i worked on a tube preamp over the weekend

It has been a while since i worked on tube gear. Not that I don’t want to but ever since toying with Monica, Charlize, Beyonce etc, it doesn’t matter what is the technology, great sonics qualifies it as good gear!

But I agreed to working on this tube preamp as this guy been sucked dry by a local audio company. He bought the preamp, found some problems, sent back for repair, was charged heavily and then spewed some bullshit here and there…

I know the manufacturer, and know how bad his work is as I “rescued” a previous victim of his. I’m just fed up of listening to this smooth talker, giving other local audio companies a bad name…

When I got the preamp, I was kind of shocked.

The signal circuitry, component for component, is a direct replica of the Simple 5687 preamp on my site! This circuit was published on my site in 2003! It’s actually not my design but a take from vt4c’s design which was published in a local paper. The power supply circuitry is totally different from mine as cost is clearly a major consideration for the manufacturer so one choke and the tube rectifier was omitted. I can tell you this, out goes the sonics!

This “victim” came to me as this preamp, despite repairs, is still giving him problems. And I could see why!

In all, it’s a sloppily done job. And the components… there’s no regard for quality at all. The same type of resistor is used for plate, cathode and bleeder. The same size for all.

The manufacturer didn’t even try to optimize the sound. I know this as feedback from diyers who built this preamp told me the sound could be optimized further. If you spend some time on this circuit, you know the sound could be improved very easily by changing some parameters. Nope, this manufacturer didn’t bother doing that.

And the volume pot! It’s not even the usual Alps Blue but a cheapo Panasonic type I’ve used before. There’s a reason I don’t recommend this Pana pot ove the Alps. Wait, scratch that. There are many reasons not to!

There’s more to it but I’ll stop here. That’s the problem, the gullible public is always taken for a ride by folks like these. You have been warned!

20 April 2009 | diyparadise | Comments