Bit Of An Oddball This One!!
This interesting amp came through the workshop in December 2006. It is owned by a young student called Will, who is currently studying down in Brighton, UK. He took the opportunity to bring me his little baby Sonus Alpha 2 combo whilst he was up here in Nottingham on Christmas holidays.
When Will first spoke to me about this one on the phone I had some recollection of the Sonus brand name, but have never actually seen or worked on one before. There isn’t much information about the Sonus products out there on the web. In-fact, all I could find was one forum topic and that was fairly brief! What I can tell you is that these amps were apparently hand-built, sometime in the 1990's, somewhere up in Scotland. (See "Postscript" below.)
I have to say that I did find this one a bit of an oddball, and much removed from the normal run-of-the-mill guitar amp; not only in design and layout but with regard to the very strange circuit design too!
Will had said that it had lost power and just basically wasn’t sound right anymore. The tube compliment in these is rather strange: 1 x 12AY7 for the pre-amp and drive, and there’s no more small bottles, plus.......... 2 x KT88’s! Yes, two KT88’s! A bit of an overkill I think here! It also has a 5V4 indirectly heated rectifier tube! All very strange and unusual!
On first test/inspection whilst Will and his father were still in the workshop, it became blatantly obvious that one of the KT88’s was completely dead. The other output tube lit up inside with a bluey/purple glow so bright it could have passed itself off as a tube voltage regulator! A shame, but these both had to go. After Will and his dad had left, I jumped back onto the amp later that evening as Will needed it back fairly quickly for his return to Brighton in a few days time.
This really is a strange bit-of-kit. The circuit design is weird to say the least. The amp has one volume control which, when pulled, gives some boost. There is a single tone control (tone-cut) which also if pulled acts as a bass cut and…….that’s your lot!
The way the output stage is driven is also strange. It’s like a sort of single ended paralleled pair. I have to say that this is not the neatest of "hand-built" amplifiers I have ever seen. I would even go as far as to say that the wiring is pretty untidy!!
Another function that comes with the amp is a double foot-switch along with a pair of LED’s: one red and one green. One of the switches is marked "Power" and the other "Pre". When the Power switch is pressed, the power is increased from the output stage. However, in reality, this switch lifts the output tubes’ by-pass capacitors from ground, leaving them still on ground but now through a 470 ohm resistor which basically lowers the output of the amp. The other foot-switch ("Pre") does a similar thing, but this time to the cathode of the second half of the 12AY7 giving a drastic drop in gain, of which I personally think the amp is lacking of anyway, even at its best! As well as the other initial problems described above, this pre-amp gain boost was not working.
So, after a few duff component changes, all started to come back to life. I tried every kind of output tube known to man; right from a new pair of KT88’s, to a pair of cheapo 6L6’s. However, no matter what I used, the amp didn’t really change much at all in performance. It seemed at its best with a nice pair of JJ 6L6’s, which beat most of the others out there anyway and, Will was more than pleased to have these in it as he fancied seeing what it sounded like with a change of tubes.
And……that’s about it. I can’t say that I was very impressed with this amp. Maybe it sounds OK to some guitarist out there; who knows? I’m sure Will will let me know his opinion after he has had the time to thrash it and, if so, I’ll paste his comments on the article herewith.
Oh, and by the way, as for the colour..............!!!???
Cheers all you cool dudes….John.
An Email received from Will, the owner of the Sonus, a week or so after picking the amp up:
"Hi John, just got the chance to listen to the amp properly and it's sounding great; well its never sounded this good anyway.
It's also about 3 times louder than it used to be which can't be a bad thing and, it doesn't make weird noises any more.
Great work, decent price, and a really quick turnaround. Cheers John.