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

[thomasha]

Unfortunately the short could be elsewhere, since the 12v and gnd lines are very long.

Have you tested desoldering the mosfet?
If it fails and shorts it would connect 12v directly to ground.The 6 ohms you are seeing could be a result of the resistance of the inductor+mosfet.

[jma38]

Unfortunately the short could be elsewhere, since the 12v and gnd lines are very long.

Have you tested desoldering the mosfet?
If it fails and shorts it would connect 12v directly to ground.The 6 ohms you are seeing could be a result of the resistance of the inductor+mosfet.

I'll try that. Unfortunately it looks like I shouldn't have bought my wire from Amazon, the wire connected to the ground lug on the 1M pot just broke off when I was repositioning the amp and a little while later the signal input wire also came apart. Live and learn I guess(I'm still having a ton of fun doing this though  )

[jma38]

I tested the amp and got sound! For about 5 seconds then it went silent. Still I'm like a NASA control room technician when there's a successful launch. What a rush!

[jma38]

So since I've been testing my Superfly build with a real guitar cabinet(Egnater 1x12) instead of a cheap test speaker, the amp works pretty damn well(loud too!). There are a few things I'll still have to debug like the random lowering in volume and the occasional what I can only describe as a "wump" sound. That being said I'd like to thank everyone here who gave advice and helped debug this build!

Video of the test(sorry in advance for my unpracticed guitar playing, I'm excited so my hands were shaking): https://www.youtube.com/watch?v=jSNoMhYVotQ&ab_channel=JonathanSilasBull

[thomasha]

Nice! Congrats!
The "wump" could be an intermittent connection or just a bad part somewhere.

If you want to check the circuit closely, you can use an audio probe and follow the signal path. Just be careful, to not connect it to the tubes plates (unless you coupling capacitor is rated over 300v). This also helps to understand where the sound goes, where there is something weird going one and how the stages change the tone.

I would also check the voltage after the diode with a multimeter to see how high it is (200v?) or if there is some problem there. I guess it will read OK, since you have a loud output after all.

My suggestion for next builds is: use as little solder as possible! Touch trace and component with the soldering iron and touch the trace with the solder. At some point it will melt and form a thin film. That is enough. The large drops have a different wettability (the angle between the sphere and the surface), so that the drop might only be attached to the component, but not to the trace, and you will not notice it.

[GibsonGM]

If you don't have much experience with high voltage circuits PLEASE be very cautious in audio probing an amp...the filter caps and many other places are exposed, potentially fatal points you can touch. In the power supply, you're looking at over 400V.  What are your meter leads rated for?  That PCB is a little difficult to probe, as well - it's not clear where the signal path is, as may be the case in a point to point model.  Just sayin'...

Intermittent volume changes...possibly a bad drive or master pot (or dirty)...does the pilot light go up and down in brightness when the volume changes?

[jma38]

If you don't have much experience with high voltage circuits PLEASE be very cautious in audio probing an amp...the filter caps and many other places are exposed, potentially fatal points you can touch. In the power supply, you're looking at over 400V.  What are your meter leads rated for?  That PCB is a little difficult to probe, as well - it's not clear where the signal path is, as may be the case in a point to point model.  Just sayin'...

Intermittent volume changes...possibly a bad drive or master pot (or dirty)...does the pilot light go up and down in brightness when the volume changes?

I'll let you know as soon as I add the pilot light to the build.

[jma38]

Nice! Congrats!
The "wump" could be an intermittent connection or just a bad part somewhere.

If you want to check the circuit closely, you can use an audio probe and follow the signal path. Just be careful, to not connect it to the tubes plates (unless you coupling capacitor is rated over 300v). This also helps to understand where the sound goes, where there is something weird going one and how the stages change the tone.

I would also check the voltage after the diode with a multimeter to see how high it is (200v?) or if there is some problem there. I guess it will read OK, since you have a loud output after all.

My suggestion for next builds is: use as little solder as possible! Touch trace and component with the soldering iron and touch the trace with the solder. At some point it will melt and form a thin film. That is enough. The large drops have a different wettability (the angle between the sphere and the surface), so that the drop might only be attached to the component, but not to the trace, and you will not notice it.

I'll see about getting(or building) and audio probe.

[Ben N]

If you don't have much experience with high voltage circuits PLEASE be very cautious in audio probing an amp...the filter caps and many other places are exposed, potentially fatal points you can touch. In the power supply, you're looking at over 400V.  What are your meter leads rated for?  That PCB is a little difficult to probe, as well - it's not clear where the signal path is, as may be the case in a point to point model.  Just sayin'...

One hand in your pocket whenever you are poking around a HV circuit, and rubber souled shoes, so there is no possible path for HV through your body.

[frequencycentral]

All this excitemakes me wanna build a Superfly!

[GibsonGM]

If you don't have much experience with high voltage circuits PLEASE be very cautious in audio probing an amp...the filter caps and many other places are exposed, potentially fatal points you can touch. In the power supply, you're looking at over 400V.  What are your meter leads rated for?  That PCB is a little difficult to probe, as well - it's not clear where the signal path is, as may be the case in a point to point model.  Just sayin'...

One hand in your pocket whenever you are poking around a HV circuit, and rubber souled shoes, so there is no possible path for HV through your body.

Certainly good advice...avoiding a path thru your chest (and heart).  It would be beyond the ability of most people to prevent a shock entirely in the 'home lab', though.      Even with rubber shoes.    Sh*t happens - ask me how I know...

