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 2014

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M2Tech HiFace 2
Hello,
do you think that with a usb hub powered HIFACE2 sounds better? Instead of connecting directly to the USB port of the PC. THX,
Riccardo - E-mail: rccrdlchtt (at) gmail.com

NW
Hi Riccardo,
I haven't tried it but I don't think that it would be much better. The power supplies for the hubs are not exactly great quality. I do urge people to try a separate power supply with items such as the HiFace DAC as they do make a significant improvement. You need a special Y-lead (like the TNT 221) and you could start by making up a simple battery supply using 4 AA batteries, or 4 li-ion batteries. Another option would be a simple 5v supply made from a transformer and suitable voltage regulator.
Using something like the Paul Hynes SR3-05, or the Astin Trew Concord will improve the hiFace a lot but of course you are paying a lot more for them. If you want to try a USB hub first, it won't damage the hiFace.
Regards,
Nick Whetstone

T-Amp with Goodmans
Nick,
Thanks for your thorough information on the t amps. I am running my Goodmans Triaxiom open baffles with with a 2050 chip based amp. Sound is a shocking contrast to my dynaco st70. No time for ab testing but the absence of the 60hz hum that has plagued the dynaco is a revelation. Is there any risk of burning the vc on the goodmans with these amps? My system is an active crossover triamped setup. El84 for tweets ss marantz for 15" wharfedales. Crossover points are 150 hz and 3000 hz to wharfedale super3 s.
Thanks,
Jason - E-mail: jdnovetsky (at) gmail.com

NW
Hi Jason,
If the amps are built correctly there should be no danger to your drivers. There should be DC blocking caps on the inputs of the amps and/or the outputs of your active crossovers. If you are worried about the drivers, you could include some sort of speaker protection on the output of the amplifiers.
Regards,
Nick Whetstone

PGA2311 preamp and Gainclone
Hi Andy,
What do you think about the of PGA 2311 preamp in use with a gainclone chip amp (LM3875)?
Do you have an idea?
Thank you in advance.
Best regards from Belgium,
Eric - E-mail: eric.vdauwera (at) skynet.be

AN
Hi Eric,
I think that is likely to work well. I used a similar set up myself briefly. It will give a very clear and transparent tone with the right speakers. You need to be careful though to pick speakers with an undemanding load as the chip amps tend to be fairly low output. In the end I found that system didn't give enough drive for my taste I think that was probably the chip amp rather than the PGA2311.
Good luck,
Andy Norman

Headphones section
Dear Andy,
I've just read your headphones guide on TNT-Audio. I completely agree with you. Today, many people experience high fidelity sound when they connect a pair of decent headphones. It happens both for younger people and for anyone - like me - who travels a lot for work or commuting. I'd like to contribute to your publishing with some highlightings and a request. As is known, Hi-Fi experience comes from speakers/headphone as well as from the source we pair with them. For this reason I'd strongly appreciate a little digression on the difference between a range of sources (IPhone vs Android - HTC One has one of the best sound for example - PC vs mp3 reader, etc).
Last, I'll take the liberty of recommending some devices to your consideration. It's in-ear buds with mic, something I find comfortable for travelling, jogging, etc. Is it possible to have hi-fi with systems like that? Are these headphones for everyone and for every source? What an interesting argument! Again thank you very much and congratulations for your nice job.
Best regards,
Simone - E-mail: simone.revelli (at) gmail.com

AN
Thank you for your kind feedback Simone. Headphones are really important and a much cheaper way of getting really great sound than loudspeakers. Ill see what I can do on the specific suggestions, but at TNT we tend to be a bit limited by what we can get for review from manufacturers. I will try and get some more headphone focused articles out though if there is enthusiasm for that.
Best wishes
Andy Norman

30V PSU
Hello!
I have read your review of the Dayton dta-100a amplifier. You mention that it is possible to enhance the sound quality changing the psu from 24v to 30v. I have done a research on the web, but can not find any good 30v power supplies. Do you have any idea where can I purchase a 28v or 30v / 5a psu (in Europe)?
Thanks, have a nice day!
Wanek - E-mail: mgbiker3 (at) gmail.com

