Siltech battery operated tube preamp

[Gregadd]

While I see the preamp in its twilight years, there is one worth watching. (okay there are many worth watching). If a preamp is just a straight wire with gain Siltech should have a leg up on the wire part anyway. The batteries should help the gain aspect.

I pulled this from the Stereophile website:

Siltech's Edwin van der Kley handed me his new preamp. There were no wires attached, but the four tubes were glowing. "It's battery-powered, and I could use a low 25V voltage rail for the tubes because they are ECC86 dual-triodes, which were developed for car-audio and microphone use." Edwin went to explain that as this tube uses a 6.3V heater, he could run the heaters of the four tubes in series from the same 25V supply. It also offers very low 1/f noise for a small-signal tube, he told me. Siltech has a plentiful supply of the tubes and the preamp wil sell for $28,000.

 

[microstrip]

While I see the preamp in its twilight years, there is one worth watching. (okay there are many worth watching). If a preamp is just a straight wire with gain Siltech should have a leg up on the wire part anyway. The batteries should help the gain aspect.

Nagra also manufactures a battery operated preamplifier, the Nagra PL-P. I hosted one for a few months. It used a block of eight rechargeable NiCd D-cells for power, and for an emergency could work on alkaline cells. It sounded good and looked wonderful, unhappily it did not have a remote.

 

[Gregadd]

Did the Nagra use tubes?

 

[microstrip]

Did the Nagra use tubes?

Yes, 2x 12at7 and 4 x 12ax7. Even the phono section uses tubes.

As they are sometimes available at nice prices second hand it is a fantastic buy - Nagra built quality is outstanding, it should last for decades without problems!

 

[flez007]

I am a Siltech fan (at least for cables) - will love to try this preamp anytime...

 

[FrantzM]

Hi

I don't understand why we have not seen more of these battery operated preamps and , yes, amps... To me the best DC is ..well... DC... not filtered AC derived DC... A battery is the purest DC one can find ... True Batteries tend to be big and unwieldy but for preamps and few D cells of the rechargeable variery is all one needs.. I think Rowland has some of thes too and others.. Audiophiles have not cared much about DC operated gears, I wonder why ... maybe not worth the bother?

 

[Gregadd]

I expect it has something to do with battery technology which has taken off with the advent of so many wireless mobile devices. AT RMAF Harry Pearson devoted significant tiime to clean and battery power. It would have significant impact on low level signal amplification.

Rechargeable batteries are important.

 

[amirm]

This reminds me of my dad buying an *LP* tube based car player in early 1970s! The thing was a marvel of engineering with suspension and such and glowing tubes. It couldn't stand many bumps but we had fun loading 45s into it.

Back to this unit, how does this work? Do you use it until the battery dies and then charge it before using again?

 

[mep]

Frantz-It seems the knock on battery powered preamps by reviewers is the reviewers feel that battery powered gear lacks dynamics. If it is true (and I have never heard any battery powered gear so I personally don't know), maybe the power supply can't deliver alll of the current that is demanded during really trying/taxing passages of some music. Batteries typically have low current ratings meausred in milliamps while a regular power supply is capable of delivering amperes of current.

 

[microstrip]

Hi

A battery is the purest DC one can find ...

Frantz, this is a strong statement, but it is not of great help for the discussion, as purity does not have a defined meaning in terms of electrical properties.

A DC power supply should be analyzed in terms of long term stability, transient behavior and noise. After you check all this properties may be a battery is not so pure!

Engineering aspects, such as lifetime and evolution of battery parameters during its usable life, are also to be taken in consideration.

Worst of all, can you imagine a forum thread about the sound of different types of batteries?

 

[mep]

For me, a battery represents a pure DC source in that it should not carry any AC artifacts such as hum and ripple. All of the things that can ride on a DC signal that has been converted from AC should be absent.

 

[FrantzM]

Microstrip

Not a strong one. A DC from a battery is absolute DC, with no Ac components at any frequency.. No infinitesimal level, no-qualifier needed DC, simply no AC, none at all ... For the most part the DC derived from AC has some residual AC riding over it albeit filtered by capacitors banks. Circuitry must be devised to stabilize such voltage. A DC battery of sufficently low Internal resistance, Voltage and current capacity, is the real deal, simple DC... DC only, no AC on the best oscilloscope ever devised, no ripple, nothing a line . So What I term "purity" is objective, absolute non pulsed non alternative current .. Hum is absent since, there is no AC and high frequency which find their ways into the circuitry ... In truth one must find a way to derive different voltages and has to use DC to DC converters which add some amount of noise... else DC only, yes, "pure" DC.
Keep in mind that most circuit in are DC powered. The cleaner the DC the better the performance everything else being equal so if DC is in required quantity then , the transient behavior of the circuit, so powered is not affected in any negative way. One must realize that a battery is in essence a super-capacitor in term of discharge ... it holds vast amount of energy and the limit to the delivery is the internal resistance.. almost instantly ...

