Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: frank57 on October 20, 2024, 12:43:33 pm

Title: Hammond 260E power transformer good for preamps?
Post by: frank57 on October 20, 2024, 12:43:33 pm
Would this 260e be good? https://www.hammfg.com/electronics/transformers/classic/260.pdf (https://www.hammfg.com/electronics/transformers/classic/260.pdf)
How important would lack of end bells and the VA rating be?
I might use it for a 2 x 12ax7 zen preamp from kevin O'connor.
but it looks like it has enough juice to do an el84 amp  as well.
Title: Re: Hammond 260E power transformer good for preamps?
Post by: mresistor on October 20, 2024, 12:52:47 pm
That PT will run 2 x 6v6/EL84 no sweat.  Could use for Princeton reverb or 18 watt type amp.


260E 80VA 450V C.T. @ 115ma.  5V @ 2A   6.3V C.T. @ 3A


No end bells   it would be OK mounted outside of a chassis    but it is certainly not as safe so should be protected for little ones fingers or your fingers     so in a cabinet would be best.,
Title: Re: Hammond 260E power transformer good for preamps?
Post by: Willabe on October 20, 2024, 02:46:58 pm
Would this 260e be good? https://www.hammfg.com/electronics/transformers/classic/260.pdf (https://www.hammfg.com/electronics/transformers/classic/260.pdf)
How important would lack of end bells and the VA rating be?

Why this PT?

Hammond has lots of PT's with end bells. Why not just get 1 with end bells on it?

Title: Re: Hammond 260E power transformer good for preamps?
Post by: Latole on October 21, 2024, 06:34:12 am
Why a so powerful transformer for only preamps tubes ?

'cause you have in hand ?
Title: Re: Hammond 260E power transformer good for preamps?
Post by: frank57 on October 21, 2024, 01:12:02 pm
Would this 260e be good? https://www.hammfg.com/electronics/transformers/classic/260.pdf (https://www.hammfg.com/electronics/transformers/classic/260.pdf)
How important would lack of end bells and the VA rating be?

Why this PT?

Hammond has lots of PT's with end bells. Why not just get 1 with end bells on it?
I'm not sure which route to go with this Zen Soldano style Preamp.
I'd like to have a CT for the 6.3 too.
Title: Re: Hammond 260E power transformer good for preamps?
Post by: frank57 on October 21, 2024, 01:13:47 pm
Why a so powerful transformer for only preamps tubes ?

'cause you have in hand ?
If I went the preamp route what would be a good little transformer for it?it's just 2 12ax7's. I don't see too many with a 6.3v ct on hammond unless you go bigger.
Title: Re: Hammond 260E power transformer good for preamps?
Post by: Willabe on October 21, 2024, 01:35:13 pm
I'm not sure which route to go with this Zen Soldano style Preamp.

What is a Zen Soldano style Preamp? From the OP, it's a Kevin O'Connor zen preamp.

Your not giving enough detail for us to answer you.  How many tubes, what tubes does it need to power?

1st you say 2 x 12AX7, then you bring up EL84 tube.

I'd like to have a CT for the 6.3 too.

Why?

You can use a faux CT.
Title: Re: Hammond 260E power transformer good for preamps?
Post by: Brownie on October 21, 2024, 02:16:11 pm
Check out the 290WX. It has enough juice for the 5G15 stand alone reverb unit. A couple of 100ohm resistors in a faux center tap for the heaters is often the quietest
Title: Re: Hammond 260E power transformer good for preamps?
Post by: mresistor on October 21, 2024, 02:49:45 pm
I was thinking more along the lines of Hammond 269AAX  with a SS recto.
Title: Re: Hammond 260E power transformer good for preamps?
Post by: frank57 on October 22, 2024, 02:31:49 pm
I'm not sure which route to go with this Zen Soldano style Preamp.

What is a Zen Soldano style Preamp? From the OP, it's a Kevin O'Connor zen preamp.

Your not giving enough detail for us to answer you.  How many tubes, what tubes does it need to power?

1st you say 2 x 12AX7, then you bring up EL84 tube.

I'd like to have a CT for the 6.3 too.

Why?

You can use a faux CT.
yes it's this thing here:
https://londonpower.com/electronics/high-gain-preamp/
I have it all done and it's just lying around.
2 12ax7 follows the topology of a soldano slo high gain channel but with more filtering.
Don't know if I can post it or not.
He does have a power supply for it, but it seems rather expensive:
https://londonpower.com/electronics/tube-preamp-power-supply/
 
If I went the preamp route, what is the best type of transformer for it?I was thinking 250v through a ss rectifer bridge and then a filter cap , a dropping resistor another filter cap, resistor  and into the b+ on the pcb.
how big would the resistors be for a faux ct? 3 watt?