DIY set amp build newbie help please

[M0XNA Neil]

I have built as number of valve amps and get my HT and output transformers from Sowthers:

www.sowter.co.uk

They have a large selection of valve matched output transformers in difference physical packages with really good power handling and audio bandwidth.

Neil.

[Whaam68]

I built this amp last year as my 2nd foray into electronics! It sounds really nice (& loud) with my vintage speakers. I used NOS 1950's 6B4G's from a guy in Russia on ebay (about £20 the pair), a power transformer from dynakitparts.com (recommended by the designer for 240v countries) about £30 and 3K outputs from Transcendar in California (these are great value), about £75 the pair (edcor are also great for budget transformers), sundries & steel chassis from Phillip at Bluebell, Russian PIO coupling caps from ebay about a fiver. All in was probably about just under £250You don't really need the cad file as the PCB makes a great template. The people at the diytube forum were very helpful with questions. It's been my main amp for about 9 months & hasn't missed a beat. You can see what the TX look like here (I changed the caps to smaller PIO's in the end as I was tight on space)

http://www.diytube.com/phpBB2/viewtopic.php?t=2896

Mike

[woody78]

Hi Mike

wow that chassis looks good

yep got the power transformer dynaparts in New york , i was trying to get the output transformers here but no luck as yet ...............may just go down the USA route as well ............

can i ask what speakers you drive with it ? i have a pair of Klipsch heresey 1 old ones from the 60s ............ hope they work ok sensitivty is about 94db i think ?

may change my chassis plan after seeing yours , did you cut the holes yourself? punch or holesaw ?

too many questions to ask you

[Whaam68]

Hi Woody
Even with the £/$ the transcendars are great mid level TX & superbly built & finished. That said Ed Dinning here on this forum wound me some TX for a similar sized point to point 2A3 amp, unfortunately due to work & other commitments I haven't got going on this one yet so I can't comment on the sound of those vs the Transcendar. The only tools I used on the Chassis were a couple of chassis punches about £12 each (you really need these), a set of mini files from Maplin etc, a homebase cordless drill & a selection of HSS bits. If you saw where I built this you would laugh... it's a wonder it turned out so well. The way I did it was marking out onto thick card template cut to the size of the chassis top plate (cereal box will do) ...use the PCB to markup mount holes for the insulated standoffs & the Preamp & rectifier valves then work out TX mount holes (my trusty Aldi digital calipers were handy here) , & the valve sockets for the 6B4's....sellotape template to chassis & drill & punch carefully. The only major bind is the square hole for the IEC power socket...I drew round it using card, drilled a load of small holes around the edge then filed out the excess....I've since picked up a square punch as I hated that bit so much. You could also use round Bulgin plugs that would be easier. Basically just take your time before drilling! Re the parts list you don't need the punch/stake/anvil bits ...just the plastic conn blocks...this knocks a load off the price.

At the moment this amp is driving a pair of 50's 60's "Grampian reproducers" 15 ohm full range(ish) drivers in big non matching vintage BR cabs (the cabs & one driver were free & I don't have the skills to make horns)...they sound great & go loud....I also use them on a mid 60's set of 15ohm Wharfedale Teesdales 3way 15 inch bass driver & some 15 ohm 1959 Wharfedale W3 3 way's 12" Bass driver....I don't know the sensitivity of any of these but they sound marginally louder on the Grampians & almost too bassy on the W3's (I need to get some support cones for them) but loud enough on all.

Hope that helps a bit
Mike

[JLH1969]

A couple more suppliers you could try for transformers are Majestic and VVT. (Both in the UK, do a search)
There is also that chap who has transformers for sale and Kate Bush on his website, but I can't remember the name. I think he did the Maplin valve amp designs.
LOL I don't mean he's got Kate Bush for sale!

Don't get carried away with buying platinum-plated components from Rolls-Royce encased in Dodo eggs.
The circuit is more important.