Unknown SE EL84 amp schematic...

[eschertron]

Excellent! Thanks immensely for the follow-up. Sounds nice, low noise... can't really ask for more than that for a first build.

[Dr. Tube]

I made that amp, but i modified the schematic a little bit, removed a power transformer (that dual 220V transformer), i know its not safe but, what can I do... because i live in europe i used the direct 220V faze from plug with full-wave rectification 1N4007... Made a preamp section a little bit "deeper" and added alittle bit more distortion, great build... i would recommend it to anyone... Reminds me of 1956 Knight EL86 amp... thus its great even for veteran builders or rookies... lol it does not have the stomp or "stop" as fender Showman TFL's have but its exeptionally nice... HAHAH and one thing... i didnt have the money for the Output trafo so i used a big 220 to 6v transformer... aded some resistors to not blow the speakers out of the cabinet... yup i damaged the ohmage... but it works just fineee... Sweet sounding

And for the ones who asked seeing the rig in action, i added 400v 47uF cap on the beginning to raise the plate voltage and have more distortion, but all others are 350v 47uF... Plugged my SG to it... Jesus that thing rocks...

[Dr. Tube]

Keep in mind that i am 13yr old and I am not still quite sure what am i doing lol...

[g1]

i used the direct 220V faze from plug with full-wave rectification 1N4007...

Direct AC from the wall into a rectifier without a transformer is strictly forbidden.
None of us would be pleased to find out about a 13yr. old casualty due to ignoring safety precautions.

[Enzo]

When you are working on that circuit, there is absolutely NOTHING between you and the full current of the mains coming out of your wall outlet.

[Dave H]

I made that amp, but i modified the schematic a little bit, removed a power transformer (that dual 220V transformer), i know its not safe but, what can I do... because i live in europe i used the direct 220V faze from plug with full-wave rectification 1N4007... Made a preamp section a little bit "deeper" and added alittle bit more distortion, great build... i would recommend it to anyone... Reminds me of 1956 Knight EL86 amp... thus its great even for veteran builders or rookies... lol it does not have the stomp or "stop" as fender Showman TFL's have but its exeptionally nice... HAHAH and one thing... i didnt have the money for the Output trafo so i used a big 220 to 6v transformer... aded some resistors to not blow the speakers out of the cabinet... yup i damaged the ohmage... but it works just fineee... Sweet sounding

And for the ones who asked seeing the rig in action, i added 400v 47uF cap on the beginning to raise the plate voltage and have more distortion, but all others are 350v 47uF... Plugged my SG to it... Jesus that thing rocks...[ATTACH=CONFIG]43334[/ATTACH]

This has to be a troll. Nobody could be that stupid.

[Dr. Tube]

Okay! Thanks for reminding me, really, I was stupid to build it whitout Isolation transformer... I knew before it wasnt safe but, I thaught if old radios and old Gretsch and Knight amps had no Power tr. That i could build it... Look up on youtube: Alamo Dart; restored from death" A video made by uncle doug... That amp has no Power tr. Anyways thanks, i made myisolation by connecting two toroidal transformers... They re not autotransformers, but they isolate... Primary:220v sec:12v to secondary of transformer no2... And there it is... Much safer, i watched a yt video how to make isolation circut... And that popped up, luckily i had 2 toroidals, same voltage and same amperage...
Does somebody know where to buy 220v isolation transformers... I have a little bit of a problem with money and I cannot afford a fancy 325V transformers for big amps... Thanks for reply

[Dr. Tube]

Okay... I was really stupid, now I added a Power Transformer, i hope i am safe now, I dont know a whole theoretics of tube amps but i know I can do something... That was really stupid of me, i thaught i will save the money that way... Yup... Thanks again for pointing me to right direction, and amp even sounds beter isolated. But there were amps whitout PT like the Alamo Dart from 1965, look it up on youtube and google

[eschertron]

Okay... I was really stupid, now I added a Power Transformer, i hope i am safe now, I dont know a whole theoretics of tube amps but i know I can do something... That was really stupid of me, i thaught i will save the money that way... Yup... Thanks again for pointing me to right direction, and amp even sounds beter isolated. But there were amps whitout PT like the Alamo Dart from 1965, look it up on youtube and google

I recently did some refurb to the bathroom in our house. Basically just replacing one part of a system requires the whole system to meet code. Vacuum breakers, larger size drain pipes, all that had to be added in order for the county to allow me to do the work. Same with electronics. As safety regulations evolve, so do our techniques to meet those regs. A professional tech would not (could not, by law) release a repaired piece that doesn't meet today's standards.
It's not just a good idea, it's a human life.

[Leo_Gnardo]

But there were amps whitout PT like the Alamo Dart from 1965, look it up on youtube and google

Yes, we know. We warn people about their "widowmaker" finds all the time, not a week goes by without one.

Does somebody know where to buy 220v isolation transformers... I have a little bit of a problem with money and I cannot afford a fancy 325V transformers for big amps.

Transformers are cheaper than coffins. You're in Europe? Mouser and Element 14 have huge parts selections, parts of allsorts, including power and iso transformers to suit your needs. There's a couple of smaller companies that focus on guitar amp repair & builders too, TAD for instance. I'm sure other MEFsters will ring in with their suggestions.

[Dr. Tube]

In the schematic that abram posted, 12AX7 is biased with 1.5 kOhm resistor and a 25v 25uF cap... That cap was not in the original schematic

... and can someone tell me the value of EL84 bias cap, it says 100uF... but how many volts? I had a wild guess and soldered a 100uF 100v cap...

[Dave H]

... and can someone tell me the value of EL84 bias cap, it says 100uF... but how many volts? I had a wild guess and soldered a 100uF 100v cap...

100u 100V will be fine. The cathode voltage is only 10V or so.

[Dr. Tube]

And if somebody could tell me is it ok to use 12v PT as an output transformer(and could it be the cause of hum in my amp) I know that current saturates inside EI iron... But if its grounded...? So i saw that people in history used cca 6-24v toroidals in Hi-Fi amps, but is it okay for this SE amp?

[Dave H]

So i saw that people in history used cca 6-24v toroidals in Hi-Fi amps, but is it okay for this SE amp?

I wouldn't try to use a toroidal PT as an output transformer in an SE amp. Toroids don't have an air gap and will saturate with the DC current of a single ended output stage.

[abram]

i concur with Dave here. also, the purpose of the output transformer is to match the impedance of the output tube (which is usually a few k-ohms) and match it to that of a speaker (4-16 ohms typically). voltage transformation is inversely proportional to the turns ratio, but the impedance ratio between the primary and secondary taps is the square of the turns ratio. in a 120V-12V or 220V-12V PT, that's a pretty poor match which makes for wasted power. it could also put undue stress on the output tube and maybe even result in oscillations. probably best to just look for an output transformer.

this is the one i wound up using in my build.
https://www.tedweber.com/w022905m