Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kagliostro on May 29, 2012, 10:23:20 am

Title: 5c1 with 6au6 & 6aq5 - can I use a 6x4 as rectifier ? 310v AC are enough ?
Post by: kagliostro on May 29, 2012, 10:23:20 am

I think I can build a 5c1 champ using 6au6 in place of 6sj7 and 6aq5 in place of 6v6

can I use a 6x4 as rectifier tube in place of the 5y3 ?

the 70mA of the 6x4 are enough for the 5c1 ?

310v AC (80mA) are enough ?

Thanks

Kagliostro

Title: Re: 5c1 with 6au6 & 6aq5 - can I use a 6x4 as rectifier ? 310v AC are enough ?
Post by: kagliostro on May 29, 2012, 01:06:38 pm

So it will be better I go a step back and build it with SS rectifier (as you told, no 5v winding, if I don't find one other PT)

Kagliostro

Title: Re: 5c1 with 6au6 & 6aq5 - can I use a 6x4 as rectifier ? 310v AC are enough ?
Post by: kagliostro on May 29, 2012, 01:19:57 pm

I've find this, but don't know if this can be mod as guitar amp without heavy mods

http://www.retrovox.com.au/03556AQ5.pdf (http://www.retrovox.com.au/03556AQ5.pdf)

Kagliostro

Title: Re: 5c1 with 6au6 & 6aq5 - can I use a 6x4 as rectifier ? 310v AC are enough ?
Post by: sluckey on May 29, 2012, 01:21:37 pm

The 6X4 can handle 70ma of dc current which should be plenty for a 6AQ5 and 6AU6. All three tubes can be heated from the same 6.3VAC winding.

Title: Re: 5c1 with 6au6 & 6aq5 - can I use a 6x4 as rectifier ? 310v AC are enough ?
Post by: kagliostro on May 29, 2012, 01:24:59 pm

Thanks Sluckey

Kagliostro

Title: Re: 5c1 with 6au6 & 6aq5 - can I use a 6x4 as rectifier ? 310v AC are enough ?
Post by: DummyLoad on May 29, 2012, 01:36:12 pm

6au6 in place of 6sj7 and 6aq5 in place of 6v6

yes.

can I use a 6x4 as rectifier tube in place of the 5y3

with 6AQ5 idle set to 9W with 310V you'll need ~35mA + screen and pre-amp - another 8-10ma worst case.

yes.

it's class A single tube. ditch the vacuum recto and go SS - you won't notice any diff. in tone, however, with SS recto, you can kick up the filter size considerably and improve audible PS "buzz" at idle.

--DL

Title: Re: 5c1 with 6au6 & 6aq5 - can I use a 6x4 as rectifier ? 310v AC are enough ?
Post by: kagliostro on May 29, 2012, 01:46:52 pm

Hi DummyLoad

thanks for clarifications

my transformer is 310v AC is this too high if rectified SS ?

K

Title: Re: 5c1 with 6au6 & 6aq5 - can I use a 6x4 as rectifier ? 310v AC are enough ?
Post by: jjasilli on May 29, 2012, 01:56:48 pm

My quick research shows that 6X4 & 5Y3 both max out at 10uF for the 1st filter cap.  I suspect, but cannot prove, that such a low value contributes to overall muddy tone.  Personally, I would keep the tube recto > 10uF cap "pre-filter stage" > dropping resistor > say 40uF "1st filter stage" > plate, etc.  The dropping resistor's main function is to isolate the "pre" from the "1st" filter stages.  It's value could be chosen to precisely target your desired plate voltage under load.

Title: Re: 5c1 with 6au6 & 6aq5 - can I use a 6x4 as rectifier ? 310v AC are enough ?
Post by: sluckey on May 29, 2012, 01:58:06 pm

SS will yield 438VDC unloaded. That PT is probably too high for the 6AQ5 even with a tube rectifier.

Title: Re: 5c1 with 6au6 & 6aq5 - can I use a 6x4 as rectifier ? 310v AC are enough ?
Post by: kagliostro on May 29, 2012, 02:05:34 pm

Thanks JJasilli & Sluckey

I think I'll go for one other PT

K

Title: Re: 5c1 with 6au6 & 6aq5 - can I use a 6x4 as rectifier ? 310v AC are enough ?
Post by: jjasilli on May 29, 2012, 03:00:12 pm

Another solution is a 12V bucking transformer.  It should knock the wall voltage down by 12.6V.  The PT converts 120VAC in, to 310 out.  310/120 = a factor of 2.583;  120VAC - 12.6 = 107.4VAC X 2.583 = 277VAC X about 1.1 conversion factor for the little bottle tube recto = 305VDC!!! Not bad, especially if dropping resistor is added (per above post).

Title: Re: 5c1 with 6au6 & 6aq5 - can I use a 6x4 as rectifier ? 310v AC are enough ?
Post by: DummyLoad on May 29, 2012, 06:19:06 pm

OT source:

http://www.tme.eu/html/EN/speaker-transformers-for-vacuum-tube-amplifiers-tgl-series/ramka_7135_EN_pelny.html (http://www.tme.eu/html/EN/speaker-transformers-for-vacuum-tube-amplifiers-tgl-series/ramka_7135_EN_pelny.html)

PT source:

http://www.tme.eu/html/EN/mains-transformers-for-vacuum-tube-amplifiers-tsl-series/ramka_7134_EN_pelny.html (http://www.tme.eu/html/EN/mains-transformers-for-vacuum-tube-amplifiers-tsl-series/ramka_7134_EN_pelny.html)

go to direct to manufacturers transformer website

http://www.indel.pl/gb_sp_prod.html (http://www.indel.pl/gb_sp_prod.html)

Title: Re: 5c1 with 6au6 & 6aq5 - can I use a 6x4 as rectifier ? 310v AC are enough ?
Post by: kagliostro on May 30, 2012, 12:36:12 am

Very interesting link

Thanks DummyLoad

K