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Tube amplifier El Cheapo
Page 1: Quality out of the box
Last updated: Monday March 8, 2010
Some time ago I decided that I wanted to build a small amp based on either EL84, 6P43P, 6P14P type of tube. I was looking around for components when I saw the very cheap Chinese amp from Suppo. I decided to buy it, maybe I was able to modify it, or just reuse some of the components for my own amp etc.
People say: You get what you pay for.
In this case, as the sound of the amp is really OK, it's the design, component quality and Safety that is far below acceptable. So, I'm not at all promoting you to do as I did. please do buy a better kit to start from or start from scratch. This unit is not for everyone!!
This "project" deals with a super cheap tube amplifier made by SuppoAudio.com in HongKong. The amp is advertised as being an EL-84 based PP design, but the actual amp shipped is based on 6P15 Pentode tubes (cheap Chinese). As the cost of this amp are just 90 Euro for the amp and 55 Euro for shipping, the initial component quality is not somehing to worry about.
Let's be fair, we all expect the manufacturer to save on anything possible as long as the amp continues to make music. And he did... I mean it did. So why do I buy a tube amp that you think is not good enough?
I have the plan to mod this amp a few times to try for myself whether it will really improve with a few simple modifications. The goal is to spend as little money as possible for improving this cheap amp. That's why I call this project not EL-84 but El-Cheapo. ** (I found out that there is another project on the web with same name .... hmmm.)
There are however a few things that I really do not like about this amp, and those have little if not nothing to do with the sound produced. Most are related to safety and quality of the design.
And regarding to the build quality:
Until now, nobody seems to have cared about this as the price is low. But it makes the amp in its current form not suitable for novice users other than experienced DIY people. Suppo recently (March 28) sent me an email with these and other points as a waiver for warranty and health issues etc.
Also, looking at the Suppo presence on the forum of diyaudio.com it is clear that Joe of Suppo Audio does not always know what he is talking about. He makes claims about sound quality that are difficult to believe and suggests all kind of tube rolling possibilities that are sometimes either impossible, downward dangerous or at least questionable.
Maybe this little amp is best to be used by experienced audio DIY people that know what to do and can solve issues themselves when necessary. Maybe Suppo could better sell parts to the community, as enclosures and transformers are the most expensive and difficult to get items for a DIY tube project.
The amp arrived in a double box. As you can see, it has been beaten up a little but nothing serious.
And within a few minutes it was ready to play... As you can see on the picture, the tubes were labeled 1 to 6, numbers 1 and 2 in the front row and numbers 3 to 6 from left to right in the second row. I cannot check myself, but assuming that Suppo maybe did match the tubes before shipping I decided to maintain the numbering.
Well two weeks later I can only tell that the amp is dead quiet so apparently the tubes are matched.
Suppoaudio has posted the following schematics for the circuit on diyaudio.com. Unfortunately the schematic does not show all the components, and some components are NOT present on the PCB. But in general it gives an idea how simple the design of this little amp is.
Please continue on page 2 for an updated schematic and a description of the work done on this amp so far...
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