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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March 2012

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DIY cables resources
Dear TNT-Audio,

  1. Is the UBYTE-2 Speaker Cable the most current TNT-Audio DIY speaker cable guide?
  2. Where does one find "low loss satellite coax cable with a single solid copper center conductor, a full copper foil shield, a plain copper braid over the foil and either foamed teflon or air-cell polyethylene/gas insulation"?
I've search the web for the coax and so far I haven't found it.
Tom - E-mail: stellastudio1 (at)

Dear Tom,
we have many other DIY speaker cables designs on our website and the UByte isn't the most recent one. Anyway, don't think that if a design is older than it's necessarily worse...our DIY designs don't get obsolete as that commercial stuff. Only HiFi Companies NEED to update their catalogues every couple of years or so to prove they're always improving their products but, trust me, most of the times they just perform facelifts....
Have a look at our list of DIY projects here and choose the one that seems easier to build. Finding the right wires for our DIY cables shouldn't be difficult, several years ago we published an article with various links and suggestions on where to start searching. Perhaps some of those codes we mention are obsolete, but the online stores we refer to are still active.
Hope this helped!
Lucio Cadeddu

Best implementation of a TA2024
Thanks for your review of the LYM Audio integrated amplifier. Please have a look at this:
I own a couple of them (I had the privilege of being a "layman" beta tester of Notsobad) and I know what I'm talking about.
Piermario - E-mail: piermario.clara (at)

Thanks Piermario,
that does look interesting - although unfortunately I have no DIY skills so won't get the chance to try. Glad you enjoyed the Lym review - the basic converter must be pretty good - it's a sweet little amp. If it's possible to DIY more economically (which it usually is) then that's a good deal.
Best wishes,
Andy Norman

Get active!
Hi Mark,
I finally got active. Meanwhile I read a dozen of books on room acoustics, absorbed the first reflections, build some bass traps and some Schroeder absorbers tuned to the specific frequencies for my listening room.
I'm now using a notebook with JRiver, M2TECH Hiface, Behringer DCX2496, one Fenice 20 per channel as power amplifiers, Acoustic Research AR44BX without the passive crossover and all self made cables.
Along the way, as you suggested, I also tried the speakers with passive crossover outside the box and yes, improvements were clear.
It took me a little more time than expected to set everything to sound the way I was looking for. Even if I set the DCX crossover frequencies same as the passive crossover frequencies with the highest db/oct and didn't try all the filters and db/oct avalaible. While setting up I found very important the Time Alignment Function built inside the DCX2496: an issue I hadn't ever considered before. I can't compare with the system was using before because too many things have changed, but I think the sound I'm getting now is worth the effort and is what I expected from active filters.
I find the notebook/JRiver/Hiface much better than the Squeeze Box Duet was using before (both coax connected to the DCX) and read about the WASAPI audio output being better than the Direct Sound I'm using now, but can't use it because the Fenice 20 doesn't have the volume remote controller.
So now I need your help to find the way to remote control the volume after the crossover.
Thank you again.
Kind regards.
Stefano - E-mail: Stefano.Galli (at)

Hi Stefano,
I'll answer in more detail as soon as I have time. Meanwhile, I agree with all your findings :-)
Also, I intend to use your letter as the basis for more articles extolling the vices of passive x-overs and the virtues of 'going active'.
Remote volume is easy: train a child, whose height is below ear-tweeter axis height, to adjust all post x-over channels by the amount you tell them :-)
Failing that, I've become a fan of transformer based gain controls, so would suggest any of these, that can be remote controlled, will suffice.
Kind regards,
Mark, The Old Scribe
Mark Wheeler

Previous weeks letters

Beefier power supply for a phono preamp
Dear Lucio,
I have a Music Hall Pa 1.2 phono preamp, the outboard power supply voltage is 15V/300mA, do you think I can get any better performance from this preamp if I would beef up the power supplies mA's, I believe I read a long time ago that you suggested to do this with a particular preamp, not to increase voltage but mA, if so what would you suggest and would it make any difference in your opinion of which I much respect.
Thank you Lucio for your time, I look forward to your reply.
Best Regards,
Jeffrey - E-mail: jlnordi (at)

Dear Jeff,
absolutely yes! A beefier power supply is definitely the way to go. Do not be afraid to try an outboard unit with 1000mA (= 1A, that is) o even more, provided the output voltage is the same (higher voltage might damage the unit, higher mA's don't). A linear, stabilized PSU would be even better. Just pay attention to voltage phase (±) as a wrong connection might destroy the preamplifier. Do not expect a kind of night/day difference, as usual everything depends on the quality of the system you are using, since differences/improvements might be masked by system limitations.
Hope this helped, keep me updated!
Lucio Cadeddu

