TNT-Audio Readers' Corner
Monthly section devoted to your letters, positive and negative feedback about everything related to Audio and HiFi.

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April 2005

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Northstar 192 CDT and DAC
Thank you for the comprehensive review of the Northstar 192 CD Transport and DAC in TNT. I have ordered this set and expect to receive them early in May. I was curious about the decision by the manufacturer to include upsampling to 24/194 in both the transport and the DAC. Thus using the l2s IC, the 24/192 upsampling in the DAC is bypassed, as you point out. But isn't that an extra cost to the include two upsampling capabilities and use only one. I would assume the NS transport would not include upsampling, like most traditional transports.
Wondered what you thought about this?
If one did not use the J45 cable interconnect, what would be the next best thing w/o losing any of the wonderful sonics. Perhaps the balanced IC, but with the sampling switch which way?
Many agree that upsampling the digital stream from PCM 16/44 to 24/192 improves the sonics, and may even create analog-like sonic results. (The upsampling with the NorthStar 192 CDT and DAC may be a good example of this).
How can upsampling improve the basic information in the PCM 16/44 stream and lead to such an improvement in sonics (such as with the NorthStar pair)?
As a mathematician, you know one cannot add information to a data stream out of nowhere. However, as in digital photography, certain algorithms can improve resolution. But, with careful inspection, this improvement in photo resolution can be discerned with the trained eye. Is there any correlation of this with HiFi upsampling?
Thanks very much,
Glenn - E-mail: Gsherwood53 (at)

Dear Glenn,
There is at least a couple of reasons for NS doing this. First of all, the DAC has been released way before the transport, so it _had_ to include the upsampling circuit. Secondly, the upsampling included in the transport allows to fully exploit all the potential of the I2S connection between transport and DAC. Finally, I don't think the upsampling circuit is so expensive to represent a concern.
To get the best out of this combo, you need to use the I2S connection. The second best option could be the balanced IC but I see no reason for doing this.
The effect of upsampling is highly controversial. I can just cut and paste what Mr. Rampino (North Star designer) has to say about up/oversampling. Funny you haven't read this, it has been published on the Model 192 DAC review.

First of all, let's say the upsampling method CAN'T improve anything. The sound of a digitally upsampled DAC is better because it is the non-upsampled one to be worse.
For, let's see what happens to a standard 44.1 kHz digital signal when it is converted directly by a DAC. Before going into analogue, the digital signal crosses a digital filter that oversamples it (normally 8 times, 8x oversampling, as usually called) and a second digital filter with very high slope that cuts off all the garbage above a certain frequency, quite close to the audio band.
Once the signal has been converted into analogue, it crosses another filter, an analogue one, normally of the 2nd or 3rd kind, that introduces phase rotations into the audible spectrum.
Now, how can we consider the effect of a phase rotation in the time domain?
Let's suppose to have a musical instrument that plays its fundamental tone and its harmonics. The first ones normally are reproduced fine...but the higher order ones are delivered to your ears with a phase rotation (with respect to the first ones) and hence with a time delay that can be heard as distortion.
What happens with upsampling? The standard 44.1 kHz digital stream is interpolated and the samples are calculated as the original signal had a 192 kHz sampling rate. BUT!!!! This process adds NOTHING to the original signal!!!! Even at 192 kHz the signal is still extended till 20 kHz! The difference now is that the signal crosses digital filters centered at 96 kHz and the following analogue filter will be centered far from the upper limit of the audio band (actually, near 96 kHz!!!). This means the analogue signal coming out of the DAC will be more faithful to the original one in the time domain (less phase rotations, that is).
Hope this helped,
Lucio Cadeddu

Knosti Disco-Antistat
Dear editor!
After long deliberations, I have finally bought the Knosti Disco-Antistat record-cleaning device - no doubt Geoff Husband's excellent review article was instrumental in that (thanks again!).
Although this is but a humble hand-operated affair, it is highly effective and I am very pleased with the results. I am a regular buyer of used LPs (there's not much else around these days), many of which look like well-used ashtrays. Need I tell you that many of these now sound as great as the day they were pressed?!
A big thank-you is in order!
Peter - E-mail: pinghels (at)

Dear Peter,
thanks for the feedback! The Knosti is, indeed, a clever and very cost-effective record cleaner.
Lucio Cadeddu

