SKA GB150s

Hi,

Not sure if this belongs in DIY or reviews, I'm new here

Anyway I have just finished building a pre and poweramp from Greg Ball's SKA kits http://www.ska-audio.comand they are so good I thought I would post a quick review.

I built the SKpres and GB150 class AB amps powered from a single toroid. My source is a modded Arcam Alpha 5+ and the amp really lets the CD player do it's business. My old Rotel 920 has fond memories but was blown out of the water!

The kits were really easy to build and needed no more than a bit of soldering skill which is about all I have. It was a fun project but for me building a pre/power amp was all about getting better kit at a price I could afford. I was blown away but how much performance I got for my money. The thing that impresses me the most is the purity and clarity of the music. High pitches are delivered perfectly with exquisite timing. They sound like they should with no colour or delay. Equally the mid tones are delivered superbly. The bass in my system is not quite correct yet but I feel this is due to my JPW sonata's which I don't think handle the power well here. I don't believe this is a facet of the amps themselve.

This is the first time I have built an amp and I didn't believe I could get the purity of sound I have long wanted but not been able to afford but these deliver.

I have listened to a variety of music so far and it copes superbly with everything from Aida to Abba to Nine Inch Nails. I hate amps that add "colour" or "bloom" to the music and these don't. Quite simply there are notes and tones in some of these recordings that I simply have not heard before as they were hidden in the background. The soundstage created by the amps is really quite impressive. It's hard to describe the effects of an amplifier, I feel that an amplifier should not have an affect on the music and that is exactly what happens here.


I'd love to know if anybody else has built these and would highly recommend them to anybody in the market for a new amp.
Cheers

Iain

 

Had a quick look at the kits .....I would imagine you can get some significant sonic improvements with the substitution of certain critical parts....The caps for instance appear to the standard types substitution for better ones will make a difference.

What cable have you used to hook the signal up to and from the boards ?

The rectifier diodes may need swapping for schottky types these imo sound far more musical than standard diodes ...remember the psu is the hart of the amp and work done here will reap dividends through out the amp chain.

Have you used silver loaded thermal compound ?

 

I've made them as standard with the exception of the zener mod that Greg has incorporated into the the higher model (GB300)

I am a newbie to this but as I understand it the topology of the design is such that it is quite resistant to a lot of the usual problems. I may send him a message to pop in and provide details as it's beyond me and he's a helpful chap. He does provide pointers of certain areas where modifications such as black gates may be played around with. I thought I would listen to the vanilla build for a while before I try playing around so I can get a feel for these things.

Signal cable wise I have just used some shark cable from Maplin which I had lying around to get this up and running. I woud be interested in some recommendations for signal cable. The temp sensing transistors are recessed in a drilled hole in my heatsinks and I have just used standard thermal grease. I contemplated using some Artic Silver I have left over from PC builds but as the heatsinks I am using are fairly massive I wasn't too worried about this side of things.

I have these running from a single 30 0 30 toroid at the moment but may move to monobloc at some point.

These kits have certainly got me very interested in this diy field because of the quality of what can be achieved. I'l let you know if I implement any tweaks.

Cheers

Iain

 

I thought these amps looked pretty tasty and have been considering one to run my tweeters/midranges when I finish my main speaker design. I like their simplicity and the fact they still manage to maintain good measured specs.

 

Certainly sound good to me. There are a few folk using them for running amp hungry orions who seem to be pretty pleased. They were also very nice to build, Greg's a very helpful chap, runs a nice forum for users at his site which is a nice touch.

They are a nice simple build, I spent far longer on the case than the boards themself.

If you get them let me know how you like them

Iain

 

signal transfer .....I like silver which I sleeve in ptfe. But the cheap skate alternative is 0.4mm dia wire wrap ....if you take 5 cores of this and twist them together you get a litz cable [as each stand is insulated]...this makes a very good [for copper] connection. IMO is should blow the shark away and dance on the remains twice with a posh hat on !

 

How refreshing to hear some sound common sense!

It is natural for people on forums, with the best will in the world, to offer advice to newbies about teaking this or that. But it is no good changing anything, if you don't know what sound you have as a reference point! So bide your time before you make any mods! ;-)

You didn't tell us how you housed these amps. Do you have any pictures?

By signal cable, do you mean internconnects or internal wiring? If the later, the lengths involved should be so short as to make hardly any difference. Solid core is easier to work with if it is not to thick, and CAT5 works very well.

BTW, PTFE is a good insulator for practical reasons like using a cable in harsh conditions. For audio (and I'm talking longer lengths than internal wiring) it is not so good as it can smear the sound.

 

Thanks! Yes I have some pictures, not great but here you go.



And



I have tidied up the wiring a bit since then though.

I have then fitted onto some huge heatsinks in a fairly large case which is overkill but it looks good

I mean internal wiring, I have some fairly standard cable in at the moment. I suspect I can get improvements by tweaking the cabling some but as I said it sounds great so I am listening for a while.

Iain

 

Will try this as my first tweak after a good few weeks of happy listening, thanks for the suggestion. Your cable test article was very interesting btw.

Cheers

Iain

 

Looks nice. Anybody tried these with Dynaudio Focus speakers? I think I need a bit more oomph than my Akpha 9P to drive my Focus 110s and fancy a bit of DIY

Thanks
Ed

 

Not me and I'm new here so I don't know many folk yet. They have plenty of oomph for me, and there is the GB300 alternative. They are certainly a pleasure to build, years since I picked up a soldering iron and they went very well.

ShinOBIWAN has built the GB300 version, see his thread with the amazing speakers. He may know someone.

Cheers

Iain