[Tube] My new webpage about subminiature tube amps

[el84]

JJS !!!!!!!!! 
Class AB Subminiature Tube Guitar Amp --  GREAT AMp !!!!

I hope you will do same demo-sound ... I'm really interested 

Bye
Antonello

[km-r]

id rather have this thread in the members only section... 

[Auke Haarsma]

awesome!

And yeah...clips please if you can find the time!

[MartyMart]

Beautiful work on that from start to finish, well done indeed
I Also look forward to sound clips .....

[trevize]

the toroidal OT idea is brilliant! can't wait to hear samples of the pushpull amp!

[T_u_b_e]

As far as making a general knock-off of my nano head amplifier, someone already beat you to it a couple of years ago.

Me too 
Note how much more compact it is compared to the nano with it´s caps sticking up on top 



Regarding the power supply, which is close to what I also use....If not a complete coincidence I think that some credit to where the original design was found would perhaps be  appropriate
It is a nice supply but it has a lack of safety measures in the current state IMHO.

Very nice builds though  and fantasticly nice web pages.

[jjs]

There seemed to be quite some trouble while I was not online, but it's probably better not to touch that.

Regarding the power supply, which is close to what I also use....If not a complete coincidence I think that some credit to where the original design was found would perhaps be  appropriate
It is a nice supply but it has a lack of safety measures in the current state IMHO.

This is the first time I see your amp. So if it uses the same 555 oscillator and is tamed by zeners this is coincidence, indeed.
I must admit that the supply is not particularly safe in case the zeners fail and the amp does not draw current (most probably because a tube failed / is missing). Then the output voltage rises and may endanger the filter capacitors.  I said so on my page.
Another problem would be the oscillator failing. Imho this is the worst case scenario because it would constantly turn on the MOSFET, which means that the supply voltage is shorted to ground through the transistor and the inductor. Both will get very hot till the MOSFET dies of excessive heat.
The latter could be handled by addition of a fuse, the first only by pulse width modulation in the oscillator.

I think these issues can be handled if some care is taken. I know that I wouldn't let anyone without technical experience borrow this amp, something could go wrong and till he notices it is too late. But if you know what to look for, it should be fine.

Anyway I think this amp is in fact inferior to my second one in almost every ascpect, including sound and safety.

T_u_b_e: I like the shiny transformer. Did you polish it or is it actually chromed? I have tried polishing a transformer once but couldn't get a mirror finish. Couldn't totally stop it from rusting, too.

[vanessa]

Great work JJS! Very professional I do say!

There's a wealth of information about subminiature tube amps (on the web and in books). This type of engineering has been around for years and was at its peak in the late 50's for use in portable and car audio applications.

You can take that old portable (tube) radio that's collecting dust in Gandpa's shed and with a few tweaks make a very nice little practice amp out of it.

[T_u_b_e]

There seemed to be quite some trouble while I was not online, but it's probably better not to touch that.

Regarding the power supply, which is close to what I also use....If not a complete coincidence I think that some credit to where the original design was found would perhaps be  appropriate
It is a nice supply but it has a lack of safety measures in the current state IMHO.

This is the first time I see your amp. So if it uses the same 555 oscillator and is tamed by zeners this is coincidence, indeed.
I must admit that the supply is not particularly safe in case the zeners fail and the amp does not draw current (most probably because a tube failed / is missing). Then the output voltage rises and may endanger the filter capacitors.  I said so on my page.
Another problem would be the oscillator failing. Imho this is the worst case scenario because it would constantly turn on the MOSFET, which means that the supply voltage is shorted to ground through the transistor and the inductor. Both will get very hot till the MOSFET dies of excessive heat.
The latter could be handled by addition of a fuse, the first only by pulse width modulation in the oscillator.

I think these issues can be handled if some care is taken. I know that I wouldn't let anyone without technical experience borrow this amp, something could go wrong and till he notices it is too late. But if you know what to look for, it should be fine.

Anyway I think this amp is in fact inferior to my second one in almost every ascpect, including sound and safety.

T_u_b_e: I like the shiny transformer. Did you polish it or is it actually chromed? I have tried polishing a transformer once but couldn't get a mirror finish. Couldn't totally stop it from rusting, too.

You have certainly not got the design from me or my amp so no problem there  . I got the original idea or inspiration myself from a nixie power supply design that was available on the internet years ago. I thought that yours was so much alike it that you probably got the ideas from the same source but it is a pretty simple solution so anyone may come up with something similar I assume. There is a company selling a kit:
http://www.ledsales.com.au/kits/nixie_supply.pdf
It is not tamed by zeners hovewer but I think that monitoring the output voltage (voltage divider and trimpot) in turn controling a transistor switching the oscillator on and of is somewhat more clever design. That way you almost have a built in power scaling  and can trim the output voltage to what you like.
At least heat monitoring and/or thermal shut down should be a minimum for safety though.