Sorry guys, I conflated replying here to the Hot Rod Deluxe post!! Different thread entirely, guess I didn't have enough coffee.   It's not 400v, god no, lol.  And the switching supply does offer some current limiting, tho you do need to be careful and respect the high voltage.     Yes, be sure the audio probe coupling cap can handle the switch supply's B+...and yes, THIS one is probably a good build to 'listen in' and check out the audio path, being small and easy to manage.   

Biggest offense I make on things like this is to have it floating loose on the desk, and trying to probe around, moving it all over...so maybe some kind of hold-down would be a good idea 

I want to make one too, now, ha ha

[jma38]

Question for those who've already built and enclosed their Superfly: What size of enclosure did you end up using for yours? I have a metal enclosure I can start drilling but due to the much larger capacitor near the 12v input I won;t have as much height room for it with the enclosure I have.

[cab42]

I want to make one too, now, ha ha

Me too! Today, I received some subminis bought on ebay 

[thomasha]

Question for those who've already built and enclosed their Superfly: What size of enclosure did you end up using for yours? I have a metal enclosure I can start drilling but due to the much larger capacitor near the 12v input I won;t have as much height room for it with the enclosure I have.

It should fit in a 1590b, as used for pedals. There is plenty of room for the capacitor.

[jma38]

Question for those who've already built and enclosed their Superfly: What size of enclosure did you end up using for yours? I have a metal enclosure I can start drilling but due to the much larger capacitor near the 12v input I won;t have as much height room for it with the enclosure I have.

It should fit in a 1590b, as used for pedals. There is plenty of room for the capacitor.

Thanks! Off to Tayda I go...

[jma38]

Does anyone know what intermittent lowering in volume of the Superfly could be? I was testing it with a Tube Screamer today and the signal occasionally lowered in volume considerably for a few seconds and then came back to normal volume consistently while it was on. Turning the amp off and on again led to a consistent volume for a few minutes and then the lowering in volume came back. I have the transistor of the circuit in a socket I made and it feels a little bit loose, could this be part of the problem?

[GibsonGM]

Anything loose could be part of it, yes, if good contact is coming and going. Even a bad cable can cause that (tip, move them around, make sure that's not it.  Use 1 guitar cord direct to the firefly, make the signal chain simple).  You can use the eraser end of a pencil to 'move wires and things' around to see if something is loose.

Does it do it both with the tube screamer in the signal chain, and also with it not there (completely removed)?

Any way you can make a recording/video of the issue in action? 

[thomasha]

It is probably caused by an intermittent connection.
This mostly occurs when you have a component or wire that is not properly soldered and moves, or something in a socket, that will not fit correctly.
I had the same problem with several amps, because the IC sockets will not give you a good connection with the tubes (in the end I soldered my tubes to the board, and that solved the problem. 

You can verify this by tapping the tube while the amplifier is on. If there is a volume drop and it comes back when you wiggle the tube in the socket (be careful, the tube can get hot), you found the problem. You won't be electrocuted if you just touch the glass of the tube. Be careful anyways!

[amptramp]

Sockets are not allowed for transistors and IC's in military products.  They run the typical "shake and bake" environmental tests of MIL-E-810 and no one has ever seen a socket that didn't cause a problem with loosening or corrosion.  The usual tests are:

1. Sinusoidal vibration, 5 Hz to 2000 Hz in three axes on a vibration table
2. Random vibration in three axes using a random noise generator powering a vibration table
3. Shock in three dimensions, both directions in each
4. Operating temperature, low and high (a Fuzz Face usually would fail to operate with consistent characteristics due to inadequate range)
5. Storage temperature (wider limits than operating temperature)
6. Salt spray
7. Humidity
8. Electromagnetic Compatibility (required for any commercial product having an internal oscillator of 9 KHz or higher)

out of a comprehensive array of tests to be called for where any possible environment is listed:

Test Method 500.6 Low Pressure (Altitude)
Test Method 501.6 High Temperature
Test Method 502.6 Low Temperature
Test Method 503.6 Temperature Shock
Test Method 504.2 Contamination by Fluids
Test Method 505.6 Solar Radiation (Sunshine)
Test Method 506.6 Rain
Test Method 507.6 Humidity
Test Method 508.7 Fungus
Test Method 509.6 Salt Fog
Test Method 510.6 Sand and Dust
Test Method 511.6 Explosive Atmosphere
Test Method 512.5 Immersion
Test Method 513.7 Acceleration
Test Method 514.7 Vibration
Test Method 515.7 Acoustic Noise
Test Method 516.7 Shock
Test Method 517.2 Pyroshock
Test Method 518.2 Acidic Atmosphere
Test Method 519.7 Gunfire Shock
Test Method 520.4 Temperature, Humidity, Vibration, and Altitude
Test Method 521.4 Icing/Freezing Rain
Test Method 522.2 Ballistic Shock
Test Method 523.4 Vibro-Acoustic/Temperature
Test Method 524.1 Freeze / Thaw
Test Method 525.1 Time Waveform Replication
Test Method 526.1 Rail Impact.
Test Method 527.1 Multi-Exciter
Test Method 528.1 Mechanical Vibrations of Shipboard Equipment (Type I – Environmental and Type II – Internally Excited)

If you sell the device to a hip-hop group, gunfire shock could be a possible test to call up.

[antonis]

I could vote for a number of above mentioned test methods to apply for most of groups gigs..
(especially 504.2 should be  a sacrosanct proviso..)