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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June 2009

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P&S Opto-potentiometer
Hi Nick, Good day...
My name is Gary and I live in the UK in the West Midlands, and I have been looking for a preamp and came across your article on the P&S OPC271 OPTO-POTENTIOMETER...I WANT ONE!!! This sounds so interesting and just what I am looking for, but the problem is I am not very good at DIY projects when they involve Mains Electricity!!!
Do you know how I can get this type of preamp with a minimum of 2(TWO) switchable inputs, remote control, digital volume read-out volume knob, but in a nice case well finished safety tested and ready to buy?...I have cash waiting as I have been saving up to purchase a preamp of some sort...please advise.
I have found the Lightspeed Attenuator (from Australia) and the EVA but they fall short of what I would really like... any other suggestions Nick???
Kind Regards,
Gary (Thank you in advance for your time and any replies)
P.S. Great TNT site by-the-way
Gary - E-mail: g1960j (at)

Hi Gary,
First off, the Optopot is just a passive volume control, ie there is no active stage that you MAY need to go between your source and power amplifier.
That said, if the Optopot with a selector unit still appeals to you, the only real suggestion that I can make is to have somebody put one together for you locally.
I appreciate and respect your healthy concern about building mains powered equipment so somebody experienced in building these items should do the build even though it only involved connecting the power supply module to a fused IEC inlet socket (and grounding the case if it is metallic of course).
It's a great pity that P&S don't supply finished units but I suspect that this is down to not wanting to go to all the trouble and expense of getting them safety-approved etc in the various countries.
And at present, I don't know of another option for this type of volume control.
Sorry I can't be of more help.
Nick Whetstone

T-Amp clones
Hi there,
Many thanks for your website and infos. There is a proliferation of T amps found on Ebay eg Zero, Muse, Topping brands from China. Are they any good?
And how long do they last - I'm assuming because there's very little circuitry that they'll last quite a while? Obviously there's some debate on whether the more expensive Trends Audio and other premium charged amps actually sound better?
Many thanks for your help,
Kindest regards
Kenway - E-mail: isoprocess (at)

Dear Kenway,
not all Tripath-based amps sound equal. Even between the old Trends TA 10 and the new TA 10.1 amp there are noticeable differences. Yes, they use the same chip but passive components and different power supplies might make more than a difference. I haven't tested them all so I can't comment any further. As for durability, there are few things that can be damaged inside a chip-based amp...the chip being the weakest part! This can be damaged by wrong power supply polarity, excessive voltage and overheat. I'm pretty sure the manufacturers of these clones have taken care of these basic aspects. Being Ebay vendors I assume the feedback score is quite relevant. Have a look at that rating before purchasing.
Hope this helped,
Lucio Cadeddu

Vibration control
Dear Mark,
Fascinated to read your four articles I am glad to find others as mad as I.
The largest single improvement I have generated has been using 3M Viscoelastic Damping Polymer (Part # 40374) to line the inside of steel cases and the outside bottom of cases. It comes in 4in x 10 yd rolls and can be cut easily with scissors or any sharp blade, all you need is a bone folder to ensure even application, cutting away to leave any vents clear. It takes about 20 / 30 minutes maximum including removing and replacing case screws. 3M tell me that its intended use is in the inside of aircraft and it should be stable between 0 and 60 C well exceeding any heat generated in the average audio component.
My other "tricks" have been using platforms underneath formed in three layers, maple / MDF / MDF/ separated by damping sheets: the platform in turn supported on 4 1/2 racquet balls (Penn ultra blue) the dome against the board the diameter against the supporting shelf. The most crucial part is the CD player, supported on five 1/2 balls, one cupping each of the original feet in a U. The fifth half ball is placed with diameter against the platform and underneath the CD tray, I have found this is roughly about the center of gravity of most players. The fifth ball can be moved forward/back & left/right to fine tune the damping effect. In fact I have found that different recordings will require a slightly different position of the fifth ball for maximum audible impact. In my system the problem seems to be reducing removing the octave resonances of the upper quarter of keyboards, particularly with NY Steinway pianos made in the past 40 years. These resonances are present when listening to the same instrument live and in certain halls can be equally offensive but some engineers filter them.
Anyhow, glad to communicate with another "lunatic", thanks very much for what you have written.
Michael - E-mail: robinsonmf (at)

