I got home late last night and decided to get the system fine tuned. This is now by far the best system I’ve ever owned.
First, there was some hum when using the turntable at ridiculously high volume levels with the arm lifted. Not audible at any reasonable volume level but I know it’s there. It finally dawned on me. The amp was next to the turntable with a Grado on the arm. Could the Grado be picking up interference from the Stingray’s transformers? It couldn’t be that simple. It was. I moved the amp as far away from the turntable as possible. The hum disappeared, although there was still some residual noise. A big improvement.
Then I started thinking about the tubes. Especially the driver tubes. The output tubes all biased well and I had to turn down the voltage to set them. Likely they have plenty of life in them, especially being mil spec heavy duty tubes. When you have to keep turning the voltage up is when you know the output tubes are on their way out. Not the case here. While there was some hiss and grunge with the gain cranked to stupid levels, it wasn’t “noisy tube” noise, so I suspected the input tubes were fine.
But the driver tubes? I couldn’t even tell what they were. The Stingray used to ship with 6414 tubes. Now they ship with 12BT7 tubes. I had a new pair of the 12BT7s. I checked with Manley’s parts department and they said you can drop in the upgrades with no other changes to the amp and that they are better performing as well. I pulled a tube this morning and very faintly on the glass, I saw that they were 6414s, so I replaced them. The new tubes are a bit quieter. I rebiased the output tubes and had to turn down the voltage yet again. All were 7-10 mV high.
I listened for a couple of hours. It’s substantially better, but I wonder if there’s more musical enjoyment to be extracted. I swapped the hotrod Gold3 for the Grado Reference3. I aligned the Grado with the Vinyl Source protractor- it was off just a smidge from the Geo Disc. With the thought that I probably have enough gain and don’t listen loudly, I left the gain setting the same- 46dB- which is low. I’d normally go for 50-52 dB. I was surprised. Yep. Even with a 1mV cartridge, I’ve got sufficient gain.
I then cranked the volume up with the arm lifted. Silence. CD level silence. The Grado Woody is so much quieter, it’s silly stupid.
And listening, bass is substantially better- even more important when running in triode mode. The sound has more body. It sounds crazy good.
So a couple of hours of time got everything sorted for free, right? Not exactly. It’ll cost a grand to exchange the Reference3 when the time comes. And I won’t even flinch. It’s worth every penny. The Gold3 is now my backup.