DacMagic and Rega DAC
Dear Andy,
A few months ago I read your DacMagic review on, and helped me a bit to make the better choice. So I had the chance to sell my DacMagic and I bought the Rega Dac. Much better in every way. I would like to have your opinion about the Rega, have you ever heard it?
Best Regards,
Nuno - E-mail: nbaptista007 (at)

Thanks Nuno. The Rega should be better - it's twice the money :-)
I heard it at a show when it was first launched - it sounded great but I've not had the chance to listen to it in my own system. I'm sure you'll enjoy it - I know a lot of people hold it in very high esteem - and good value for money.
Andy Norman

Re: DE400TN ++
Hi Mark,
thanks for this. I had not considered an MTM config. Yet now that you mention it, I do recall seeing many photos from various builders of of such a config with the TAD compression units in the middle position. Maybe even seen a few commercial offerings too. very high end stuff from those over the top Japanese audiophiles.
I should tell you that currently I have a DIY 300b amp (two mono amps) feeding an early 1970's Electro-Voice tri-axial 15 inch (~381mm) driver called the LT-15. It is a larger woofer with whizzer and horn tweeter in the center. This driver was first mounted on the classic JE labs open baffle and last year I moved to a taller and narrower baffle with little wings on the side to improve the WAF. All it has is an L-pad and 1.5uf cap on the tweeter, the woofer is fullrange. Changing the baffle certainly reduced the bass as the dirver is further from the floor, but I still get that open baffle experience which I seem to like after years of using sealed box speakers. But the bass is present and detailed just not loud enough.
Recently a friend lent me a cheap home theatre subwoofer. I can see the potential but it is very easy to muddy the bottom octaves and lose resolution. Although maybe two small subs each behind my open baffles might be something worth trying. But in the end... the horn tweeter on this electro-voice certainly doesn't match the DE400TN in refinement.
So that's why I was thinking of 1 (or 2 bass drivers in parallel) that could live on an open baffle with the DE400TN for the top part. I see two different crossovers for the DE400 on the BCspeakers page which I guess I can start with. That;s why I was wondering what you are using. And I guess I have to find woofer with high QTS to live on an open baffle.
Another fellow suggested I insert a passive high pass just before my amp and use the amp only for the mid and highs and use a commercial subwoofer unit for the bottom with the tap prior to the amp (fullrange) .
Paul - E-mail: paul.baptista (at)

Hi Paul
Thanks for the immediate response to my suggestions. I do believe many TNT-audio readers will be interested in your project so I am sharing this response on our letters page.
The MTM idea is really appealing with a wavefront controlled horn tweeter. I would not recommend using a sub up to the lower cut off of the B&C DE400TN. With a 12dB/8ve crossover slope, (2nd order sealed box, transmission line but not TQWP, open baffle in domestic room because of cancellations even though the driver response and anechoic output is 6dB/8ve) the sub-to-sat crossover point should be 120Hz or below in order to minimise output above 180Hz. Why not use a pair of 16 ohm (or 8ohm if your 300B has a 4ohm transformer tap) highish Q drivers in an MTM configuration wired in parallel, with one open baffle loaded and the other transmission line (not tuned quarter wave pipe)?
This combination would produce equal upper bass and midrange output from the two drivers either side of the DE400TN. As the frequency descends to the free air resonance of the open baffle driver (the top one), it's impedance rises. The impedance curve of the transmission line is flattened by the acoustic load of the line, so the two drivers should act as a voltage divider, controlling the resonance of the open baffle mounted driver and increasing the output of the line loaded driver. The line loaded driver will drive the room better, being nearer the floor (a la Allison et al) while the upper driver will benefit from greater distance from the first reflection.
The WAF can be increased, perhaps by a clear perspex open baffle for the top section and the reduced frontal area enabled by the TL loading of the lower driver. The line can emerge from the lower chamber as a narrow 'chimney' behind the open baffle (especially if round sectioned or at 45deg to the front) without interfering. This will save space. I'm almost tempted to try it myself!
Please keep us posted. I'd be happy to write up your build if you like.
Happy woodworking,
Mark Wheeler

