I've had my little Guanzo 2.2 two-tube 6N3 buffer/preamp for 4 days now. Here's my first impressions, along with a question/dilemma.
Ok, hooking it up was easy. Just soldered on a power cord to the primaries of the transformer and hook the secondaries up to the correct terminals on the board, plug in the tubes and go.
Since it was small and easy to move to my test bench I started with an unmodified Sony Playstation 1 (model 1001) as my source, with a modified TPA3116 amplifier and a pair of modified Pioneer SP-BS22-LR speakers. I started with the included Chinese tubes, to make sure everything was working, and then quickly switched to the Russian 6N3P-EV tubes. Even with neither set of tubes being burned in, the improvement was quite noticeable with the Russian tubes - as everyone says, the sound just opens up with these Russian tubes.
In general, I was VERY pleased with the sound. Based on this thread and others I've read, it was what I expected. I quickly moved the set up to my master bedroom system, and spent the next two days enjoying all my favorite Redbook CDs with the Playstation as the only source. I swapped back and forth between the little Pioneers and a pair of KEF 104/2 speakers I picked up last weekend. It sounded great with both sets of speakers. The most noticeable difference I heard, compared to my solid state preamps and integrated amps, was the bass with the little Pioneers. I don't have any measurement equipment to measure the actual bass response. So, I doubt if it actually plays any lower (the little 4" Pioneer midbass driver being the limiting factor), but the bass definitely had a much fuller sound than anything I've previously heard out of these little Pioneer speakers. In fact, poor bass performance was one of my initial complaints about the TPA3116 when I first built and modified them. In my experience, the TPA3116 really needs a preamp to provide acceptable bass. One thing I've notice with the little Pioneers in general is it's very easy to overdrive that little 4" midbass driver to the point where audible breakup is quite noticeable. For whatever reason, I could drive the little Pioneers louder, with fuller sounding base, before hearing any audible breakup, with the little Guanzo than any of my solid state gear. Any theories why that's the case?
Anyhow, for a low cost bedroom system, it would be tough to beat a TPA3116, paired with the two-tube Guanzo, a first gen (model 1001) Playstation 1 (from local Goodwill for $9.99) and a pair of the modified Pioneer SP-BS22-LR speakers. The little modified Pioneers, which sound pretty great already, never sounded this good before. The improved bass performance was very noticeable and an unexpected surprise.
However, not all is perfect. First, as OLK pointed out, as assembled on the 2.2 board, the rectifier gets VERY hot. I haven reversed it yet, but will do so when my Claritycaps and Alps Blue Velvet volume pot arrive. So, easily fixed.
The bigger concern comes when using sources other than the Playstation 1. After hearing how good it sounded with the Playstation, I was eager to try it with other sources, including a Sony DVP-NS3100ES SACD player and my Mac Mini with AIFF files played through a Cambridge Audio DACMagic 100 DAC. This is where disappointment set in. I fully expected things to sound BETTER with the SACD player and the AIFF files played through a much newer, more expensive DAC. What I heard was the exact opposite. When pushing the volume to anything close to moderate listening levels, everything sounded harsh - the bass broke up much sooner and gone were the smooth, non-fatiguing highs I've come to love from the Vifa tweeters in the modified Pioneers. The quality was so poor, I was concerned I'd damaged the speakers somehow. So, I switched back to the much larger KEFs - same result, just very harsh sounding overall. I thought maybe I was just driving the TPA3116 into clipping. So, I switched back to the Playstation 1 as source - magic back, problem solved (well, as long as I'm willing to only listen to Redbook CDs as my only source media).
So, what gives here? I suspect it has something to do with the output of the Playstation 1 being a good match for the input stage of the Guanzo. My Playstation 1 is another new acquisition, and I have not yet performed any of the recommended mods. One of the first mods is to up the output voltage of the PS1 to 1.7 volts (simple resistor change). I haven't measured the peak-to-peak output voltage of my PS1, but as it's in unmodified condition, I assume it's 1.1V maximum, as reported in several online test reports. That's barely half most CD players that are speced at 2.0V max peak-to-peak. So, is it possible the outputs of the Sony SACD player and Cambridge DACMagic 100, while within spec, are overdriving the inputs of the stock Guanzo 2.2 and causing this harshness I am hearing? I had planned to do the recommended mod and bump up the output voltage of the PS1 to 1.7V peak-to-peak to be closer to my other sources. So, what I'd really like to do is come up with a solution that makes the TPS3116/Guanzo 2.2 combo sound as good with all my sources as it currently does with the unmodified PS1.
So, where to start? Any chance this is a supply issue due to the incorrectly (from the factory) rectifier that is overheating? I suppose that's the easiest experiment to try. Would reducing the gain of the TPA3116 help? Right now, it's at the factory default setting (which I believe is 26dB). With the the unmodifed PS1, it's a very good match, but with the SACD and DAC as sources, it gets VERY loud even before turning the volume pot up to the 12 o'clock position, and the stock pot isn't the best at low volume settings. Or does the solution lie in modifying the input section of the Guanzo. I have the 2.2uF Claritycaps on the way, and the Alps volume pot.
All hints, theories, suggestions greatly appreciated.
