Aesthetix Io-Reliability Problems???

I've been asked by Rush Paul to contribute my experiences with the Io. I purchased the Io w/attenuators in early 1998 from my dealer in Denver. This was prior to the numerous favorable reviews in rags like TA$, etc, which caused Jim to be swamped with orders.

While I may differ on some tube choices, I agree with Albert Porter that the unit benefits greatly from NOS tube replacement. The choices will rely personal taste and require experimentation.

With respect to reliability, I experienced only one problem in the two years I owned the Io. I had inadvertently left the unit on for several days and the left channel went out. I emphatically disagree with leaving it on 24/7 unless you are providing your on clean power.

If you've been under the hood of the Io, you will see that Jim has used both plate voltage regulation (SS) and constant current sinks to better linearize the cathode followers. These devices, unlike tubes, can fail instantly with line spikes. My Io was plugged directly into the wall outlet (dedicated circuit) because there isn't an "audiophile" power "conditioner" out there that doesn't limit dymanics. Obviously, the unit had seen some trash on the line and it took out the first stage VR and CCS. Jim fixed the unit rapidly under warranty.

I sold the Io in February, 2000, to the reviewer for Ultimate Audio and it was used in the UA review. At the time, I considered it the premier commercial unit available.

Can the Io be bettered? Absolutely! Anything built to a price point can be bettered.

I think there is likely only one commercial unit on the market that would exceed the Io's performance, and that's the Wavac phono designed by the late Nobu Shishido. I don't know how much longer that unit will be available since Hirata Electric closed their Tango transformer division last October. The Wava uses a Tango step-up on the inputs and the excellent low impedance Tango LCR RIAA module. The use of high quality transformer and inductors in the EQ is a far superior approach to the typical stringing together of CF gain stages.

IMO, there is no unit using transistors at any price that would even merit consideration in the breath as the IO and the Wavac unit.

The preamp I am currently using is a variant on the Soul Sister (line) and Groove Thang (phono) published in the e-zine VALVE. (www.bottlehead.com). It has a custom step-up at the inputs (1:20, from Sowter in the UK wound
with wire from PHY-HP in France). Those feeds a first stage 6ER5/EC95 (a frame grid single triode) that is actively loaded (CCS) and shunt regulated
with a pair of 0D3 gas regulator tubes. Passive RIAA that employs correctly the 3.18 uS time constant between that and the second 6ER5, also actively loaded with a shunt reg. The phono section is cap coupled to a single 76 (again actively loaded and shunt regulated) in
the line section. Output is transformer coupled in parallel feed topology using a MagneQuest nickel core line output tranny (15K:500). Power supply is separate and is larger than the Io's. Completely dual mono, including
separate AC cords. Separate, DC current-regulated heater supplies for each stage and channel and no electrolytics in the B+ rail.

Better dynamics and a greater ease of presentation than the Io. Does all the ersatz "audiophile" tricks the reviewers fawn over, but also gets, most importantly, tone and timbre correct, which is a weakenss of the Io by comparison. Pace, rhythm and timing are set by the musicians and are free of the constrained and slightly sluggish presentation of commercial units. In short, there's more there there.

Those interested in this DIY apprach and the planned revisions to the preamp described above, feel free to e-mail. I'm not an Audiogon member and do not frequent the board, so replies here will likely go unseen.

Well, when he received the unit from me he said it was damaged and didn't make a sound. Turns outr one of the EL-34s had worked loose in it's socket and blew a fuse. Of course, being a reviewer he didn't check the fuse and sent it to Jim White for "repair". At my expense.

I spend more time at my workbench now and less paying attention to mainstream high-end, so the unit's reputation for unreliability was news to me. My one problem was my fault, I believe, because I failed to turn the unit off and the failure was either thermally related or due to line spikes (or both).

As for sound, I said it was quite good, perhaps the best commercially available - I haven't has the opportunity to hear the Wavac, assuming it remains available. But there are DIY circuits out there that improve on the Io.

One of the unavaoidable weaknessess of commercial tube units is that they must rely on current production tubes. The 12AX7 and its variants aren't very linear but are chosen solely for the ease of use (size) and amplification factor (100). The tube was developed in the early '50s in response to what was perceived as a market trend toward minituization in home electronics. Two triodes in a miniature package with a high mu is a bean counter's dream. The 6922 is marginally a better tube, as is the 6SN7. The use of the popular cathode follower circuit and variants for the low noise and gain offered ignores it's tendency to wander all over the map in terms of operating points means that additional steps in the forms of voltage regulation, active plate loading and a current sink must be used to clamp the tube's OPs with a narrow, desireable range.

None of these tubes, however, exhibit the low level linearity of the directly heated single triodes from radio's early days. Unfortunately, these tubes are no longer made and are therefore not feasible for a commercial venture.

In addition, these are low-mu triodes with amplification factors ranging from 3 to 9. So the problem is where to get the extra gain. The solution is in the use of high-quality interstage transformers and plate chokes. This produces a stage-to-stage stability that can't be equalled by cap coupling and it gets the cap out of the signal path. It also allows employment of the simpler anode follower topology, and even topologies like parallel feed which removes the chore of handling DC current from the interstage primaries. This nallows more permeable core materials to be employed and the result is better clarity, better low level detail, and an overall ease of presentation. Of course, your replaced a $1 part with something that will cost $60 on up to several hundred dollars, depending on circuit requirements and core materials.

This makes it difficult to turn the necessary profit since the market is small and the high-end rule-of-thumb sets MSRP at 5x to 8x the cost of parts. But it undeniably a superior approach if cost is no object. See the schematices at Sakuma-san's Direct HEating site (http://www5.big.or.jp/~dh/) for both amps and preamps that employ these techniques.

All of these circuits are invariably less complex - a good thing - and make liberal use of high-quality transformers and chokes that replace highly variable (in a QA/QC sense) resistors, caps, and silicon devices. As Einstein said, "Make is simple as possible but no simpler." The Io's complexity, coupled with increased demand for a product that is essentially the designer's second job, may have something to do with the reliability issue.