6N16B True tube overdrive with SMPS supply

[phatt]

I resume this post for some questions..

Today I finished my valve pedal..it works flawlessy except for boring HUM, it sounds similar to a 60hz cycle hum, but that's strange since my power adapter is hum free..as soon as I connect other dirt pedals with a daisy chain they became useless as the hum rises up with the gain..


On a side note my build is a bit different:

I put togheter the first two gain stages of a plexi, built around a 12AU7, my SMPS is built from scratch, and while I'm waiting for the right mosfet, it now pumps out 70V from a 9V boss style PSU..

Hi Emanuele,
Be aware that not any old mosfet may work with this,,,better minds here can explain details.
70VDC seems rather low?
I would think you should get 150/190 VDC from a 9 volt supply?
As too good old hum;;
Make darn sure you watch the ground path for the heater as this can cause all sorts of issues if you get it wrong in the layout.

Keep Audio and heater ground on separate wires/traces until they meet at supply node is the best way I can explain that.
Phil.

[Niquel]

[quote="DarkRain"]Hello guys, log time no talk and i'm verry happy that FSB is back online (i rilly missed this comunity). In this whole time i've made some experiments with submini-triodes.
I've bought some 6n33b wich is a double triode with a maximum anode voltage of 100v and amplifiocation factor of 80 (very nice double triode IMHO).
The latest buid is a submini amp - 6n33b in preamp section and 6n16b in power amp, the OT is a Hammond 125A with 8k primary impedance - the power amp section is self split. The clean power is about 800mW and in at full blast is 1.2w - in a 1x12" cabinet with Celestion (spl 100db) is way too loud for hours over 22:00 and @ full blast is loud for any hour.

I will post the schematic here when i will have a little time to transcribe it in Eagle. Till then, some pictures and a sound clip recorded by a friend of mine (no postprecessing was done).

Hi there,
I konw it's an old thread but could you post some schmatics of this amplifier, please? specially about the split 6n16b output section. Is it the same schematic you posted for the 6N1P firefly?
I have already built a 2 x 6n17b hotbox with T-M-B tonestack fed by the Nixie SMPS giving about 240V B+ and I was thinking of plugging it into some kind of subminiature power amp class A using the 6n16bs I have on hand and the same PSU. I know that Va is much lower for 6n16b than 6n17b, but one of my question is about power consumption for the hole amplifier.
Any help will be welcome.

Thank You
Miquel

[Thomas_H]

Hi, it's not an overdrive, but a whole submini amp with russian tubes.
The preamp is based on JCM800 2203 with 6N17B tubes, and a big muff tonestack after the cathode follower.
The power amp is based on Dmitry's 5-tube push-pull Fender derivative, without the presence pot, and a 100k feedback resistor.
http://www.dmitrynizh.com/submini-vibro-reverb.htm
The SMPS is the max1771 circuit presented by Frequency central (FC amps are my inspiration).
The speakers are old 3W oval computer speakers, and the amp has an output for a bigger cab.
Power supply is 12V 2A. I made the amp as portable as possible, but using a small ptp layout.
My crappy cellphone camera is the only thing i have now, so, here are some videos:







Hope you enjoy!

Thomas

[Thomas_H]

Some pictures folks!





Thomas

[Thomas_H]

Hi you all,
finished a 1590b layout for this amp, take a look!


Until now it only has 73.4x44mm, without potentiometers, still some space for board mounted jack's.
It was NOT TESTED yet, that's why I'm accepting suggestions before I build this.
It probably has some noise, but after the JCM submini combo I think it's only a matter of tweaking the circuit layout/values/grounding.

Cheers!

Thomas

[caspercody]

Is your power supply regulated? If not, especially with tubes, this might be your source of hum.

[Thomas_H]

Hi,
I'm using a regulated power supply. I read some articles about SMPS layouts:
http://ecee.colorado.edu/~ecen5797/cour ... layout.pdf
http://cds.linear.com/docs/en/applicati ... an136f.pdf
and made some changes in my layout:


After some reading about PP output stages I tried to design a new power stage for the 6N16B based in optimal operation points.
A friend from another forum, Matec, ploted the load lines for the 6N16B tube using the Paint KIT V2 from here:http://www.dmitrynizh.com/tubeparams_image.htm

The Load lines for 150V, 180V, 200V and 230V are:





For 150V and 180V a 22k transformer was used, for 200V a 34k and for 230V a 44k transformer.
As the images show, the 180V 22k configuration, very close to the one I used in the first amp, runs the tube with a 0.8W dissipation to output 0.75W.
In this configuration a lot of heat is produced, and the tube's life is reduced. Matec suggested to use de 44k configuration, that has an output of almost 1W with a 0.7W plate dissipation.
To bias the amp the 1.2k cathode resistor will now be 2.2k, as 2*2.1mA*2.2k=9.24V, right?

To achieve this, i'm going to use the 4 ohms tap of my 22.5k transformer with a 8 ohms speaker, and change the SMPS trimpot to output 230V.
With the increase in voltage and impedance there is a decrease in plate dissipation, current consumption and an increase in output volume.
If you guys are using the russian subminiature tubes like I do, this small change will make the amplifier louder and cooler!

Cheers
Thomas

[Dirk_Hendrik]

So damn cute!!

[phatt]

I agree with casper cody, re reg supply.
I read some of those links and although it's useful it won't solve the hum issue on it's own.
You need to separate the Smode supply common from analog circuit common.
Ideally 2 separate boards or create two separate ground paths on the one board.
Having succeeded in building a hybrid circuit which uses a similar Smode supply for valve I found 2 separate boards easier and negates all the fuss of having to learn all the hidden problems smode can cause. I also used a LM 7812 to be sure of supply issues.

This might well turn out to be a simple case of ground path layout problems moreso than those complex issues in the links. checkout Valve wizards grounding issues pages and get the basics sorted first.

Anyway Great effort, sounded ok to me and no real evidence of bad hum, any hum will never be heard over good guitar playing anyway.. winky

Phil.

[Thomas_H]

Well,
SMPS and high gain preamp on the same board is asking for noise,
I'm thinking of giving up and starting another combo, have found new pc speakers, exactly like the first amp...

and made another video:



Cheers,
Thomas

[Thomas_H]

Hi,
finally did a comparison video between the PC speaker and a Celestion Greenback 12" for this sunminiature tube amplifier.

Unfortunatelly the mic is from a Nikon 5300.


Cheers

[Thomas_H]

Hi guys,
after some time a finnaly finished the head version, hope you like it




and during debugging:


cheers,
Thomas

[Peppercorn]

I LOVE it! any chance of getting the pcb transfers and layout for this old muso who'd just love to play a gig thru a small amp like that?

[Thomas_H]

Hi,
I have a pdf file with some information here:
https://dl.dropboxusercontent.com/u/104 ... ianJTM.pdf

and made some videos:





Cheers