Btw, I have just polished my transfomer. And yeah it will rust a lot if you not put some clear coat for protection on there 

Best regards 

[jjs]

Thank you for posting that link, if I had known about this I had definetly experimented with it. I will try it out (maybe at the weekend) and if it works good, I may change my page accordingly and give credit where its due. Every piece that makes this amp safer / easier to build / generally better is most welcome.

[T_u_b_e]

Thank you for posting that link, if I had known about this I had definetly experimented with it. I will try it out (maybe at the weekend) and if it works good, I may change my page accordingly and give credit where its due. Every piece that makes this amp safer / easier to build / generally better is most welcome.

You may have to adjust some components to handle enough current and improve filtering etc.

A very simple solution to some thermal control without adding or changing the circuit could be adding a small bi-metal switch which create open circuit of the the incoming 12V (12.6) at the (not  ) desired high temperature. They are available from 5-200 degree celcius.

Something like http://www.elfa.se/pdf/69/06937981.pdf

They are a bit big but perhaps small enough to be able to stuff one in there. It would probably also be possible to  put a resistor and a LED over the switch and have it lit as soon as the switch is open  . red alert 

Best regards


btw A thermal fan control is pretty simple to do also. No need for extra noise 

[zachary vex]

I use a chemical fuse, which works pretty darned well, and lights an LED if it becomes open.

[MetalGuy]

Just to note that my experience with MC34063 is it produces whistling which goes into the audio unless you make it go out of regulation.
It looks like the problem with most of these powers supplies is they can't produce higher current /like say 30mA/ without complications.

[britelite]

Very nice work. The amp's are wonderful projects but I am most impressed by the format you use describing the projects. The informational content and presentaion is excellent. Thank you.

Peace

[jjs]

I added some quick audio samples of the class AB amp to its project page, featuring me randomly hitting notes.

No samples of the other amp yet as I have it disassembled at the moment and am trying out the regulation from the Nixie pdf.
I will also experiment with selfresetting and temperature fuses.
Thank you for the suggestions!

I'm not sure about variable fan speed. I think that because of the steady current demand there is no room for less ventilation than there is now with the fixed fan speed. Only benefit could be at startup and also only for less than 5 minutes or so till the final temperature has been reached, I think.
Btw, it's interesting that the air flowing through the case makes more noise than the fan motor itself.

[John Lyons]

Those clips sound nice. It has a nice chimey sound to it.
I'd imagine that with humbuckers there is not much clean headroom as the single coil samples are a bit gritty.

Thanks for posting those.

John

[T_u_b_e]

I added some quick audio samples of the class AB amp to its project page, featuring me randomly hitting notes.

No samples of the other amp yet as I have it disassembled at the moment and am trying out the regulation from the Nixie pdf.
I will also experiment with selfresetting and temperature fuses.
Thank you for the suggestions!

I'm not sure about variable fan speed. I think that because of the steady current demand there is no room for less ventilation than there is now with the fixed fan speed. Only benefit could be at startup and also only for less than 5 minutes or so till the final temperature has been reached, I think.
Btw, it's interesting that the air flowing through the case makes more noise than the fan motor itself.

These fans comes in many flavors (speed etc). If the flow with the current fan is allready just about right there is not much you can do.
You can experiment and analyze how efficient your supply is. How much power is going in and how much is used by the amp. The rest is generating heat and there may be room for improvements.
I think that you will find that the switching on/off of the oscillator method (if sucessfull with your supply) will generate less heat than now.
The air must have enough room to escape on both "suck and blow"    side.
If there is a to small air flow area the noise will tend to  increase. I think that the noise level generally will be lower if the fan is sucking hot air from inside the case (blowing out) but this way may not necessarily be the most effecient way to use it.

Best regards / Bo

sorry for bad english and spelling errors..written in a hurry 

[MetalGuy]

To avoid the problems with switching supplies I started running my tube pedals on an external wallwart PSU based on a 250V/10mA, 12,5V/300mA custom made power transformers. This way you have a lot of free space left.  I'm using a PC grade 3 prong /0.75sq.mm each/ cable /H05VV-F, VDE0281 certified/ but I don't know whether this complies to any safety standards for mass production. Maybe Zvex should be more competent on this subject?

[frankclarke]

I love the webpage design as much as the amp. Great photos too. You have a knack for design!

[cox]

i'm looking a quite lot for the class A amp, and now that i understand better the switchmode power supply, i think i'm gonna build it!!

so, does anybody built this sucessfuly? there are any mods that i can apply to this? i like stuff with a lot of switches and knobs

thanks in advance