REVIEW: Graham Slee Solo Ultra-Linear headphone amp - Page 2

Very nice reviews and pictures, thanks indeed.

I am about to purchase a GS Solo, and still hesitate between the SRG II and U/L... I have read that the U/L can be noisy with high sensitivity cans, which would be my case (110dB/mw for the DT48A). Anyone can confirm this ?

The GS Solo is one of the very few "affordable" amp around that I know of and has a high impedance output at 120 ohms. I guess this explain why it does offer good control even for demanding headphones like HD800.

Thanks

Thanks, Zoldar.  The digital front end is a Cambridge Audio 740C (modded).

Shamu, I am not sure about noise on the Ultra Linear when paired with highly sensitive cans.

I have no trouble with noise with the HD800, though.

Thank you Zoldar and Kachui for your feedback. Unfortunatley, HD800 and K701 are not what I would consider high sensitivity cans, and I find it difficult (maybe too risky) to extrapolate... I reckon Graham Slee himself did acknowledge on its forum that the U/L could be a little noisy with some highly sensitive cans...I guess I will go for the SRG II as a starter .

Quote:

Originally Posted by shamu144 

Thank you Zoldar and Kachui for your feedback. Unfortunatley, HD800 and K701 are not what I would consider high sensitivity cans, and I find it difficult (maybe too risky) to extrapolate... I reckon Graham Slee himself did acknowledge on its forum that the U/L could be a little noisy with some highly sensitive cans...I guess I will go for the SRG II as a starter .

Thanks for reminding us. Just read the following explanation from Graham's forum:

"So far I have two "complainants" regarding Solo Ultra-Linear noise...

If you swap from a high impedance phone to low impedance phone without swinging the volume down to where it should be, you will hear noise...

This is very reminiscent of valve noise...

So I guess the Solo Ultra-Linear does the valve job here too... Great!

Unfortunately, the one thing I or anybody else couldn't do all those years ago, is make valves noiseless (and still can't), but hey, it didn't matter because the sources then were not noiseless neither.

Since then we have noiseless CD and all sorts of other digital "music". If you read up on how digital "music" works you'll see how the noise floor is cheated by "bit shifting"... you can't shift bits if you don't have any bits, and you don't have bits in analogue...

The Solo Ultra-Linear is a purely analogue amp that does not use great lashings of negative feedback to achieve ultra low noise, so, as the transducers (phones) are strapped  in close proximity to your eardrums - when you wind up the "wick" - you will hear hiss and hum (like valves...!)

Now please don't play music whilst the volume's right up there or you'll probably kill your hearing, but turn it down to your usual listening level, then listen again for the noise...

...did it go much quieter? Thought so...

You see, this is a thing called signal to noise ratio (SNR) and with the Solo Ultra-Linear it is -79dB. How do I know? I measured it with a thing called an AUDIO TEST SET. Audio test sets are precision analysers that do all the measurements such as noise, distortion, frequency response etc...

image courtesy Thurlby Thandar

This is our new one (not much change out of £6,000), and the old one was a Wayne Kerr AMS1. We also have oscilloscopes like this one...

image courtesy Farnell

-79dB is the level below the actual musical signal where the noise appears. If you park the volume control up full when it needs to be at say 12 o'clock to blow your eardrums out, then the noise will be heard. But if you turn it to a comfortable (rockin') level then listen to the noise it will be sufficiently back (79dB back, or 10,000 approx. times back) that although you will be able to detect it, it will be of no worry to you.

Now, the argument will now, I'm sure, go something like this...

"But I have a valve power amp/integrated amp and that isn't as noisy full up"

And my answer is this...

A speaker amp is designed for 8 Ohms. It will have enough latitude to drive 4 or 16 Ohms and that's a ratio of 2:1 or 1:2. With the Solo, the latitude is much more (much more). It spans 25 Ohms to 300 Ohms going on the sort of headphones in use today. That's a ratio of 12:1 or 6:1 and 1:6.

Therefore that's 3 times more latitude than a speaker amp obtainable on the Solo volume control. In fact it's more than that because the Solo is designed to do 8 Ohms to 2000 Ohms giving a ratio 125:1 or 1:125.

Now I hope it can be seen that with signal to noise being a relative thing (relative to the music) that the Solo has a much bigger job to do, impedance wise, than a speaker amp?

Conclusion

If the reader still thinks that the Solo should be completely noiseless, and I say it can't be, and the reader wants no compromises, then the reader must not buy it.

If such a reader has already bought one and is not happy with the way nature works, then, prior to leaving planet earth to find a utopian planet where all things are fantastic all the time, the Solo Ultra-Linear can be returned for a refund.

