Classic amp topologies made with submini tubes

[Taylor]

I'm in the middle of building a submini tube amp based on FrequencyCentrals [http://www.diystompboxes.com/smfforum/index.php?topic=78302.0]Superfly[/url].

I am a total noob with tubes, but I'm wondering if it would useful to do the same conversion with other amps that people like, similar to the tube-to-JFET conversion at Runoffgroove.

What sort of changes would need to be made to something like a Deluxe Reverb to use subminis instead of full-size tubes? Would copying the topology make for something pretty close in sound, or do the subminis inherently sound different from standard tubes?

I've seen the Submini Wreck, but am wondering about other classic amps.

[wavley]

I think that this is an awesome idea!  I don't have any experience with sub mini tubes, but I do have some decent experience with regular tube amps.  I think that it might be a good idea for me to do a sub mini copy of one of the amps that I own and compare the sound.  I have a Traynor Bass Mate and a Kalamazoo Model One that would both be fairly easy to copy, I been looking for a reason to try sub mini tubes and I think this is it!

[frequencycentral]

http://www.dmitrynizh.com/submini-vibro-reverb.htm

[Taylor]

I think that this is an awesome idea!  I don't have any experience with sub mini tubes, but I do have some decent experience with regular tube amps.  I think that it might be a good idea for me to do a sub mini copy of one of the amps that I own and compare the sound.  I have a Traynor Bass Mate and a Kalamazoo Model One that would both be fairly easy to copy, I been looking for a reason to try sub mini tubes and I think this is it!

That would be awesome; I'd love to find out how these subminis compare to their big brothers in a fair comparison.

http://www.dmitrynizh.com/submini-vibro-reverb.htm

Whale Oil Beef Hooked! Awesome, thanks.

[puretube]

Puretube shooting at small tubes... :





German-lesson: "Röhre" = tube;
                        "Röhrchen" = small tube;

[sean k]

I love Dmitry's page and it's wealth of information... but it'd be absolutely beautiful if the man had put in the specifics of the transformers he has used as well as the power supply requirements.

I recently learned something that is basic ohms law which states that the anode resistor to ground will give you the current required and that has made it easy to get the approx current needs for each stage, given the voltage is at the top of the anode resistor. That simple equation solves a bunch of problems with schematics like this but then we still need to be able to figure out what kind of transformers he is using for output and reverb duties. But then if we look at the bottom of the page I suppose we could guesstimate about 15mA at 230V which is about 15k but then by my reckoning we'ed want to bias the cathode at 5V at 5mA and that equals a resistor of 1k.

So, indeed, a very useful page. I'll be book marking that one.

And if one looks at merlins page (the valve wizard) hes got a bunch of reverb drivers that can be used with higher impedance tanks so one can bypass the reverb tranny using a single dual triode as a driver.

But, for myself, the beauty of full size tubes, is the amount of room available and the whole point to point thing which takes me away from PCB's and into a realm altogether different in space and scope. But who knows!

[Brymus]

Here is a mini Train Wreck (using sub mini tubes) built by Dana (UR12 at 18watt and SE and PP watt) it sounds amazing.
http://www.ppwatt.com/node/16013
It was this thread that got me interested in sub mini designs then google found Ricks over here at DIY stompboxes.
He (Dana) also has a thread at amp garage on the micro wreck ,both places require registering to view,(no biggie if your interested in tube design)
I have seen several others basically scaled down versions of classic amps using sub minis.
When and as I remember them I will post links here.

[davent]

A couple more sub-mini amp ideas.

http://www.jjs.at/electronic/index.html

dave

[Brymus]

This page has a nice list of sub mini projects from around th eweb including the ones we already mentioned.
WHAT SUX is that sub mini Princton PDF is missing all the pics and schematics 
I have the Powerman bookmarked I had forgot about it.
But ALL of the Harmonic Appliances projects are top shelf stuff !! Listen to his song High Tide.
What should be a big plus to you guys is all the schematics and data sheet links 
http://amps.zugster.net/projects/subminiature

[Taylor]

I guess to pull the focus of this question back a little, I really am just interested in how subminis differ from full-size tubes. I'm wondering: what changes need to be made in general to adapt a circuit designed for other tubes to subminis?

[John Lyons]

Some submini tubes are just lower voltage versions of the more common high voltage amplifier tubes.
Make a lower power supply and the rest of the preamp/signal chain values would be the same I would think.

