DIYstompboxes.com

Hello guys,

Long time no posts. Had a lot on my back and a lot of projects to be done, so after a while, i've managed to finish this project that was on my mind for some time now.
It's a small full tube practice amp that uses 6N16B double triode as an output tube (submini) and a 6N16B / 6N17B double triode as a preamp tube.
The schematic is based on Marshall 18W and the power stage is made in a self-split configuration.
Controls are: 1 volume and 1 tone knob and one switch that will enable a single or parallel preamp stage
For the HV it uses a SMPS module.

Project documentation is available here: https://dl.dropboxusercontent.com/u/15275178/OSEQ_UPLOADS/THE_SFA/THE%20SFA.pdf (https://dl.dropboxusercontent.com/u/15275178/OSEQ_UPLOADS/THE_SFA/THE%20SFA.pdf)



Here you have some renders of the amp and also some views of the PCB

(http://s8.postimg.org/7st690okx/1239067_1661436777424002_1852273283209473372_o.jpg) (http://postimg.org/image/7st690okx/) (http://s8.postimg.org/ryrmasdwx/11267509_1661436784090668_4092555911672014676_o.jpg) (http://postimg.org/image/ryrmasdwx/)

(http://s8.postimg.org/momnjhto1/11700779_1661436780757335_5038450487652784701_o.jpg) (http://postimg.org/image/momnjhto1/) (http://s8.postimg.org/dv0szid0x/11722485_1661436860757327_4310159712126947929_o.jpg) (http://postimg.org/image/dv0szid0x/)

(http://s8.postimg.org/519wieq29/11728963_1661436864090660_8111552797079352144_o.jpg) (http://postimg.org/image/519wieq29/) (http://s8.postimg.org/psxbgaagh/11754257_1661436787424001_4139145830907843007_n.jpg) (http://postimg.org/image/psxbgaagh/)

Regards,
Gabriel Tudoran aka. DeXTeR

Hi, I like your SFA amplifier.  I have a couple of questions - What voltage is the B+ and what advantage is it to use the 6N16B in parallel for the first stage?

Thanks & regards Tony.

Hello Tony,

- The B+ voltage can be dialed between 90 and 350V (a maximum of 200V is permited on the anode of 6n16b).
- Adding a parallel stage  it will add some distortion to the sound (the input stage is the same as the one from the 18w marshall)

If you have any other questions please do not hesitate to ask.

Regards,
Gabriel

I'm excited for this one. For setting the B+ do you just set it for where it sounds best?

I'd be interested in one of these pcbs.   What's the cost on them?

@Luke - the B+ value will be set according to the primary load of the output transformer and secondary load of the transformer also the maximum voltage on the anodes of the power tube and not to exceed the maximum anode dissipation of the  tube (which is 1W per triode)

@Slacker - i will PM you with the details

Regards,
Gabriel Tudoran aka. DeXTeR

gtudoran - are you at all familiar with the English term "sweet fanny adams"? or the not so polite version? dextor- is there a connection?

> the B+ value ... primary load ...maximum voltage on the anodes ...maximum anode dissipation

For people who don't compute these every day:

The rated dissipation is 0.9W per triode or 1.8 Watts per bottle. In non-military applications you can round to 2.0 Watts.

The OUTput power is much less than the dissipation. For any self-bias amp, for any small triode amp, and especially for self-bias triode.

Suggested starting points for push-pull self-bias 6N16B power amp--

200V supply 22K load  9mA 750r bias (820r a good first-try)
170V supply 20K load 10mA 500r bias (about 0.25W output)
140V supply 20K load 12mA 270r bias
100V supply  7K load 13mA 150r bias (much lower output)

Supply voltage over 200V may be bad for the tube, and will require an impossibly high load impedance for good results.

0.25W may seem small compared to the monster Marshalls it is inspired by, but with a good speaker it can be really loud in a home situation. The 100V condition may be useful if there are other people in the house. You can leave the primary load near 20K, the bias resistor near 750r, and get down to flea-power at 100V supply. If the SMPS voltage knob is front-panel you have a wide range of maximum powers at your fingertip.

