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Messages - blackcorvo

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Tubes and Hybrids / Re: 6v6 power amp circuits
« on: July 16, 2016, 07:27:20 PM »
I was just wondering how feasible it would be seeing as 1 tube is every so slightly less work then 3 or 4 lol. Im working on building my first full tube guitar amp. Im going to build a fender champ clone first then replace the preamp section with a marshall preamp circuit i found. I didnt know if i should just keep the single 6v6 power amp or go for a little bit more power so i could play with some friends.

I'd recommend you check out if you wanna get some nice ideas of tube amp designs, and they even have "bulding block" projects, that you can use to mix-and-match preamps and power amps as you see fit.

Tubes and Hybrids / Re: Who Needs A Heavy Power Transformer?
« on: July 16, 2016, 11:29:37 AM »
One thing I would advise you to do is get a power supply with a ground connection, and make sure you get your amp's chassis and your circuit properly grounded.
I say to make sure, because some laptop power supplies have a bad habit of keeping the output completely isolated and not grounded, even when they have a ground connection to the mains plug. In such cases, that introduces background noise when you work with audio.

Preamps and Effects / Re: Sentient Machine
« on: April 27, 2016, 09:40:50 PM »
BIG improvement compared to what it was originally, well done!

Preamps and Effects / Re: Monarchy Drive
« on: April 27, 2016, 09:03:28 PM »
Here's the so-long-awaited soundclip of this simple circuit:

All gain settings were achieved with Gain Max and turning the volume on the guitar down.

I had built it and lost the circuit in the middle of all my stuff, but I found it today. For some reason, it has some bad connection issue at some point in the circuit and it sometimes doesn't work, but I managed to make it work using a "brute force" maneuver  :trouble :lmao:

I simply connected it directly to a PAM8403 board and connected one of the outputs to my "French Bulldog" cab (1x 8" Vox Bulldog from a PF15R stuffed in a France-themed suitcase).

I rather like this combination, but I think I'll work on changing the circuit a bit so I can add tone controls to get a better control over the sound.

Amplifier Discussion / Re: Feng - Mini Amp using PAM8403 (2x 3 Watt)
« on: April 15, 2016, 11:20:17 AM »
Cool project irmão  :dbtu:

That said, I'm also amazed that TL072 works at all with 5V ; TL062 is better suited and LM358 is *designed*  to work on 5V single supply as mentioned by tonyharker .

The minimum voltage usually stands for the device working linearly. Not recommended for precision circuitry, but guitar preamps are much more forgiving.
I do not have a proper way to test how much the linearity changes, however.

Amplifier Discussion / Re: Feng - Mini Amp using PAM8403 (2x 3 Watt)
« on: April 14, 2016, 03:06:06 PM »
Does the TL072 work OK at 5v as the datasheet shows a minimum of about +/- 3.5v (7v total)? The TL062 would be better as this shows a supply of less than +/- 2v. The LM358P would also be suitable it has a minimum supply of +/- 1.5v.

I did not notice any problems with it working at 5v, but it's good to have other options. I simply used what I had in hands.
The worst that might be happening is that the TL072 is not as linear as it would be at 7v, but that isn't exactly a bad thing when it comes to guitar circuits.

Amplifier Discussion / Feng - Mini Amp using PAM8403 (2x 3 Watt)
« on: April 14, 2016, 12:00:59 AM »
Recently I started working on a project that required a small, 5-volt stereo amplifier for sound, so I decided to buy a bunch of them to have a few spare ones in case anything caught fire or whatever.
After playing with one of them for a while, I decided to try and make a guitar amp out of it.

Here's the result:

Sample (Guitar: Vintage V100GT, bridge pickup)

Images of the test setup, schematic and (possible) layout in perfboard:

As funny as it may sound, the name came from me bashing my fingers on the keyboard after drawing the schematic, half-awake, at 4AM. It was not a joke about the power amp being from chinese manufacture at all.

Preamps and Effects / Re: Sentient Machine
« on: April 12, 2016, 06:44:58 PM »
You could have used a 3mm LED to make it closer to the "eye-sized" red dot, but I bet you can simply put a dab of Hot Glue on the tip of the LED, then paint it all black and, after dry, remove the hot glue to reveal the clear plastic.

Amplifier Discussion / Re: Laney Amp power boosted
« on: December 23, 2015, 07:26:04 AM »
Now that's what I call an upgrade! Well done buddy!

Tubes and Hybrids / Re: 12AU7 Hybrid power amp - Evil_Food
« on: December 08, 2015, 12:21:39 PM »
...Speaking of Music Man amps. They are known for their high plate voltage vs. reliability.... but few seldom mention that they also operated at exceptionally low (on generic guitar amp standards) screen voltage. The same little detail was also the key difference of prototype Ampeg SVTs (that failed catastrophically even with extremely reliable and rugged output tubes) and later SVTs that didn't (which no longer had tubes of equal ruggedness but simply much lower screen voltage). Something to ponder at.  ;)

Yeah, I noticed those voltages were like 1/2 B+ right?
If I understood correctly, this is to keep plate-screen grid voltage within maximum limits. With the help of the cathode transistor keeping the cathode at a rather large, positive voltage (negative relative to the grid, which is fixed-biased), so the plate-cathode and control-grid voltages are within limits...

