Siltech battery operated tube preamp

[Joao@altheamusica]

"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. [/I]

I wonder because the ECC-tubes are parallel filaments and the mentioned heater supply with the tubes in series is for PCC tubes. So what? Mixing different tubes or is it a mistake in typing?

Onto battery supply... I experimented with it some years ago because we thought of using tubes in a MC-headamp and battery is perfect for this. The problem is that batteries own an ionternal resistance which increases with the frequency and you can easily see that this isn't the perfect power supply when you don't use a shunt regulator after them.

Then you can ask the next question, why to handle with problems when a "normal / conventional" power supply with a shunt regulator works in the same way?

Just some thoughts....

 

[microstrip]

I wonder because the ECC-tubes are parallel filaments and the mentioned heater supply with the tubes in series is for PCC tubes.

Although the filaments in the E... tubes are not intended to be connected in series, usually the consistency of manufacture of two tubes of the same type and manufacture run allows the series operation.
Surely Siltech will match them also for filament resistance.

 

[FrantzM]

I wonder because the ECC-tubes are parallel filaments and the mentioned heater supply with the tubes in series is for PCC tubes. So what? Mixing different tubes or is it a mistake in typing?

Onto battery supply... I experimented with it some years ago because we thought of using tubes in a MC-headamp and battery is perfect for this. The problem is that batteries own an ionternal resistance which increases with the frequency and you can easily see that this isn't the perfect power supply when you don't use a shunt regulator after them.

Then you can ask the next question, why to handle with problems when a "normal / conventional" power supply with a shunt regulator works in the same way?

Just some thoughts....

I am not an Audio designer, just an EE but your explanations lost me.. about the internal resistance of batteries varying with frequency... For any well designed circuitry shouldn't the power supply be isolated from the circuitry it powers? Can you elaborate? Besides, you likely would observe the same with any conventional power supply wouldn't it?

 

[microstrip]

I am not an Audio designer, just an EE but your explanations lost me.. about the internal resistance of batteries varying with frequency... For any well designed circuitry shouldn't the power supply be isolated from the circuitry it powers? Can you elaborate? Besides, you likely would observe the same with any conventional power supply wouldn't it?

A perfect DC supply should have constant voltage independently of the current it supplies. Unhappily this is not true and this effect is usually modeled as if the perfect battery had a resistor in series (the internal resistance). Because the magnitude of the voltage drop also depends on the frequency of the load current the value of the internal resistance increases with frequency - it is why the battery must by bypassed with capacitors and series/shunt regulators must be used after the battery.

There is an interesting analysis of battery noise in this site:

http://www.tnt-audio.com/clinica/regulators_noise1_e.html

 

[Gregadd]

I don't know if it's practical but given the number of 12v DC devices we now use, is it time for the power companies to start offering a direct feed?. Or maybe we should have a transformer at the power box in our house?

 

[FrantzM]

Microstrip

Very, very interesting read...made me change my stance on entirely battery powered gear...maybe a combination of Capacitors and batteries then..??

 

[microstrip]

I don't know if it's practical but given the number of 12v DC devices we now use, is it time for the power companies to start offering a direct feed?. Or maybe we should have a transformer at the power box in our house?

Greg,
Are you wanting to start the War of Currents again?
Although there are some places where you have this 12V DC supply - e.g. caravan parks, it would be of very limited used in houses. Also, as the current would be very high for a reasonable power it would be a dangerous game.

 

[Joao@altheamusica]

I am not an Audio designer, just an EE but your explanations lost me.. about the internal resistance of batteries varying with frequency... For any well designed circuitry shouldn't the power supply be isolated from the circuitry it powers? Can you elaborate? Besides, you likely would observe the same with any conventional power supply wouldn't it?

Hello Frantz

Microstrip- thanks a lot - already explained it very well so I will not describe it twice. Another thing in dealing with batteries is: what type, implementing a controller for charging etc. So why doing this all when I can get it with a conventional designed power supply? For 1% more theory?

Some designer using batteries has only one reason, they are using switched power supplies ... but this is another story