DIY cables white paper
I wanted to drop you a line at TNT-audio to inform you about a potential resource for your site. Pear Cable is a high-fidelity audio cables company that manufactures and sells cable. One of our primary goals is to educate audio cable consumers of all types, including DIY's. I too began my fascination with audio cables as a DIYer.
I have prepared an extensive and informative "white paper" on audio cables (specifically interconnects) to explain the principles behind our products.
This resource will probably be useful to DIYers trying to build their own cable. I hope you will take a little time to check out the "white paper" and consider it for inclusion on TNT-audio. Again, since our mission at Pear Cable includes the general education of consumers about audio cables, this is in-line with our overall corporate strategy. The link to the tech paper is:
Thank you in advance for your consideration,
Adam - E-mail: adam (at)

Dear Adam,
thanks for sharing.
Lucio Cadeddu

DIY "honeycomb" turntable mat
Dear Lucio,
 You are certainly right. Our Garrard zero 100 SB's have a warm but rather dim sound, and they lack liveliness when compared to modern turntables. Therefore, I visited a beekeepers store where I bought a pure virgin wax holder on which bees build their cells (honeycomb).
These sheets measure 20cmx40cmx2,5mm, so I needed two (both of them, here in Buenos Aires, for the ridiculous price of one Euro) with which I made a turntable mat for the Garrard.
The result: it sounds much livelier, has a better definition and improves focus. On doing this, one most take the precaution of putting a thin transparent sheet of polystyrene in between the mat and the vinyl to avoid wax from staining the disc. It looks pretty, it smells good and avoids static buildup.
  After a couple of days of running in, it looses its natural dampness and fragrance, the sound is slightly less forward, but keeps details and vivacity.
I have tried it on the Garrard GT 55, but the result was inferior. I therefore believe it is an ideal mat for the Garrard Zero 100 SB. Maybe one should try if it works the same for other turntables
Antonio - E-mail: andreslionetti (at)

Dear Antonio,
thanks for the tip, your idea is fascinating. Honeycomb (so to say) has very good damping properties, indeed.
Lucio Cadeddu

Minima Amator
Dear Lucio,
I am paying off a pair of Minima Amator speakers. I have not heard these speakers but am buying them by reputation...I can return them if I am not satisfied. I am a bit concerned about possible lack of listening room is 9x4.5metres with higher than normal ceilings. Could you please tell me if these speakers are superior to current model concertos. Also would the Unison research unico p or unico hybrid amps be a good match in this room.
Best regards,
Shane - E-mail: shaneleete (at)

Dear Shane,
I wouldn't put the Amator in such a large listening room. Bass will be lacking, to say the least. A pair of Concerto's will be a better option, in my opinion. Minima's are very different from Concerto's. They are highly transparent minimonitors while the Concerto's are all-purpose bookshelf speakers. As for amp-matching, the Unison would be just fine, but - let me insist - the room is too large for such a diminutive loudspeaker...unless you listen to chamber Music at low listening levels. Anyway, perhaps your needs are different than mine, and since you can give the Amator's back...give them a try. Then let me know.
Hope this helped,
Lucio Cadeddu

Rebuilding speakers
Dear Lucio and TNT team,
Keep those newsletters coming and help me rebuild my speakers .
I look forward to every new week and the latest TNT newsletter to read on Monday morning as I take my first coffee - coming from England I naturally drink tea for breakfast, but my concession to living in Sweden is to drink (far too much) coffee the rest of the day. So it's really not fair to us fans when you take a holiday, but of course you deserve it for all the effort you put into making TNT such a good forum for all audio and Real Stereo fans!