For Hammond 125A:
For 20K primary load:
4r load: 5&6
8r load: 2&4
For 7K primary load:
4r load: 4&6
8r load: 3&6

Sorry duck_arse, no i have to say i'm not (searched on urban dictionary but i do not see the connection).
I do not have any connection with "dextor" - Dexter was my nickname for a long period of time.
... I hope that i didn't bother you in some way.

Quote from: duck_arse on August 13, 2015, 12:00:51 PM
gtudoran - are you at all familiar with the English term "sweet fanny adams"? or the not so polite version? dextor- is there a connection?

Indeed PRR and there is not much to say. The prototype was tested using a 12" / 100db SPL Celestion speaker and i can say that in an apartment there is now way of using the volume over 12 o'clock.
And after 10PM i can't use it over 9 o'clock.

Quote from: PRR on August 14, 2015, 01:11:22 AM
> the B+ value ... primary load ...maximum voltage on the anodes ...maximum anode dissipation

For people who don't compute these every day:

The rated dissipation is 0.9W per triode or 1.8 Watts per bottle. In non-military applications you can round to 2.0 Watts.

The OUTput power is much less than the dissipation. For any self-bias amp, for any small triode amp, and especially for self-bias triode.

Suggested starting points for push-pull self-bias 6N16B power amp--

200V supply 22K load  9mA 750r bias (820r a good first-try)
170V supply 20K load 10mA 500r bias (about 0.25W output)
140V supply 20K load 12mA 270r bias
100V supply  7K load 13mA 150r bias (much lower output)

Supply voltage over 200V may be bad for the tube, and will require an impossibly high load impedance for good results.

0.25W may seem small compared to the monster Marshalls it is inspired by, but with a good speaker it can be really loud in a home situation. The 100V condition may be useful if there are other people in the house. You can leave the primary load near 20K, the bias resistor near 750r, and get down to flea-power at 100V supply. If the SMPS voltage knob is front-panel you have a wide range of maximum powers at your fingertip.

For Hammond 125A:
For 20K primary load:
4r load: 5&6
8r load: 2&4
For 7K primary load:
4r load: 4&6
8r load: 3&6

Quote from: gtudoran on August 14, 2015, 02:46:05 AM
Sorry duck_arse, no i have to say i'm not (searched on urban dictionary but i do not see the connection).
I do not have any connection with "dextor" - Dexter was my nickname for a long period of time.
... I hope that i didn't bother you in some way.

Quote from: duck_arse on August 13, 2015, 12:00:51 PM
gtudoran - are you at all familiar with the English term "sweet fanny adams"? or the not so polite version? dextor- is there a connection?

Gabriel,

I think he was referring to "The SFA - 1W all tube guitar amplifier" more so the "SFA" part...  I don't see any connection either other than the initials being the same as "sweet fanny adams" which is not really that odd..  There was a hair band back in the late 80's early 90's called Sweet F.A. and perhaps there was some connection there?

(http://photos1.blogger.com/blogger/7923/2644/1600/SWEET%20F.A.%20Temptation%20front.0.jpg)

Hahahahah J0K3RX - duck_arse explained it to me on PM :)) funny as hell. As for the amp name ... the answer is even easier: is "The Small F6%$^ Amp"

And on another note, some preliminary tests that i've done today: SMPS oscillator OK / Filaments OK

(http://s23.postimg.org/tg8iw6vlz/IMG_3871.jpg) (http://postimg.org/image/tg8iw6vlz/) (http://s23.postimg.org/ovmch9bwn/IMG_3873.jpg) (http://postimg.org/image/ovmch9bwn/)

(http://s23.postimg.org/8hxrkd6dj/IMG_3875.jpg) (http://postimg.org/image/8hxrkd6dj/) (http://s23.postimg.org/htoev28av/IMG_3908.jpg) (http://postimg.org/image/htoev28av/)

(http://s23.postimg.org/6ouuw1l6v/IMG_3909.jpg) (http://postimg.org/image/6ouuw1l6v/) (http://s23.postimg.org/uz3x1626f/IMG_3911.jpg) (http://postimg.org/image/uz3x1626f/)

Looks awesome, I'll be in on one too.

