[amplifierguru]

Hi all,

Well our thread disappeared into the ether... so we'll have to start afresh. Let's kick off with that great little BassXt build -



the review -

http://www.diyaudio.com/forums/showthread.php?s=abbd47178a0848374c9d625d7dd5a5bb&threadid=94808

the details -

http://www.diyhifi.org/amplifierguru/guru_009.htm

This is a neat, simple way to achieve an extra half to one octave of cleaner, tighter bass from your existing speakers. One DIYer's wife has a dance studio, and she uses it tuned high to emphasize the dance beat for lessons, then he retunes it down for critical listening.

Cheers,
Greg

[amplifierguru]

And here's the recent link for those looking for amps for Orions or other multi-amp applications -

http://orion.quicksytes.com/viewtopic.php?t=266

The SKA's are cutting edge design openly based on good science. The foundation - my article Distorting Power Supplies published in Electronics & Wireless World.(copies available). The reason and way Class AB can perform as well as Class A without the size, weight and cost impost.

Greg

[amplifierguru]

Here's another review by an AC member, retrieved from limbo-

Another SKA experience
« Reply #6 on: 31-03-2006, 11:14:20 » Quote 

--------------------------------------------------------------------------------
Greetings Everyone,

      I recently finished a GB150D and wanted to take a moment to provide my impressions.  But first, let me say that Greg's customer service is first class.  This was my first project of any kind and Greg kindly answered each question and was extremely helpful.  He even created additional documentation commensurate with my novice understanding.

     My system is an unmodded Squeezebox 3 fed into a NADT762 receiver's analog inputs.  The GB150D is connected to the NAD's pre-outs.  Speakers are the Ascend Acoustics 340s and cable is Kimber 8PR.

     The amplifier has been running about a week and I now feel I can attempt to articulate its attributes in my home.  Let me reiterate this is my experience in my home, so please consider this is my opinion only.  From the time I switched the unit on, I was struck with how quiet and tuneful it was.  I let the amp run continuosly for a number of days and nights and then began seriously listening (it souned so nice out of the box that it was a chore to not just keep listening).  Taking things from the bass first, I went to turn off my Adire Rava sub and just listen with the Ascends.  To my surprise the sub was off.  The amplifier has solid control over the bass, not only at moderate listening levels, but also at low volume.  The SKA provides quick, tight, and accurate bass that was absent with the NAD.  I don' tuse my subwoofer anymore for music.
       The midrange and the treble are first class.  I am hearing details that were absent before and find all types of music simply sound realistic.  Vocals, instruments, and high notes are clearly improved over the NAD.  The strange thing is I have no listener fatigue at all.  I assumed with the added detail and clear highs I would become fatigued.   The image is also improved.  Complementing an increase in image size is a better separation of instruments.  Not only is lateral dispersion better, but vertically as well. 
      I am happy because it is as if I built an amp and received a free new pair of speakers as well.  The sound is greatly improved and I am now planning to have my SB3 modded because I feel my electronics can respond to improvements. 
     Greg, thanks for an easy build, unprecedented value, and sweet sound.

Regards,

Chad

Greg

[gitarretyp]

I finished my dual mono GB150D a little over a month ago and am now prepared to write a review. But first, the details of the build: I used dual 500VA +/-40V transformers (got a great deal, so why not?) with a soft start module. The PS boards themselves are stock. I used silver mica caps on the input HF filter and in the feedback chain. I also bypassed the large electrolytics on the amp board and performed the zener mod (increased PSRR). All signal wiring is solid silver, RCAs are cardas, and speaker terminals are Eichmann. The case is from Par-Metal and the heatsinks from ebay. The build itself was pretty simple --though i made a stupid mistake .

My system is listed in my signature, and pictures of the build and my speakers are in my gallery. My musical tastes are varied. I listen to everything from jazz, bluegrass, classical, and choral to heavy metal, classic rock, and electronica with some mediocre "audiophile" music thrown in for good measure  .

My previous amp was a PS Audio HCA-2 to which i've performed several mods.

Now, to the actual review:

The GB150 is hands down the best amp i've had in my system. Compared to the HCA, the GB150 is far more detailed, more dynamic, and the soundstage is larger and more well defined. The highs are airier and more extended and the bass is tighter. The mids are more detailed and have more texture --less texture than some tube amps i've tried, but much better than the HCA. Despite the increase in resolution, there's no trace of sibilance or other anomalies. In fact the mids are super smooth.

With the HCA, i'd thought my system was lacking a little in dynamics and sounded hard/strained on some tracks. The GB150 ameliorated both issues, and i'm happier with my system now than i've ever been. Honestly, in switching between a few other amps, the changes i noticed were rather small. This was not the case with greg's amp. The improvements i noticed were immediate and obvious.

I'd also like to add that Greg is a fantastic person to work with. I had some trouble with the initial build, and he went way beyond the call of duty to get things straightened out. 

