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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May 2012

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KingRex UD384 - Digital to Analogue Converter
I have just read your interesting and informative review of the above item. I have one question. I was thinking of getting an M-DAC but its USB is only 24/96. It has co-axial which takes up to 24/192. Can the UD384 therefore be used to feed the M_DAC coaxial enabling me to enjoy my 24/192 recordings?
Thanking you,
Ruwelly - E-mail: ruwelly (at)

Hi Ruwelly,
Thanks for your kind words. That's right - you can use the UD384 like that. It will take a USB feed and send it to its Coaxial output so that it can be used to feed a higher rate input on a co-axial device. It is also a very capable DAC in its own right of course, although I've not had the chance to compare it to the M-DAC.
If you get the chance to compare it, you may find the UD384 is enough. Having said that, if all you need is something to convert the USB from your computer to coaxial, there are cheaper alternatives that will do just that job, including KingRex's UC192.
For example, Musical Fidelity had a similarly specialised device and I think their latest V-DAC will do that job too. I'm sure there are others. Having said all that, it may be worth checking whether you can really hear enough difference and have enough 24/192 recordings to warrant adding a device to the signal chain.
The restriction with USB used to be to 44 or 48Khz and (I think) 16bit - so it used to be an appreciable difference. Now it's just 96 versus 192 on some DACs I doubt you'll hear much, if any, difference. I hope you can get a chance to audition some of the options, there are so many! Good luck, and let us know how you get on.
Kind Regards,
Andy Norman

Tube preamps
Just a follow up.
I recently purchased the Trends PA-10 hybrid tube pre-amp. Will this give the same effect or will the Audiodigit TubePre give better results?
Allen - E-mail: ranger3 (at)

Hi Allen,
I would say try the PA-10, it's actually quite good. That will give you an idea of whether it's the sort of sound that you are after. If it is, you could look to try another option.
Nick Whetstone

Will direct sales replace traditional HiFi stores?
Hello Lucio,
I am one of those people that live far away from Hi-Fi stealers, oops sorry dealers (for the last 4 years). The nearest one is a good 250 miles away.
I have to say that I have purchased nothing from a trad Hi-Fi dealer for around 15 years. I have to say that when I used dealers I didn't always enjoy good service. I remember handing a product in for repair at one Stockport dealer and waiting several months, only to find the guy hadn't sent the item (pre amp) back. Another time I ordered some springs for a turntable from the dealer only to be told that they were now not available and no, you cannot have your money back! Another dealer tried to fob me off on a speaker repair which they said was impossible to complete. The bass/mid drive unit was missing and he wasn't going to tell me! They had lost it.
I would have to say that if I am buying direct then I expect direct prices. Hi-Fi dealers and distributers put up retail prices massively and I don't see why I should be paying them hundreds or even thousands of pounds just for putting a stamp on a box.
The Americans are much better served with direct suppliers, Decware & Tekton Audio to name but two. They offer excellent products at more affordable prices. If their products were marketed through the dealer network the retail ticket would jump twofold or more.
Many workers have seen their jobs go in the last 50 years. Why should Hi-Fi dealers be any different?
Mike - E-mail: mikebooth (at)

Dear Mike,
thanks for your precious feedback on my recent editorial. Your experiences with traditional dealers are very sad, but we can't think these behaviours are the standard ones. There are many serious and professional dealers out there, and those ones, I'm sure, will survive. Those who offer a pre-sales service (listening, second-hand gear evaluation etc.) and post-sales service (installation, service etc.) are going to survive and, eventually, sell even more.
And yes, I completely agree with your last sentence, many workers have lost their jobs in the last 50 years. Perhaps there are too many traditional HiFi dealers for a market that is no longer what it used to be. They will, sadly, disappear.
Thanks for your feedback!
Lucio Cadeddu