Batteries do change in time but not so much as not to power a preamp. The Internal resistance of a lead battery for example under the low current draw a preamp represent is likely to be extraordinarily stable through years of use, especially if a "trickle" charge maintains the charge of the battery at a constant high level.

No. Batteries should not sound different if all they provide is DC current , the baseline ... I, also do not believe in specialty (read "audiophile") AC cord only in quality AC power , something cords can't do much for ...

 

[Jay_S]

Battery power supplies seem like a good idea, but for tubes? In my opinion, many line stage preamps are overpriced, throwing expensive parts at problems that I don't care about.

 

[microstrip]

Frantz,

I am not a battery expert, but batteries have noise and absolute DC should not have noise. Battery noise has been studied - look for papers at IEEE publications and you will find it is dependent on battery type, current, age of battery, temperature and may be some other parameters I am forgetting. It is known that when you use batteries to power amplifiers for low level signals such as microphones you should use capacitors and passive devices as filters to lower this noise.

Some designers claim that it is easy to design circuits with very high power supply rejection ratios at hum frequencies (tens and hundreds of Hz) , but that keeping these values at noise frequencies is almost impossible without affecting audible parameters. The extra components needed in the power flow can affect the ideal performance of the battery.

Absolute DC does not exist. A good teacher of mine used to ask his students what is the voltage of an ideal voltage supply of 2V DC connected in parallel with zero resistance wires with another ideal 3V DC power supply? Do you know the answer?

BTW, it is curious that you do not believe in Audiophile AC cords (a very reasonable and scientific position) but believe you can hear the effects of hum in DC power lines lines after is has been reduced by more than 120 or 140 dB ...

 

[FrantzM]

Battery power supplies seem like a good idea, but for tubes? In my opinion, many line stage preamps are overpriced, throwing expensive parts at problems that I don't care about.

Valid point ... hard to derive the >100 Volt tubes seem to like, batteries in series maybe but that becomes a lot of batteries or DC to DC converters .. but for SS ..why not?

 

[microstrip]

Rewinding my memories to fifteen years ago, when a Keithley battery operated picoameter was my companion in low level measurements (the currents we were measuring were so low that we had to machine some Teflon feet to replace the normal rubber ones to eliminate this leakage), I remembered that the main advantage of battery operated equipment is avoiding the current loops due to leakage through the mains AC transformers. Here operating with DC batteries can have a strong point. Still, properly designed transformers and circuits can overcome this problem.

 

[Gregadd]

The tubes used were designed for car and microphone use. Better suited for batteries. Let's not forget the real beneifit of batteries-no nasty transformer.

I would like to see a battery designed for use in a preamp.

 

[FrantzM]

<snip> Let's not forget the real beneifit of batteries-no nasty transformer.

<snip>.

PLease don't let the Tubes people see this

@microstrip

I am not sure I inferred to the absence of hum as the main benefit of DC power... Nor did I mention "absolute" anything... I do know about battery noise but it is very, very low and several order of magnitude lower than the noise from a rectified AC to DC conversion... Batteries noise magnitude is on the order of tens of nanovolt ... not a factor in the big scheme of things ... DC from batteries remain better than what one gets from any rectifier circuits... Plus it is rather practical in term of simpler circuit design
Whether or not the advantage translate into audible bnefits is another matter. I like the concept but would not say that it automatically leads to sonics superiority...

As for Power cords ... They , for the most part don't filter what comes from the main AC outlet... and frankly there is quite a bit of junk that comes through these ... I have voiced my view on power quality and fancy, expensive power cords are not part of what I see as the solution..
Now back to the Battery powered gears ...

 

[microstrip]

Now back to the Battery powered gears ...

As I had the same feeling as you, I owned a few in the past: a battery phono moving coil preamplifier in the late 80s that sounded much worst than an Ortofon transformer (unhappily I do not remember the name), a three box DNM preamplifier from the UK that sounded great, but had many problems with the battery charger, and a few years ago a Dartzeel preamplifier. A friend of mine had a Rowland preamplifier that was powered by batteries.

The units could be powered also by the mains, but naturally sounded better in the battery mode, as the mains power supplies were just an add on to charge the batteries, not a expertly engineered one.

A sad remark - all these units had problems with their chargers that conduced to a battery lifetime much shorter than expected. Designing an automatic charger that does not rely on the user control for optimal use of the battery is not an easy job for an audio designer!

One very interesting product is the ASR Emitter amplifier from Germany - the best versions use a lot of lead/acid batteries for powering the input stage and a large conventional power supply for the power stages.

In the 90s Jean Hiraga published in l'Audiophile a project of a small power class A amplifier, called The Monster, that used the batteries in parallel with large capacitors as part of the filter of the power supply. It was for some time in my project list, but I never decided to built it as I did not own a matching high efficiency speaker.

 

[JackD201]

I think the bottom line is that Edison was a better businessman than Tesla

BTW I recall one of Jean Hiraga's demo rooms caught fire in an audio show in Europe not too long ago. Hmmmmm.