I'm thinking of making one of these kits. Has anyone compared the finished products (preferably of similar power outputs)? If so, I'd be interested in your impressions.
Hi studley
Here are some SKA reviews that I have collected from DIYAudio.com
Enjoy the reading
KL
27/03/03-----------------------------------------------
yggdrasil/GB150D
I finished my GB150D yesterday. This is my first DIY electronics project, so naturally I have some problems.
Here are my listening impressions: Very impressing. Very dynamic. It has the same dynamics all the way down. From 1K and up it is different from my old amp which is a little tube-like. I won't say anything about preference there yet, but from 1K and down it is incredibly much better. Same level of details, same dynamics and steel control. E.g. the cello made my couch vibrate significantly more than with my old amp. My chest too. The amp seems equally powerful and dynamic throughout the whole spectrum. Plays really effortless. I'm eager to play more in the days to come...
Music played on a Pioneer PD-S06, passive pre-amp and on DIY 4-way JBL monitors.
This is an amp I can recommend
25/03/03-----------------------------------------------
stoeffle/SKA, Greg Balls "wonder box" 300D / SMPS
Hi, all together.
Having skimmed the audio forums for months, looking for an almost perfect amp, I also stumbled over Gregs SKAs. The first listening reports were so impressive, that I decided do dive into matters.
Meanwhile the kits were sailing their way to Europe, I started to build the powerhouse. My goal was a sturdy +/- 48VDC supply. So, instead of getting a pair of laaarge & heavy toroidals, I opted for the SMPS route. The Meanwell 320W units with PF-correction seemed the right choice.
To put things right at once: I have been involved in EMC design work for quite a while and we always mastered these "noisy" power supplies in our equipment. To make things short: it must be understood that the most annoying noise current path is not the one of differential mode ripple across the output terminals. Nope! It is the common mode noise riding both terminals in parallel, against chassis ground. This floods your neatly designed equipment and drives you nuts. There is a simple cure: Once you insert a balanced choke in your output LC-filter, together with a pi-filter for that hoppy triangular switching ripple, this former "impossible" noise vanishes. My DC supply has a high frequency noise of <0.5mVpp and a residual 100Hz hum of < 50 mVpp under full load (6.7 ADC).
Greg’s amp topology promises an exceptional figure for PSRR. And believe me, the amp I built is so quiet, that you think the supply is switched off. No hiss, no hum, just plenty of nothing. Dead silent. I measured -99.5 dB re FS (250W/4 Ohm). Without the input wires to the floating socket at the rear panel, the SNR achieved was > -100dB (limit of my voltmeter).
If anyone is interested in this matter, I would be happy to supply the info on my design. Give me some time to draw the schematics, so we can discuss this matter further.
So long,
stoeffle.++++
06/03/03-----------------------------------------------
Macka/GB150D
Today I replaced the C9 47 uf green electro with a Panasonic FC series 220 uf 35 volt electro.
I tried BC N series 10uf in place of C 4 and C5 but without 100 hour burn in it was inconclusive so I removed them entirely for the time being.
I have listened to it and it sounds more neutral than previously and is now similar to my PSS 600 (Pro A/B 150/150 Bjt). I suspect C 4 and C5 effect is subtle and need to be carefully selected
Macka
Hi Macka
Have you tried the Blackgates yet?
I fitted some 100uf standard types to C4 and C5 that were left over from a mod to my 55N+. I've also fitted a 47uf Blackgate N type at C9.
I've been listening to them this weekend and think that I can hear some definite improvement to the overall sound and especially with the lower end. I've also got two modules that don't have the mod so I'll be comparing them later today hopefully but I've got to drill and attach these modules to the heatsinks and then wire everything up. Once I've done a direct comparison of standard vs. with blackgates I can offer something more conclusive.
