[mordy]

Our Italian member @lupoal discussed the importance of correct heater voltage previously. I found this quote on this site tonight: .http://www.emissionlabs.com/datasheets/EML300B-25V.html

"Heater Voltage: Some people experiment with lower filament voltage, to expect better lifetime. This is essentially wrong to do. If the magic was that easy, we would make the tubes like this ourselves. Under Heating can lead to early loss of emission, though new EML tubes will fully recover once the heater voltage is corrected, older tubes will recover only partially. The specified filament voltage at 0% tolerance is the one for best lifetime. The voltage we specify, is at the TUBE PINS itself. Any voltage drop by the socket contacts must be compensated for. For 2A3 tubes, some sockets have 50mV voltage drop per pin, because the heater current of 2.5 Ampere is very high. Causing a total drop of 0.1V for both pins together. So a voltage of 2.6Volts at the socket pins is needed, to make sure there is 2.5 Volts at the tube pins".

I have nothing to add to this due to lack of knowledge and experience. I don't know the magnitude of loss of lifetime, if so.

In my Little Dot days, using external power supplies and voltage regulators, I used to measure the voltage at the tube pins. For power tubes there was always a drop, but not much. With 2.5A tubes the voltage regulator had to be set to 6.7V to get 6.3V at the tube pins with certain tubes.
Usually data sheets for a tube will show the specified voltage +- a percentage range.
https://frank.pocnet.net/sheets/049/6/6080.pdf
If you look at this data sheet for an RCA 6080 you will find the factory voltage specification 6.3V +-10%. That means that this tube will function according to factory specifications between 5.67V - 6.93V.
Perhaps certain tubes must be run at a very specific voltage without any variations, but IMHO all the tubes we normally use have a range where they perform according to factory specifications.
It seems to me to be unnecessary to fuss over minor voltage variations. Many people report using the same tubes for years without problems, and slight variations in the voltage are not going to affect tube life.

 

[TrollDragon]

Back in the day, tubes ran for years and years just off of a filament transformer. The AC mains voltage would fluctuate by 10% at times and the tubes kept right on going. I think there might be a little too much worry over tube longevity.

Plug them in, turn them on and enjoy! Keep a few spares on hand just in case one dies down the road.

 

[triod750]

Plug them in, turn them on and enjoy!

Most important part in this hobby!!

 

[mordy]

Back in the day, tubes ran for years and years just off of a filament transformer. The AC mains voltage would fluctuate by 10% at times and the tubes kept right on going. I think there might be a little too much worry over tube longevity.

Plug them in, turn them on and enjoy! Keep a few spares on hand just in case one dies down the road.

And while we are speaking about obsessing over tubes I would like to bring up something else - something that was a real insigt into measurements for me.
I discovered that I could not tell the difference in sound between tubes that measure just above good and tubes that measure as new. (I do not have a tube tester and have to rely on the values provided by the seller.)
A fellow headfier has a calibrated good quality tube tester, and he wrote that he bought eight tubes as NOS. When he measured them all were good, except for one. I asked him to pair the NOS tube with the one that did not measure good to see if he could hear a difference - to his great surprise they sounded the same.
There are headfiers that have used the same tubes for ten or even twenty years, and they still measure acceptable and work fine.
Perhaps there are very fussy amps where everything has to be just so, but IMHO most of the amps we use are not in that category.

 

[TrollDragon]

And while we are speaking about obsessing over tubes I would like to bring up something else - something that was a real insigt into measurements for me.
I discovered that I could not tell the difference in sound between tubes that measure just above good and tubes that measure as new. (I do not have a tube tester and have to rely on the values provided by the seller.)
A fellow headfier has a calibrated good quality tube tester, and he wrote that he bought eight tubes as NOS. When he measured them all were good, except for one. I asked him to pair the NOS tube with the one that did not measure good to see if he could hear a difference - to his great surprise they sounded the same.
There are headfiers that have used the same tubes for ten or even twenty years, and they still measure acceptable and work fine.
Perhaps there are very fussy amps where everything has to be just so, but IMHO most of the amps we use are not in that category.

Exactly, and then there are the people that insist you have to have matched tubes. The only time matched tubes are required are for push pull output amps, these are power output tubes and need to be matched so you can bias them to have the same current draw, otherwise one of the tubes will be burning out long before the other.

 

[mordy]

Exactly, and then there are the people that insist you have to have matched tubes. The only time matched tubes are required are for push pull output amps, these are power output tubes and need to be matched so you can bias them to have the same current draw, otherwise one of the tubes will be burning out long before the other.

And I thought that matched tubes were required to increase profits for tube sellers - now I see that there is another reason lol...

 

[TrollDragon]

And I thought that matched tubes were required to increase profits for tube sellers - now I see that there is another reason lol...

