Firefly tube amp build running charge pump or 110v stepdown

[maiko]

I keep reading about the firefly being built with a charge pump running off 1044/7660  up to voltages running at 90V

the orginal shematic is b+1@ 265v b+2@ 220v and b+3 @210V   

will using a chargepump mean i 90 for all ??

Also i live in a country where the mains voltage is 220v .    Step down transformers are common and readily available pri 220v sec 110v  wouldnt this be better to use if 90v is enough to make the amp go.

Any help would be greatly appreciated

[Phoenix]

I'd still recommend decoupling between the various B+ nodes (B+1, B+2, B+3), the firefly is quite high gain, especially with the cascode boost, so you'd be inviting oscillation without it.
People already report many noise issues with this design, so don't make things harder for yourself by including more potential noise problems (beyond the one you're already adding by using a charge pump).
Just replace the transformer/rectifier with your charge pump circuitry.
If you'd like to keep the voltages higher for the B+2 and B+3 nodes, you can reduce the values of the dropper resistors and increase the values of the decoupling caps appropriately to achieve the same level of decoupling without as much voltage drop.

If you do try using a step-down transformer, make absolutely certain that it is an isolation transformer (completely independent primary and secondary). Most step-down transformers are auto-transformers because they are cheaper to manufacture and provide far superior voltage regulation, especially with light loads, but they do not provide galvanic isolation which is absolutely essential for safety.

[maiko]

Thank you for the reply and for pointing out about the autotransformer vs isolation transformer

i did a continuity check on it and boom it is infact a autotransformer so i wont,will not be using this at all.

[LightSoundGeometry]

I keep looking at these schematics and they look basic like a Rm with minimal parts ..yet I cannot get one breadboarded now in over 8 weeks worth of trying ..I bet i have 200 hours in breadboarding these

i did get the pentaboost working and my 70 v + but cannot get any further ...wtf is going on with me?

I perfed a rat clone so my perf is coming along nicely and its time to try the 6111 and 5672 tube amp again. i am reaching out to the community for help so i can keep my sanity. there has to be a error someplace I cant see or know about.

but good work man. I hope you have much better than I have had

almost about to spend the 250 bucks and just buy a working kit on pcb from tube depot ..but then that defeats the point of a real diy project

[maiko]

Tried the 7660 charge pump

Must have 30 diodes and 30 caps cascaded but only getting 20v+ dc or 50v+ac ( should it be ac or dc by the way ?)

What could i have done wrong.    my input supply is 9v

[Phoenix]

Tried the 7660 charge pump

Must have 30 diodes and 30 caps cascaded but only getting 20v+ dc or 50v+ac ( should it be ac or dc by the way ?)

What could i have done wrong.    my input supply is 9v

I think most people who've built small 12A*7/ECC8* amps like the Firefly with smps power supplies have used 12VDC inputs, so that the heaters can be powered directly from that supply, so that'll bump up your output voltage.

Also, it sounds as though your circuit is too heavily loaded (you're drawing too much current from the power supply), or you do not have adequate filtering (not enough capacitance). Your supply voltage may also not have enough current capability or be too high impedance and be sagging under load.

The output of your charge pump should be DC, but will have some ripple which will show up as AC on your meter (and it is, it's AC ripple imposed on a DC offset). Your meter may also be being confused by an unexpected waveform and not giving accurate results, an oscilloscope is a better tool for this job.
If you're reading 20VDC and 50VAC you've got over 60% ripple, which is far, far too much. For tube circuits we usually aim for at most 5% (less is better).

If you could post a schematic of what you've done, you'll get much better help, and the more detail you can provide (like what's your 9V source? A battery? A wall-wart? A bench power supply? What type of diodes are you using? What value/type of capacitors are you using?), the better.

[maiko]

Thank you for the reply sir.  Im basically using the layout by RG keen.

http://s69.photobucket.com/user/Valoosj/media/Voltagepump.gif.html

his choice of diode is 1n4001.    but since im planning to get the voltage up to 90v maybee ill try a 1n4002