chance..

I get pretty steamed with tactics like this.. and think that they probably are as guilty as we think.. but it very well could be a defective unit missing some EQ parts, and not an intentional liqudation of a flawed design. So maybe we call off the dogs, till they prove themselves..

It would take careful measurement and maybe good lab equipment, to actually measure how closely the EQ matches the RIAA standard.. Though a test record and Cool Edit might do.. anyone know if there are test sweeps for this, on those test records?

Trying to think of a good, honest, easy test.. some kind of calibrated frequency sweep.. that always stays the same amplititude (comes out flat, with perfect RIAA) on a record.. I think you can get such tracks on test records.. I'll check..

2BDecided... having just got my Cool Edit back up and running, I now realize that funny icon I couldn't make out in your program box, was what Cool Edit looks like in XP! I thought the overall look of that box looked familiar.. I'm trying to reproduce your results... and it looks a little different.. is there an averaging feature I'm missing? I'd be interested in discussing settings. (offline, if it's too OT or boring to the rest of the thread)
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fewtch
post May 31 2002, 07:07
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If anyone REALLY wants to test the Techlink preamp, I'll sell it to you for $20 wink.gif. Really though, I would like to see a review of it somewhere... if someone wants to contact Tracertek, all the info. is two posts above this one.


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2Bdecided
post May 31 2002, 09:39
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The fault could be as simple as a dry solder joint - that's where it looks like it's soldered, but it's actually come loose. A single capacitor lead with a 0.1mm gap in the solder (due to dropping the unit in transit) would be all it would take to wreck the performance.

I said the measurements weren't scientific - let me explain how I did them...

An impulse is a reasonable test signal with which to judge the frequency response of a device - put an impulse in, and FFT the output. This would be perfect (apart from background noise).

Now, on the recordings provided by fewtech there are plenty of vinyl clicks, and these will do as a poor mans' impulse! (!) I just chose one of them (a loud click at a quiet point in the music), set the fft to the lowest value (this gives terrible frequency resolution, but only "looks" at 128 samples - which meant it wasn't picking up the nearest "loud" bit of the music), and used the frequency analysis in CEP, with the cursor on the centre of the click.

Measured this way, the absolute frequency response isn't reliable, because it's contaminated by
a) the spectral characteristics of the click on the vinyl, and
b) the music happening at the same time as the click.

If we don't assume that the Denon is OK, then, because of these possible problems, all that can be said is that the techlink is much brighter in sound. However, the flat-ish Denon measurement indicates that the measurement is quite accurate and/or successful (I'd expect a gentle fall off at around 2kHz which isn't visible, but we'll ignore that).

So, if we assume that the Denon unit is OK, then the Techlink has a huge treble lift, which is both audible, and visible in the measurement. It seems more than coincidence that applying the RIAA curve corrects this huge treble lift. With this evidence, it's likely that there is a fault in the RIAA stage - a more accurate measurement could confirm or deny this.


A useful hint: if there are no isolated clicks on the vinyl, you can scan the frequency response of the run-in groove (using CE or CEP) - this should give you at least a rough indication of the response of the RIAA filter (if present) because without it the background noise on a LP is approximately spectrally white (i.e. you would see a flat line frequency response). You could also see mains hum and turntable rumble in there, so take this "measurement" for what it's worth: a very very rough guide, but better than nothing, and very easy to do.


Cheers,
David.
http://www.David.Robinson.org/

P.S. As noted by bryant, it's almost more likely that the Denon is doing something strange when you disconnect the pre-amp. So dispite all this careful consideration (which shouldn't convince anyone that I actually know what I'm doing ;-)) it's still unlikely that all Techlink phono pre-amps have a problem. (Will that sentence stop them litigating?)
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fewtch
post May 31 2002, 09:46
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Check new thread I started: "The last phono preamp thread (?)" smile.gif.

The Denon turntable appears to be working fine, I found another preamp which I think sound better than the one built in (the only disadvantage is 3.7dB of "extra" 60Hz hum on the right channel, dunno where it's coming from but it's inaudible at normal recording levels).


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JonPike
post May 31 2002, 19:03
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Well fewtch.. welcome to the "keeps huge amplifier just for tiny included preamp" club..
;-)

Actually I do use mine for amplfying and driving speakers now and then..

As for the hum.. if you're motivated, you might check your grounds (all those RCA plugs making good sheld connection?) or even the internal wiring layout.. possibly there is something too close to something else, and moving wires away from transformers or power leads might help.

2B.. great technique!! A click would be pretty close to a pure impulse, at least to the cart/phono pre system.. You'ld need a track with pure white noise to do it right otherwise, kinda hard to find.. Is it true that an empty groove is pretty close to white? Only thing is, it's (hopefully) pretty low level.. but it shouldn't be too hard to find a fairly worn record..

I noticed in my testing of the mp3 files (yeah, maybe the pac's would be an idea) that you couldn't get a very clear picture, exactly like you said, the music content "colored" the result..

I guess we need nice, nearly silent passages with sharp clicks, rather than music, as our test files!

Off to "ping" my own system... wink.gif
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fewtch
post May 31 2002, 21:15
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QUOTE
Originally posted by JonPike
Well fewtch..  welcome to the "keeps huge amplifier just for tiny included preamp" club..
;-)

Actually I do use mine for amplfying and driving speakers now and then..   

As for the hum..  if you're motivated,  you might check your grounds (all those RCA plugs making good sheld connection?) or even the internal wiring layout..  possibly there is something too close to something else, and moving wires away from transformers or power leads might help.

Thanks... I did some checking last night, and I'm convinced the problem has something to do with the turntable. The hum isn't there (and the preamp output is balanced) when the turntable is unplugged or disconnected, but when I connect it the hum is back. The RCA connections are solid, so I figure a grounding issue (none of this crap is grounded properly, both the turntable and amp have 2-prong plugs!).

Anyway, the hum is at ~-66dB (right channel) and the left is at ~-69.7dB, so it isn't audible anyway.


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