THE SFA - 1W all tube guitar amplifier

[Perrow]

As if I need another submimi tube amp build

I think I've got the 1N16B tubes though. I'll have a look when I get back home.

[aballen]

Wow man if you are selling these pcbs I would really love to grab a pair.   I still have not built a good micro tube amp.  The smallest I've built are my firefly amps,  which are great, but the clean channel is not real all that clean.

[Perrow]

I've built the Superfly, similar to this one (although I crammed it into a 1590A) and I suspect this ain't that clean either. I've been toying with the idea of combining a submini tube preamp with a TDA2030 power amp kinda like the Orange micro terror. I'll have to get to that some time.

[sajy_ho]

I've built the Superfly, similar to this one (although I crammed it into a 1590A) and I suspect this ain't that clean either. I've been toying with the idea of combining a submini tube preamp with a TDA2030 power amp kinda like the Orange micro terror. I'll have to get to that some time.

Excelent idea, then we can get rid of the output transformer.
I have a similar idea with GTFO as the preamp in front of TDA power amp both powered with a 12V wall wart.
Also we can add PT2399 delay after the preamp for lead purposes...

[Cozybuilder]

Perrow-
I can't wait to see the curly PC layout of all the above for a 1590A.

[Perrow]

Now you're just trying to flatter me into doing it

[MetalGuy]

Good job on the amp!
I've played with submini tubes a lot (including 6N16) and I never liked how a triode amp sounded in any configuration maybe because I'm more into thrash, speed, death metal and stuff. However that changed when I discovered some submini pentodes.

[Jaicen_solo]

Brilliant work!

If/When PCB's are available, i'm 100% getting a pair.

[gtudoran]

Annddd is done!

[danielzink]

Come on man....

Get another Google docs order form together

[vigilante397]

Come on man....

Get another Google docs order form together

Seriously! I need one of these really bad

[gtudoran]

Thank you all of you for such nice words and for the interest shown on this project.
Because there were so many persons interested in this, i've set up a small preorder page on my site, where you can place preorders for PCB only or for a full product.
The preorder page is here: http://oseq.org/pre-order/
If you have any questions, please let me know and i will gladly answer any of them.
Thank you again for your interest.

Regards,
DeX

[waltk]

Couldn't wait to try this.  Made a single-layer layout with separate PS and amp boards.



Got a nice supply of tubes



The power supply is an alternate design using an MC34063 (jelly bean boost controller) instead of a 555.  About the same amount of parts and stable/reliable.



First amp build.  Some things socketed for tweaking.  Used a slightly different switching arrangement for the parallel first stage that allows two separate inputs or both combined, but I'm not sure this is really useful.



The tone control doesn't work like I expected.  I Would welcome any suggestions for tweaking.  Overall, I really like the sound - thanks for sharing the design, DeX!

[gtudoran]

@waltk nice build you got there. Regarding tone control you should experiment with values or you can omit it and add a bright cap on the volume pot with a switch. Or, for a nice tone control you can use a switch to switch the cathode bypass capacitor (half the original value and add one of the same value in || with it )

Please keep in mind that:

- 1 the value that i used for the cathode resistor in the power tube is 560ohm / 190V anode voltage / 22k (pins 2 and 4 on the output transformer for a 8ohm speaker)

Also, for the anode resistor of the preamp tube i've used 150K instead of 100k (you can use 200k), the bypass cap's value from the anode can be experimented with it (anything between 4n7 to 20n would change the sound character of the amp)

The PCBs will be available at the end of the month.

Also, care to share the schematic for the SMPS?

Best regards,
DeX

[waltk]

Thanks for all the tweaking suggestions.  I was planning to revise the layout to allow for different-sized components anyway, so I think I'll add an option for switched parallel bypass caps.

The PS is a hybrid that uses the switching functions of the MC34063 to drive a MOSFET boost section (like the 555 timer version).  I'll start a separate thread with the schematic and a complete description of how it can be customized for different output voltage, amperage, and ripple.  I tested the one in the picture above to 25ma, and it worked fine - the 555 timer versions that I've built seem to have significant dropout at higher power levels.

-W

[blackcorvo]

Waltk, have you seen this? http://www.imajeenyus.com/electronics/20111010_40-400V_supply/index.shtml
Sounds very similar to what you've done. I stumble upon it yesterday searching smps supplies.

[slashandburn]

First thought when I noticed the title was "ah, so thats what the Scottish Football Association do with their days."

Ah, I jest. Just quietly admiring your skills here.

[waltk]

Waltk, have you seen this? http://www.imajeenyus.com/electronics/20111010_40-400V_supply/index.shtml
Sounds very similar to what you've done. I stumble upon it yesterday searching smps supplies.

Yes, I've seen that.  It is very similar to the design I've been using.  As you look around, you'll find about a dozen slightly different versions of the same thing.  My goal was to make a stable, reliable, flexible, and efficient SMPS - so I've tried to use the best ideas from the various versions that are out there.  Not surprisingly, there are a few trade-offs, and you always have to compromise something (like output ripple, efficiency or output range) based on the components you select.  My current thinking is that the best approach is to tweak the component selection for the particular circuit you are planning to power, and compromise on the flexibility.  It always seems to help to use a MOSFET with low RDS_on, an inductor with high current ratings (3A+), and a reasonably-sized output cap to reduce ripple.  I still haven't gotten around to posting a final version because I'm not sure I have all the answers yet. 

[gtudoran]

A low ESR value for the output cap is more important then the value of the cap (of course you can add several in || or you can add a small ceramic over the electro. )

Regards,
DeX

[blackcorvo]

Yes, I've seen that.  It is very similar to the design I've been using.  As you look around, you'll find about a dozen slightly different versions of the same thing.  My goal was to make a stable, reliable, flexible, and efficient SMPS - so I've tried to use the best ideas from the various versions that are out there.  Not surprisingly, there are a few trade-offs, and you always have to compromise something (like output ripple, efficiency or output range) based on the components you select.  My current thinking is that the best approach is to tweak the component selection for the particular circuit you are planning to power, and compromise on the flexibility.  It always seems to help to use a MOSFET with low RDS_on, an inductor with high current ratings (3A+), and a reasonably-sized output cap to reduce ripple.  I still haven't gotten around to posting a final version because I'm not sure I have all the answers yet.

I'm super interested in seeing your circuit. I have been considering building an amp using some 6J6 tubes I have here and a power supply like that would be perfect for that!