ShinOBIWAN
0403/03-----------------------------------------------
KLe
Hi All
Another friend listened to my GB300D based system, on Sunday (now about 30 hours of run in), and I asked him to write a summary of his listening experience. This was his experience ...
quote:
Dear KLFirstly, let me thank you for introducing me to the GB300D. I had only read about it in the various audio forums and was very interested to hear it for myself. The following is taken from notes I made whilst auditioning the amplifier at your place, I was also able to compare this to the notes I had made at other listening sessions we had had with your previous (and highly regarded) amp.My first impression was of an incredible smoothness to the music, certainly the best I have heard to date. The next impression was the total abscence of any sense of speaker location. When doing a critical listening session I always do so with my eyes closed in order to focus better on the music and these two features positively lept out at me immediately.At first I thought the soundstaging was a little narrow, then another CD was played and the soundstage was well beyond the width of the speakers and had futher depth as well. This amp really shows up any flaws in the recording as you can clearly hear if the recording engineer has done his/her job properly. Dynamics were sensational as well, but yet again, the quality of the redording is paramount to getting the best dynamics. People who get this amp will certianly be searching for audiophile quality CD's as there is the quality there to show up whatever signal the amp is fed.Now onto the various levels of the musical spectum. Bass was clean and clear, definitely not a one note bass amp, this one. It was very easy to discern the bass was played on either an electric or accoustic guitar. Mid range was exceptionally smooth and all the instruments played within this range were there right in front of you. Treble was also very good but perhaps not as prominent as your previous amp.One feature I always look for is the quality of reproduction of the piano as this is the instrument I play. I can report that the GB300D has the honour of being the best I have heard to date. Prior to taking up playing the piano I had always found the reproduced piano music lacked a lot and it was only on hearing it played live that I found what rich harmonics this instrument has. As you would know the piano is a large instrument and this is because it has a large sound board in order to produce it's beautiful tones and harmonics, I am pleased to say that the GB300D is easily the best I have come across, well above all previous amps.Lastly, I had an unusual experience during the latter part of the listening session, as mentioned before, I had my eyes closed whilst listening and at some stage I started visualising the group in front of me. I know critics have written of this before but it was my first experience of this and I found it quite startling to have this happen to me.All in all an exceptional amplifier.best regardsIan PS: I do have one criticism in that I felt it lacked some "sparkle" in the top end.
mine still to come
06/02/24-----------------------------------------------
KLe
Hi All
A friend listened to my GB300D based system, on Wednesday (< 12 hours of run in), and I asked him to write for me summary of his listening experience. This was his experience ...
quote:
I'd be happy to summarize my listening experience at your home this past Wednesday.A brief recap.The system in general performed at a very high level, and seemed to get sweeter and smoother as the afternoon wore on. What I heard was a very relaxed, effortless, and lifelike musical presentation. It was engaging and thoroughly enjoyable. The stage was wide and deep, and retrieval and resolution of micro detail was excellent. Most important to me, was the obvious coherence. Time related linearity bettered some of the obscenely expensive systems I have heard.The interconnects were a major component in the chain. Changing them out made a huge difference, which also attests to the ability of the loudspeakers to reveal these subtle--or not so subtle shadings.Hope this proves helpful.Randall
mine to come
rgds
KL
06/02/21-----------------------------------------------
ShinOBIWAN
For my point of view its doing just that.
It doesn't need comparisons for me, nor measurements, and certainly not an analysis into its inner workings.
Its just a fine amp that has brought me to that threshold where I don't care anymore, I don't feel the need to immediately try something else. Contentment is the best word to describe the whole thing. And I can't say I've completely had that before with my other amps (both commercial and DIY), the AKSA was very close but I just think my tastes got in the way of what it was doing, the SKA pampers to those same tastes very well.
I'm a bit of a serial swapper and rarely sit on anything for more than a few months. If I come back later this year and I've still got the SKA's - then that should speak volumes. In terms of audio there are a few things that I can say I truely lifetime keepers for me:
ATC's SM75.150S midrange driver
Digital room compensation (in its ever evolving state)
Bit perfect playback
The rest is up for constant swapping and I very much doubt I feel as strongly about the SKA as those but I think I'll be keeping it for more than a few months.
2006/02/17-----------------------------------------------
Macca
Well Greg wanted to know how the GB 150 compared to the Aleph so here you are Sir:
Tonight the air has cooled to make class A a reasonable alternative. In the comparions I used an Aleph 60, a BOSOZ - X cc pre amplifier and JBL 4345 studio monitors. Everthing has be checked and calibrated, even the monitors were carefully postioned to exacting standards to ensure precise imaging. The program material was a special recording from the Max (Australian Icons) Acoustic series live at the Forum theatre.