Yeah, that's it! This is a fixed-bias stage that's driven from the cathode instead of the grid.
Would then the transistor be simply a common-emitter stage, with the tube working as it's "collector resistor" and at the same time, the transistor working as the tube's "cathode resistor"?

If that's it, it's SO much easier to understand!

Tubes and Hybrids / Re: 12AU7 Hybrid power amp - Evil_Food
« on: December 06, 2015, 05:08:47 PM »
The principals applied to triodes still apply to pentodes.  Common grid is still common grid.

Maybe I am lucky, to me the cathode drive seems intuitive.  The tube works on the relationship between grid and cathode, not necessarily those elements and ground.  Hold cathode at ground and wiggle the grid, you get signal at the plate.  But hold the grid to ground and wiggle the cathode, the same thing happens.

In a common 6L6 push pull output, I might ground the cathodes and have -50v on the grid.  In a PV Heritage VTX, I might see +15 on the grid and +65 on the cathode.  In both those cases the grid is biased -50 with respect to cathode.  In practice, the amp examples I cited are running closer to class B than something like a fender twin Reverb would be.

I prefer colder-biased amps anyways. The best way I can describe it is that they're louder and clearer.

For now, I'll try to simulate a single-ended 6V6 @ 250v in Proteus with the cathode circuit from the amp in this topic, and just play around with values. It's what I usually do on my bench anyways, but until I have the SMPS working, Proteus will have to do.

My problem isn't really figuring out how common-grid works, but the math behind the values used for the circuit. I'm no engineer, I barely understand the math behind most simple amplifier stages (and don't ever ask me about filters, it's far too complex to me!), but I wanna start being more careful with my power amp designs.
Don't wanna make a tube-burner, after all.

Tubes and Hybrids / Re: 12AU7 Hybrid power amp - Evil_Food
« on: December 06, 2015, 01:11:47 PM »
Of course you can build a single ended.   It is just a triode stage, use two for push pull.

Look up either "grounded grid" or "common grid" amplifier, both mean the same.  The signal is fed into the cathode instead of grid.  Music Man amps are maybe the best known examples of this.  The various Peavey VTX series amps use it.  Classic VTX, Heritage VTX, etc.  And others.

I couldn't find anything talking of this type of circuit using tetrodes nor pentodes, only triodes, and it didn't have any formulas, only brief comments on how the circuit works.
I was thinking about using a 12AQ5 SE with this topolog,y and the SMPS I posted here, so I could use a SS preamp with it.

Tubes and Hybrids / Re: 12AU7 Hybrid power amp - Evil_Food
« on: December 05, 2015, 04:23:12 PM »
I have acquired the MC34063 and most of the components for the HV supply, but they did not have the MOSFET, fast diodes, or even the inductor on the local stores I went to. Even told me that high-current inductors were unavaiable for being "old stuff", go figure!
Gonna have to buy online.

Now, I'm very curious about the design process of such an output stage. Is there info anywhere about how to do it? I looked up "hybrid cascode push pull" but I didn't find anything close to this specific topology.
Also, seeing as each triode is biased separately, does it mean one could build a single-ended version of such design?

Amplifier Discussion / Re: fix Fuzz/distortion from AMP
« on: December 04, 2015, 08:19:00 PM »
I pluged my studio headphone a little back in the output jack to check whether its the speaker...... headphones fuzzed too....
in the picture i uploaded it cannot be seen but there are capacitors and transistor in this amp......... how to check them?

Do you have basic knowledge of electronics? If not, it would be best to talk to a friend who knows of it and is willing to help, or take it to a trusted tech. "Fuzz" could be many things, from the power transformer to a single bad resistor. It's very rarely a "look and shoot" kind of thing (speaking as a tech who sees weird, new issues everyday).

Tubes and Hybrids / Re: 12AU7 Hybrid power amp - Evil_Food
« on: November 28, 2015, 12:30:06 PM »
The power amp is reasonable, but avoid the multiplier if you need any power, get HV from a proper HV winding.
Bias with a scope until you get rid of the crossover notch, we are talking very low current anyway, almost pure Class B

What about something like this smps with the MC34063 for the high voltage?

And if I'm not wrong, you could use another chip to get -12v. I bet you could make it all run off a single 12v gel battery or a cheap laptop-type supply.


I have run some simulations of a similar circuit on Proteus and I got to the following results, with the output adjusted for 280v with no load.

- 5K Ohms load: 280v, 56mA (15.68 Watts)

- 3K Ohms load: 247v, 82.5mA (20.37 Watts)

So, in theory, this could be a suitable power supply for small tube projects (probably up to 10w, depending on the tubes used).

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