need a lot help on an el34 project :P

[Ahmad_tbp]

hi all ..
i want to build a tube amp w 2 el34 for guitar and for the first time ... but i ll not find any transformer for input/output , here ...
i asked it once here but answers was too professional for me and honestly i couldn t understand anything from them .. so i ask it again and hope i understand this time :P ..
wat s the easiest way to wound the transformers ? wat exactly i need and i have to know ?

[cerrem]

Hi..
I take it you would like to wind your own Output Transformer????
Designing it and winding it can be a bit tricky at first....
Since it is for guitar amp, you can then get away with a lot more than in Hi-Fi application....
I will spare you any heavy math and analysis...
I can provide guidelines for a "quick and dirty" transformer.....
For 50W 2-tube AB1 amp EL34 amp running roughly 400V to 450 Volts figure a plate load in the area of 3.2K to 4K .......
I would arbitrarily choose 3.5K plate load.....
From experience the core to use would be a EI lamination EI-125, use a square stack....this means using enough laminations so that the thickness of the transformer core is also 1.25" ......
For Core material try using a M-19 ......
AT 50W you get roughly 420V AC acrss the 3.5K primary.....this corelates to roughly 120mA of AC signal current..a safe primary wire gauge would be either AWG#29 or AWG#30, whatever fits best will do.... Next figure on the primary turns....Lets say you want to push the steel up 10,000 gauss at 50W at a certain low frequency I prefer for guitars...This equates to roughly 1700 turns...Give or take a 100 turns will vary flux density slightly..go for best winding fit...
use 115 turns for secondary 16 ohms...
Tap at 81 turns for 8 ohms....
I will leave the rest for you to figure out.....

Chris

[Ahmad_tbp]

hi Chris and thnx a lot man so lets collect wat i found out and understood from u :P ( sorry the biggest problem here s my bad english , i cant understand the expressions and technical words )
so for power supply i need a transformer to give me 400v to 450v ,and 120mA AC , i think thats not a big problem for me ...
but for output transformer ... i heard that the size of core ,the material of core and wires r important for the quality of sound , yeah ?
and for output transformer , i need a core w 1.25" thickness ... and u said for material use m-19 , wats m-19 , and wat if i don find it ? can i use any material ?
and guage of wire for primary should be awg#29 or #30 ( wats awg ??? material of wire ? )and i need 1700 turns ,and for secondary i need 115 turns for 16 ohm output and tab on 81 for 8 ohm , yeah ? ( use same wire for secondary ? )
sorry man , i completely virgin in tubes and transformers , sorry if i ask some silly questions , i ll be soooo thankful if u help me build my amp ...
i have a few questions ;
1-wat s a 3.5K plate load transformer ? :P its for supply transformer yeah ?
2-wat s EI lamination EI-125 ? it should be the material of the transformer ?
3-and wat s the diameter of transformer ?
4-wat informations exactly i need to know and give to a local transformer wounder to wound my transformer ?

and one thing i forgot to mentioned s i wanna build a bass guitar amp if it helps ...

[kathodyne]

why do you so desperately want to wind the transformers if this is you first amp?!?!

you would be way better of starting with bought, or salvaged transformers......
Then try to understand what is happening........, trying to change things and see if the results are what you expected.....

use the internet for getting stuff, rather than electronic shops....(yeah some shops are good, but most only have stuff in the ratings for SS )

google, or maybe people over here can point you to some nice vendors...

If you like some learning material for tube gear (also most of the quistions of your last post are answered here.....)

http://www.audioxpress.com/resource/...lass/index.htm

designing and winding a transformer is a sort of art with a lot of variables and also the schematic 'hanging' in front or behind it determine a lot of things in the equations.....
then the physical construction and the different winding techniques.....
just not something 'just do it, and hope for the best' and remember 450v IS a killer.

I hope you don't hate me now , and of course this is just an advice....

[Ahmad_tbp]

thnx kathodyne ..
but the problem s i can t buy anythin online , cuz there s no international credit card here , and there s no site that shippin to my country ... and it s becomes toooooooooooo expensive for me if i wanna order a company or someone to bring a transformer for me and i couldn t find any salvaged or used transformer for tube here ... i just searched a lot and a lot and was very happy when i found these two used el34 from a marshall amp that its transformer was corrupted !!!
and i ll be very thankfull if anyone help me build a transformer for it ...

[SY]

The good news is that if you're doing this for a bass amp, the bandwidth isn't terribly critical. The bad news is that winding a transformer is still not easy.

One thing you may want to consider is salvaging a power transformer with the right turns ratio and trying it as an output transformer. For example, if you can find a power tranny with dual 120V primaries (often in equipment meant to be used both in Europe and the US) and a 12V secondary, that might be pressed into service. The dual primaries are put in series (watch the phasing!), with their junction acting as the center tap.

[Dominique_free]

You must be aware as finding good laminations for an output transformer can be as hard as to find a good output transformer.

A thing you can try, is to use the lamination from the marshal amp. If it is not easy to deconstruct it without breaking the lamination, it must not be impossible.
After you have removed the lamination, it become easy to deconstruct the coils inside the transformer and to count the number of turns for each winding, how they have implemented those winding, and where the have put isolations sheets.

You will not get the best possible transfo by doing this, but you will get a much better transfo as the one you will get with laminations designed for main transformers.

[Bas Horneman]

Are you looking for a Single Ended (SE) or Push Pull (PP) output transformer for your guitar amplifier.

Or let me put it otherwise. Do you need a lot of power? How big are the parties you play guitar? Or is it just for a practise amp?

Regards,
Bas

[Ahmad_tbp]

hi , thnx for replies and sorry for delay ...
i don have the whole marshall head , i just bought the el34s , the whole amp was completely in a very bad situation ,... i saw the transformers , and it seems someone was already opened it and make it completly unusable ...
and how much power i need ? mmm .... not that loud , between 35 to 50w will be enough for me , i want this amp for practicin w guitar players in my room ,,,
and i already have a transformer w 120-0-120 primary and 12-0-12 secondary ... can i use it as a output transformer ???????

[Bas Horneman]

30-40 Watts ok..That means PushPull.

Mail me your address and I'll send you a 6K UL output transformer for free.

Regards,
Bas