I finally have the amplifier. Snail mail delivery of my check to Blair, and [insert your own words] absurd bank policies concerning check clearing, were the holdup. UPS got the package to my location in Pennsylvania, 15 miles south of Wilkes-Barre, overnight via Standard Service from Blair in mid-state New York. Very nice packaging, well padded on all six walls. Also, a very nice tubeset, new JJ rectifiers and outputs, and old regulator and driver/phase splitters.
Here are my first day listening impressions, a quote from a reply to me from Blair, second day observations, and an item that I would appreciate comment on by Blair and by other Audiocircle members.
It had been running for six hours this first day. I had sold a high powered hybrid amp that I had been using, and was temporarily using a pair of 25 watt Class-A push-pull amps that use 807 output tubes. I knew that this was way too little power for the 87dB sensitivity speakers, so I was running at a lower listening level than I usually like. No problem with this new amplifier. There is now more "there" there. The musicians are now more in the room, with now more front extension added to the rear extension that I had previously, and a much better center fill. My usual live listening is small groups in small spaces, where I am seated generally 5 to 20 feet from the performers. Instrument tonality from my system is now much closer to that which I hear at live performances. The variable controls for bias and for feedback were much easier to use than I had expected. Gross adjustment took very few minutes. Small adjustments from these starting points has produced nothing bad, only a variety of good.
Any problems so far? Only one issue, mechanical noise from the big power transformer, hum and buzz, reading 82 dB down when I hold an inexpensive RTA near the transformer. Noise from the heating system, the refrigerator, and almost all music, drowns out this noise. I will want to make a padded shield to put in front of the unit. I emailed all of the above to Blair. He has allowed me to post this part of his email reply to me:
"If you make a transformer enclosure, make sure it has adequate vent slots or holes. Those large power transformers do exactly what you say- it's normal. The only way around issues like these is to use potted transformers which are virtually noiseless but considerably (around twice) as expensive. ........It is normal for the unpotted variety to produce some noise. Despite this issue, they provide the best specifications per dollar."
On this second day, I was more observant of the manner in which the amplifier powers up. I first turned on the main power switch, which powers up the filaments. After a minute, I turned on the Standby switch, which powers up the high voltage. This produced a not insignificant pop, then a brief low level whistle followed by a sizzling noise for about 8 seconds, at the speakers. I presume that the whistle and sizzle are the gas rectifier tube stabilizing, and not my speakers melting. These possibilities occur to me to remedy this situation:
- a relay and timer circuit at the amplifier outputs, to run the output through a power resistor for 15 seconds, then switching to the speakers;
- forget the Standby switch and use a soft start circuit at the primary of the power transformer.
At powerup tomorrow, I will not use the Standby switch. Perhaps there will be a sufficient soft start effect from the nature of these GZ34 indirectly heated rectifiers.
I will end this post by saying that I am very pleased with the effect that this amplifier has had in increasing the pleasure that I get from listening to recorded music.