The article last year by Dejan Veselinovic on rebuilding the AR94 speakers gave me the thought that it is time to do something about my old Celestion Ditton 15 speakers. An e-mail to the TNT discussion forum earlier this year solved my question about the passive radiators which I mistakenly thought were just dummies to make people think they had bought a three-way speaker when it only actually had two drive units. I have since learned from audiofiles in England and here in Sweden that the Ditton 15 is in fact a fine speaker.
I also reread Hartmut Quaschick's review of the DIY Newfoam kits. But I found on taking my Dittons apart that the cones and rubber surrounds seem to be in good shape so maybe a little silicone on the rubbers will keep them supple for years to come. What I will do is change the internal wiring and the cross-over so that I can bi-amp or at least bi-wire them. So I need some advice now on changing the cross-overs. Here the information in yet another TNT article from 1999, "Tweaking the Spendor SP 2/2", looks very useful. Giuliano Nicoletti presented a new cross-over. Would this design suite my Dittons?
Here are the details of my Ditton 15 speakers: 8" mid-range driver, marked SP558DDC - 8" passive woofer, no manufacturer markings. - 13/8" tweeter, no markings. Cross-over: 1 large coil (no name) marked 782 (connected to the mid-range driver). - 1 small coil (no name) marked 783 (connected to the tweeter). - 1 cap (PYE) marked 50VDCREV, WG74RAS, 9748.
Unfortunately, I do not have any test instruments so I cannot give you any more info on the present components. I wrote to Celstion some time ago asking for technical info on the Dittons but they never replied. If the Spendor cross-over design would suite my Dittons I am keen to make them up, or can you also recommend a commercially available cross-over that would suite for bi-amping. I am in favor of making the cross-overs myself as this would be my first, hopefully simple, electronics project.
Another word on passive radiators. My next project is to build a sub-woofer. I notice several DIY websites that recommend a passive radiator together with an active driver in non-ported enclosure. What do you think?
Yours sincerely,
Michael - E-mail: michael.shanahan (at)

Dear Michael,
you cannot use a crossover designed for a given speaker into another one. Everything is different and there's no hope the thing will work. Considering the amount of work involved, the age of your speakers and your limited DIY skills I'd suggest to leave the Celestions as they are. Biwiring isn't necessarily an upgrade (see Thiel speakers, for example). Internal rewiring is a much better option. Use CAT5-style cables (FFRC or Triple T). Also, it could be nice to upgrade the caps but it seems you are unable to detect the correct values. The code you refer seems to have nothing to do with value of the cap (you need something expressed in uF and Volts).
As for DIY subwoofers, yes, it seems many designs use passive radiators, but there's no "one way" in the road to good sounding subwoofers. Many different approaches can give excellent results.
Hope this helped,
Lucio Cadeddu

Noise killer -> Dead skin
I read your article about the Noise Killer and found it very useful. To your knowledge the product name is now changed and comprises several products ind the same category. Dead Skin is the new name.
Thank you againg for a great TNT.
Best Regards,
Per - E-mail: per.borgen (at)

Dear Per,
thanks for the precious info!
Lucio Cadeddu

FleXy table
[Tall FleXy Table] I am writing to let you know that a TNT Audio FleXy Table has now been built in by me in England. I built a seven shelf version to hold my home cinema equipment - see pictures attached! The seven shelves are made from 18mm MDF, 580mm x 358mm (golden ratio), varnished on top and painted with "liquid rubber" roofing paint on the bottom. This is a very smelly paint so it needs to be sealed over with varnish once it's dry! I have used extra nuts as feet. This is not ideal but they won't mark the wooden floor. I had real problems finding rubber washers the right size. The cheapest I found were 50p each, which was not good because I needed 42 of them! So I looked in the Yellow Pages for rubber manufacturing companies and found a company that would make some for me for 6p each :) They are 2mm thick, 20mm inside diameter, 32mm outside diameter.
The equipment shown on the shelves is:

Thank you for a great design!
Robskillz - E-mail: robskillz (at)

Dear Per,
thanks for the feedback and for the nice pic! OTOH, have you ever planned to switch to Real Stereo instead? TV has sooo little to share with Real Music :-)
Lucio Cadeddu

Cartridge choice for Rega TT
Can either you or somebody on your staff recommend one item I need, namely a cartridge for a new Rega P3? There are so many brands and models it is difficult to select a cartridge that will mate well with the Rega table.
Thank you.
Leonard - E-mail: lbbloom (at)

Dear Leonard,
a no non-sense wise choice would be a Rega cartridge. There are many models available, ranging from the inexpensive Bias to the high-endish Exact. The reason why these carts are so highly recommendable for a Rega turntable (and tonearm) is system compatibility. For example, they come with a three holes mounting system for optimal shell installation on a Rega tonearm. This way, tracking errors should be minimized even without the aid of an alignment protractor.
And, of course, they all share a kind of Rega family-sound.
Hope this helped,
Lucio Cadeddu

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