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Graham Slee Solo SRG versus Solo SRGII

post #1 of 69
Thread Starter 
Graham Slee: Solo SRG versus Solo SRG-II

A while back I sent out an example of the Solo SRG with a PSU1 regulated power supply to various members of Head-Fi, a headphone community/forum. Interestingly we all agree the Solo SRG sounded very good and could benefit from a bit more emphasis of the bass notes. Well this feedback was given to Graham who worked hard to increase the lower register presentation, i.e. BASS.

The result is the Solo SRG-II! I have had this unit for a while and since in my experience with various of Graham’s products it would benefit from an extended burn-in process I allowed it to burn-in for 600 hours before I started to seriously listen to it. You can read more about the Solo SRG-II at: Headphone Amplifiers by Graham Slee

As typical of my evaluations I will do this over several days and with different music and headphones. For most of the comparisons I plan on using a Meridian 506.20 as a source feeding the two Solo’s via a pair of RCA interconnects built by Moon Audio using Silver Sonic BL-1 and terminated using Cardas GRCN Silver/Rhodium RCA’s. You can read more about the interconnects at: Interconnects

For the comparison I will be using the switching power supply that is part of the “green initiative” that Graham is implementing with his amps. I have a fully regulated PSU1 but only one and in the interest of consistency I am using the same power supply, source, and interconnect. Note: I realize the full potential will not be heard with the switching PSU but it should allow for the major differences to come out, then the amp could be further evaluated with the regulated PSU1. Here is a picture of the switching PSU with the proper USA plugs; additional plugs to be used through the world are included, nice touch in my opinion. For your information the power is first going through a Monster Power Reference PowerCenter HTS 3500 MkII.



Day One

For today’s comparison I decided to use the AKG K501 which has been re-cabled by Alex of APureSound using a 10’ V3 cable covered in Super Nylon and terminated in a ¼” Furutech plug. Here is picture of the K501.



As far as music I started the day with an eclectic mix from the Emerald CD, followed by a relaxing compilation provided by Corner Café: Relaxing Jazz, and finished the stint with a fast paced jazz with Swingin’ by Arturo Sandoval. Here are some pictures of the albums used.







Since I am in the mood to post pictures here is one of the gear in use during today’s comparison.



So how successful was Graham? Well as far as additional bass he was able to increase its presentation and the fact I can hear it with the K501 is in my opinion a phenomenal achievement. For those not familiar with the K501 it is a lovely headphone known for one of the best midrange presentation amongst dynamic headphones. However the K501 is not known for reproducing lots of bass which was the reason I decided to start the comparison with a headphone not known to be a “bass head” unit. Kind of stacking the deck against the Solo SRG-II, however I failed and the Solo SRG-II passed with flying colors.

As you can imagine I am very satisfied with the additional bass, it is there and you can hear it easily enough, plus you can hear a “filling out” of the lower to mid bass as well. While this may entice some what really has me “tickled to death” is the wider soundstage, longer decay of the notes, and additional clarity (beautifully heard on the opening and closing of the hi-hat) of the Solo SRG-II. I am surprised that Graham did not mention this, but I am not surprised. He does not like to put words in his customer mouths instead he rather we find out for ourselves and report back what shines and what needs additional improvement.

I will close today’s comments with the word “openness”. That is what I am hearing, an open clear sound with outstanding micro detail and superb decay. I sure hope the next round with a Grado RS-1 and AKG K701 re-cabled by Alex of APureSound is more of the same.

As with any kind of review/impression these are my opinions based on my gear, expectation and biases. Others will think differently and may reach different conclusions based on their own set of constraints. Also gear at a higher cost level could yield to different results especially with better sources, cables, and headphones. Hope you enjoyed this first step in the comparison between these very good amps. Cheers!

Day Two

I was requested to try low impedance cans like the Denon AH-DX000 series with both of the Solo’s. To that effect I chose my AH-D2000 which have had extensive mods, such as:

- MarkL Mods
- MarkL V4 Bubinga Wood Cups
- Re-cable by Zysonic using the Xev (a silver plated copper cable)
- JMoney leather ear-pads

Since I felt like mixing it up I chose my 6th Generation 160 Gb iPod Classic filled with Apple Lossless files. The dock is a Bamboo Home Dock by Ken of ALO, and I used the same RCA interconnects built by Moon Audio using Silver Sonic BL-1 and terminated using Cardas GRCN Silver/Rhodium RCA’s.

Here is a picture of today’s configuration.



For music I chose Moving On by Oleta Adams and Naked and True by Randy Crawford.





