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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 288

post #4306 of 10495
Quote:
Originally Posted by gibosi View Post
 

 

And I think you now have a Lyr in the family?  If so, I for one, would be very interested in your impressions of your LD running a 6DJ8 compared to the Lyr. Cheers. :)

 

A huge +1 to this!

 

--------------------------

 

On a different note, about this external DC battery supply idea for the driver tube heaters, would anyone happen to have any suggestions as to what type of batteries I could use to make something close to 6.3V (between 6 & 7 would be fine)?

 

I actually have some experience in making battery powered supplies for some of my hi-fi gear, having made a DC supply for my USB-S/PDIF converter using 4 Ni-MH 1.2~1.25V batteries (so 5V USB basically; seems complicated but it is extremely simple and works very well, seriously, dramatic improvement, and cheap too.

 

But, I'm wondering what the easiest way to get ~6.3V would be - without regulators preferably, the least components, the better in my book... Two LiPoFe4 batteries? 3.3V*2=6.6V - unless the batteries are too full or too empty...

 

Yeah, I know, it's crazy not to use regulators... But still, I tend to like quick, easy and highly efficient solutions above complicated and uncertain ones...

post #4307 of 10495
Quote:
Originally Posted by gibosi View Post
 

A bit off topic...

 

I do not own a CD player and on the rare occasions that I want to play a CD, I just use the computer's built-in unit, which is not so good I am told. So I have been thinking about getting a simple CD player with optical out, but most of what I am seeing are jukebox and/or SACD players and are rather expensive. It occurs to me that I can pick up a Blu-ray player with optical out for not much money, and I also notice that these players typically support SACD, in addition to CD.

 

Comments? Suggestions?

 

Thanks! :)

Hi
 I don't have any SACD's, but I've noticed u can get good quality dvd players very cheap if u play only occasionally cd's. I run my used harman/kardon through my dac with imho good results.. Ended up paying a rubber band for it, before h/k I had pioneer dvd player which was something like 5 euros w/ shipping. Look for blu-ray/dvd-players with remote control... it helps a lot :D

post #4308 of 10495
Quote:
Originally Posted by Audiofanboy View Post
 

 

A huge +1 to this!

 

--------------------------

 

On a different note, about this external DC battery supply idea for the driver tube heaters, would anyone happen to have any suggestions as to what type of batteries I could use to make something close to 6.3V (between 6 & 7 would be fine)?

 

I actually have some experience in making battery powered supplies for some of my hi-fi gear, having made a DC supply for my USB-S/PDIF converter using 4 Ni-MH 1.2~1.25V batteries (so 5V USB basically; seems complicated but it is extremely simple and works very well, seriously, dramatic improvement, and cheap too.

 

But, I'm wondering what the easiest way to get ~6.3V would be - without regulators preferably, the least components, the better in my book... Two LiPoFe4 batteries? 3.3V*2=6.6V - unless the batteries are too full or too empty...

 

Yeah, I know, it's crazy not to use regulators... But still, I tend to like quick, easy and highly efficient solutions above complicated and uncertain ones...

I've already started on my 6DJ8 Lyr comparo... the Little Dot shootout is part 2 of this lol

post #4309 of 10495
Quote:
Originally Posted by Kestovitutus View Post
 

...............I've noticed u can get good quality dvd players very cheap if u play only occasionally cd's. I run my used harman/kardon through my dac with imho good results.. Ended up paying a rubber band for it, before h/k I had pioneer dvd player which was something like 5 euros w/ shipping. Look for blu-ray/dvd-players with remote control... it helps a lot :D

 

Thank you! 

 

Yes, after looking into this for some time now, I have decided that an inexpensive Blu-Ray player feeding a digital signal to my DAC will be an excellent way to listen to an occasional CD in my system. I intend to get in touch with Santa Claus today or tomorrow... :) 

post #4310 of 10495
Quote:
Originally Posted by Audiofanboy View Post

 

On a different note, about this external DC battery supply idea for the driver tube heaters, would anyone happen to have any suggestions as to what type of batteries I could use to make something close to 6.3V (between 6 & 7 would be fine)?