The difference between the quietest Solo we ever made and this one is 10dB which means the Solo Ultra-Linear sounds twice as noisy as a 2007 Solo.

(-79dB will hardly be noticed by anyone with a vinyl source)"

Also it does not have adjustment for output level...hum...like to hear others' experience with efficient phones

 

Thank you Greeni for quoting the answer, I couldn't locate it on the GS forum.

When I look at technical specs, I see an output noise of -84dB for the SRG II vs -78dB for the U/L.... Actually, not that much a difference between both... Mmm, difficult choice indeed, I like the idea behind the ultralinear amp though.

Would be very nice if someone with experience with those amps and "above average" sensitive cans could chime in. Isee that the Denon D2000/D5000 family has a high sensitivity at 106db/mw for example, it could be a good indicator.

i am in the market for a new amp, and fancied trying a tube amp as i have never heard one.

thing is, i already own a solo srg1 and could get this upgraded to ultra-linear for half of my tube amp budget!

i could do with more feedback from people who are familiar with tube amps and have compared to the solo UL.

any advice?

cheers

pulled trigger on ultra linear diy upgrade.

seems like great value to me.

After some hesitating deliberation for choosing between the Solo SRGII and UltraLinear, I finally decided to purchase the Graham Slee UltraLinear.

I received it around christmas last year, and have been enjoying it a lot since then.

Before entering into the subjective evaluation part, I wanted to answer my own previous question regarding the possible hiss when using my ultra sensitive DT48A with the Graham Slee UltraLinear. With 5 ohms and 110dB/mw, and if I am not mistaken (using this formula I found dB/mW = dB/V - 30 + 10*log(R) ), this translates to 133dB/V, which is indeed extremely sensitive for a headphone, on par with the most sensitive IEM out there.

Well, unfortunaltely, the answer is yes, I could hear some background hiss, quite noticeable especially during quiet moments of music. However, I have been listening to the UltraLinear and DT48A combo during those last 4 months without any frustration, amazingly... Yes, there was audible background noise, but there was also something else grabbing me at the same time, and that noise was actually never messing or interfering with the music, quite unobtrusive. I finally have had soldered recently a pair of very high quality 75 ohms Z foil radial resistors directly into the 1/4" jack of my DT48A, and the hiss is now gone for good, which leaves me with pure bliss of music.

I don't have lot of experience with headphone amplifiers, and I have only owned a handfull of those (Rudistor RP5.1, Rudistor NX-33, Creek OBH21, Little Dot MKIII, Little Dot I+) and still own a Creek OBH11 and Meier Stepdance at the moment, so please be gentle with me and consider my relatively limited experience with amplifiers when reading my impressions.

Still, right from the start, the Graham UltraLinear has brought something new to the listening experience as compared to all other headphone amplifiers I heard before. They certainly was a burn in phase for the UltraLinear and it is actually the first time I noticed it so apparently with a piece of equipment. At some point (not sure how many hours but maybe somewhere between 20 and 50 hours), the sound became very hollow and dull, overly dark, before finally stabilizing and offering its quite unique liquid sonic characteristics.

I really don't know if this is linked to this "phase linearity" trick, but the UltraLinear is sooo convincing at playing back music, it indeed feels as if overtones and harmonics present in recordings are perfectly portrayed and respecting the timing of the music. This is especially apparent in the lows and highs frequencies to me. The high frequencies are completely free of any glare or harshness, but still vivid and lightfull, delicious in their extension but never out of place. The lows appear as breathing again, not congested and restricted, not sounding artifically fast or dry (ouch the Meier Stepdance sounds rather analytical in comparison, artificially fast sounding with sharp edges even in the low end). It really gives the sensation of a more powerfull foundation to the music but bass is not accentuated or emphasized, but rather sounding full and melodious again. A trully fantastic listening experience.

There is also something else going on with the outstanding stability of imaging that just feels relaxing, without having your brain busy, constantly processing information and trying to recreate a virtual image... In fact, this is the less fatiguing headphone amplifier I have heard...

Those impressions are especially true with the DT48A. The Fostex T50Rp I also own for example do respond in a similar way but to a lesser degree as they already have a rather smooth own sound character.

The level of resolution of the UltraLinear I feel is excellent, just plenty enough to look into the different recordings, ambiances, reveal differences in upstream components, power cables, etc...

Sincerely, I have a very hard time criticizing any aspect of the music reproduction through the UltraLinear. It has really become an essential part of my system which I feel is now completed, allowing me to just relax and enjoy as much music as I can. Highly seductive without obvious colorations.

Anyone compared this to the Matrix M-Stage?

Both great reviews :)