As I usually do I matched the volume out using a Radio Shack Digital Sound Level Meter, model number 33-2055 (Digital-Display Sound-Level Meter - RadioShack.com).

The differences I heard when using the K501 are far more pronounced with the Denon AH-D2000. It is much easier to perceive the widening of the soundstage (headstage). The difference in bass is also much easier to hear, there is even enough difference to say the bass has more impact out of the SRG-II over the SRG. Another thing I heard with the Denon’s is that the SRG has a bit more forward upper mids than the SRG-II.

I was so intrigue by the differences I heard with the Denon over the AKG that I decided to try a Grado RS-1 which presentation it would offer. The RS-1 gave the same contrast between the Solo SRG and Solo SRG-II, as did the K501. I then got interested in finding if the differences could be repeated with another close can the Ultrasone HFI-780 (re-cabled by Alex of APureSound and with Beyer DT250 velour pads). And … yes the HFI-780 took the path of the D2000.

So with this limited comparison it appears that I can hear a wider soundstage (headstage) and deeper bass with any of the four cans I used. However the closed cans present a wider soundstage, even deeper bass, and have a slight more forward upper mids (this last attribute is with the Solo SRG). Since this was not a scientific test and the population of headphones was only four it would he hard to draw conclusions on how other open/closed cans would perform. However it was fun experimenting.

I know which one I prefer, hint I value wide soundstage and extension.
post #2 of 69
Thanks for the review. I'll be posting about it next week around when I ship it back. Cheers!
post #3 of 69
Great review.

I'm still thinking about upgrading my solo 2007 to the new SRGII for driving my hd800's (they also need a little more bass).
Hopefully we can read more solo vs solo reviews also with the older solo models, this would make an upgrade within the solo series easier...
post #4 of 69
Really interested to see how the Goldpoint stacks up against the new GS Solo. Great review also. I like how you write.
post #5 of 69
Nice review Miguel, as always. Thanks to your generosity I was also able to listen to the Solo SRGII, and I agree with your findings completely. The SRGII has the bass weight and impact that I felt was lacking in the original Solo and SRG, and this gives it a much less fatiguing overall presentation. Instruments had more body, and this also helped the soundstage flesh out better. The SRG is a natural, transparent sounding amp. I still would not define it as lush, but it mated well with the Hifi-man HE-5, which did not sound too bright on the Solo SRGII - this was a good sign.

Definitely an improvement on this new Slee. Thanks Miguel!
post #6 of 69
i've stopped thinking about upgrading my 2007 solo to the SRGII.

I have placed my order yesterday, can't wait for it to arrive so i can start the burn-in period.
post #7 of 69
Thread Starter 
Good luck Just Julian, I sure hope you take the time to write your impressions here. Do give the amp plenty of burn-in, say at least 450 hours w/ 600 hours being better. Cheers.
post #8 of 69
Miguel was nice enough to allow me to spend some time with both amps starting with the Solo.
At first listening with the Solo, I was unimpressed and found the amp truly blasé. I called Miguel to tell him how unimpressed I was with this amp (this was with the the original basic power supply). The bass was lacking, the soundstage was narrow and the highs rolled off easily. He then advised me to let the unit warm up for a couple of hours, and OMG, what a difference. The soundstage opened up nicely ( considerably noticeable) the highs stuck around for a longer time, but the bass was still lacking.
I am no basshead, but, it was just so mediocre, that it was ruining my listening experience.

When Miguel received the SRG-II, he sent it in my general direction. I learned my lesson and from experience let this one warm up for a couple of hours, and all I can say is "wow"! Apples and oranges. It was like listening to an entirely different amp.
It appears that Graham took Miguel's advice very seriously, and went back and revisited his creation from soup to nuts. For the price, along with the better power supply, better power cable, this amp had transformed into a top notch contender. First off all, the bass was there in droves, nothing for the hip-hop aficionado, but for jazz, classical and rock, it was just perfect. Not too warbly, no mid-bass hump, and it did not deter from the mids ( a difficult task}. The mids stayed about the same, which I was already happy with on the original Solo.
The soundstage went from Giant's stadium to Carnegie Hall and the highs sustained the way way they should have.
I'm not saying that this is the perfect amp for the money, but I am saying that it's a competitive product in it's price range.
This is a relatively unknown amp in Head-Fi circles but it is an amp that should be taken seriously, especially for it's price point.
There is no fancy schmancy DAC, just a solid amp, with a high build quality, proper price point, and built by a builder who listens to it's listener's input (try that with Sennheiser).

Highly recommended.

Please note, had Mrarroyo, not turned me on to this product line, I wouldn't have it given it a second thought, which is a shame, because this amp should be in more households.

