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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December 2011

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Capacitor Sound, T-Amp, etc
As Geocities are closed I think that the page of Cyril Bateman are lost, but I have find in If someone wants to download the free reading articles can do it again:
I have listened to a T-Amp with a pair of Opera Callas and vinyl and I are very surprised. Two questions. Can you test this? Seems very good, and very cheap:
Is there any T-Amp with phono input? Maybe it's a good project for you DIY section, a MM phono preamp made with SMD components for to put inside of a T-Amp.
Raul - E-mail: coutodominguez (at)

Dear Raul,
thanks for the links! is a really useful resource, indeed. As for the Class D amplifier you mention, there is a lot of similar devices out there (mainly from China), it's nearly impossible to test them all. This SMSL is really inexpensive and seems nicely built, but claimed power output is wrong. It delivers the same power of a standard T-Amp, actually (7-8 watts on 8 Ohm with a reasonable THD).
As far as I know there's no Class-D amplifier with phono input, but I'm sure it will be available sooner or later. We have already published several DIY phono preamps designs on our website, just put some of those inside a class-D amplifier and you're done :-)
I hope high-switching frequencies of Class-D designs won't affect the sensitive phono preamp section...
Hope this helped,
Lucio Cadeddu

Hello there,
I really enjoyed reading your article about the TC-754. I was wondering if this is still the best T-Preamp and switch around or if something cooler has come out recently.
Also, how do I power up the T-Amp and the TC-754 at the same time using the same 13.8 v 3 amperes external power supply?
Federico - E-mail: federico.caiulo (at)

Dear Federico,
as far as I know there are very few preamps in the market that offer the same features (which include a good phono stage!) at this cost. Perhaps you might find cheap passive preamps on Ebay, but these don't offer an active phono stage.
As for power supply: just hook the T-Preamp up to the same PSU you use for the T-Amp, making sure that correct polarity is preserved!
Hope this helped,
Lucio Cadeddu

ProJect Phonobox
Nice writeup! I just snapped up one at the local thrift. Power supply is missing. Got me thinking after reading your review. That a battery supply mod might really open this little box up. It has a 16vac input so it shouldn't be to difficult to rig up. Should provide a super clean flat line dc with zero current limiting. Which will hopefully provide noticeable improvements.
Any thoughts?
Samuel - E-mail: dieseldude1 (at)

Dear Samuel,
you can use any external power supply with the same voltage output, provided it has sufficient power. I'd choose a 1A power supply AT LEAST (the higher the better). Or you can use a rechargeable battery, which isn't necessarily better sounding than a good linear PSU.
Hope this helped,
Lucio Cadeddu

Re: Ordering curved birch plywood
Dear Mark,
Thanks for your kind reply and sorry for late response. I am a mechanical and electronics engineer working in a company in Denmark. Before I start anything, I am planning the process really carefully.
Although my salary is an average engineering salary, i am quite fond of to build my unique speakers. I am even into modeling the speakers in a Finite Element program. I am trying to get hints regarding with the built and construction by reading different web pages. I am definitely going to inform you for the steps of my project but it will not be finished before 1 or 2 years. I might need your help though regarding with some of the process details. I will turn back to you.
By the way, I am a professional photographer so I will feed you with good photos. At this moment, I am in between to build the speakers either from plywood or maple tree. But for sure, I need to apply some heat treatment to the maple. Lets see how much will be able converge to my targets. Oh yes...This thing will eat lots of time and money. But who cares ? Should I watch TV instead and buy an IPOD or new LCD ? I don't think so.

I might need your help to ask at least some of the material names which I have never heard in my life. This will be more related with wood works. For example a technique, have you heard something like "ALBUMIN COATING OR SEALING THE MAPLE TREE CABINET to prevent the many layers of varnish from penetrating the wood."
Is ALBUMIN kind of a paint ?
Thanks again. If you drop by to Denmark, let me know please.
Niels, by e-mail

Hi Niels,
Another photographer/speaker builder! How many of us are there in the world?
Maple is great for bracing, that's why varieties of maple are used for guitar necks (my Fender bass uses Canadian rock maple) and violins (the variety is "Fiddleback sycamore - I have made 50mm loudspeaker baffles from this variety). The maple/sycamore family produces easily worked stable hardwood, which has a high speed of sound through it.

Speaker building is one of the best way to use up time and money - only opening a restaurant would use more time and money!
Speaker building also offers you the chance to justify buying expensive power tools and spending hours in the garage or shed.

I have no idea what "Albumin coating" might be, except that "albumen" is white of egg, and as a photographer you may recall the nineteenth century "albumen print" photographs. I am a big fan of something here called "Danish oil" for finishing maple/sycamore speaker baffles, and I tend to use it to finish whatever veneer I put on birch ply. I glue veneer by coating both the veneer and the birch ply with pva glue, allowing it to 'tack dry' then fixing it using a warm clothes iron to melt the layers of pva together.