 

How about a 6-volt motorcycle sealed lead acid battery?

post #4311 of 10495

6V Motorcycle batteries have three cells with a nominal voltage of 2.1 V/cell = 6.3V, so this looks like an excellent suggestion. Rechargeable batteries are available for less than $10 on Ebay.

 

However, the voltage fluctuates with the level of charge:

 

Motorcycle battery voltages

Lead acid batteries

A typical lead-acid motorcycle battery

The majority of classic motorcycle batteries are of the conventional lead acid variety. Whilst we think of these as being either 6 or 12v, this is a slight misnomer as the actual voltages are rarely these values if the battery is in good health.

The primary battery voltage is dictated by the chemistry of the lead acid cell. Fully charged and in peak condition, each cell has a voltage across it’s terminals of 2.1v. Motorbike batteries are made up from a combination of such cells connected in series to give the required voltage.

A ’6v’ battery is comprised of three cells giving a total voltage across it’s terminals of 3 x 2.1v = 6.3 volts. Likewise a ’12v’ battery is made up of six individual cells giving a total of 6 x 2.1v = 12.6 volts.

These voltages are not however fixed and will vary both with the state of charge (or discharge) of the battery, and also depending upon the electrical load placed upon it. The more the battery is used and loses its charge, the lower it’s voltage gradually becomes. Similarly, when an electrical load is connected to the battery this also drags the voltage down.

 

State of charge

It is therefore possible to determine the approximate state of charge of a motorcycles battery by measuring the voltage across it’s terminals. This is how ‘intelligent’ battery chargers work by constantly measuring the voltage and stopping charging once the desired level has been reached.

The table below shows the approximate voltages that will be measured across the terminals of a lead acid cell for various states of charge. Also shown are the total voltages for 3 cell (6v) and 6 cell (12v) batteries as will be fitted to most classic motorcycles.

Note that the voltages shown are open circuit voltages which means that there is no electrical load placed upon the battery. These readings are therefore taken with all lights etc turned off, and the engine not running.

State of charge
of battery
Per lead-acid
battery cell
(2.1v nominal)
6v nominal
batteries
(3x cell)
12v nominal
batteries
(6x cell)
 
Just charged* 2.13v 6.40v 12.80v
100% 2.10v 6.30v 12.60v
75% 2.06v 6.18v 12.35v
50% 2.01v 6.03v 12.06v
25% 1.95v 5.85v 11.7v
Fully discharged 1.75v 5.25v 10.5v

* Initially after fully charging a battery, the battery voltage will be slightly higher and this will then settle down to the 100% fully charged value over the course of the next few hours.

 

To me the question is if a tube sounds different with voltage fluctuations within a certain range. It may very well be that tubes are designed to perform well and last long within a certain heater voltage range. Maybe the real payoff with battery power is less hum and RF interference.

post #4312 of 10495
Lead acid batteries also release gasses while charging, do you really want that in your house? Just look at the corrosive mung that collects on the posts... I don't think this would be a good idea, LiPo or GelCell maybe. One would still need some sort of regulation to keep the voltage constant and that would require a higher voltage battery. The regulators today will keep the output voltage precise with the source voltage right down to 1.25 above output.

I still think a 9V 3A wall wart type supply with a regulator would be the best bet for DC or just a 120V(220V)/12.6V CT transformer for AC.

beerchug.gif
post #4313 of 10495

 

I have made up an external power supply for the heater filaments. Just an old wall adapter I had lying around and a little voltage regulator board. These little boards can be bought on ebay for less than $5. The output voltage can be adjusted with the trimpot which is the blue block with the tiny screw on top. I am using a 12v 500ma wall adapter but anything over about 9 volt DC and 500ma should work fine.

