"Superfly" - submini tube version of Doug H's Firefly

[prnet]

I've the 6021 and the 6112 in my hands.. so i can finish my amp now...

[prnet]

Hello... So I'm debugging the superfly

As it was not working at all... I triple checked the layout and the schematic.
The voltage remains the same of the input transformer... just a bit higher (about 20v) The trimmer doesn't affect the voltage in any position.
But, I found something strange at irf740..
I take a look at the datasheet, and it seems that the irf740 in the perfboard is wrong oriented.
The nixie ps too shows the pins assignment and in that layout too, the irf740 is oriented backward respect your layout..
could you confirm the mistake in your layout?

ops.. I'm taking a look at the pics of your superfly and yes, I can see the irf740 turned on the other side... respect the perfboard. so, tomorrow i'm going to turn it..
It's late now.. tomorrow hope to give you some good news..

[frequencycentral]

The pinout is marked correctly on my perf layout. Not sure if the symbol is the right way round though, that's why I included the pinout - I'm always a little confused as to how to depict tabbed transistors - did I get it wrong? I guess so.......sorry about that.......

BTW, the pinout on the PCB layout (it's not my PCB layout) is numbered backwards.

In my last Superfly (the red one) I used an IRF840 instead of an IRF740.

Good luck with your debug!

[prnet]

Thanks friend.. yes..  the pinout number are right, but the symbol is backawrds in the perfboard...
No problem, I'm going to rotate the irf740, so I really hope to give you some good news soon.. After a P1ex and a dr504 builds I'm still excited to build something so "miniature" 
The first mod will be the volume pot and the switch to use ot as preamp (I guess I've to use an 8ohm dummy load)..
but let's go by steps...

[prnet]

good news at half..  
I turned the irf740 180°.. and the power supply circuit is good now..

ok.. The mini amp sounds, but not as expected. the volume is very low, and when i increase the volume the sound begins "farting".. but I think something due to the supply because the sound became unstable, something like a "tremolo" "ta ta ta ta ta ta ta"

When I insert the tubes in the sockets the voltage drops a lot... I tried different adapters.
with a regulated 9v 300mA adapter, and without tubes, I can set the trimmer to be 180/190v, but with tubes I can't reach more than 110/120v at output tube plates..
The pre tube voltage is lower too... about 50v.

I tried also a 13v dc 150mA adapter non regulated, but it happens the same.. and less voltage too.. sound worse..

With a 17v 1A p.supply, I can turn the trimmer up to max 140v at the plates of the output tube...
But here too, when I try to increase the voltage, it become instable..
And of course 17v at heaters is too much... it should be about 6v...

did  you have any similar issue before?

[prnet]

ops.. I think i've found the exact word to define better the problem...   I didnt' know before..

"Motorboat"  

I read again the whole thread because i remembered something about the voltage issues somewhere inthere.

Finally, I think I should try another inductor. the actual one is a toroidal of about 100uH 1A..
The other one was a smaller one, I don't know the value, but it has tight lead (about 1mm).

I tought to try the irf840 too, but i guess that the real difference is only the max voltage driven.

And I guess I've to find a 12v regulated power supply to keep the heaters safe...

[frequencycentral]

I've had no issues with either of my builds, with both I was able to dial in over 200v with the tubes in the circuit. I settled on 185v as being optimal as the smps causes a small hum after some time of running at 195v, this disappears at 185v.

With my second Superfly I tried some different inductor values, 68uH and 150uH, as well as a large 100uH 2.5 watt. , there were issues with all of these, but it seems to like these little 100uH a lot: https://www.rapidonline.com/productinfo.aspx?&tier1=Electronic+Components&tier2=Inductors+And+Chokes&tier3=Leaded+Inductors&tier4=Low+current+radial+lead+inductors&moduleno=64730&catref=88-1630

I'm not sure if your IRF would have been damaged when it was the wong way round?

Something else to watch - my second Superfly I didn't connect the speaker sockets ground to the circuit, just assumed that the chassis would ground it. I had some issues which were solved by groundng the input socket to teh output socket.

Not sure what else to suggest, both my builds have worked without issue. I can only suggest that the circuit may be picky about the exact inductor, and of course a good well regulated 12v power supply, mine is only rated 500ma but is rock solid at 12v.

I should have Superfly #3 build next week, now that the planes are flying again and my Banzai order gets though - they turned down my motorcycle courier suggestion.

[Taylor]

I should have Superfly #3 build next week, now that the planes are flying again and my Banzai order gets though - they turned down my motorcycle courier suggestion.

