superfly with dm160 tube as an indicator only.

[makaze808]

Hi.

I would like to add a dm160 to the SF as an indicator only tube, not using any gain (yet)

The dm160 is directly heated requiring a 1v supply.   How is this best achieved.

The plate requires 50v                                            How is the best achieved

The grid is biased at -3v (no light)                            How is this best achieved

The grid gives of maximum light at 0v

So a feed from somewhere in the audio signal needs to be able to swing the grid from it's -3v bias towards 0v.  How is this best achieved.

I am happy to breadboard suggestions and report back alhough I am away for a week.

Sorry that i can't offer any input on the theory but I'm happy to implement the thoery into a layout.

Woz.

[PRR]

DM160 -- http://www.mif.pg.gda.pl/homepages/frank/sheets/009/d/DM160.pdf

What is a "superfly"? The 500 watt 10 pound modern marvel? Or something else?

EDIT.... oh, I had to go down several pages in Google. You probably mean this?
 http://www.diystompboxes.com/smfforum/index.php?topic=78302.0

Using these:

7327: http://www.mif.pg.gda.pl/homepages/frank/sheets/138/7/7327.pdf
6111: http://www.mif.pg.gda.pl/homepages/frank/sheets/141/6/6111.pdf (base type for 7327)

6112: http://www.mif.pg.gda.pl/homepages/frank/sheets/137/6/6112.pdf

[PRR]

[makaze808]

Thanks for that.

The grid connection turns the light on and off and all shades of brightness in between., according to the datasheet  -3v is fully off and 0v fully on.  So I was presuming that I would need to somehow create a -3v supply to the grid, then use the feed to bring the grid up from -3v too 0v (or swinnging somewhere in between) through the ac guitar signal rectified.

Have I understood that right?

[merlinb]

Thanks for that.

The grid connection turns the light on and off and all shades of brightness in between., according to the datasheet  -3v is fully off and 0v fully on.  So I was presuming that I would need to somehow create a -3v supply to the grid, then use the feed to bring the grid up from -3v too 0v (or swinnging somewhere in between) through the ac guitar signal rectified.

Have I understood that right?

In PRR's circuit he has made the cathode of the DM160 at roughly +1.5V by using the 56R resistor. This is equivalent to saying that the grid is resting at -1.5V relative to the cathode; the tube knows no different either way.

The audio swing both positive and negative, so if it drives the grid positive by 1.5V, then the grid is now at the same voltage as the cathode, or in other words, there is 0V between grid and cathode, so the tube is full on.
If the audio swings down to -1.5V then it is now -1.5+(-1.5) = -3V below the cathode and the tube is fully off.

However, this does mean that with no audio signal, the tube will be half on. I would suggest replacing the 56R resistor with 100R so the tube is more-or-less off when there is no signal. In the diagram below the tube is usually off, but will start to glow when there is audio.

[makaze808]

thanks for all the help. a temp breadboard worked well. I will build a superfly with indicator when I get back from holidays.

[makaze808]

Is there no need to rectify the feed to+only, I had presumed an AC signal wouldn't be as effective as a dc one.

thanks.

[PRR]

> with no audio signal, the tube will be half on.

The datasheet is written for "digital readout", ON/OFF. And somewhere it says that 1.5 delta-V will give unambiguous indication (with some weaseling).

> according to the datasheet  -3v is fully off

Yes, FULLY off. And "if" I have read the sheet correctly(?), it is pretty darn dark up to around -1.5V. If we biased at -3V it would hardly glimmer the small stuff, only at MAXimum lavel.



I could be wrong. The sheet could be wrong. If the "off"-glow came out bad, I figured you would ask about that, we'd fiddle the 56 resistor to 100 or 33, whatever the tube really wants.

Merlin, why use the voltage-divider to get low B+? The tube current varies from ~~0mA to ~~0.6mA. With a saggy B+ node the "bright" may only be 0.3mA, or the "off" may be more than 2V-3V down. I'm not thrilled with either Zener or Resistor dividers because this "superfly" runs a homebrew switcher with unclear but small reserve of voltage and current.

I won't point out that for little more than the heater-power of the DM160, we could run a Green LED which looks an awful lot like phosphor from across the room.

> Is there no need to rectify the feed to+only

No "need". You could get a little brighter with full-wave rectification and/or some smoothing. But simple rectifiers have 0.2V-0.7V loss which is a lot for 1.5V-3V signals. And hanging rectifiers on audio paths adds distortion. That's a big no-no in broadcast and hi-fi.... I guess here it might be acceptable (because the 220K+100K+100K is some isolation, and because distortion is not a dirty word in gitar amps).

Still: Start simple. Get tricky only when you must.

> breadboard worked well.

That's a good sign. Enjoy your holidays. Let us know how it finally works out.

[frequencycentral]

I won't point out that for little more than the heater-power of the DM160, we could run a Green LED which looks an awful lot like phosphor from across the room.

Yeah, why not configure the DM160 as a boost on the input of the Superfly, that way you'll get sonic value for money as well as a light show.

[merlinb]

Yes, FULLY off. And "if" I have read the sheet correctly(?), it is pretty darn dark up to around -1.5V. If we biased at -3V it would hardly glimmer the small stuff, only at MAXimum lavel.

From messing with them I found that -2V was pretty much off, over the usual anode voltage range, but -1.5V was rather variable with samples, sometimes dim, sometimes not dim at all. However, I think Makaze is planning to use a CCS to supply the heaters, which makes it easy toplay with the bias resistor.