Firstly I will start by saying I have played the GB150 for several weeks without switching it off or comparing it to the Aleph. This has allowed me sufficient time to appreciate the amp's finer qualities and unwind from my previous equipment listening experience. I refer to my earlier summary of GB150 and those impressions posted previously in this thread.(post 81). I played the GB 150 for an hour tonight. As noted earlier it is very exacting and has an uncanny way of articulating the upper registers. The amp images very well and is very dynamic.
Now the Aleph. It only took 3 minuties to appreciate what the Aleph is about and 10 minutes to write. In simple terms you forget the equipment and started really believing James Reyne is singing right there and your in the audience. With the SKA you are reminded of what its doing because its is exacting and to some extent a bit too full on. I think its the last ounce of resolving power and the way the Aleph depicts singers and instruments sonically than conveys this impression. Nothing is forced on you and the rendition of tonal structures is supremely natural. That just adds up to a more pleasurable listening experience.
Based on my impressions the Aleph is a superior audio amplifier.
2006/02/13-----------------------------------------------
ShinOBIWAN
Its all rather difficult to quantify, especially when tastes in presentation differ so much.
The AKSA and SKA are from two opposite spectrums, one introduces low order harmonics intentionally and the other aims to eliminate any type of distortion, the P101 also shared this same philosophy. What's clear to me is that the SKA doesn't actually sound like your typical low distortion amp, its definitely not etched and forced like the P101 was.
The P101 seemed a little on the edge in its presentation and I've spoken with another builder (still4given) who had similar thoughts. It just wasn't as natural as the AKSA & SKA or at least not to my ears.
I'd rate them as:
1. SKA
2. AKSA 55N+
3. P101
2006/02/11-----------------------------------------------
ShinOBIWAN
Here are my thoughts on the SKA after spending a several hours listening to it in the comfort of my own home. I was going to wait a little longer but in all honesty I don't think I need 100's of hours of exposure before I can offer an opinion, I've listened to many of my favourites from my collection and I'm familiar with how these sound so I can get a good feel for an amplifier or any equipment from listening to these.
First off I'd like to say a big thanks to Greg for offering a superb amplifier at a rather cheap price for a kit set, especially when you consider that the sound is amongst the best I've ever heard from a solidstate design. I had my modules constructed and tested by Greg since it was so cheap anyway it made sense to do it that way but from looking at the instructions and the PCB's its an easy amp to build anyhow - even simplier than my AKSA 55N+ looking at things.
Greg has clearly taken care with the building and his soldering is certainly better than my own, extremely neat and tidy, even down to how the resistors were meticulously lined up, I know its not important to the sound but it does highlight a care and attention to detail that's rare. He even included a postcard from Australia to remind me of just how cold it is here in the UK at this time year - nice touch The packaging was good and there was a bag of sillica gel for moisure absorbtion, again attention to detail is great and can only inspire similar confidence in the overall design and sound of the amplifier itself.
I'd thought I'd pretty much got all the bits needed to get the SKA's going on their arrival but sadly I forgot one thing - the heatsinks. I really wanted to get them going and Greg helpfully suggested that I use my AKSA heatsink along with a piece of wood and spring clamps to temporarily mount them. I did this and whilst its rather crude looking it works fine and I got to hear the amps. Unfortunately this means that the 55N+'s are out of action so no direct comparison's. If I get chance in the future I may do write up on an AB compare between the SKA and AKSA but I'm not sure its needed.
After setting bias and dc offset according to Gregs instructions I let the amps play in the background whilst I went about surfing the web, watching TV and left them running today whilst at work. The aim being to run them in a little before taking a more serious listen. Even so the character of this amp or rather the extreme lack of it was apparent without sitting down in the sweet spot and giving 100% of your attention to the sound.
Anyway I decided to start out with some of the really good quality recordings I have and the first was the Andreas Vollenweider' "Vox" album. There's some great acoustic peices here that mix synthesized with natural. The SKA really is a top notch amp to the extent that its actually hard to fault, at least for me anyway, perhaps I haven't heard enough excellent amps? Eitherway I seriously doubt anybody would rate this amp as less than very good and consider the price that Greg is asking... he could ask double and I'd still have payed it.