John

[Ripthorn]

Depending on the type of tube, there are really very few things that matter.  For a triode, mu is the most important, then there are things like transconductance, etc. that are secondary concerns.  For a power tube, you have transconductance, load resistance, output power and maybe a few other factors.  If you can match the values between submini and regular tubes, then there shouldn't be much of a difference sonically, if any.  I am going to do a submini JCM800 after I get a little more settled, though I also plan to do a submini Mark IV preamp and a submini deluxe reverb preamp at some point.  Tubes are tubes, they operate on the same physical principles regardless of package.  It is similar (though not identical to) SMD and through hole components.  Of course, the differing plate voltages and such will change, so you might want to play around so that you get plate voltages that lie at the same point on the characteristics graphs as those for a regular tube (i.e., try to find a similar response characteristic and the plate voltage that produces it as opposed to trying to straight up match voltages or simply maxing voltages).  Hope that made sense.

[Taylor]

Thanks guys, that's the sort of info I'm interested in.

[thomasha]

Hi, I see this topic is dead, but I just finished my submini JCM800 with a Max1771 SMPS.

I used the 2203 preamp schematic and 6N17B russian tubes,
and the 5-tube push-pull Fender derivative power amp  from http://www.dmitrynizh.com/submini-vibro-reverb.htm with the 6N16B russian tubes.

The tubes are running at 200V obtained with the Max1771 SMPS developed by Frequency Central, i just made another layout to fit between both computer speakers that I'm using.

OT  has a 22.5k primary.

I made a small PTP layout on a PCB. I'm using a BMP tonestack after the cathode follower and a master volume. I also made another output to uso a bigger cab.

Power supply is 12V 2A.

A made some videos with the cellphone camera:

Hope you enjoy!

Thomas

[kingswayguitar]

i think that sounds pretty darn good!!

[amz-fx]

Sub-mini Princeton 5F2-A

http://courses.physics.illinois.edu/phys406/Student_Projects/Spring01/JWicks/5F2-A_Micro_Princeton_Schematic.pdf

regards, Jack

[thomasha]

Well, I'm still trying to make this JCM in a 1590b,
so I will add some material...feel free to make suggestions
Schematic without SMPS

SMPS: http://www.desmith.net/NMdS/Electronics/NixiePSU.html

Layout with SMPS with 73.4x44mm size


Tone circuit soldered direct to the potentiometers, there is space to use board mounted jack's, but I prefer this way...
This layout is still NOT TESTED, but the circuit is the same from the videos, I just need to verify how noise his layout will be.

Cheers
Thomas

[easilyamused]

Oh no... Just what I needed to see. My submini Class AB amp (6112, 6021, 5902, 5902) project is nearing the smoke test point. I'll share the OSHPark board if it works out ok... So now I have a couple of new projects depending on how long this thread gets!

[thomasha]

Hi,
some updates:
I read some articles about SMPS layouts very interesting to reduce noise issues:
http://ecee.colorado.edu/~ecen5797/course_material/layout.pdf
http://cds.linear.com/docs/en/application-note/an136f.pdf
and made some changes in my layout, as the separated ground, smaller terminals for the sensitive points:


Another change came from some reading of PP output stages. I wanted to calculate the load line for the 6N16B tube and Matec, from another forum, plotted the load lines for various voltages and impedances:





As you can see running the amp at 180V and the 22.5k transformer could be dangerous, a better configuration is the 230V with a 44k transformer.
It's easy to use the 22.5k transformer with the 4 ohms tap to obtain that impedance.
The new cathode resistor now is 2.2k instead of 1.2k as 2*2.1mA*2.2k=9.24V, very close to the 9.1V specified.

Before I start this new build I will recalculate each stage to verify the operation points. Next stage will be the PI!
Cheers
Thomas

[Philippe]

are those 'sub-mini' tubes similar to the ones used on the z-vex nano head? if so, they can be a real pain in thes ass to change as most were designed to be soldered in. the thin leads have to be perfectly straight in order to fit properly into the tube socket & it usually takes several attempts, one of the primary reasons I opted for the rock block...it uses standard pre-amp tubes (i.e. 12ax7, ecc99 etc.) & has far more clean headroom than the z-vex which is little more than a glorified fuzz pedal running on russian satelite tubes.