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Tube power amp for first project - kit or Mullard 3 watt?

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NatJS

Member
Joined 2004
#1
Hi there,

I've been itching to build something for a while and recently thought perhaps a cheap(er) tube hi-fi amp would be a nice project.

I have a paid of passive Dynaudio BM6 and also Tannoy Eaton (the original models, 87.5dB sensitivity) with a fairly small living room. I'm going to be playing line level sources and vinyl (through a preamp).

I wondered what people tended to build as a first project? I'm not necessarily looking to build the ULTIMATE valve amp, but I'd wondered whether buying a kit is the best route to go down or whether to build something from scratch. I have built tube gear before (in another life, while I was putting together a recording studio 15 years ago), so I have a handle on the safety aspects, but my actual electronics knowledge isn't amazing in terms of layouts and such.

It'd be great to be able to do something for under £200. I've been looking at something simple like the Mullard 3-watt amp, or maybe one of the EL34 Chinese kits that are on eBay. Perhaps a solid state power supply would make the Mullard design a bit cheaper to build - has anyone experience of doing this, or is there a guide somewhere someone could point me towards?

Very happy to hear your thoughts!

Cheers,

Nat
 
#2
I think you'll struggle to get something that fits within your budget as a set of transformers will cost between £85-115 for one mono Mullard 3-3. (primary windings are pretty good value and the quality seems good) The valves will then cost around £80 for a full set. (rough cost each, EF86 - £14, EL84 - £12, EZ81 - £12) This leaves little for the passive components, tag boards and chassis. Going solid state on the power supply would save just over £20 or so as you'd no longer need the EZ81.

Personally, I'd take a scratch built mullard 3-3 over any Chinese el34 kit simply because it's a well known proven circuit that has stood the test of time and is well covered. I might be slightly biased as I am currently undertaking my first valve amp based around the mullard 5-20. (not a budget friendly project)
 
#3
I would also recommend stretching the budget to build a 5-20. The iron alone will eat up all your budget.

The Chinese kits that I have seen have poor documentation (if any), counterfeit parts, strange designs, and lackluster performance.
 
#4
Your budget may be set by finding a relatively cheap output transformer(s), which will imply the output impedance and power of the circuit.


I'd say try a cheap eBay 70W SMPS initally, there are ones that are adjustable 200 to 450V,
12V in, and use an LM2596 buck converter for the 6.3V. A 12V power brick drives both of
these, and you always have the option to spend cash on a real mains transformer and PSU section as a second phase of the project, when you'll know exactly how to size it too.
 
#5
Mark Tillotson said:
Your budget may be set by finding a relatively cheap output transformer(s), which will imply the output impedance and power of the circuit.


I'd say try a cheap eBay 70W SMPS initally, there are ones that are adjustable 200 to 450V,
12V in, and use an LM2596 buck converter for the 6.3V. A 12V power brick drives both of
these, and you always have the option to spend cash on a real mains transformer and PSU section as a second phase of the project, when you'll know exactly how to size it too.
Click to expand...

Brilliant thanks, just ordered on eBay! Will keep you posted and am sure to be back with many questions
 
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