[Rocket]

Hi,

Glad you are enjoying your new amplifier.  Do you think improving the caps in the power supply would make any difference to your system?  I also have a ps audio hca - 2 and in its stock form it sounded quite poor in my system.  I had it modified with blackgates in the signal path (bypassed with v caps) and nichicon gold caps in the power supply.  It sounded a lot better but the bass performance is a little weak in my system.

The SKA must good quality amplifier to beat the hca - 2 hands down.  Its great to have a reference point to judge the SKA amplifier.

Regards

Rod

[gitarretyp]

Hi,

Glad you are enjoying your new amplifier.  Do you think improving the caps in the power supply would make any difference to your system?  I also have a ps audio hca - 2 and in its stock form it sounded quite poor in my system.  I had it modified with blackgates in the signal path (bypassed with v caps) and nichicon gold caps in the power supply.  It sounded a lot better but the bass performance is a little weak in my system.

The SKA must good quality amplifier to beat the hca - 2 hands down.  Its great to have a reference point to judge the SKA amplifier.

Regards

Rod

Rod,

Do you mean improving the caps in the gb150 or the hca? The HCA has Jensen four poles on the main supply rail, N type black gates as coupling caps, all other on board caps are a mix of standard black gates, nichicon gold muse, and rubycon za/zl. The bridge was replaced with stealth diodes (had a MURS360 bridge similar to refereance audio mods, but one leg of them blew during a power surge) and the output wiring upgraded to kimber 8TC soldered direct to board. I've also replaced a few output FETS, one of the controller chips, and a few SMD components when one channel failed/blew. I don't consider that an upgrade, though .

I'm sure upgrading the caps and diodes in the gb150 would provide some improvements, but with the large PSRR supplied by the design, i'd expect the improvements to be smaller than those i've observed in other amps.

[amplifierguru]

Well thanks Jason - that's a great review! 

All those mornings spilling breakfast oats on my keyboard amid the streaming emails has paid off - you have a great result! Enjoy.

I have just been advised of yet another excellent heatsink from the UK -

http://www.madaboutsound.com/prod_det.asp?product_id=38

Don't worry about the (degrees)K/W instead of Celsius in the rating - this is the Kelvin temp scale used in scientific applications. It's zero is absolute zero (-273.16C) instead of the freezing point of water at STP, but the divisions are the same.

It would suffice for 2 x GB150D or 1 x GB300D for all but the hottest climates (our summer sauna).

Cheers,
Greg

[robert1325]

I am not sure where to ask the following questions?:

Is this doable for a total diy noob?   

How does it compare to the t-amps ( didn't see any comparisons in the reviews)  I'll be honest, I don't like the typical uninvolving SS sound and am happily using a trends ta-10 t-amp right now.   

I was considering to recase the t-amp and make a integrated,  I might look into your the SKA pre... ( don't know how good it is)   But I only need about 3 watts for my Hawthorne SI's (open baffle)  so I'm not sure wether I should go for the SKA amp.

Thanks

Robert

[amplifierguru]

Hi robert1325,

Chad above was a total noob (self admitted) - back when I had half the documentation. With his (and others) questions a lot has been added and the guide for the GB150D is now a 'walk through' maybe 2-3 hour stint for a first module build.

I don't like the typical uninvolving SS sound and am happily using a trends ta-10 t-amp right now.   

Me either! It's what the SKA amps are all about, retrieving the involvement, detail and emotion missing from much SS stuff.

A project like the SKpre is a small one and would quickly show you what's involved in a simple build. It needs only a 15Vac wallwart or 30Vct trafo or +/-16 to 22V DC supply, andwired RCA's to connect. Perhaps it could even be powered from your t amp PSU.



It comes standard with individual SG pots on the PCB or you can add the optional wired Alps 10K DG. About 1hour per channel to build.

Cheers,
Greg

[amplifierguru]

Bye all - they've pulled the plug on SKA here 

But you'll find me here -

http://www.diyhifi.org/forums/viewtopic.php?p=22366&sid=fdea61077194997652062d913deb700a#22366

 

or on my website.

Cheers,
Greg

[ooheadsoo]

What do they say you're doing wrong?  This is awfully weird.

[TheChairGuy]

Abe/ooheadsoo/everyone,

It wasn't one, but numerous instances of his infractions that did Greg in.

He posted malicious content in another manufacturers circle...for which he was warned.  He denigrated other designer's products - for which he was warned. He repeatedly wrote of his business and life being threatened - without furnishing substantive proof to anyone at AC.  This was done several times.

He is certainly a gifted designer and we urge anyone interested in his designs to contact him directly at his website or other means.....he simply overstayed his welcome at AC.

It simply was not one instance, but many, many that led to Greg's banishment. We don't do this for sport - it requires much careful thought as to how it impacts the AC membership, Greg's business, etc.  The clear outcome was that AC is better without him...to that the Council was unanimous.

This thread is now locked.

Sorry for the downer, folks - John / TCG