Rocket / Liverpool EU power transformer advice

[vladivlado]

Hello dear Trainwreck aficionados. Thank you for accepting me to the forum.

Would you please help me with choosing a fitting power transformer for a Rocket / Liverpool inspired project?

I have been searching online and I have managed to find these two:

Elettronica Novarria (Italy)
280–0–280 V @ 250 mA
two lines of 6.3 V @ 4 A
5 V @ 4 A
(I am thinking about using 5U4G instead of 5AR4)

Piemme Elektra (Italy)
240-0-240 @ 240mA
6.3 @ 2A and 6.3 @ 4A
(with a SS rectifier, this one has a 220V tap as well - might be able to get 250V out of it with 230V from the mains)

BTW, both manufacturers make their own version of A-470 output transformer as well (one is 4,3kΩ and the other one 4,4kΩ) - just mentioning - might be helpful for other European members.

I think that both power x-formers could work. According to your experience with Trainwreck amplifiers, which one would you choose? Will 240mA be sufficient? I know that 300mA is recommended.

Thank you very much.

Greetings from Slovakia.

Vlad

[joeboo88]

Hi. If the tranny people build in overhead. They might do.

You need 4.03A for 4 power tubes and 3 pre amp tubes. For the heaters
https://thesubjectmatter.com/calcptcurrent.html
Or use a calculator you like.

I have a dual tap PT for my Rocket sound better on the 280 tap than the 250 tap.
I also have a Liverpool and am running 275 0 275 and it sounds great
Both my PTs are Pacific for my Rocket and Hammond for the Liverpool and both have 5 amp taps.

Good luck

[vladivlado]

Hi. Thank you for your input. According to the description on the manufacturer's page the x-former should have two separate individual taps of 6,3V @ 4A - I could use one tap for the preamp heaters and the other one for the el84s. I will ask them to send me a datasheet. If my assumption is confirmed, I will go for it. I will still have the option to swap the 5AR4 rectifier for 5U4G later to try if I like it with a slightly lower B+. Are your transformers also rated 250ma or similarly? Don't they warm up too much? Have a nice evening. Vlad.

[pdf64]

Properly designed power transformers intended for use with a valve rectifier might be expected to get hot. Due to their inclusion of an adequate degree of supply impedance / protecting resistance.

[joeboo88]

Hi Vladivado
the PTs I have have ample current on them, they don’t get hot that I know.
I tried a 5u4 in my Rocket and it seems to add even more bass to a very bassy circuit, and I have a gz34 in it now.
Each rectifier type will drop different values of voltage.
They are great amps, good luck with them.
When I went to build I looked at a lot of posts to get an idea how others have built theirs
Here’s a link to mine... I since bought a great cabinet for it...

http://ampgarage.com/forum/viewtopic.php?f=1&t=30697

[vladivlado]

Thank you joeboo88. I have already read some of the other threads and posts. Always a lot to learn and discover. Your amplifier looks nice. Very neat. Vlad.