Another important thing to mention is that the SKA's I have use only base components, so no fancy blackgates or other expensive electrolytics, no silver mica's, no 0.01% resistors etc. so in other words there's actually room for improvement however small it could be. But its interesting to see that design does so well in standard guise, I guess Greg' anal approach to design looks more toward layout and topology than diminishing returns offered from the esoteric components route. But if anyone want to hotrod one of these its entirely possible.
I've come in for some flak from a particular member about the wording I use in my reviews, In fact I think their exact words were 'a review without weasel words' I think you know who you are But I don't see how just saying an amp sound very good is constructive to anyone and beside I enjoy writting about something I really like. So sod you and I'm sticking to my weasel words!
The biggest thing for me about this amp is its sharp but extremely smooth character. A contradiction? Not at all, its got top draw detail but it always seems to presented with a nice natural edge. Greg cites this design as low distortion (~0.008%) but to my ears it isn't like some of the other low distortion designs, its not bright and over hyped but its feels just as detailed with a really appealing softer edge that makes listening very easy. More refined overall I'd say is the best way of putting it and especially in the upper frequencies.
Soundstaging is amongst the best I've heard from a solidstate designs and really only seems to be limited by the recording and the rest of your equipment. I'm feeding it with some great quality DAC's and bit perfect playback so this gives the SKA one of the best signals it can hope for. The SKA doesn't flatter rubbish recordings and they still sound rough but not to the extent that you couldn't enjoy them its just that in comparison to the better/best recording you don't get the awesome realism and that really involving nature.
What it does do with the right recording is completely fool you into thinking that your actually listening to the real thing. It does a great job of creating spaces and sizes, it seems to be able to relate the whole picture with proper proportions without blowing things up or bringing details to the fore that perhaps should be so obvious. Like I said the best word for this is natural, its often used word and there's varying degree's of it but here it really does feel right.
Tonality was perhaps covered in the last bit but just to be sure; its just plain natural Go play the piano (if you have one) or another musical instrument and then go listen to something similar on the SKA. It sounds very nearly as real. Few amps I've heard do this. If only it had an ounce more detail it would be heaven but then again my speakers are most likely the weak link though that's about to sorted out in a big way.
Imaging is drool worthy. I'm sure some folks can relate to what I'm about to write; have you ever heard those systems that have the kind of imaging that suspend disbelief? Well the SKA is nearly as good and again my speakers and room are probably the weak link so I expect improvments in the future. When playback is going on you hear very precise locations of certain sound or voices. You even get a good sense of depth with it being apparent that things are further away than other sounds. Another big deal is the amps great way with folly effect. I listened to many tracks and a few had me thinking that I could hear reflections off walls behind me but what I was actually hearing was the acoustic space of the recording, its a amazing effect to hear and always puts a smile on my face.
Bass again is better than I'm used to with the AKSA. Tight, smooth and rhythmic. I think that bass performance of many amps is one the biggest let downs and that a well conrtolled bass lift the entire performance on a notch. Room problems could be blamed but I do use DRC so that isn't a big problem for me.
Overall I'd have to say that this is the best DIY design I've come across yet and just happens to be the cheapest too. Its very hard to fault and I really do think that any real improvements above and beyond what performance is offered by the SKA isn't to be had from better amp design but from considerations of room and better loudspeakers.
I've been shopping around for amplifiers to complete my reference 3-way actives and in the SKA's I've found that. Things can only get better!
ShinOBIWAN,
I agree with your impressions. In some ways the SKA a rule breaker given the long held void between diy and hi end audio commercial product. The best thing to do is to get in while the going is good.
Macka
Thanks Macka, that coming from a fellow SKA owner, its good to know that I wasn't overstating things - I do really believe that this is the best DIY design I've heard yet.
And yes, I expect that Greg will be busy and deservedly so.
ShinOBIWAN
2006/01/29-----------------------------------------------
Great even with a Handicap!
Following the inital assessment I noticed some coarsness in the midrange on some program material. On checking the wiring of a recently installed crossover network (bi amp - 3 way passive crossover) a wiring error was identified reversing the phase of one of the mid cones and was corrected.
The fact that is sounded as good as it did prior to this fix was a surprise. I am pleased to advise the amp now sounds even more fluid and its grip tightens as the challenger to class A supremacy. Time to raise the Bar to run the Turntable. If time permits I will post some more auditions during the week. An order will of course be posted for the 300 watt version shortly.