Well ... hes alive.
Yesterday i've finished the prototype of the mini-tube amp. Had some problems with a capacitor that was new (straight from the bag) - no signal passed that little bugger, but all is good now.
Here is a video with the amp (clean) and with various pedals in front(808 OD / Booster and Distortion).
Sound was recorded at the workshop using camera microphone (12" Celestion speaker in the cabinet)
So... this is the little giant, aprox. 100mW of pure tube sound (more then enough to annoy your neighbors)

i thought it was sweet f... all too , (sweet fanny adams) bad minds think alike, ;)

;)

cool amp. 8)

Sounds pretty awesome!!!  8)

Nice job on the amp!!  It does sound good!

If you guys like "Sweet FA", check out the Sweet song "Sweet Fanny Adams"...my kind of classic guitar...

https://www.youtube.com/watch?v=9NKCR1jZbwk (https://www.youtube.com/watch?v=9NKCR1jZbwk)

This is ridiculously cool. This will definitely go on my things-to-hurry-and-build-before-school-starts-again list 8)

I'd love one of those circuit boards (if you are planning on selling them).

Great work!

DeXTeR ~

Of course, you know that "Small F#@king Amplifier" is a obvious name.... You are going to have to call it the "Sweet FA" now!? Besides it being a cool name it just kinda seems fitting now.. Call it Sweet FA and just let people wonder what it means... Sweet Fanny Adams or Sweet F#@king Amp or whatever.. Clever little marketing tactic  :icon_wink: 

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.

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.

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.

Quote from: Perrow on September 04, 2015, 11:54:29 AM
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...

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

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

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.

Brilliant work!

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

Annddd is done!

(http://s5.postimg.org/4vtnq5n9v/IMG_3950.jpg) (http://postimg.org/image/4vtnq5n9v/) (http://s5.postimg.org/al9wagtg3/IMG_3953.jpg) (http://postimg.org/image/al9wagtg3/)

(http://s5.postimg.org/kwm934l5f/IMG_3955.jpg) (http://postimg.org/image/kwm934l5f/) (http://s5.postimg.org/kzaq3pe6r/IMG_3959.jpg) (http://postimg.org/image/kzaq3pe6r/)

(http://s5.postimg.org/n2l5bddzn/IMG_3961.jpg) (http://postimg.org/image/n2l5bddzn/)

Come on man....

Get another Google docs order form together :)

Quote from: danielzink on September 06, 2015, 05:23:32 PM
Come on man....

Get another Google docs order form together :)

Seriously! I need one of these really bad :-[

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/  (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

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

(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=51965&g2_serialNumber=4)

Got a nice supply of tubes

(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=51956&g2_serialNumber=4)

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.

(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=51959&g2_serialNumber=4)

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.

(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=51962&g2_serialNumber=4)

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!

@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

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

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.

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.

QuoteWaltk, 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. 

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

Quote from: waltk on November 25, 2015, 10:13:28 AM
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!

Necro bump... does anyone have a copy of the build doc for this?

Yes, I do, is it not online anymore?

Pm me your email and I'll send it over in the morning.

The link in the OP is broken. Pm sent. THanks for your help.

does anyone happen to have the build doc/schem saved for this? want to try and build up my board this weekend, dont have a local copy and the link is dead  8)

I'm pretty sure I still have it on my computer. I'll take a look when I get home and let you know, if nobody else does sooner.

Hello - Does anyone have the build documentation saved?  Would like to try this one.  Thanks.

So two freaking months later I finally got around to uploading this build doc: https://www.dropbox.com/s/te2xtq2r5srk7ix/THE%20SFA.pdf?dl=0

I pretty much never touch my dropbox so the file should stay up for quite a while. Hope this helps someone.

Thanks Nathan.  BTW, I couldn't download it directly - only to my own Dropbox account.  Anyone else tried it?

try change url to dl=1

Thank you Nathan