SRG II Part 2

SRG II Part 2

Here is Part 2 of my SRG II Review - how the Solo performed in my system.

Part 1 is here:

http://www.gspaudio-community.activeboards.net/forum_posts.asp?TID=716

My notes on the PSU 1 are here:

http://www.gspaudio-community.activeboards.net/forum_posts.asp?TID=712

The SRG II arrived by Special Delivery on 14 November 2009 and was immediately powered up for an extended burn in.  I fed it with a 3KHz sine from my function generator for a few days and then my test CD for around a week before I even listened to it.  I then spent 3 days on casual, un-assessed listening while I serviced a friend's amp.  Finally, I spent two days on critical listening, making real-time observations on my dictaphone, and which are transcribed here.

As mentioned elsewhere on this forum, here are some details of the test set up and music:

I've prepared a cd for use when testing HAs.  You may recall SandyK and others have noticed improvements to ripped wav files if they are ripped via USB key/pen.  I've tried this.

Exact Audio Copy rips to USB 2.0 Imation Nano flash drive.  These rips are then re-written with EAC (Track At Once, as Disc At Once would not work for me).  I also ripped the same 4 tracks straight to HDD and then to the same CDR.  The first of a pair is the HDD track, the second is via USB drive.  This method allows flick-flacking between versions for comparison.  In a CURSORY listen on my main speaker system, there did not appear to be much, if any, difference between the versions, but, as we know, with a decent HA and my K701s, the differences might be all the more apparent.

Test tracks are:

Track 2, Soledad by Sera Una Noche.  From MA Recordings Sera Una Noche M052A
Track 1, Bye Bye Blackbird by Patricia Barber.  From Premonition Records Nightclub KOC-CD-5738
Track 1, Save Me by K D Lang.  From Sire Records Ingenue 7599-26840-2
Track 12, Stimela (The Coal Train) by Hugh Masekela.  From Sheridan Square records TRI-CD-82020

All of these are quality, high-dynamic recording tracks.  Not much compression here, and the engineers should be proud of their work (unlike others who, frankly, should be ashamed of their "output"!).

Up against the Solo, I'll be using my tried and tested SCHA.  I had a problem with converting an ALW Super-reg to try with the SRG II, but as there is another fixed regulator inside, this ALWSR would only be acting as a pre-reg anyway.

My source was "Shigaclone" CDP, powered by a 12V wall-wart pre-reg supply into an 8V Teddy Reg.  The Shigaclone was more detailed than the Arcam A6 CD that I tried.  Cables used are Straight Thru RCA, in half metre length, using input 1 on the SRG II.

As mentioned above, I used my Silicon Chip Magazine Headphone Amp (SC HA) kit as a reference.  This kit has been partially modified to specifications from SandyK on the Rock Grotto forum, and employs a John Linsley Hood power supply ripple reducer between the PSU and amp.  Two attenuators were used with the SC HA: a Lightspeed (LDR based attenuator with super-regulated power supply) and a high-end TKD stepped-attenuator (with Bob Crump mod, using TX2575 resistive elements).  The op amps used in the SC HA were a metal can LME 49720 and dual OPA 627, biased onto Class A on a Brown Dog adapter. 

I cooked the SRG II for a couple of days before putting some music through it.  Although I was warned about making conclusions from 'scope traces as this unit uses input slew rate limiting and any square-wave measurement will not be indicative of its actual square-wave performance, I did put a square wave through the SRG II.  The trace was, in fact, very clean, with hardly any ringing.  There appeared to be a small channel imbalance of a few tens of millivolts, but this might well be down to by home-made test leads (BNC cable, cut in two and connected to a standard stereo jack. BTW, my function generator leads are single 4mm banana to dual RCA.).  By this stage, I was looking to put some music through the amp!!!



In order to accurately compare and contrast the SRG II with SCHA, I decided to first spend some time listening critically to the SC HA first.  Both amps are similar, in that they are amplified op amp units, but differ in respect of PSU and attenuation.

