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EL34 Baby Huey Amplifier

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Joined 2014
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OK i think my plan for DC heaters is developing.
Most likely going Edcor for the OPT's but still struggling to find a power transformer. Edcor will do a custom one 275V @350mA and 60V @ 100mA for $60 but require a 1 time setup fee of $180. Maybe they would waive the fee or reduce it if a few people ordered one.

Hello cjkpkg,

Check out the Toroidy TSTA0250/001, its just about perfect for the Baby Huey.
Shipping is a bit high but, I feel a better solution than the Edcor.

TSTA 0250/001 - Mains transformer for tubes - Shop Toroidy.pl
 
Hello cjkpkg,

Vunce is right, the TSTA0250/001 is much more convenient for this amplifier than two transformers. In addition the H-PS1 will not give you enough current to power heater of a push-pull of EL34, only 2.5 A and you need 3.3 A minimum ( 2 x 1.5 A + 0.3 A for the ECC83) :mad:

Beside that the Antek 50 VA will not give you enough current also, only 4 A if the two 5 V winding are in serial !

Finally all that will cost much more, and you have to take more powerful components to fit your requirement, than the solution presented on post 15 and you will have to fit two transformers and two regulators in your chassis...

Why to make it complicated when you can do it easily ?

Marc
 
OK just ordered the Toroidy - I didnt realize that it also had the on board 50V secondary as well...

Just need to finalize how to get to DC heaters - which path to follow.

Just wanted to know how much it costs you incl shipping, also did you order it directly from Toroidy or from the distributor in the US? I am also struggling to find a suitable power transformer locally without selling my kidneys. May be Marc can recommend one from Hammond which is more readily available locally.
 
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Hey Vunce

Have you hooked up the transformer yet?

I am curious if we get a little more voltage on the 6.3V windings since it looks to be configured for 115V. I pretty consistently get 120V at my house - maybe a little higher.

115/120 = 1.0435 X 6.3V = 6.57V X 1.41 = 9.26VDC - 2V for rectification = 7.26VDC "regulated" if i use the Broskie/Tubecad H-PS1's. That could just maybe get me enough headroom to not have to wire in series for ~12.6V to rectify back down to 6.3V.

If this is "true" then I think all I need to do to make the H-PS1 work is a higher rating (5A) regulator LM338 and higher wattage resistors to set the voltage and a suitable heat sink on the regulator.

If my math is right using that "Buck" DC/DC converter is only getting fed 5A using 2 of the 6.3V windings. Wired in series you only get the available 7A less 2 after rectification so you only have 5A available to the buck converter for both channels which need at least 7.

Now I dont really understand how the buck converter works so someone correct me if my assumptions are wrong.
 
I ran my heaters using 6.3Vac with great success.

one channel with absolutely no hum present, the other channel only very slight hum with my ear next to the speaker woofer.

My DC heater board arrived, but i did bother to put it into the BH amp, coz its totally acceptable performance to me running heaters in AC mode.

Try it while you awaiting for your dc/dc heater converter to arrive...You may like it too.
 
Hi cjkpkg,

If you want to go the 6.3 VDC way, the best solution (that I am also using) is to use a DC/DC 10 to 20 A converter like the one on the picture, with the two 6.3 VAC 7 A in serial = 12,6 V x 1.4 = 18 VDC, and if you take 2 V for the bridge you will have about 16 VDC on the DC/DC converter. With this input voltage it will have a good efficiency and you will have only 7 to 8 W dissipated in the bridge instead of 15 W at 6.3 VAC :)
 

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@ silvercosworth & bandol83,

silver cosworth, could you show how you have this wired.

@ bandol83, is running heaters in AC a recommended practice for tube amps.

Newbie trying to get it right,

Thanks,

Myles

DC is "typically" quieter - less chance for hummm buzzz interference VS AC. AC is doable and more "practical" since you can feed right off the transformer with a typical 4-7 Amp 6.3V winding per channel.

The problem is that getting 3.5A DC power per channel is a challenge but not "unsolvable".

I was thinking that another revision of this board should have jumpers for the heater circuit to be able to feed it 12.6V by running the power tube heaters in series VS parallel. Look at any Tubecad/Broskie Aikido board - they all have this feature...pretty slick...since you can power the 12AX7 with 12V.
 
@ cjkpkg,

You should not think about DC/DC switching converter like linear regulator, in a switching converter efficiency is very high, about 85% to 95% and even if the input voltage is high you don't dissipate a lot because at a similar power level on input and output the current on the input will be a little more than half the current in the output if the voltage in the input is twice the voltage in the output :) In our case you need about 7 A under 6.3 V and you will consume less than 3 to 4 A on the 15 V input.

@ Kokanee,

Heater can be powered in AC or DC, in the past it was too expensive to make DC and most tube amplifier used AC, now it will be a pity not to take advantage of cheap semiconductor technology when it can help to run tubes in the best condition like solid state rectifier and current source by example :D

@ Vunce & LKA

Thanks for the links :cheers:

Rgds,
Marc