Dear Michael,
Thank you for sharing your experiences, we are indeed sharing a folie a deux!
I will seek out the 3M stuff as it sounds as effective, if not more so, as any of the specialist audio damping layers and being designed for the aircraft industry presumably has a good damping vs mass ratio.
The squash ball trick is really effective (the slower grade the better) and has a long history. Did you know one of the last gasps of the old Leak company (makers of the TL12 tube amplifier for example) once they were taken over by the Rank organization (an entertainment conglomerate taking over a valve amplifier manufacturer had as much credibility and management skill as when AMF took over Harley Davidson in the same period) was a subchassis turntable using squash (racquet) balls as suspension. They rarely reached audio stores as Rank thought it better to target department stores, but they were good at their price point.
I agree with the tuning effect below the cd player drawer axis, regardless of what support you employ. Sometimes the axis of a toroidal transformer is a good place to support cdp and amps. Have you tried mixing a firm support under the cd tray (for example a cut pyramid of pumice stone as sold for foot care) combined with squash balls in the other locations? It is even further into the realms of audio insanity but it does work!
Happy tweaking,
Mark Wheeler

Stubby stands
Hi there, I've already tried to send a mail to Scott Faller but it came back with a "non delivered message. I've seen (and printed) the speaker stands project and I'm thinking about building some stands for my Infinity Ref 1i's but instead of 1 central pillar I'll build a 3 pillar stand with thinner pvc pipes. I'm thinkind on building stands with one pillar on front and 2 on the back using a small tube (thin electric installation tube) inside one of the pvc tubes to pass the speaker wires (you know, those tubes used inside walls...).
Later I'll send some photos if you're interested. Please let me know.
Best regards,
Artur - E-mail: a-soares (at)

Dear Artur,
Scott Faller now writes for EnjoytheMusic magazine, hence his TNT-Audio e-mail account has been deactivated.
Feel free to experiment a variation on the Stubby theme. Three pillars will work but I suspect the construction will be trickier. When finished, please send one or two pics with a few lines of comments, if you wish.
Hope this helped,
Lucio Cadeddu

Mains cables
Hi Lucio,
I was thinking of a cheap way to use the existing cables I have, but using aluminum foil, heatsink cable then pvc on that. My 80s Technics class A amp already sounds really nice as I am using Supra Ply3.4S and Atlas interconnects.
A less spec Technics amp I have, used Supra LoRad on it, first didn't notice much but using standard rca interconnects, sounds good still, so I think change the mains did that.
Sam - E-mail: sclmacdonald (at)

Dear Sam,
mains cables can actually make a difference. Generally, the better the components, the stronger the difference one may perceive. You don't need to buy esotic and insanely expensive mains cables, even a basic DIY design can do the trick. For example, you might try some of our DIY designs - Merlino or TNT TTS - they are easy to build and very good sounding. The Supra LoRad you have is a very good mains cable, you might try to use it in a "triple" configuration as in our TTS cable, for example.
In any case I believe that spending time and money on mains cables might be useless as long as you want to keep those '80s Technics amps. I have nothing against them (owned one of them in my early days) but, trust me, modern integrated amplifiers can sound much better in any area.
Hope this helped,
Lucio Cadeddu

Michell Tecnoarm
Hello Mark
I have just finished reading your article on the TecnoArm (2005), I am in the final stage of rebuilding a Lenco L75 (200.00cnd) and I have to choose an arm, on the Audiogon forum they recommend the RB250, I have invested a lot of time and effort in this project and I would like to without going overboard invest in a better quality arm, after much research and also considering that the suspension will now be rigid (3 layers of 2" thick Bubinga wood) would you recommend that arm still, my music taste is very diverse from classic rock to jazz to classical and even some opera (when the wife is out of the house), I also own a old Denon DP37 that I like a lot, its a no hassle deck; just check the cartridge alignment once a month....
No rush for the reply when you get around to it I know your very busy so thanks in advance.
Best regards
Alain - E-mail: alainbelleau (at)

Bonjour Alain, au Canada
The Tecnoarm is way better than a stock RB250 but I am not sure it would look right on a Lenco L75. I am very familiar with the L75 and its L78 stablemate. I loved the corkscrew bias weight support that was such an elegant solution to keeping the bias thread at 90 degrees regardless of the force applied. I even used one on my early prototype Hadcock GH Unipoise as it made set up easier. However, I suspect that a Rega based arm solution would suffer the same problems it does on a Linn, dumping energy into the arm base predominantly on vectors that the Lenco (and Linn armboard) are not designed to control.

The Lenco has such a cool vintage look to it that it might be visually incongruent too. I would be inclined to look for a vintage arm that is less energetic, especially as a great strength of the RB family is bombastic bass and you do not list tecno, hip hop and trance among your tastes. Perhaps a classic like the SME 3009/II (with bronze bearing conversion), a 228mm Hadcock, and Acos Lustre (rebadged as Linn Basik) would be a more synergistic match. More beautiful to look at and much more beautiful to hear, an old Alphason HR100S would probably be a perfect match sonically and visually. This is an almost forgotten arm and I can still recall hearing its beguiling and perfectly controlled sound mounted on a Logic DM101 (Immediately after hearing a SME 3009/III on the same deck) and comparing it to its rival Linn LP12/Grace/Supex.

The plinth you have made should be wonderful, Bubinga is great on electric bass bodies.
Happy arm hunting,
Mark Wheeler

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