That should really get the Ball rolling!
Macka
2006/01/26-----------------------------------------------
Macka
Dazzled and Confused..The Song Remains the Same.......
There are a lot of similarities, anyone who owns an Aleph knows how romantic and engaging that design can be. What strikes me with this amp is the utter clarity of it.
There is a spatial transient capability and naturalness in the mid and the upper registers that enables very clear resolving power of individual notes. Transients snap cleanly like chalk, no blurr, no fuzz, no over shoot. The result is sound staging that draws you in and solidarity of imaging borders on the finest Class A perfomance. The amp is easy to listen, tonally very neutral and never overplays a particular area. But it draws your attention because it's so real sounding. I think its got the best front end of any A/B amp I have ever heard. I am playing James Reyne "Reckless" from the album "The Horse You Rode in On" ... stunning magic.
Greg should be very proud of what he has done with this design ... I am … another brilliant Australian design.
Five stars *****
Ian
2006/01/10-----------------------------------------------
Hi Kanwar,
Have you heard of the compound loop version of the SKA using a FET cascode chip front end driving a SKA?
Guess what - I've got them here (30 in fact) and THD 1.3ppm% on sim - way better than Halcro I believe, but SKA sonics.
That's 0.0000013%, can't measure it anyway. It wasn't the goal. Nor was the >10,000 damping factor or the DC - 3MHz response, but the 160 dB PSRR was.
Sorry, comp was very tricky, no schema or detail. Not even the module pics I have handy.
Cheers,
greg
2006/01/04-----------------------------------------------
Rellum
Hello,
Yesterday I've increased Iq to run one channel at 1.4A and replaced input RC filtering caps with some silver mica 100pf/500V caps. Good overall stability. No overrun. Exemplary offset stability. To perform some comparisons, I decided to run one channel AB and the other class A. I made some mono listening tests yesterday evening with manual swapping. First impressions : no changes. Tomorrow, I connected my switcher. It's a self made one with wired remote controled relays. Many contacts are in parralel, the off contacts feed a dummy load to keep each amp allways loaded and
ground is also switched to avoid ground loops. The only change that I noticed when swapping is in the bass region. No more impact but a fuller bass sound, with slightly more energy. I connected my
scope at the inputs of the amps and with the ADD+INVERT mode had a flat line in the middle.
Connecting the probes on the speaker outputs, the flat line is somewhat modulated but at low frequency only. The less efficiency of the bootstrap caps at LF gives less open loop gain and thus, increase the output impedance. It wasn't noticeable on two way speakers or with a low bass content on my own one. In class A, higher transconductance of the output mosfets gives some more gain that allows for that bass extension. Clearly, this amp has nothing to gain with class A. Energy waste.
The bootstrap caps could be replaced with some biggers and best quality. The P mosfets could be replaced with some IRFP9140. Sadly, I have only two of them on hand and they are not easy to provide.
A more clever solution could be to add an error correction circuit. But not an Hawksford one, output stage has gain here. Why not an opamp based one wich action could be limited to the low frequency range ? A bass extender could also do a nice job...
This amp is clearly a HIGH FEEDBACK design, but a clever one. Won't suit everybody's taste.
To summarize, it combines : low cost, high power if needed, very low distorsion, good definition and an incredible softness wich allows for long listening sessions.
Cheers,
Francis
2005/12/30-----------------------------------------------
Rellum
I'm one of the few people here that decided to acquire a Simple Killer Amp. When I first saw the topology, I was impressed by its simplicity and specificities. Never saw such a thing, so I ordered a GB150D to test it by myself. The PCB is nice, well done, compact. I didn't test the mosfet’s but the small trannies : well matched. The instructions are clear for a trained builder. The GB150D can output up to 150W in AB or 50W in class A. I decided to go for a light class A and built a big dual mono power supply with what I had on hand. Four 300VA earth screened transformers, two high power bridged rectifiers, a CRC arrangement wich per rail is composed of 10mF + 1R + 2x22mF low ESR. It's actually oversized because I first made the amps run in AB mode with 50mA per mosfet to test overall stability. Offset and bias are stable enough though the trimming principle is incredibly simple. There's no cap in the signal path and the bootstrap caps are those provided in the kit.