Small amplifier
Hi Mr.Whetstone, My name is Paul, sorry to bother you but I sure would like a suggestion for a audio-pc combo I am running Windows 7 with a M-Audio Delta Sound Card with RCA jacks.
Thinking of hooking up PSB Bookshelf but I don't want to keep using my bulky old receiver. I would like something small and simple to push my MP3's and Dvd Ect. A simple amp or pre amp (at) around 40 w per ch. Stereo
Does Kingrex have something like this?
Paul - E-mail: rpdorts_58 (at)

Hi Paul,
If I understand your question, you are asking about amplification. If size is the main issue, I would recommend the Trends PA-10 tube preamp and their matching power amp, the TA-10.2P. Not just compact, but very decent sound quality too.
Nick Whetstone

DE400TN ++
Hello Mark,
I really enjoyed your TNT article on this compression driver. So much so that I'm tempted to build something using it even if I've never heard this driver.
I was wondering if you would be willing to share your crossover for it? And also what you are using as other drivers for Bass or Mid-bass etc...
For now I was thinking a 2-way design. For the bottom, I was thinking maybe two 8 or two 10 inchers which should give the same Sd as a 12incher and provide a more narrow baffle. But I suppose a single 12 or a single 15 could be an option as well. If I go with two drivers one could be given the full range up to the bottom of the tweeter and the other could be given just the lows up to say 400Hz or so to get a 6db boost of bass.
Anyway, I not looking for crossover design service (free) so don't be afraid that I will send tons of email.
But anything you can share is appreciated. And I of course will share my final iterations once I get real parts and start experimenting,
Paul - E-mail: paul.baptista (at)

Hi Paul,
Thank you for your kind words about my article.
You are clearly a man after my own heart, thinking BIG when it comes to loudspeakers. To quote either Walter Chrysler or Carroll Shelby (depending who you believe originated this gem), "there's no substitute for cubic inches", or Scotty the engineer, "Ye canna change the laws of physics". So big boxes are the order of the day. The key to a well balanced in-room sound is even dispersion, especially around the crossover point. I explained the general rules of thumb in my review of the DE400TN so any bass driver that extends above 1200Hz while maintaining a 90° dispersion will be good enough in that respect.

Personally I loathe passive crossovers with a venom it is hard to put into words; it is only my reviewing role that keeps them in my system so often. The claimed 106dB sensitivity of the B&C DE400TN would allow them to be driven by a tiny flea powered 2A3 SET or similar if you decide to opt for an active crossover (there are many inexpensive pro audio crossovers that will be superior to the most expensive audiophile passive crossover). Then bass can be handled by something with more oomph.

If you use an active crossover, the likely alignment will be 24dB/8ve (fourth order) in phase (constant summed amplitude) and you can play with the crossover frequency from a lower limit of 1200Hz to an upper limit defined by the cone break up of the chosen bass units.

With this tweeter's excellent dispersion characteristic, an MTM driver arrangement would be ideal. MTM equals mid-tweeter-mid, a vertical array of drivers with the bass-mid at the bottom, the treble unit in the centre and the other bass-mid unit above that. This will produce an ideal wavefront minimising vertical dispersion, which will in turn minimise early floor and ceiling reflections, depending on the distance between the bass-mid drivers. It will maintain horizontal dispersion at whatever the driver can manage at the chosen crossover frequency.

If you do insist on passive crossovers, in-phase third order 18dB/8ve are often the best compromise between insertion loss and out of passband behaviour. Third order is also magical with MTM arrangements as it produces a true D'Appolito alignment.

How about a 250mm driver above and below the B&C DE400TN, mounted as close as possible to the tweeter? Perhaps load the bass by using side mounted passive or auxiliary bass radiators (ABR) on each side near the floor to drive the room evenly, or a bottom slot port or a true transmission line if you are up to the woodwork?

What do you think? You are well served by loudspeaker parts suppliers in Canada.
Once you start designing your own projects you will never look back!
Happy building,
Mark Wheeler

Miniwatt N3 as power amp
Hi Nick. I enjoyed your review of the Miniwatt N3. Do you think it would be worthwhile to use as a power amp with a Marantz 2226b as preamp? I am looking to test the tube waters.
John - E-mail: signaljw (at)

Hi John,
Simple answer is that I really couldn't say. In theory they should work OK but it depends on the output level of the 2226b as to whether it may clip into the Miniwatt.
Sorry I can't be of more help.
Nick Whetstone