LC
Dear Wanek,
linear, non-switching DC power supplies should be quite easy to find as these are used on CB radios and medical/lab equipment. You can also find switching PSU's as well. Just put 30V DC power supply on Ebay, for example, and browse through the results. There are also fully adjustable power supplies like this one. An adjustable-output PSU is a wise choice because lets you experiment with different voltages and avoids pushing the Tripath chip to its max allowed voltage limits. If you're not confident with online stores, pay a visit to any electronic parts store in your city, I'm pretty sure they have something for you. Prices should vary between 50 and 100€.
Hope this helped somehow,
Lucio Cadeddu

Yamaha CA-1000 as a pre-amplifer? Your views and opinions please
Hello TNT-Audio,
I found your website when I was buying 2 x Yamaha AX-592 amplifier's and on the strength of Dejan Veselinovic's review on your site I bought them at a steal of a price, $165 for the both of them, a university in Melbourne was selling all its sound gear, I'm extremely happy with these 2 units however I have to agree with Dejan on the pre-amplifier side of these integrated amplifiers. Connectivity isn't too good either.
I also own a CA-1000 Yamaha which died after 22yrs of excellent service in 1990 and at that time it was almost impossible to have it repaired here in Sydney, but recently I have noticed lots of American's and Canadians are bringing CA-1000's back to life, I would like to do the same however I would like mine to be only used as a pre-amplifier once repaired for use with the AX-592, they both have pre-main switching, would it be possible to have your guys talk it over please or even maybe Dejan, the CA-1000 was an excellent amplifier with a very good pre-amp and I'm very sure it'll be saveable at a descent cost.
Any and all advice would be very greatly appreciated, thank you.
Yours truly,
Carlo - E-mail: biscotto.carlo (at) yahoo.com.au

LC
Dear Carlo,
first of all, you should check whether your CA1000 died because of a failure in the power amp section or elsewhere. Perhaps the power section can be excluded and the amp can work as simple preamp. Just switch the coupler off (have a look at the rear panel) and the preamp/power amp sections will become independent. If I were you, I'd try to repair the CA1000 and then sell it on the second-hand market, where you'll easily find vintage-addicts ready to spend a lot of money for it. Once sold, you could purchase a modern preamp (even a passive one, maybe) to take full advantage of the power section of your AX592. Just a tought.
Hope this helped somehow,
Lucio Cadeddu

David Smith interview - I
Hi,
I've just read the David Smith's interview. Very interesting. A quick question: what does David mean by a broad spectrum of software ??? (Part1, last paragraph)

"My current approach is to design for flat anechoic response for midrange and up and then see how the low end interacts with the room, do a lot of listening and fine tuning until it seems right across a broad spectrum of software."
A typo?
Thanks for sharing such great stuff on your website :-)
Al - E-mail: alkasar (at) free.fr

RA
Hi,
Apologies for the delay in responding, I had been away on travel. I'm not speaking for David, but I think what he meant was that he uses more than one software to look at the response. Different software may have different ways of representing/calculating the response. For example, HolmImpulse and ARTA can do different things and are used for different things.
Does that answer your question?
Thanks for writing!
Rahul Atalaye

David Smith interview - II
Fantastic. Great technical insights and points about the future of commercial and audio in general. Thanks for that. I learned a lot.
Ben - E-mail: burninater (at) gmail.com

RA
Thanks for the letter and the compliment! Hope to bring you more of the same!
Rahul Atalaye

Phono capacitance load
May I please ask a question. I'm trying to load my cartridge with the proper amount of capacitance and resistance. With a meter I have been able to measure my turntable leads and tonearm wiring capacitance but I have not been able to determine how much capacitance might be included in the input section of my phono preamp.
Is there an average amount of capacitance that one might figure for a tube phono? Any help or advice that you could give me would be appreciated. I've included a schematic of one channel of my phono (below) if that helps. Thank you again.
Best,
Rod - E-mail: rwcrouse1 (at) verizon.net

LC
Dear Rod,
capacitance load slightly affects high frequency response of MM cartrides. Average values of capacitance of phono inputs vary from 150 to 300 pF. You can start with a low value and eventually increase capacitance to find the best compromise with your cartridge. There are carts that are claimed to be not sensitive to capacitance (Grado, for example) so your mileage may vary. Remember that you need to sum the capacitance load of the phono preamp to the ones you measured on the phono leads. For small variations of capacitance values the differences are SUBTLE!
Here you can find some in-deep technical explaination of how capacitance affects frequency response of MM carts.
Feel free to experiment and keep us updated!
Lucio Cadeddu

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