Pictures!

[solderman]

Looking cool, Anders!  A question though: is it safe to leave the grid floating like it is on the first triode?

Good question, I don't know. I haven't thought about that really. It  won't be a problem to hook it up to the switch and send it to GND when it's  switched out.

BTW I see that there still is a 1uF in cap and a R-1M that is a leftover from when I was planing to have it as a combined dist box/amp with the ability to take the signal before the tone stack in front of an amp and switch off the rest but I ditched that idea.

[Kitarist]

So many beauties in here!!!

[deaconque]

Hi all,

OK another ...not a pedal but... is a great platform for testing/auditioning them. Built it some time ago based on a Fender 5f2a schematic that was on,  i think, Steve's Amp Pages which seem to be MIA,  to use as a tube auditioner for my little collection of tubes. Turned out to be great with pedals as well, turned up plenty loud enough it stays clean so you get a good aural picture of what is going on with the pedal.

  Has parallel preamp sockets so i can try out  the various tubes of the 12a_7  family, the 6s_7  family as well as the 6eu7's that i have, (allows parallelling the different types too).  Can run fixed bias or adjustable/cathode bias and has a switchable 4k/6 OT primary for the different octal output tubes stashed away someplace.  Switchable cathode caps on the preamp triodes so when needed - lots of snarl. NFB can be varied or turned off if not wanted.

Had just used transparencey/overhead film and clear packing tape to make labels when i first put it together but this week finally got around to doing a faceplate.

Take care
dave

That is some amazingly clean wiring   .  nice job.

[earthtonesaudio]

workalike

What proximity sensor did you use?

[Thomeeque]

Hi
Since amps have become more common here I thought I would show mine too. 

As you can se it is not finished yet. It's called Pravda. its a two channel aprox 2W apm. The preamp is based on the SOVTEK MIG 50 head. And the power stage is based on the Fender Champ but with an EL90 as power source. Its a back to back transformer setup with an 12V-1A AC wall wort and a 12V-2A transformer, the one on the top. After rectifying, the HP delivers 265V (we have 240V 50 Hz here)

...

Hi! This switch..



..will probably generate pretty loud pop when toggled, as it moves bias on plate by tens of volts. Or am I wrong? Did you already tried this part?

T.

[kurtlives]

I have done similar "boost" switches with cathodes before, like that. They will indeed give a nice loud pop.

[EARNEST]

I think he means Van Halen, and he's referencing the criss crossing lines on your pedal.

Yes

[kvb]

Piggybacked Shin Ei fuzz

[button]

Hi All,

Long time lurker around these parts and I finally threw together my first creation, a GGG red llama clone.  When ordering I accidentally chose the optional smaller enclosure which made things a bit more interesting, but it all ended up working in the end.

Guts (wiring technique needs some work):



Glory!  Named my version the Prometheus Fire Driver...

[snarblinge]

Nice First Build!!!

[davent]

That's a great looking build Dave!

I really like your construction technique. You seem to over design while being creative, I love doing that with my builds as well.

Do you have a schem for this? A few things intrigue me...
Whats the transistor on the bias board do?
What do the three knobs on the front do?
Are the two 3R resistors in parallel to drop the heater voltage?
What octal are you running now? Looks to stat with 5...5881?

Anyways, looks like a killer amp.

Thanks Chris & thanks Ian for the compliments!

Chris, how are things going in the hallowed halls of higher learning?

Love doing the planning, PCB design, eyelet boards, chassis layout, start out with paper, pencil and big eraser then CAD and ExpressPCB, next full size modelling and finally may get around to building the thing.

Easy stuff first; knobs from left are Tone, Volume and Master Volume which i never use but it's there for the day i figure out how to shoe-horn in the power scaling circuit.

The 3r resistors,  yes, big under rated Hammond PT.

The tube you know as well, bought a Quad of NOS Tung Sol 5881's way back when, didn't have boxes so got a great deal on them.

The bias circuit is taken from The Champ chapter of TUT3, the BJT is the switch between the bias pot and the fixed bias supply.

Take care,
dave

[mr.adambeck]

Piggybacked Shin Ei fuzz

Wow.  What is that thing?  Any more pics?

[Slade]

Introducing my new delay pedal, the Flashback Delay, just for psychodelay-ics! 





Soon I'll be uploading a video demo to my site.

Regards,
Fernando.-

[solderman]

Hi
Since amps have become more common here I thought I would show mine too.  

As you can se it is not finished yet. It's called Pravda. its a two channel aprox 2W apm. The preamp is based on the SOVTEK MIG 50 head. And the power stage is based on the Fender Champ but with an EL90 as power source. Its a back to back transformer setup with an 12V-1A AC wall wort and a 12V-2A transformer, the one on the top. After rectifying, the HP delivers 265V (we have 240V 50 Hz here)

...

Hi! This switch..



..will probably generate pretty loud pop when toggled, as it moves bias on plate by tens of volts. Or am I wrong? Did you already tried this part?


Yes, I can see that now. I'll just have to decide if the pop is worth the flexebility. Since I haven't heard it yet i might hardwire it in the position that i like best.

[armstrom]

You could always look for a switch that shorts out both positions while in transition from one to the next. Your preamp tube bias would go a bit wonky while the switch is being toggled, but it shouldn't produce a loud click like you would get when your cathode is floating and then suddenly shorted to the other position.

I'm not sure if such a thing exists, but I think it must..

[Thomeeque]

You could always look for a switch that shorts out both positions while in transition from one to the next..

I doubt it would help, you still change bias (and plate voltage by many volts) discontinuously, so huge peak will be generated (and it would happen twice when using this kind of switch as you would change bias twice in transition).. maybe if you would use photocell as a switch, but I'm not sure what current photocells can hold.. T.

[John Lyons]

Piggybacked Shin Ei fuzz

Nice! I love it.

[JKowalski]

use a photocell as a switch, but I'm not sure what current photocells can hold.. T.

That's an idea, the current going through preamp tubes is very small in the mA range so it would work fine. But you would still get a pop unless you use a ramp to control the resistance slowly

[earthtonesaudio]

use a photocell as a switch, but I'm not sure what current photocells can hold.. T.

That's an idea, the current going through preamp tubes is very small in the mA range so it would work fine. But you would still get a pop unless you use a ramp to control the resistance slowly

How about keep the DC bias fixed, and the cap always in the circuit, but put a large series resistor between the cathode and cap, and just short that resistor for your gain boost?

[Thomeeque]

use a photocell as a switch, but I'm not sure what current photocells can hold.. T.

That's an idea, the current going through preamp tubes is very small in the mA range so it would work fine. But you would still get a pop unless you use a ramp to control the resistance slowly

How about keep the DC bias fixed, and the cap always in the circuit, but put a large series resistor between the cathode and cap, and just short that resistor for your gain boost?

Yes, that would be simple, but by switching DC bias (cathode resistor) you can achieve more dramatical boost.. one have to choose

..But you would still get a pop unless you use a ramp to control the resistance slowly

Are not some types of photocells slow enough to take care about it themself?