Tube amp?
I've read many of your reviews over the years. Thank you for helping me get back into my love of music. Your reviews have guided me well. I currently have a pair of Medallion II's with (well broken in) DX3 drivers which I've been listening now for about a month. I'm still tweaking, but I like what I hear so far.
I am currently driving them with a Virtue Audio Two.2 amp. I am wondering how bringing in a tube amp will change the sound over the Virtue Audio amp. Specifically, Jon Ver Halen recommend I consider a Miniwatt N3. Since I have no tube experience, I am interested in your opinion on how this will effect the sound of my Medallions.
My room is approx. 15 wide, 20 long. It has an 18 foot ceiling. It's carpeted and I have the Medallions in the corners about 1 ft. of the back wall and the side wall.
I listen to 60s -2010s rock, acoustic, alt. etc. Some of my favorites are Supertramp, Steely Dan, Henry Mancini, Joe Jackson.
Any thoughts would be well appreciated.
Allen - E-mail: ranger3 (at)

Hi Allen,
If we at TNT have helped you regain your love of music, then we are doing our job. I don't have experience of your speakers but I do have knowledge of the Virtue amp, and others like it. Rather than going for a valve (power) amp I would suggest keeping that excellent little Virtue amp, and adding a valve pre amp or buffer. The combination of valve and class T(D) works very well, and is what I currently listen to.
There's a lot to choose from (see reviews on TNT), and if you fancy a small amount of DIY, there are some modules that can be bought off Ebay although sadly, none of my requests to review them have received a reply.
I still use and like the Audiodigit Tube Pre.
Nick Whetstone

Using Yarland with vertex coupling system
Hello Nick,
I'm thinking of purchase a Yarland FV 34 CIII, now I'm reading your review about coupling to a Vertex system. Can you explaim me more about this if it is possible with some pictures, how it works?
I'm living in the Netherlands and I'm going to use this equipment with Sovtek EL 84 tubes and two General Electric 5670 NOS tubes.
I also want to know where I can get this system if I want to buy this and what's cost in euro's,
Kind regards,
Peter - by E-mail

Hi Peter,
I described the Vertex range of products in my review.
It explains the theory of how it works and gives the prices at the time of the review. Vertex should be able to tell you where your nearest dealer is so you can get latest prices. You must remember though that the Vertex products stop noise going from one place to another in the system. So if it is not used throughout the system, you may be 'trapping' noise in one part by blocking it going to another. If you can't afford the 'real' thing, and don't mind a bit of DIY, have a read of this: As regards the valves, in my experience coupling them to some granite is better than simply damping them.
Nick Whetstone

Dayton APA 150 review
Hi Arvind & Lucio,
Just read your review on the Dayton APA150 amp and clicked the link to Linn Audio of New Hampshire's web page.
Not only is the Dayton Amp on view but also the Behringer A500. I have used two A500's for the last 8 years and they are very good amps. The only bother is one input only but that isn't a problem for me with a digital only system.
Mr Linn is certainly expensive but I suppose he is playing on Hi-Fi neurosis, I mean how can an amp for 150 be any good!? Far better to change a couple of caps and put the price up and up!
I have had Hi-Fi components modded in the past but never felt the need to mod the A500's. If the Dayton is as good as the A500 it will be an excellent amp with no need of Mr Linn's services.
Enjoyed your review.
Mike - E-mail: mikebooth (at)

Hello Mike,
Interesting thought on "audiophile neurosis". There, of course, is only one way to test it a comparison. I just reached out to the folks at Linn Audio and offered to review their version. Now, let's see how they respond, and if they are confident enough in their product to submit a review sample.
In my mind there would be 2 questions to answer -

  1. Is there really any improvement in sound quality, and how much of a difference is it?
  2. If there really is an improvement, then is it worth the price? The first question is what I can provide my perspective on, the second question of course is up to each hobbyist and their "utility curve".

