Piecing together my first amp... preamp draft

[exabrial]

https://123d.circuits.io/circuits/19707 ... -amplifier

If you guys could, take a look at my preamp design. The goal is to eventually have a 10w-15w single ended amplifier in a package that's light enough to be portable. I'm going to do this by only have a single transformer (the output transformer) and use all solid state power supplies and filtering.

Really need to have some people audit my design though! My design philosophy is not be afraid of silicon, but use it to enhance the vacuum components abilities.

cheers,

[ajaxlepinski]

Welcome to the forum dude! This is the best guitar/amp forum on the interwebznet!!!

There are a few guys, on GAB, that have the kind of knowledge you seek. I'm sure they will chime in soon.

I see that you are using a ring/tip/sleeve. With my lack of circuit knowledge, I'm curious as to the purpose of this?

[exabrial]

For the input? It doesn't really matter electrically. During construction you could easily sub an equivalent jack. That's the only part I could find in 123D circuits though

[ajaxlepinski]

OK, just wondering... thought you had a new design or were considering a stereo amp.
Good luck!

[exabrial]

Stereo amp??? hmmm...

[Zozobra]

Is the thinking to use a SMPS DC-DC boost converter fed from laptop supply or will you build/source a high voltage SMPS? You might struggle to get enough current out of the former but you could build a dual triode push-pull amp rocking 1-4W with a boost converter. There are some good mosfet cathodyne PI designs out there you could use if you go down this route btw.

[exabrial]

Is the thinking to use a SMPS DC-DC boost converter fed from laptop supply or will you build/source a high voltage SMPS? You might struggle to get enough current out of the former but you could build a dual triode push-pull amp rocking 1-4W with a boost converter. There are some good mosfet cathodyne PI designs out there you could use if you go down this route btw.

https://smile.amazon.com/gp/product/B01 ... ge_o04_s01

I actually found a source and have the modules in my possession! I hooked them up to a resistor and they each were able to pump out 10w or so each into my resistor bank before it started to smoke. They could easily push more.

I don't have a buffered probe for my oscilloscope, so I can't check noise and ripple yet... but with a single-ended amp, noise on the main plate of the output tube won't be much of a problem, it's usually just the preamp tubes.

[Zozobra]

Yeah zvs flyback is pretty serious. Folks use them to make super high powered Tesla coils and Jacobs ladders. I would have thought the ripple and regulation would be horrible for audio amplification and be careful as they can output serious current!

[exabrial]

Regulation? This is a guitar amplifier... pssh. Nearly every guitar amp on the market has an unregulated PSU.

Yep, ripple, coil ring, and noise will be a problem with zvs, but your 120vac lines coming into your house are probably just as bad. I'm not sure what frequency these guys run at, need my high voltage problem for my oscilloscope to come in. Nice thing is, they should be able to pump out a enough milliamps to power a tube.

And yah, you're right, these things are in the death zone for amperage if it connected across one's heart. Definitely will be a lot of "hands off" measurement and a grounding clip available on my workbench.

[Zozobra]

Yeah but you still want some level of load regulation and consistent voltages Cool project for sure though!

[Zozobra]

So did you get anywhere with this and have you measured the ripple?

[exabrial]

Yes! It was absolutely successful and I've been using the amp since November. I learn a TON.

The good:

* Ripple and Noise: Not a problem for ZVS power supplies. They're -extremely- quiet until they approach their max limits. After my power filtering section, ripple and noise were so small my scope couldn't detect them (http://www.sainsmart.com/sainsmart-dso- ... scope.html)

* Regulation: This didn't occur to me till later, but a single-ended amp draws the same amount of power at full blast as it does idle. The preamp section will vary by a few ma, but the output section always draws full power from is PSU.

* Output Power: WAAAAY TOO LOUD. I wanted an 8 watt, but when I set the plate dissipation to 23w, the damn thing would wake the neighbors. I have a feeling my 10w output transformer was probably also being strained. Instead, I biased down to 19.5w, which should put me in the region of 8w-10w.

The bad:

* Tone stack: Mine is too complicated and rather useless. I'm thinking I'm going to build a 2 knob James tone stack for the next design.
* FX loop: The solid state FX loop ROCKS. However, I need to front panel mount the return volume control. This *could* be then used as a built in booster to send the output tube into overdrive. That little-high-voltage-depletion-mode-mosfet-that-could can send 60vpp to the grid of the output tube and give you some true 2nd order distortion.

Overall hugely successful project. Checkout clips of my crappy guitar playing and the schematic here:
https://drive.google.com/drive/folders/ ... sp=sharing

[Zozobra]

Thanks. I saw your post over on AX84 and I've bought a ZVS boost and a DC DC step down to play with. What enclosure is that btw? Looks huge!