The best glue to use for joining panels and braces is a urea formaldehyde 2 pack glue (with formic acid hardener catalyst). I established this with listening tests correlated with a test jig that tested different adhesives using a 1m joint.

Last time I was in Denmark, my observation was that in Danish homes, loudspeakers are like dogs in NYC apartments (in NYC the smaller the appartment, the bigger the dog): the smaller the Danish home, the bigger their loudspeakers.
Happy building,
Mark, The Old Scribe

Ordering curved birch plywood
Dear Sir,
I live in Denmark and would like to build my loudspeakers. However, I couldn't find or maybe reach a manufacturer which can help to provide the best quality birch marine grade Finnish plywood. I am planning to built a cabinet with curved side walls.
Do you know who can help me ? I would really appreciate any kind of help.

Best regards,
Niels - by E-mail
"Without deviation from the norm, progress is not possible!"

Hi Neils,
I love the epithet accompanying your digital signature; it is a perfect summary of evolution.

Hence, I am also pleased to read of your desire to make curved plywood loudspeaker walls. There is a long history of successful curved loudspeaker cabinets, and comparison of the aluminium JR149, chipboard Kef Coda (mkI) and Linn Kans with the birch-ply BBC LS3/65a quickly illustrates the difference shape and materials make to the sound of the same 2 drivers. I have made these comparisons and the ideal cabinet would be curved birch-ply!

Given your location in Denmark, nearer the Baltic Sea than your old scribe, I would have expected you to have better access to plywood furniture manufacturers than we do in the rest of Europe. Denmark's pre-eminent position in modernist furniture design in the 20th century would imply ability to manufacture curved plywood panels will be well developed. Those 1930s 'streamline moderne' architectural styles, later known as 'art deco' were always plywood before the arrival of the dreadful chipboard and the even more dreaded MDF. Hence, contact furniture makers in the hope of them having reject curved plywood panels available.

The other source of well seasoned inexpensive wood is the used furniture store. These small companies usually get their stock by clearing the houses of the recently deceased and often have items they cannot sell. These items often lurk in stock rooms for a few months before being broken up for firewood. However, they are a splendid source of high quality timber. Wardrobes are the best source for most speaker builders, having large side panels perfect for loudspeaker walls and the internal hardwood fillets are perfect for bracing. In your case, I expect the typical 1930s curved sided dressing table or bedside table will be a good source of curved plywood with years of seasoning. A quick glance locally here soon reveals a dressing table of dubious aesthetic qualities (therefore difficult to sell) with panels approximately 50cm radius.

Good luck with your project and please do keep me supplied with updates and pictures we can share with our readers. This sounds like an interesting project.
Happy building,
Mark, The Old Scribe

MiniDSP DAC/sound quality
Dear Nick,
After reading reading some articles about the miniDSP I'm thinking about buying this dsp for some nice tinkering with active crossovers and or sound shaping.
I have a few questions though and TNT, especially after your article about the miniDSP, would seem the best place for an objective answer. I'm curious about the quality of the DAC chip used in the mini dsp. In your article you didn't mention anything about the sound quality of the miniDSP. Is it good enough to perform on its own or would you recommend an external DAC.
Also recently a new version of the miniDSP, the 2 x 8 kit, is released with an other DAC chip. This is the CS42528. Would you think that this DAC chip is an improvement over the old DAC chip?
To put things in perpective, I'm using a modified Monica USB DAC with a 90 watt HLLY T-amp.
Best regards,
Tijs - E-mail: kohnuz (at)

Hi Tijs,
One of the disadvantages of using items like the MiniDSP, Behringer DCX2496 etc is that you either have to use multiples of your favourite DAC (prohibitively expensive), or go with the ones in the equipment.
From the reviewers point of view it is almost impossible to do a like-for-like comparisons between internal DACs and external ones.
Like you, I very much like the sound of the Monica DAC. Why not use the MiniDSP but with an output to your Monica DAC. That is the MiniDSP will act as a USB converter, and do the DSP, and then pass the signal to your Monica. At least that way you could get some idea how good the DAC in the MiniDSP is. But as I said, if you wish to make active crossovers, then you either have to use a second Monica DAC, or rely on the DACs in the MiniDSP.
When I did my review, I relied on the DACs in the MiniDSP so didn't have anything to compare the sound to. The results were very good though but unless I could repeat the same set up using multiples of my other DACs, I can't really say if they would make an improvement or not.
I've not heard the MiniDSP with the new DAC chip so I'm afraid that I can't comment on that either. I'm sorry that I can't be of more help.
Nick Whetstone

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