Merlin, why use the voltage-divider to get low B+?

No particular reason, only because I thought he might not have any 47V zeners in his parts box, whereas everyone has resistors. Also, the anode voltage is not critical. These things will happily glow from 40V to 100V, and maybe lower too. 

> Is there no need to rectify the feed to+only

If you're in any doubt, my DM160 frequency indicator uses no rectification! As long as the audio signal is big enough (and I guess it will be after the Superfly's preamp) then you won't be disappointed.

[makaze808]

Thanks a lot. I'm gutted I'm on holiday this week.

Rick I'd love to add the dm160 as part of the audio signal..........I'm just finding it very hard to get my head round much of this. I've never wanted to be able to play with things so much that requires so much knowledge.

Im stummped oon why a heater that needs 1v max can have a 12v feed into it, i see the resistor is doing something, then on the diagram it states there's 3v on the other side of the heater. So that's where my understanding is stuck at the mo. On an art analogy I'm still scribbling with crayons 

[PRR]

> Im stummped oon why a heater that needs 1v max can have a 12v feed into it, .... scribbling with crayons

In crayon:



You want a 1-inch board. You have a 12-inch board. You simply waste-away 11 of the 12 inches.

You want 1V. You have 12V. You simply waste-away 11 of the 12 volts.

The "waste" is quite small in the overall scheme. You have about 4 Watts in the other heaters, 2 Watts in the high-voltage, and about 0.33 Watts to get the 12V down to 1V for the DM160 filament. Total power demand is 5.5% higher than it "could" be. While there's ways to reduce this, they are more complication for negligible advantage. (A current-source has the same loss.)

We have an additional requirement. We want one end of the filament up at 1.5V to 3V above ground, so the DM160 glow will go-dark at idle. While there are other ways to do this, it is expedient to divide the excess 11 volts as 2V and 9V or 1.5V and 9.5V, so that the bottom of the filament stands somewhat above ground.

[makaze808]

LOL thanks miss.

[Scruffie]

I've tried Merlin's version of this on a Sub-Mini Champ circuit, I recalculated the 220k/100k divider to 150k/75k (to replace the champs 220k output tubes grid resistor instead of the superfly's 330k) and it does work, but only once the volume is up to about 5 which even with the tiny speaker i'm using is too loud for late night playing.

Would I be better off diddling with the grid divider (maybe 120k/100k?) or lifting up the cathode voltage up so it's not biased completely off to get some light flashing at lower levels?

I'd experiment but I (foolishly) went straight to PCB and I don't want to mess about too much and lift the traces.

[amptramp]

I take it you are talking about the tube on the left:



Three subminiature tubes.  From left to right: 6977/DM160, ИВ-15(IV-15), 1M3/DM70

The 6977, CV5412, CV6094, and DM160 are exact substitutes.

Here is an article on using magic eye tubes as precise db monitors:

http://home.comcast.net/~jlrmsousa/precise_db_monitoring_with_eye_tubes_november_2006_audioxpress_joe_sousa2667.pdf

Happy soldering!

[thomasha]

Awesome stuff!

Scruffie, please keep us updated with your tests!

[PRR]

> does work, but only once the volume is up to about 5

DC voltages.

[Scruffie]

Here they are;

-f = 2.91V
+f = 3.95V
g = 3mV
a = 63V

Thanks!

Also, while i'm here, i'm using the MAX1771 SMPS supply seen here - http://desmith.net/NMdS/Electronics/NixiePSU.html and used by Frequency Central on a few designs and it's working just dandy but i'd like to lower the output voltage slightly, at the moment the minimum I can get is 180V which is a bit above my output tubes maximum rated voltage (165V) I know I should be able to tweak the voltage divider going in to the feedback pin but it's a tricky design and I don't want to make a mistake with it, I went over the chips datasheet but it's rather bulky and I couldn't find the answer but I think if I lower the 10k resistor to say... 8k2 that should suffice? Or would I be wiser to increase the 1M5 resistor.

[Scruffie]

Awesome stuff!

Scruffie, please keep us updated with your tests!

I'm guessing you're more interested in the actual amp than the indicator tube? 

I'm using a 5902 output pentode and a 6948 dual triode (similar to a 6112) as that's what I had and i'm using basically the same values as the 5E3 champ except at a lower voltage. I would assume it'd be fine with Russian 6n17B-V & 6P30B-R and IV-15 indicator tubes.

For the heaters i'm running them from 12V in series with a 1W/56R resistor to ground between them to account for the different current requirements (450mA & 350mA respectively) which would need a little tweaking to work with the Russian tubes.

It's quite current hungry so good SMPS layout and component choice will be important, I can share my SMPS layout although it's designed to suit my specific build which may not be so useful to others (going in to a scrap Roberts R200 radio enclosure I bought and cleaned up).

[thomasha]

That R200 radio looks very nice as a small tube amplifier combo, good choice!

In fact I was interested in the schematic, It would be nice for a battery powered headphone amplifier?

My intention was to use the indicator tubes as the amplification stages, but I guess it won't work and I would need to use regular subminiature tubes with lower current requirements, like the tubes that were used in the old portable radios. I think a battery powered guitar amplifier could also be a nice build, but the lack of output power in lower current tubes is a problem. Even the murder one isn't loud enough with a small speaker, and the 5276 only draws 50mA.

Anyway, I'm interested in your final results and some pictures of the final product, I guess it will be an awesome build.
I have enough subminiature amplifiers sitting at home at the moment to start another build , but you never know...