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    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

This Schematic Sounds Great

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Eddiegnz1

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Joined 2013
#1
Which amp should I build for sound quality? I've been back and forth between

1) a kit (I found several kits available)
or
2) piece together on my own parts to build an amp from a proven schematic. I would do this point to point and I'd source every single part my self. My friend even has access to a professional that can bend, cut and create a perfect chassis.

The most satisfying thing for me would be option two (2) which means no kit. At first I had no confidence but I've been reading so darn much and I printed out NEETS I'm finding it to be very clear and understandable. So sometime soon I will probably go with option two (2), point to point with all parts sourced by me.

So my question is, which proven tube amp schematic should I consider if I have the following two objectives;

1) most accurate music reproduction. By this I mean that the amp has no unique sound of its own, rather it reproduces the original source as accurately as possible.

2) over 45 watts per channel

I want to start researching the various schematics that y'all recommend so that by the time I'm ready to pull the trigger and start buying I will be confident in the expected sound quality.

I need lots of opinions from y'all because I want to consider & research all of the top tube amp designs for which the schematic is available.
 
#2
Mullard 5 tube 20 watt amplifier with Acrosound TO-300 OPT. rated at 35 watts by American standards. I built this pair based on the beam echo/ avantac chassis back in the 90's, And of all the amps I have, This is a go to pair. Oh and I have too many amps. Look it up in a search, it will come up. The beauty of this chassis is that it'll hide ugly transformers. If you get this circuit correct, I promise you won't be disappointed......
An externally hosted image should be here but it was not working when we last tested it.
 
#3
Right on the cusp of the power you want is 1 of the very best implementations of Mullard style circuitry, the Harman/Kardon Citation V. I've uploaded the schematic in 2 parts.

To get over the power hump, you will need to use Tubelab's PowerDrive and take the 6L6GC category power O/P tubes into a mild positive control grid current regime. A look at the data sheet shows this is "legal". 😉

An obvious improvement to the Cit. 5's setup is the incorporation of a constant current sink (CCS) in the tail of the phase splitter.

O/P transformers make or break a tube power amp. IMO, nothing lower in quality than an Edcor offering should be considered. The Edcor model I suggest for this project is the CXPP100-MS-6.6K. Yes, you need 100 W. rated "iron". Plenty of magnetic headroom is needed to support the global NFB loop.
 

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#5
You may be better to start with something simple and less than perfect. Make your mistakes and do your learning on a simple cheap design. The desire to make just one 'perfect' amplifier is very common among beginners, but it often leads to tears. This is because basic mistakes are likely on a first build, yet there is little or no diagnostic capability (and there is only so much we can do remotely).

I had built valve receivers and transmitters before I built my first valve stereo amplifier. Also spent some years repairing radios and TVs for friends. I could fault-trace long before I could build.

Sorry to rain on your parade.
 
#7
Eddiegnz1 said:
you guys are getting me excited....this sounds like the sort of quality I'm looking for. And thank you so much for including the schematic. kind thanks,
Eddie
Click to expand...

A schematic is just the beginning. There are a million ways to screw things up in the process of translating schematic into reality. Although I lean toward DF96's tragic view, I would suggest that if you decide to build on your own, you first read and thoroughly understand "Building Valve Amplifiers," especially the chapters on layout, grounding, and thermal management. The second edition will be out in about 2-3 more weeks and has a lot of useful new material, especially on troubleshooting.
 
#8
For the first build, definitely go for a kit.
I trust you can build a good one, starting just with a schematic on a piece of paper, but sourcing **everything** , down to the last nut and bolt, will drive you crazy, or at least pull a lot of fun from the project.
As they say, "the devil is in the details"
You'll be happy for getting, say, an excellent extra high voltage rated tube socket ... only to suffer from not getting the stainless steel ring needed to mount it or the odd sized screws or it won't fit into the chassis hole you have, and so on.
The main attraction of a kit is that those annoying little problems have already been solved.
And there are *very* good kits available.
I'm sure fellow DYA members will suggest a few.
 
#9
Another circuit with lot's of popularity as it came before the Mullard is the Williamson. I t has a plus in that you don't need SS CCs to make it sound it's best like many have added to the Mullard.

The Dynaco Mark III circuit (simplified Williamson) I think would be a great one to start with using KT-66 or the latest TS 6L6 coke bottle for nice sonics and the power you want. They are easier to drive than the big tubes (6550/KT-88) so sonics will be tops. It can be tweaked for the best operation of the driver tube.

I like this plate method as you could do it this way to try different circuits and make the construction simple and faster which is good for someone starting out. Mono block might make things still easier along with the sonic advantages and as a bonus it can help with troubleshooting. It could be done on 2 old or new ST-70 chassis to make it easy.

diytube.com • View topic - Overhaulin' the ST70

Remember the Output Transformers are the Heart of a tube amp so save up for the best you can afford!
 
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