That too.

 

[lupoal]

I’m going to upgrade my heaters power supply in these days… now it is based on LM317, I will add an additional stage and will become like a Teddy Pardo, I will do two of them, one per channel … to be honest I’ve no idea if that will improve the sound or not, I’m convinced the quality of power supply is a key factor for a good sound, in any case this is just a game for me giving me opportunity to discover something new

this is the circuit http://www.acoustica.org.uk/t/teddyreg.html

 

[lupoal]

Does anyone have any recommendations for power tubes on the Little Dot MK II?

input … C3g… or 6BE6 (Brimar or Telefunken )
output… 6SN7… with Mouse Ears 6BE6… 6H8C from Russia can be good too, unluckily in the last times seems they are crazy increasing prices too

 

[triod750]

I’m convinced the quality of power supply is a key factor for a good sound

You are probably right here, good enough is needed, but maybe that is mostly about the rest of the electrical operation and not that much about the heaters. Just a guess from me. But there is no reason for not making things better if you are capable of doing it. Just like tube rolling; it might not be neccessary but it can be fun.

 

[lupoal]

tube rolling without proper power supply imho could be like put Ferrari engine inside a Zastava chassis… the engine could push more but the chassis is what it is

the power stage inside LD MK2, last hardware version, is not bad… one of my friends with big deep knowledge in electronic and hifi told me that the components used are not bad at all, capacitors for example are quite good… imho what could be better is the rectifier that is just a standard one instead of a scotky one, I’m going to install four bypass capacitors around that to improve, or to say better minimise, high frequency commutation noise coming from diodes inside (pass easily trough the filter capacitors in psu stage)

heaters… if you consider how bad is the transformer inside the LD (see my post with measured values) and the fact that the voltage from the wall in not stable over the time, unfortunately, the result is that the tube are probably not working at proper working point almost all the time… the quantity of heat produced not constant, not repeatable

the fact is that 6,3Vac are cheap … 6,3Vdc are more expensive, more complicate, require space and dissipate some heat in the psu… in short are not compatible with target selling price for products like LD Mk2

p.s. sorry for boring speeches… I promise, next time I will post picture about my new, but NOS, Mouse Ears… quite rare tubes… slurp

 

[triod750]

p.s. sorry for boring speeches…

Not boring at all. All contributions are welcome, at least in my opinion. I cannot comment on LDMKII, neither on unstable voltage from the wall since I have utterly stable voltage and a MKIV. I don't doubt that upgrading an amp might be beneficial if there are problems of one kind or another. Some are of the opinion that it is more reasonable to get a better amp from the start. Pushing the limits with what you have has always been interesting to me. I am a clever fellow who realises that it is better for me to keep my hands off from the innards of my amp. But I welcome your reports from your endeavours. Posts like these makes it interesting to visit the thread.

 

[Freia]

Hello, I've bought the LD I+ a week ago, and I am having a blast playing around with it.
Seems that this thread is quite inactive and as a layman I would like to share some initial impressions.

Tubes I got are the GE JAN 5654W and Voshkods, there really is no reason using the stock Chinese tubes.
While the original one was decent, I also rolled the op amp with two OPA445BM-1. One thing I find interesting is that when you turn on the amp, a faint pop is heard, and when I changed the op amp, the pop was louder and distinct.
The high and low gain switch is confusing too as the manual's description and the amp is in fact reversed. I didn't realized I was on high gain for the first few hours and to this day I am still not 100% sure if I am correct about the settings.

One flaw I do find is the pot. As the amp is loud I normally have the knob under 20, however there are times I need to dial it down and the left channel will be silent. I see people recommend upgrading it to a Alps, but I'm a total noob to DIYing and was wondering if it can be done. Are there any alternative pots that are the same size as the stock ones?

 

[triod750]

I read a good post in another thread here on head-fi and want to share it on this tube rolling thread: https://www.head-fi.org/threads/woo-audio-amp-owner-unite.428570/post-16644158

 

[Deleeh]

Hello,
Is there anything new for the Little Dot 1+?

Yes, there is. After the repair months ago, it runs mostly stable and normal and better than ever before.
I have no problems with the temperature, after x hours of listening it stays warm to the touch.
So the repair was worth it.

The second point.
By chance I got a set of Lm Ecrission W403B tubes.
And it's really divine to listen to music with them.
Great tubes, the best I've had so far, which I don't think will be topped.
The Ef 92 Brimar were already relatively good, but the Ecrisson are a good deal better in all areas of music.
So if anyone sees them, go ahead and pair them with the Little Dot 1+.
Just don't forget to remove the two dip switches if you haven't switched to Ef 95.
Also, the Little Dot remains stable through the conversion.

In summary, the small investment in the LD1+ was in all respects a huge advantage and leap forward that can be recommended.