The SC HA was initially fitted with the LME 49720 op amp.  I used both the TKD attenuator and Lightspeed.  My preference was for the Lightspeed (just a little more liquid delivery), but the TX2575, newly fitted to the TKD were a temporary install, with long leads and there were green.  These high-quality resistors have a notoriously long burn in time, allegedly.  I think they sound great from the moment they are installed.   The SC HA sounded pretty good, as I suspected it would.  It had a smooth delivery, lovely timbre, well-rounded with good air.  This was with the volume control on the Lightspeed at the 12 o'clock position.  It was pretty impressive, in fact, and the use of LDR-based attenuation in headphone amps warrants further investigation.

On 28th November, I started to seriously listen to the SRG II.  I had spent many hours listening to it on a casual basis, while working on my friend's amp, and despite not critical listening, it was effortless and fatigue free.  I was concerned that I was going to become bored listening repetitively to the same 4 tracks, but I'm pleased to report this was not the case!!  In reality, I was able to get to know music I thought I knew well in great depth.  Details and nuances of the music, that were always there, but not readily apparent, were singled out for extra attention while still taking an overall note of the music.

The SRG II had been powered-up since I received it (as it is designed to be), and, as mentioned above, was fed with a varied diet of sine wave and music.

I started off with Sera Una Noche, Soledad.  Track 1 was ripped to CD from hard drive.  Volume control at 10 o'clock.  You could hear the modulation of the player's breath through the clarinet.  As the vocal comes into the mix, the soundstage is wide, and you can easily feel the scale of the recording venue.  I must say now that when I first had a cursory listen to the SRG II on delivery, the sound stage was reduced, feeling a little closed in, if you like.  This is definitely not the case after a period of burn-in and stabilisation.  If you first hear this in your SRG II, then do not worry!!  The sound stage WILL widen considerably.  I have no complaints about it at all, and found the guitars in the piece were beautifully separated, had had a very life-like sound to them as the nylon strings were plucked.  The percussion bells had a shimmering twinkle to them and all the instruments were placed rock-solidly in space.  Separation between instruments and voices is very good - you can easily follow an individual part.  You can hear the emotion in the singer's voice and hear the odd rasp from his throat as he's singing this particularly haunting tango.  The mid-range is just so insightful, and there is no lack of bass here, even with the AKG K701 headphones.  Bass is taut.  If you used "bass-head" cans here, you'd get what you wanted, but with grip and control.  It's a smooth overall delivery, but not particularly rolled off.  Definitely an iron fist in a velvet glove style of presentation, and, as the song fades to nothing, you can still hear the guitar on the right hand side as it drops off in volume, but is still discernible.

Track 2 was the same song, but ripped via a USB key/pen to CD.  Apparently, this has some benefits.  I can't  really put my finger on it!  Is there really more air here, or is there a tiny bit more detail.  It's driving me nuts, because I can't quite get it!!  Guitar sounds so lifelike on both recordings.  I'm not going to make a comment either way, because I can't… at the moment!

Track 3 is Bye Bye Blackbird from Patricia Barber's Night Club.  Volco still at the 10 o'clock position.  This is, as before, a HDD rip.  Bass is very deep in this recording and has a lovely timbre to it.  The brushes on the snare drum are believable and you can hear the tension on the drum skin as the drummer is playing.  The piano is slightly rolled off, but this might be the jazz piano they used for the recording, or a result of the mix, as this is not the case on any of the other instruments.  The piano does sound lifelike, bass is very good and there is impact to the notes.  During a complex piano part, the double-bass line is still there, and discernible, but has lost its timbre slightly.  Generally, you can hear that bass string vibrating away nicely!  There's lots of air around the cymbals and the whole presentation is toe-tappingly fast.  There is a nice ambience around Barber's voice and you can hear the nuances of her breathing; even her mouth opening before she starts to sing.  Track 4 was the USB rip version.  This is really odd, but I think there *is* a bot more air in the recording.  Just every now and then you get a little bit extra of… well, I don't really know how to describe it!  Perhaps a bit of extra resolution (or it might be me going mad!)?  there is a good "crack" to the rim-shots and the drumming is, overall, nice and tight.  The music certainly doesn't seem to be rolled off the top end, even though it's a smooth delivery.