Favorite Class T amps
Hi Nick,
Thanks for your review of 2005. May I ask your currently favorite (and alternate) T-amp...Brand and model? Is 2020 the best chip...or ?
Thank you,
Steve - E-mail: sb (at)

Hi Steve,
If I had to pick one, it would be the Bantam Gold, and the alternative, the Virtue One although that appears to be sold out, so make that a Virtue Sensation.
Nick Whetstone

Alacrity Audio Caterthun Loudspeaker system - I
Hi, my name is Clyde Lindsay and I am in the States.
What are your reference speakers? What amplification seems best suited to the above speakers, i.e., only valves or can a valve-like transistor so the job? (I have a 200 watt Mcintosh integrated amp).
The other question I had was how good are these Caterthun speakers off-axis? Must you sit in one place or do they have a sweet spot wide enough for everyone in the room to appreciate them?
Thanks very much.
Clyde - E-mail: clyde.lindsay (at)

Hi Clyde,
I don't think that if it is at all useful to tell you what my reference speakers are, as they are built by myself, and the main drivers are not available anywhere so they can't be reproduced. But they are the open-baffle speakers referred to in the review.
Also, as I said in the review, the Caterthuns are very particular as regards the system that is driving them. Therefore, I can't state what sources/amplifiers will work best with them. It really will be a case of trying a pair and seeing what you like best with them. I know this makes deciding on a pair difficult, but they really are a no-compromise design. Again, as stated in the review, the manufacturer recommends valve amps but I got very good results with valve pre amp and class D amps. I also found that not all the valve amplifiers I tried worked as well as the Miniwatt.
The sweet-spot is not particularly narrow but again, a lot depends on your room, and where everybody is sitting. I have yet to hear speakers that can offer a truly stereo effect right across the width of the room. But at least in this respect, the Caterthuns are better than my open-baffles.
I hope this answers your questions.
Nick Whetstone

DIY speaker stand
[TNT Stubby DIY stands]
I just wanted to say thanks for your DIY speaker stand tutorial. I built a pair over the weekend. Even my wife likes them. I think they sound great. Have you ever thought of experimenting with rubber pads between the wood and PVC? I thought that might further help dampen vibration.
Also, any thoughts on where to pick up some soft rubber pads for the bottom? I am using rubber because I have hardwood floors. What I found at home depot are too hard.
Thanks again.
Tom - E-mail: thoscheidt (at)

Dear Tom,
congrats on your DIY skills! Your TNT Stubby stands look really great! No, we've never tried rubber pads between wood and PVC, I believe these pads might create stability problems with heavier speakers (oscillations, maybe?). If you wish, try by youself and report back your findings.
As for soft feet, I believe doorstoppers are among the best solutions. They come in different sizes and softness, just find the ones that suit better for your floor.
Hope this helped somehow,
Lucio Cadeddu

Record cleaning
some people in the record industry claim that it's bad for records to use alcohol/ethanol to clean them? On the other hand many people use it in a mixture, what's your opinion?
Ed - E-mail: edmosveer (at)

Dear Ed,
several years ago we published an article which contained many recipes on how to prepare a good record cleaning solution at home. Many of these use a mixture of isopropyl alcohol with other solvents. Used this way this alcohol isn't dangerous for vinyl. On the other hand, I'd strongly suggest to AVOID using pure denatured alcohol on vinyl, though, as it can be too aggressive.
If still in doubt, purchase some commercial fluid (Disc Doctor's is a very good example) and clean your LPs with it.
Lucio Cadeddu

Alacrity Audio Caterthun Loudspeaker system - II
I just did read your review for the Alacrity Audio Caterthun Loudspeaker system. When you say "Do remember though that these are not speakers that you can put into any old system" Does it mean that my new old McIntosh MC2200 is to old for this?
I am so proud of my new amp, it sound really good, I tought that was the best buy I made.
What can be wrong?
Alain - E-mail: informactique (at)

Hi Alain,
'Any old' is an English expression that really means 'any' and not specifically 'old'. A bit confusing to others, and I will try and avoid the phrase in future. The point about the Caterthuns is that they are tuned to work with a very narrow choice of equipment (source/amp) where other commercial speakers are often designed to work with a wider range of equipment. In other words, the designer is going for the best sound, rather than the highest number of potential sales.
So your old McIntosh may work perfectly with the Caterthuns but it would be necessary to hear the result before parting with your money. It's the usual issue of 'system synergy' but much more critical with the Caterthuns.
That was what I wanted to convey in the review.
Nick Whetstone

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