I thought all deliveries in the UK were by umbrella?



Surely this mode of transport is exempt from volcano grounding?

[prnet]

ok, I tried a similar inductor, so the situation is better than before..
The volume increased a bit, but the motorboating is still there.. and I cannot reach more than 130v..

I tried a 7812 (to220) to try a  regulated supply from the 15v adapter.
(without load the voltage is 10,5... i tried different is's too.. maybe I need a cap as stabilizer)
so, after a minute of use, i fried the 7812.... what happened? it seems the amp ask more than 1A current?


But there's a thing I can't understand...
The 12v should be good for the heaters right?
ok, i was expecting that the voltage was a bit balanced between them, I found instead that the first tube has 7,5v at pin3, and about 3,5v at pin3 of the output tube... (i cannot measure the other pins theyre behind some other wires)...
What' happening???

[frequencycentral]

Here's my #3, Superfly Special, with the addition of tone and master volume controls, just finished it. With the tubes in their sockets I can dial in between 125v and 310v.

[frequencycentral]

Here's the schematic of the Special. All I did was remove the grid stopper between the two 6112 stages and replace it with a tonestack, and replaced the 330K grid leak resistor between the preamp and the power amp with a 470k Log pot. The combination of the gain and volume controls is really useful and flexible. The tonestack makes this Superfly not quite as loud as my last two, but a useful addition I guess.

[merlinb]

Another engineering masterpiece Rick!  
Now I'd love to see you make one with DM160s. They're so small they make those subminis look like lumbering giants!

[Taylor]

Another engineering masterpiece Rick!  
Now I'd love to see you make one with DM160s. They're so small they make those subminis look like lumbering giants!

Do people use them for audio? It says here it's a voltage indicator:

http://www.r-type.org/exhib/aai0056.htm

Sounds interesting if so, I'm always intrigued by misuse of electronics.

[merlinb]

Do people use them for audio? It says here it's a voltage indicator:
Sounds interesting if so, I'm always intrigued by misuse of electronics.

Yes they became popular in car radios. Plus they light up blue in sympathy with the music, and nothing is cooler than that!

[frequencycentral]

Oh thanks Merlin, I thought I had enough obsessions, and now you find me something else to be obsessed about.    So tell us more about the DM160, are you suggesting using it as a visual thing (very cool - how would one incorporate it?) or do you mean that they could be used as an amp? Their max voltage is 100v, and they're directly heated, so if you did mean an amp it would have to be SE as you couldn't use one for a PI, or self split. I notice there are also Russian equivalents.

[prnet]

 

Nice work Rick... I'm a bit jelous.. I've still troubles with mine..
Maybe i'll do the voume mod when my amp will be fixed.. I want to try another inductor and new ic's before turn on again the beast..
I've seen that the voltage drops a lot after few seconds.. i guessit's because the dissipation is not enough..

wow dm160...   I was trying to stop build fx but... I think we've to inform better about them... I'd like to build something smaller too....

but i've to finish the G2 from FSB first..   then I think i've to really stop with pedals building.. I'm not playing guitar anymore because i'm spending all my time with fx buildings.. I've built tons of fx but it's time to hear them

[merlinb]

So tell us more about the DM160, are you suggesting using it as a visual thing (very cool - how would one incorporate it?) or do you mean that they could be used as an amp?

Well I was suggesting a Superfly variant using the DM160. The fact that they also glow is just a bonus!
They are directly heated, but that shouldn't make things very difficult. PP should be possible with a little lateral thinking. A paraphase arrangement would be possible, if nothing else. i.e., Hang a cap+potential divider off the anode of the output valve that is driven, and use the resulting signal to drive the second valve's grid.
Here's a very crude video of a DM160 frequency indicator I built last week for a forthcoming competition
http://s81.photobucket.com/albums/j207/merlinblencowe/?action=view&current=CIMG4628.flv&newest=1
After this I will probably dismantle it and try something Superfly-esque with the tubes.

[Taylor]

Whoa.

[frequencycentral]

PP should be possible with a little lateral thinking. A paraphase arrangement would be possible, if nothing else. i.e., Hang a cap+potential divider off the anode of the output valve that is driven, and use the resulting signal to drive the second valve's grid.........after this I will probably dismantle it and try something Superfly-esque with the tubes.

I wanna build one too! I'm ordering a bunch of DM160 right now. Will you share your schematic? 

[prnet]

wow.. it's a cheap tube too.. i can find 4 for 15€ shipping included on ebay ...
the spectrum analyzer is very cool too..