Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: leevc5 on April 14, 2018, 09:57:17 am

Title: Two 5F1 output xfmrs- looking to build a modified 10 Watt ~5F1- xfmrs in series?
Post by: leevc5 on April 14, 2018, 09:57:17 am: With all the buying and building have come up with an extra 5F1 output xfmr. How to make use of it? Can I build an EL34 10 Watt amp and somehow wire two 5F1 output transformers instead of buying one big higher output transformer?
Title: Re: Two 5F1 output xfmrs- looking to build a modified 10 Watt ~5F1- xfmrs in series?
Post by: PRR on April 14, 2018, 02:28:36 pm: Yes.
Title: Re: Two 5F1 output xfmrs- looking to build a modified 10 Watt ~5F1- xfmrs in series?
Post by: leevc5 on April 14, 2018, 02:35:59 pm: Quote from: PRR on April 14, 2018, 02:28:36 pm
Yes.

How? like from what wire to what wire to what wire to what wire and the on the other side rom what wire to what wire to what wire to what wire.

You perhaps don't recognize me as the repeat doer of dumb mistakes that usually require someone to bail me out,
Title: Re: Two 5F1 output xfmrs- looking to build a modified 10 Watt ~5F1- xfmrs in series?
Post by: PRR on April 14, 2018, 09:36:32 pm: > what wire to what wire to what wire to what wire and the on the other side rom what wire to what wire to what wire to what wire.

What wires do you have?

Specifically: what TRANSFORMER(s) do you have?? Lots of different things are sold as 5F1 OTs.
Title: Re: Two 5F1 output xfmrs- looking to build a modified 10 Watt ~5F1- xfmrs in series?
Post by: leevc5 on April 15, 2018, 09:06:03 am: Here is a picture:
Title: Re: Two 5F1 output xfmrs- looking to build a modified 10 Watt ~5F1- xfmrs in series?
Post by: PRR on April 16, 2018, 12:21:11 am: Quote from: PRR on April 14, 2018, 09:36:32 pm
what TRANSFORMER(s) do you have?? Lots of different things are sold as 5F1 OTs.
Title: Re: Two 5F1 output xfmrs- looking to build a modified 10 Watt ~5F1- xfmrs in series?
Post by: shooter on April 20, 2018, 05:16:46 pm: If you have the one's I got from Doug, used for the Revibe reverb driver, this is what I did with mine to get ~ 7W
Title: Re: Two 5F1 output xfmrs- looking to build a modified 10 Watt ~5F1- xfmrs in series?
Post by: PRR on April 20, 2018, 05:31:40 pm: > this is what I did

What speaker impedance?

Is the "~7W" verified or guessed?
Title: Re: Two 5F1 output xfmrs- looking to build a modified 10 Watt ~5F1- xfmrs in series?
Post by: shooter on April 20, 2018, 06:35:05 pm: 8ohmies, here's a couple screen shots, clean 5.something, grunged out ~10ish
I lay the max wave squarely on the OT's, I think :laugh:
Title: Re: Two 5F1 output xfmrs- looking to build a modified 10 Watt ~5F1- xfmrs in series?
Post by: leevc5 on April 21, 2018, 10:21:09 am: Quote from: shooter on April 20, 2018, 05:16:46 pm
If you have the one's I got from Doug, used for the Revibe reverb driver, this is what I did with mine to get ~ 7W

Very cool! Thank you. Think I will give it a go. Will report back unless I go up in smoke or something.
Best regards, Lee
Title: Re: Two 5F1 output xfmrs- looking to build a modified 10 Watt ~5F1- xfmrs in series?
Post by: sluckey on April 21, 2018, 11:15:21 am: Quote
Will report back unless I go up in smoke or something.
Hey we like to hear those stories too. Usually a valuable lesson involved. :wink:
Title: Re: Two 5F1 output xfmrs- looking to build a modified 10 Watt ~5F1- xfmrs in series?
Post by: shooter on April 21, 2018, 12:30:01 pm: Quote
unless I go up in smoke or something.
self immolation is hard to recover from :icon_biggrin:

the el34 data sheet I looked at wants ~~ 3.5k at 300vdc plate, so I would wire it like mine since I believe the primaries are 7K. the secondary's are 4ohm (each). so I wound up with 3.5k : 8ohm.

You will most likely get a grungy-ish sound, in a good way since they are so small they are gonna saturate fast.
mine was chimey happy at clean, ~ 1/2volume. I found speaker choice wasn't as big a thing with this build :dontknow: