powering a ECL82/PCL82 using a small smps?

[Marcos - Munky]

I have two spares here, and I was thinking about to build a small tube amp for bedroom playing. Smaller as possible, to fit a 1590B or even a 1590A. So I won't have space for the power transformer. I know I can power a ECL84/PCL84 with a small nixie smps, but can this be done with the ECL82/PCL82? I really don't mind on using a lower HT, resulting on lower power output, I just want to know if this can be done with the spare ones I have or if I should forget about this idea and buy a ECL84/PCL84.

Datasheet: http://www.alldatasheet.com/datasheet-pdf/pdf/230116/PHILIPS/ECL82.html.

[PRR]

May depend how much power a " small nixie smps" can deliver?

[allesz]

If I rember rrght the heaters should draw arond 0,7 -0,8 m.
The pcl84 should have more gain ib the triode section, I worked with the ecl82 and the gain of a  single triode can't clip.

[Marcos - Munky]

Sorry, I forgot to add more info on what I'm planning to do:

- power it with a 12V DC power supply
- triode as the preamp, anode current is 3.5mA
- pentode as the power amp, anode current is 41mA
- heaters need 780mA, so they'll be powered directly by the 12V DC power supply (the spares I have are PCL, heater voltage is 12,6V). SMPS will power both anodes (44,5mA)

[allesz]

Nice plan with the pcl.
About gain, a french guy (username kleuck) did something similar, but with a standard power supply, and he put a fet (or mosfet?) booster in front of the triode. He reported good results, you should find the project on tdpri or fsb; can't remember if it's on diysb too, anyway the username is the same on all the above mighty boards.

I would go at least with a 1590b box instead of the 1590a; I don't think it's impossible to squeeze the build in the small box, since the tube and the ot will be on the ouside... but my masochism level is not enough, what's yours? 

[thomasha]

Hi,
there are some different SMPS designs that could work, the 555, the MC34063 and the MAX1771 would be my suggestions.

Some time ago someone posted a schematic for the MC34063 used in a blackstar design that could suply almost 100mA , or was it the 555?

You could even run the tube at lower voltage arund 150v to reduce the anode current.

Another thing is, keep in mind that the ECL has a 6v filament 780mA, while the PCL has a 16v filament at only 300mA.  If you use the 6v you'll need to burn 6v 780mA from your 12v supply. Plus the SMPS, you'll need more than 2A for your 12v supply.

If you use the 16v (PCL82) or 14.5V (PCL84) you can save some power. Consider using a 15v or 16v wall wart, it will reduce the required filament current and you won't need to burn half the power in resistors. You just need to verify if your SMPS can work at 16 or 15v. I know that the MAX1771S can work at 15v without problem. And dropping 1V for the SMPS is much better than 6v at 780mA.

About the size, the 1590a barely fits all the components. I build mine PCL84 amp with only one volume pot, PTP, and the IN and OUT jacks were difficult to fit. On the other hand, the 1590b seems more feasible. Some time ago I found this build in a german forum>




You can find the schematic and the layout here, posted by Uwe aka Lmkv15:
http://musikding.rocks/wbb/index.php/Thread/20061-Gitarrenamp-mit-PCL86/
Looks to me a nice idea! I would definetely build one with the Pcl82 since it's less expensive than the Pcl86.

It uses an external 12v AC supply and another in the amp. It's not common to use AC supplies for pedals, but since it only powers the amp I see no problem.
I have a wall wart that has different output voltages. It would be easy to mod it to have an unrectified output for small amps, problem is it only has 1A at the 12v tap, so I use a separate wall wart for my amps.

Because it only has one preamp stage it won't be a high gain amp, but you can get some extra crunch by using a VVR, or even using an external pot to vary the SMPS output voltage. I think Rick (frequencycentral) did that in one of his amps and called it the brake pot.

[Marcos - Munky]

That 1590B amp looks very similar of what I was planning to do. Well, I think the best thing to do is to use them for a "regular" size amp, using a power transformer or 2 back to back transformers, and maybe try a mini amp using a PCL84. Thanks for your help.