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Recommend design for low cost DIY valve amp


2015-10-20 8:20 pm
A friend has just inherited a pair of Wharfedale Dalesman speakers (rather, rescued them from the skip) and is liking the sound. I helped him replace the rather useless sockets for cheap but functional speaker posts, checked things out, tightened bolts etc. Quite interesting listening to them on my PX25 amp, rather different to my Lowthers. Nevertheless it's fuelling his slide down the long slippery slope, I mean it's fuelling his interest in the hobby.

He's currently driving them with a 50W Kenwood tranny amp. The speaker posts are those plastic things, the threads don't grip cable. I wondered about helping him to replace them but the connectors are tightly bound to a PCB and I try not to mess with them unless I have to.

He's already talking about building a low cost valve amp and I wondered if anyone could recommend a suitable low cost design. I don't know the sensitivity of those speakers nor what design would suit them.

I've built a couple of amps and designed my phono stage based on a Broskie circuit but I'm no expert. Is a low-cost design just one using cheap components (or whatever is to hand) ?
The snag with a low cost valve amp is that it often means a low cost OPT. Best to buy a decent OPT, and then save money elsewhere e.g. by using perfectly ordinary commercial components rather than 'designer' brands - this might even improve the sound as in audiophilia you often don't get what you thought you were paying for.
My old Parsimon can still be built at very low cost. It's good for 5~6 watts per channel and sounds great for the money. Under-chassis photos and BOM are available on request.


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2012-05-27 7:34 pm
I guess you are in the UK? Here in the USA, there were in the 60s and 70s many console amps that were powered by single ended el84 tubes. I don't know if your country had these units around. They can be had for around 100 on flea bay and rebuilt for just a few dollars. They can sound excellent rebuilding the original circuit or trying something like the RH84 circuit. I have built several rh amps, with different output tubes . Some with new output trans and some using the stock ones. To me and their new owners they all sound really good. If you can get one of those console amps they make a good entry into tubeampdom. btw, some of these amps are small enough to ship in a US post office large flat rate box for about 40.00 international shipping. good luck