To be able to test it easily and as I don't have a dc coupled preamp on hand, I replaced the input 1nF polystyrene cap with an 470pf one and added an 10K ALPS pot. A few other resistor have been downscaled to fit the +-29V provided by my actual PSU. At this time I have no cabinet, everything is on the floor. When time permits (next year), I will increase the bias (have to mod some resistors that are actually a safety for not over biasing) and test class A performance. From what I can hear now, it will be putted in a cabinet and not dismantled like many others.
My actual system, a CD14 by Marantz, an AKSA amp, a kt88 cathode coupled push pull amp and Cabasse Iroise LS given for 92dB/W/m. An easy task and load for all my amps.
The first thing that impressed me, was the very low residual output noise with shorted inputs. My 2mV/div Tektronix in diff mode give me a nice 0.6mV rms noise. I have to put the ear in close contact with my dual concentric medium/treble driver to detect something.
The sound is precise, more than my other amps. The bass are tight and very well damped. No distortion is audible, totally uncoloured on the whole range. The music flows easily without any agressivity and that's the second thing that impressed me. It's not usual for me as I most the time listen to tube amps or hybrids. Overall impression that it's as usual less life-like than a
tube amp but it's so nice and where is the truth? I like that amp and will try to get the best from it!
To follow are the listening impressions of Hubert, a friend of mine, who is way better than me when it comes to put into words what we hear. It's an experienced speaker builder and he has my AKSA at home too. It's somewhat different from the usual techno babble we can read on this forum, but will give you an idea of what you can expect from such a schematic. And of
course, I have no financial interest with the designer of this project.
Happy new year to all,
Francis
---------------------------------------------------
Hello Francis,
Here are my feelings about this new amp we listened yesterday afternoon.
The stereo was my current system:
-source: not a true performer but I perfectly know its listening
characteristics: a Micromega Optic BS using a bitstream DAC, at least the "music flow" is preserved in term of fluidity and details remain present.
-speakers: 1801's Ellis audio, a standed monitor 2-way using a 7" Seas magnesium and a 1" Hiquphon tweeter, with a perfect filter (for these drivers): not the ultimate performer in bass range but very revealing on the global bandpass, particularly free of distortions; its relative lack remains in macro-dynamics but only if compared to very good 3-way and...84db efficiency...
IMHO, a real killer amp must be dynamical, revealing, with an extanded bandpass from sub-bass to top ends and neutral.
So, lets go with this one:
- dynamic: particularly equaly reproduced from sub-bass to top end. Often amps have more dynamic in midrange or trebles, this one not; good point. In a first view I guessed a little lack in this area because of the poor efficiency of my 1801's but finaly no.... certainly more "near to the truth" than others.
- details: as with the other solid-state amp I currently use (no no, I will not write its brand-name but as you know because you are its owner, it is a well-known and very appreciated kit in the worldwide audioholic community) here is THE problem: inner details (micro details) are not on par with my tweaked valves-amp Rogers E40a: i.e. the lack of reverberations and prolongation of musical notes is obvious, not only in the upper range but also in the low-mid. Thus, timbres are affected, but not the musical flow; fluidity is preserved even if a few harmonics are "breaked down".
- frequencies extension: a perfect straight line, allowing to create a right image in term of sizes of the instruments and place of recording, in relationship with true soundstages; good point.
- neutrality: the last criterion, for a reason: NEVER HEARD SUCH A DISTORTION FREE ELECTRONIC: very, very uncommon: my bad cds aren't so bad, they don't become good cds but they are less bad, obviously. NO, my speakers aren't harsh sometimes, no the magnesium driver doesn't distord in the upper-mid on some cds as I guessed before !!!
To summarize: An almost perfect amp; if the lack of inner details could be avoided, this amp would be THE killer for anyone enjoying neutrality but only once linked to a top source and to top speakers at "real" listening level. Others (me included) may prefer less accurate electronics, with different listening characteristics (notably to compensate less accurate sources and/or speakers or to match bad room acoustics or to listen at moderate level), but that's another "commonly discutted" issue.
Thanks again letting me listen to all your electronic buildings, always very instructive.>
Cheers,
Hubert
