Audio Research Ref: CD8

It seems ARC is replacing the bypass element of the regulator (2x6h30) with a 5881. Considering they have to fit an adaptor board, the 6550 would not fit as it is a high tube - the 6881 is much shorter.

My CD8 is now spinning the Purist Audio Design System Enhancer in repeat mode and I will wait at less 24 hours before listening to it. I just measured it and did a spectral analysis to be sure everything was correct and comparing it to the CD7 could find that the CD8 output level is 3.5dB lower, as I confirmed later from the respective manuals.
When comparing these units one must carefully match the volume, otherwise the CD7 is much louder!

The CD8 output is 1.8V RMS RCA and 3.6V RMS XLR .
The CD7 is 2.7 and 5.4V RMS respectively.

I am using the Purist Audio Design System Enhancer CD for break-in, so I hope that after 100 hours the CD8 will be listenable. I went through two CD7s and I still remember how disappointed I was when I replaced one with more than 1000 hours play by one taken from the box.

My perception after a few minutes listening is that the CD-8 is more detailed and has better bass definition - air moves faster - the fly at track 10 minute4'44'of Paniagua LaFolia is clearly heard!

The two 6h30 problem drift was solved with an upgrade kit that was fitted by my distributor free of charge, after I noticed some hum in the CD output when used in single ended mode. This was traced to a defective 6h30, but after this upgrade I had no more problems. Before parting with the old CD7 I checked the tubes - after 2500 hours they still measured as new.
Although the CD8 is still burning-in, one thing is sure - bass is better articulated and more controlled. Three walls in my room are 2 feet wide solid stone and there is almost no bass absorption. As I am currently using Soundab A1PXs, bass performance is critical and the difference between the two players is easily noticed.

Although it is still too early to have a definitive opinion - my CD8 has only around 250 hours continuous playing time with same breaks - it is now very different sounding from the CD7. The sound balance is different, the CD8 bass has better definition and resolution. During the last days the CD8 has become somewhat bright, sibilants seem enhanced. I hope that after burn in the tonal balance becomes fuller again!

Hi,
I have fitted myself the two tube upgrade kit to my old CD7 and did not find it deteriorated the sound - truth is it did not change, compared to a good set of matched 6h30.
Later a close friend also had it fitted to his player by the distributor and considered it an improvement. As he was listening to an unit with defective 6h30s in the power supply immediately before it is not a good case.

Owners using RCA units immediately noticed the hum noise when the tubes were not matched, people using the XLR output only noticed a much poorer sound.

My CD8 is still burning in ...

My CD8 has been now been playing almost continuously for 22 days approaching 500 hours. Happy to tell that after burn in the bright, sometimes almost edgy sound is completely gone.
During the burn in phase I had to remove the Valhalla cables from my system as they exacerbated the sibilants and splashiness, but today I could use them again.
One thing is sure - the bass control and depth are improved and it is more detailed than my previous CD7.
I will wait a few days more before borrowing my old CD7 to make a direct comparison.

76doublebass,
Can you tell us what cables and amplifier were being used in this system?
My CD8 is now approaching the target of 600 hours burn in. As soon as it stabilizes I will compare it to the old CD7.

My CD8 is sounding better than ever. I am currently hosting a pair of JM Labs Grande Utopia Be - great speakers, that have a tilted up balance in the upper frequencies above 2 kHz. Until two weeks ago I could not listen for longtime to to the CD8, as the sound was very clear an defined but too bright, I even preferred a CD3 mk2 for longtime listening. However, currently the CD8 evolved in a sweeter sound, matching the tweeter of the GUB perfectly. I feel the same as Elberoth2 concerning resolution, but I reserve my comments to a direct confrontation of my old CD7 versus the CD8, to be done soon.
Beware that during burn in the sound of the player will become dull during at a certain phase before stabilizing at its definitive (I hope!) balance. Even with the Purist Audio System enhancer CD burn in took over 600 hours.

Please do not consider me pedantic, but I think that such thing as the "6h30 sound" does not exist.
I owned Audio Research REF2 mk2 , REF3 , conrad johnson ACT2 and ACT2 series 2 (all using the 6h30 exclusively in the amplifying stages) and could not find a common trait between these four preamplifiers. A friend of mine owns a BAT phono unit and it does not sound as a cj or an ARC!
Circuit topology, operating points, power supply and choice of passives have great importance in sound balance. I think that the main reason why many manufacturers are using the 6h30 is because it is reliable and lasts long - I recently measured the 6h30s of my REF3 that have 4093 and they still measure as new!

Turko,
Difficult question - no CD is close to analogue presentation. I own a SME30A/2 and I can not say that the CD8 is closer to the analogue sound than the CD7 or vice versa. The type of sound of the CD8 is quite similar to the CD7, but has a more defined bass and more detail in the higher frequencies. You can have much larger differences in analogue with the same turntable and tonearm just changing cartridges.
I have not compared the CD8 with the CD7 with the upgraded 5881 power supply - the friend who got my CD7 had it modified and told me it was a considerable improvement.
Even long term A/B comparisons are not absolute - you just testing if a piece matches your system better than the other.
In my opinion comparing analogue with digital in the same system is unfair - you are just establishing if this system is optimized for analog or digital. Unhappily I never saw a system optimized for both, the best analogue systems I heard were a disaster with CD and the best digital ones were un-interesting with vinyl.