Seems to work just fine. I adjusted the voltage with a multimeter and it is happily powering my 600ma 6SN7 octal.

post #4314 of 10495
Quote:
Originally Posted by Ctritical Bill View Post
 

I have made up an external power supply for the heater filaments. Just an old wall adapter I had lying around and a little voltage regulator board. These little boards can be bought on ebay for less than $5. The output voltage can be adjusted with the trimpot which is the blue block with the tiny screw on top. I am using a 12v 500ma wall adapter but anything over about 9 volt DC and 500ma should work fine.

Seems to work just fine. I adjusted the voltage with a multimeter and it is happily powering my 600ma 6SN7 octal.

 

Cool!  And a question: If I want to run 12.6V tubes, will a 9 volt DC/500ma adapter work? That is, can the output voltage be adjusted higher than 9 volts? Or do I need something like a 15 volt adapter?

post #4315 of 10495
Quote:
Originally Posted by mordy View Post
 

6V Motorcycle batteries have three cells with a nominal voltage of 2.1 V/cell = 6.3V, so this looks like an excellent suggestion.


That cell voltage is largely the reason why we have 6.3 and 12.6 volt tubes.

 

Quote:
Originally Posted by TrollDragon View Post

Lead acid batteries also release gasses while charging, do you really want that in your house? Just look at the corrosive mung that collects on the posts... I don't think this would be a good idea, LiPo or GelCell maybe.

 

I did say sealed, did I not? Gel or AGM batteries gently charged with an intelligent charger shouldn't be a problem, should they?

post #4316 of 10495
Quote:
Originally Posted by Oskari View Post
 

I did say sealed, did I not? Gel or AGM batteries gently charged with an intelligent charger shouldn't be a problem, should they?

Yes indeed you did...

My Bad.

post #4317 of 10495

Hi Ctritical Bill,

 

Being unfamiliar with electronics, perhaps you could describe in more detail how to connect this regulated power supply? Could you take a wall wart of say 15V 1 A and connect it to the voltage regulator and then connect heater wires 3&4 (instead of putting these wires into the Vector adapter)?

 

Would the voltage regulator described here do the job? Looks like it has a built in voltage display. Also, would it be possible to use a driver tube that draws a higher current than the LD amp provides, as long as the external A/C adapter has enough capacity?

 

http://www.ebay.com/itm/New-LM317-Adjustable-Voltage-Regulator-Step-down-Power-Supply-Module-LED-Meter-/281168816716?pt=LH_DefaultDomain_0&hash=item4176f7aa4c

 

post #4318 of 10495

"Shenzhen Willie's"

Cheap Deals of the Day

*if it doesn't burn your house down first*

 

 

Note Cheap AC adapters out of China are really spooky and I would unplug them when not in use.

 

24V 1A Wall Wart

http://www.ebay.com/itm/AC-Converter-Adapter-DC-24V-1A-Power-Supply-Charger-US-plug-DC-5-5mm-1000mA-24W-/350833307159

 

Adjustable step-down buck module

http://www.ebay.com/itm/Adjustable-LM2596-DC-DC-4-75V-35V-to-1-25V-26V-step-down-buck-module-Regulator-/261345233407

post #4319 of 10495

The 6H9C's have arrived from Romania.

 

Also in the mail was a very nice gift from P.Q. :L3000:

 

Here is the 6H9C mounted on the Little Dot MK IV.

Listening to Paul Simon's Graceland 25th Anniversary Edition and for an inexpensive tube it actually sounds quite good.

:beerchug:

post #4320 of 10495
Quote:
Originally Posted by gibosi View Post
 

 

Cool!  And a question: If I want to run 12.6V tubes, will a 9 volt DC/500ma adapter work? That is, can the output voltage be adjusted higher than 9 volts? Or do I need something like a 15 volt adapter?

 

For 12.6 volt tubes a 9v 500ma adapter would not be sufficient. There are 'step-up' voltage regulators similar to the one I have, that will output a higher voltage than the input but with reduced current. Remember Watts = Amps x Volts so as volts increase, current decreases and vice-versa. So for 12.6 volt tubes a 15v adapter would be best and 500ma should be okay.

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