Give it a try, you won't be disappointed.
post #9 of 69
It'll be interesting to see what price they finally come up with for an SRG I to SRG II upgrade.
post #10 of 69
Thread Starter 
paulb09 if you visit Graham's site you will see the upgrade (all Solo's in the silver anodized enclosure) is already listed. He replaces the entire board: Headphone Amplifier Upgrade | Solo SRGII Headphone Amplifier

Aaron, glad you enjoyed the SRGII. Nice impressions btw.
post #11 of 69
I got the impression there might be a lower price for SRG models. Whatever is involved in making the changes, half the price of a new Solo with PSU1 is far too steep for me, and I'd imagine I'm speaking on behalf of others too.

Shame, because if I'm not satisfied with the SRG's performance using a future headphone I'm in a lose-lose situation; upgrading is expensive (especially considering there will be no way to compare the sound difference with an upgrade), and selling off will provide poor returns because the SRG will be pretty much as obsolete as the older Solo versions, even though it may be possible that its performance is as far ahead as people say.

[edit]Though I suppose I shouldn't worry because I can't even seem to sell off my OBH-21SE, so I'm not buying any new headphones for a long time anyway. UK equipment seems to be held in very poor regard around here.
post #12 of 69
Thread Starter 
paulb09 it might be better if you contact Graham directly using his site. I do not know if he reads HF or not so contacting him directly will be best, who knows he may offer you or others in a similar situation a better solution. BTW, the entire internals of the amp are replaced, only the case is re-used.
post #13 of 69
I meant to add, that if you dig Arturo Sandoval and his style, you gotta check out his album "Danzon". It's a winner and the sound quality is top notch (in the days when DDD actually sounded really good from the Grusin/Rosen period {GRP}).


post #14 of 69

MINI-Review: Grahm Slee Solo SRG-II amp

I received the SRG-II loaner right before Xmas and I've only just started my listening to the SRG-II last night, after 2 days of warming up the amp (it was recommended to leave it on all the time, and for over 24 hours for critical listening). My source is Marantz CD5001 > PS Audio Digital Link III DAC via anti-cables RCA interconnects.

I can already say that the SRG-II sounds like a different amp than the previous SRG that Miguel sent me to listen to, and the bass presence and fullness to the sound are definitely improved. I feel the amp's sound is more balanced and refined, and not with that slight treble tilt like before (although before was better than the Beta NOVA ever was). The imaging seems a little more spacious as well, but it was nice before, although it is not as open and transparent when the amp is cold. So far I have tried it with my HD600, Grado HF-2, and HiFiMan HE-5, but I will try the HD800 and IEM soon.

It always had plenty of power, and it can produce very loud volumes from my low impedance and low efficiency HE-5. However, as the volume levels get to be close to max with HE-5 on the the SRG-II the treble starts to get strident and grainy, while my 300 ohm HD600 on the SRG-II don't do that with very high volume levels. I don't know if this is due to the low efficiency headphones and the high current drain on the amp, but I would never listen to music at those ridiculous volumes anyway. I didn't notice this stridency with the EF5 amp that is designed for the HE-5, nor with the SAC KH1000 amp, both of which can go just as loud or louder with HE-5. The SRG-II has more power to drive the HE-5 than my maxed Woo WA6 (non-SE), but the WA6 doesn't get strident with HE-5 at max volume, although at max the WA6/HE-5 is not nearly as loud as with the SRG-II, SAC KH1000 or EF5 amps. The HE-5 are even quieter with the ALO Amphora, which normally drives my Grados and HD600 and HD800 to decent volume levels, so the HE-5 is not a typical headphone to use for amp eval since they say it needs an amp that can do 2 watts into 32 ohms (which my SAC, ZDT and EF5 can do). The SRG seems to come close though.

The Solo SRG-II sounds like a great competitor to amps in this same price range ($692 after conversion for Brittish pound). Since I can only have two of the amps connected at one time, one balanced amp and one single ended, it's not that easy to quickly A/B compare all the amps via the same source. In general, with the headphones I've tried so far I still prefer my WA6 sound signature despite having less power for the HE-5 (coming in at $1250 with upgrades and tubes). And with other phones except for the HE-5 maybe the Amphora comes in above the SRG-II as well ($1000), although with the HE-5 I would pick the SRG-II over the Amphora. The differences between all these amps are less than the similarities, and they are all very nice amps.

