Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Lindsay on December 12, 2017, 06:43:06 pm

Title: 5F2A build
Post by: Lindsay on December 12, 2017, 06:43:06 pm

I've posted this on a few other forums so apologies if you've seen it already. Given the build is based on the Hoffman layout I though a few may be interested. I built three amps at once, one as a birthday gift for a mate and the other two for Sydney muso's.

I folded and TIG welded my own aluminium chassis',  and wound my own transformers and choke (15H). The cathode has a switchable bypass cap on the preamp, the NFB can be switched on/off at 6 db (22K as per Dougs schematic)

Using the 5Y3 rectifier I have 315V on the plate. Substituting a 5AR4 gives 340V but I prefer the lower voltage sound. Technically the 5Y3 puts out 2 W's at 10% distortion and the 5AR4 3 W's. I can't really tell the difference in output volume.

The OT is a bit larger than a typical original, and is wound on  grain orientated core so has a wider range.

The attached video was just a bit of fun and not meant to be a full amp test. Played by a friend using a loop pedal and a dose of Tennessee Whiskey.

Lindsay

(https://i.imgur.com/PGIgrTE.jpg?1)

(https://i.imgur.com/0P30Omk.jpg?2)

Title: Re: 5F2A build
Post by: sluckey on December 12, 2017, 07:10:31 pm

VERY IMPRESSIVE!

Title: Re: 5F2A build
Post by: Joel on December 13, 2017, 12:05:20 am

Hi Lindsay,

Those are some nice looking amps!  Beautiful work.

Would you mind telling me where you got your transformer parts?  When I made my own transformers I recycled some older ones.  Couldn't find any suppliers in Adelaide.

And I'd love to know how you did your faceplates or where you got them from.

Title: Re: 5F2A build
Post by: TIMBO on December 13, 2017, 12:17:20 am

 :thumbsup:

Title: Re: 5F2A build
Post by: Lindsay on December 13, 2017, 03:44:11 am

Quote from: Joel on December 13, 2017, 12:05:20 am

Hi Lindsay,

Those are some nice looking amps!  Beautiful work.

Would you mind telling me where you got your transformer parts?  When I made my own transformers I recycled some older ones.  Couldn't find any suppliers in Adelaide.

And I'd love to know how you did your faceplates or where you got them from.

G'day Joel,


Core purchased from : http://www.brightsteel.com.au/


You have to purchase 30kg at a time  :BangHead: .


Bobbins and sleeves from : Engineering Enterprises
                                            376 Bayswater Rd, Bayswater VIC 3153
                                            Phone (https://www.google.com.au/search?q=engineering+enterprises+melbourne+phone&sa=X&ved=0ahUKEwj-69jT14bYAhVCebwKHVf6CNwQ6BMIbzAQ): (03) 9729 3333 (https://www.google.com.au/search?q=engineering+enterprises#)


This business is run old style so no internet, phone call or fax only. I don't know how much longer they will remain in business but have great product with no minimum order quantity.


I have a large stock of wire/insulation/tapes on hand, but if I need any it's from: http://www.bew.com.au/  in Sydney


The face plates I created in Corel Draw. Two were laser cut/engraved on plastic material and the 3rd was done on laser engraved aluminium but I had to drill the holes myself (very thin 0.5mm material) Both products look okay and were $30 each from a Canberra based trophy shop.


I hope this helps,


Regards


Lindsay
Goulburn NSW

Title: Re: 5F2A build
Post by: Joel on December 14, 2017, 03:19:38 am

Thank you!  Info duly saved.

Title: Re: 5F2A build
Post by: MFowler on December 15, 2017, 01:53:08 pm

The chassis, transformers and boards all look professional and it sounded great.


A real Renaissance Man.


Mark