Track 5 is K.D. Lang, Save Me.  This is a HDD rip, with the volco at 10 o'clock.  This track starts off with such a rich fullness of sound.   Delivery is detailed, and this beautifully recorded track is very melodic.  Each steel-sting guitar sounds great, marimbas and electric piano are so clear, and the slide guitar is rock steady in the centre.  There's a beautiful stereo effect of the two guitars playing the riff in each ear, with Lang absolutely nailed in the middle.  there's plenty going on in the background - backing singers, guitars, percussion.  But it's all there in the mix - nothing is lost at all.  The walking guitar melody on both sides is just fantastic.  I could not hear any difference between this and track 6, the USB ripped version.  Both sounded excellent!

Track 7 and 8 are Hugh Masekela's Stimela, from the Hope album.  I initially left the volco at 10 o'clock, as this is a highly-dynamic live recording, and I might regret a higher setting later on in the song.   I relented, because of the lack of weight in the kick-drum in the early part of the recording.  Despite this, the ambience and scale of the venue was very realistic, and I was looking forward to hearing the rest of the song.  With the volco now at half-past 11 o'clock, Masekela's voice was beautifully presented.  Electric piano was anchored on the far right hand side of the mix, and the electric guitar on the left.  As the drums build up, the bass weight is there, with a big kick on the bass drum.  Cymbals and high-hat are very clear with a little sting to them.  Rim-shots and cow-bells are all absolutely spot on.  You can easily follow any instrument in the mix.  Saxophone is lovely, with a great rasp to it and it changes tone as the player hits each note.  Timing is fast and tight, and as the song moves toward crescendo, there are some pretty high sound pressure levels while still remaining coherent.  You can hear the audience shouting during quieter passages, and their enthusiasm is easy to share!  Masekela's trumpet playing is breathtaking!  Sometimes mellifluous and sometimes with a realistic "blat" to it.  Not harsh in any way, and you can just imagine him stood in front of you playing.  Brilliant, wow!!  Backing singers are clear, and do a first-class job.

The thing is that, if you've heard to this track as many times as I have over the past couple of weeks, you might think I'd be bored of it.  I'm not bored of listening to it; I'm not bored of listening to this amp!

Conclusion

The SC HA was much leaner in presentation, but the sound stage and detail was of the same quality as the SRG II.  The SC HA certainly does not have the mid to low range extra weight, but there is a very liquid sort of detail in the mids and the highs.  If you want more weight in your presentation, I'd recommend the SRG II.  Perhaps this might go some way towards explaining why people think the K701s are bass-light.  They are a reasonably difficult load to drive.  The SRG II has a much more meaty presentation - there is more of everything in the mid to upper bass range.  In fact, more bass full stop.  It does seem to be very slightly less liquid that than the SC HA, but it's had to put your finger on it as there's so much more of everything coming.  "Velvety, but with lots of detail" is a good way of describing it.

The SRG needs to go to someone to test who can compare it with the previous Solo versions.  I see that Miguel has already done this, but the more the merrier!  If I remember the Novo correctly, the SRG II does much more - but so it should at the price.
I like the SRG II very much.  It's a great amp and one I'd recommend.  Whether existing owners should upgrade is another question - and would be down to the taste of the individual.  I believe an upgrade is being considered by GSP, and as it will be a full PCB change, then you get the meat of a new amp for your money. 

Cheers

Jon

P.S.  No doubt, there will be the odd typo in here.  Sorry for that.  I'll. correct them as I find them!!


Edited by jonclancy - 09 Dec 2009 at 10:42pm

Very detailed and thorough review, I can see you spent a good amount of time doing it. I really like the SRGII and was surprised w/ "musical" being a very good description of the unit. Cheers.

Thanks very much.  I posted pretty much verbatim from my realtime notes.  I hope it's of some use!  I had a lot of fun doing the review.  A big, big thanks to Graham and the Crew for making the beta model available.

Cheers

Jon

Graham, I also have the SC HA amp built by Alex (from Australia). Enclosed are some pictures of my amp.