Just heard back from David Linn. He was surprised that the website had a price on the amps!!!??? He says he gives those away with his speakers [the speakers list is 50k and 30k USD). He did say something like - he just put a price on the website to give customers the impression that they are getting a great deal by a free amp being part of the speaker package [disingenuous, no?].
So he is not going to submit the amp for review/comparison. I'm not surprised he found an excuse to back away from a comparison. Makes one wonder what value his customers get for those speakers as well. Now, he is looking to have his speakers reviewed - if anyone is interested.
Arvind Kohli

Do it yourself Audio Tweaks
Hello Lucio,
I have read through most of the Do it Yourself Tweaks on your online site. I find them very interesting. I am wanting to build a Power Outlet but was wondering if it is even worth it. Here's a link one, I couldn't find one on your site. Have you had any experience with a power outlet that improved sound quality?
I'd be very interested in your opinion before I pour $300 on Wattgate Contectors (USA).
Thank you.
Ian - E-mail: enushalu (at)

Dear Ian,
it seems you have missed our TNT Hydra DIY outlet! Anyway, improving the way power reaches our system is always a good idea. Before spending silly money on these tweaks may I humbly suggest to improve the quality of the power line that feeds the wall outlet? A dedicated mains line, with a good shielded cable, independent from the rest of the house electronic and electric appliances, for example, is a major upgrade for any HiFi system. Two of these dedicated lines would be even better (one for the amps and one for the sources). It costs less than other expensive tweaks and it works fine.
Hope this helped,
Lucio Cadeddu

Power output figures
Hello again and excuse me for bothering you,
I can't seem to find an email for Dejan Veselinovic. I wonder if you can help me with something. I intend to buy a Karman Kardon amplifier from an online reseller. I have a pair of Magnat Monitor 880 loudspeakers. In his review Dejan Veselinovic says that:

It is an integrated amplifier delivering nominally 85/130W per channel, into 8/4 Ohms, 20 Hz to 20 kHz with no more than 0,08/0,3% of distortion. Using IHF tone bursts, it will deliver 110/170/240W into 8/4/2 Ohms.
I don't understand! So nominally it delivers 85 watts into 8 ohms? When does it deliver 110 watts into 8 ohms? When you turn the volume to play the music louder?????!!!??? How does the IHF tone burst function?? I read that IHF peak power is usually used by lower quality gear to give a higher output rating. Is it true??
Thank you and I'm waiting to hear from you
Stefan - E-mail: stefanfurduescu (at)

Dear Stefan,
simply put, one is the CONTINUOUS power output, the other refers to brief PEAKS. During peaks an amplifier normally delivers much more power than in "continuous" mode. Furthermore, power output increases as the impedance decreases (at least, good amps should do that).
Of course, this is almost useless information, since you'll probably NEVER need all that power delivered to your speakers. Your Magnats have pretty high sensitivity, you'll just need a fraction of all that power. Excessive power is never a problem, though.
Hope this helped,
Lucio Cadeddu

Bantam Monoblocks + Kingrex Preamp vs Kingrex T20 + Kingrex Preamp
Dear Nick,
I am a happy owner of a Kingrex Preamp and a Kingrex T20 used as a power amplifier. This is part of my only chain and it sounds great. Nevertheless I know that due to the constraints and limits of the TA 2020 chip I would never be capable to drive speakers around 85-86db of sensitivity. So there is much in the world that I am missing.
A couple of days ago I have been offered two Temple Audio Bantam Monoblocks. Second hand, the price is a bargain (200). Six months lifetime. On the one side I am really seduced on the other side I do not want to set up a second chain and that would mean that I would replace the T20 with the two Monoblocks that, by the way, I have never listened. The monoblocks should provide me more power to drive whatever speaker I will ever buy. But what about the sound?
I have no way to organise a listening test. Take or leave it.
What do you think of the Bantam creatures if compared to the Kingrex T20?
And what do you think about the coupling of those with the Kingrex Preamp in term of electrical compatibility and sound?
Paolo - E-mail: paolo.bottiglione (at)

Hi Paolo,
I would snap up those Bantams at the price. Even if you don't think that they are better than what you have now, you should be able to sell them on easily. If you like the Bantams, I would seriously suggest that you sell the KingRex preamp and buy a valve preamp. I found the combination of valves and Bantams to be very good.
I'm not sure that the Bantams will drive low sensitivity speakers much better than the T20 though. For that job you should be looking at one of the amps using the 2050 chip, eg Virtue ONE/TWO or Sensation (there are others).
I hope that this helps you with your decision.
Nick Whetstone