As far as where I think the SRG-II stands vs my SAC KH1000 or EF5 amps, I will need to spend more time in comparisons before I say these impressions are set in stone. So far when using HD600 I prefer the SRG-II to the SAC KH1000 as the treble is a little more transparent and the bass is a little more powerful, but with HE-5 I prefer the SAC amp (designed for AKG K1000). For the HE-5 headphones the EF5 amp is a better choice than SRG-II or SAC because it makes the phones sound richer and fuller and more complete; but for the Grado and HD600 the Solo SRG-II is my preferred choice, while still not bad with HE-5 until pushing the limits.

For my impressions on the original Solo SRG prior to the SRG-II upgrade, you can find my thoughts in the old thread from around CanJam at the end of May. I thought it was great with all my phones, except it was not remarkable when paired with my HD800 because it wasn't warm sounding enough. Graham Slee's Solo SRG w/ PSU1

I have to have the SRG-II back to Miguel by the 8th, but I will probably listen more on Monday and Tuesday and then ship it back on the 29th or 30th (don't let me forget to include the HD650 cable in the box!).

PART 2: I also listened to the SRG II with my HD800/Warren Audio Double Helix cable last night and today, plus my Westone ES3X, UE11Pro and JH13Pro.

The SRG II is now a very nice match with the HD800 vs how it was before the stage II upgrade, with strong bass on the level of the Woo WA6, good tone and soundstage, and the highs are not as sharp as before with the original SRG. The WA6 is still a little more refined sounding and richer in the mids, but the SRG II is much closer than before and I actually like the HD800 paired with the SRG II more than with my ALO Amphora now. I would have no complaints listening to the SRG II with these phones if I didn't have a couple of better but more costly amps to reach for. SRG II reminds me a lot of my $1249 balanced Single power Square Wave XL amp with HD800, but without needing to go balanced to get a big soundstage (which the WA6 also does); but the Sq Wave XL with blackgates is also no longer available. The SRG II steps in and fills that gap between $400 and $1000 in SS amps nicely.

In the $700 - $750 or so price range, if you have the HD800 then the SRG II (or the WA6 with PDPS and Sophia Princess 274b) would be my recommendation over the EF5 and SAC KH1000 amps which are a little bright with HD800, and the SRG II is also a little warmer and smoother with HD800 than the Apogee mini-DAC headphone out which I have always enjoyed with them while I wait for my tubes to warm up. In my comparisons I did find that I like the Travagans Red/OPA627 or EF2/Raytheon 6AK5 with the HD800 for those with a budget under $250, but I still prefer the HD800/SRG II a bit over the lesser amps; as it has a bit more power, stronger bass, and better micro-detail, ambience air and space.

However, all the above amps mentioned are better in their own way than the SRG II with my custom IEM, as I tried the SRG II with my ES3X, UE11Pro and JH13Pro. There is some hiss in the background with these sensitive IEM, especially with the ES3X (like the Amphora); and the volume knob has some channel imbalance at very low volumes. Fortunately it isn't playing too loud with IEM after turning the knob past the channel imbalance (even with the PS Audio DLIII DAC hot outputs). And if used with the Nuforce uDAC you can lower the input levels going into the amp to keep you out of the area of imbalance all the time.

In my rig all three custom IEM still sound best with the Woo WA6 or Square Wave XL over the SRG II, as they just seem to have mad synergy with all my custom IEM. The gap in sound quality moving to the SRG II is bigger with IEM than with the HD800. Leaving out these best two amps and only looking at the remaining ones, the SRG II with UE11Pro is slightly better than the Amphora, and a good bit better than the SAC KH1000 or EF5, as the SRG II controls the bass and fills in the mids better.

The SRG II with the ES3X is also better than the SAC KH1000 or EF5 amp which are noisier with them, but not as good as the Amphora, EF2, Headfive or Micro Amp. This is because with the SRG II/ES3X sound a little thinner and lack the full body to the sound that I am used to hearing with them on other amps. I had the same issue with the JH13Pro on the SRG II amp.

The JH13Pro were the only customs that sounded better on the SAC KH1000 amp, because their lower sensitivity hides the background noise better, and they sounded fuller and more dynamic with the SAC amp. The SAC KH1000 is designed for the power hungry AKG K1000 phones and never intended for IEM, so this was a bonus to discover that in a pinch I could use it for the JH13Pro.
post #15 of 69
Thread Starter 
Larry, the Solo SRGII like most amps was made for dynamic headphones. So I am very surprised (in a good way) that it matches so well w/ the HE5. I have yet to listen to that combo since I received my HE5 after I had sent the Solo SRGII on tour!

It is also good to see that you would have to spend well over 50% to surpass the sound and that w/ only some of the headphones, the Solo has come a long way since I first listened to Green Solo of over a year ago. Look forward to reading the rest of your write-up.
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