Confused pleb
Mr. Wheeler, [respectful greeting from plebis chorus scaena sinister],
I have been reading through your article on air volume acceleration on tnt-audio and I found the following a bit confusing,
"The problem is as bad at a typical 400Hz crossover between bass driver and midrange unit in a big 3-way system. Here it is rhythm that suffers though, and spotlighting of individual instruments in dense orchestration or complex mixes. Higher bass ?.a (e.g. ?.a=15 in a 250mm driver) and lower midrange ?.a (e.g. ?.a=7 in a 110mm driver - real examples) sounded lively but confused. The opposite condition of a high ?.a bass driver (200mm ?.a=7) crossed over with a moderate ?.a midrange (165mm ?.a=20) sounded sluggish with turgid rhythm. Both test situations used the same stereo power amp (Naim NAP110) to drive from a 400Hz 4th order active crossover and all drivers were capable of flat response operation at least two octaves beyond the crossover..."

Should the second example be a low ?.a bass driver?

What you present seem to be very useful rules of thumb, which have caused me to re-assess my thought of using Gradient W160AL drivers (I'm a cheapskate) for a future mass loaded tapered quarter wave tube project: I assume the rules of thumb still apply to this type of cabinet. Your experiments with MDF and plywood are causing me to re-think casing materials too.
Many thanks for the web pages,
Slinger (member of plebian throng - stage left) - E-mail: sling (at)

Hail, Slinger,
3 years after it appeared you have successfully sub-edited my article! Yes, you are correct, that second example should read "a low ?.a bass driver".

I am very pleased that you are thinking carefully about cabinet materials. They will make a big difference to overall system performance. I find that as long as the main structure is birch ply, and perhaps there are hardwood braces, it is possible to use cheaper more malleable materials elsewhere. I have some midrange enclosures that use fiddleback sycamore (aka rock maple in some markets) as baffle, 25mm baltic birch ply central brace and damped glass-fibre and copper mesh reinforced resin as curved walls and they are very successful. However, they would not contain the pressures from a large bass driver.

I am a fan of both transmission lines and the superficially visually similar but operationally different mass loaded tuned quarter wave pipes (ML-TQWP). My experience is that both are very successful at preserving bass rhythm unless the designer tries to squeeze a 'quart from a pint pot' as they said in pre-metric days. If too much mass loading is used to try to drag the system resonance down too far, the effect is like a high Q reflex system. If the line cross-section is too small, it sounds like a too small reflex cabinet. But done right, with cross section always above Sd (radiating area) and gentle taper (see Augsperger's Speaker Builder articles) the sound is like a Q=0.577 Bessel alignment sealed box with better power handling and flatter impedance curve. There is a good summary of the thinking process for designing pipes here and a summary of which type does what here.
Happy building and listening,
Mark, The Old Scribe
Mark Wheeler

Concordant Excelsior
Dear Mark,
I just got a Concordant Excelsior!
Partly on the strength of your review and a vague recollection from the 1980's, when I was too poor to afford one. Now I can hear what the fuss is all about.
It goes beautifully with Quads. I'm yet to try it out with more "upmarket" gear.
Thanks for a first class review of a great piece of kit.
Jehan - E-mail: j-ft (at)

Hi Jehan,
I am glad you trusted the memory of your ears' impression from the 80's backed up by our review.
I am so glad that your ears agree with my ears, or the plebs chorus would never let me forget it.

Which Quads are you using with it? Quad II's or later power amplifiers?
I would recommend replacing the power supply electrolytic capacitors (with good commercial grade, low ESR types or audiophile types) as they will have deteriorated by now. The same applies to whatever power amp you use if it is more than 15 years old. The polyester capacitors inside the pre-amp are less liable to deteriorate, but there are some electrolytic caps in there too worth replacing. You will hear the difference.
Your Concordant Excelsior is a classic piece of kit, outperforming contemporary Audio Research and Conrad Johnson.
Happy listening,
Mark, The Old Scribe
Mark Wheeler

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