Preamp Deal of the Century

Bryan, Albert Porter was experiencing a similar problem with his IO. It turned out that by placing a small weighted bag of shot on the lid, the problem went away. The frequency of his problem was different than yours, so this may or may not work in your application. I'm sure you are aware that woofer pumping is subsonic, and could be generated from the turntable or even the record.

It's an interesting idea, just setting the gain on the IO to be compatible at a single volume for your listening preference. If you can feel comfortable with a single volume level for everything, then that would be the ultimate transparency as far as volume control goes. No volume control is about as clear as it gets. That would really be "pushing the envelope" regarding short signal path philosophy, wouldn't it!?

I think your system is cool, and I like to watch what you are doing with it. Hope you don't think I'm "butting in".

Tom - absolutely not. I don't think you're butting in. We're here to help one another right? I appreciate your help. Thank you.

Regarding the "same problem" that Albert Porter experienced, are you referring to the woofer pumping? I thought he used Sound Lab Ultimate speakers - which have no woofers.

I am aware that woofer pumping is subsonic. Prior to installing a wall shelf for my turntable, I had a miserable problem with woofer pumping which got progressively worse every second the music played - but it was somewhat different than what I experienced running the IO direct to the amps. With the IO direct, the woofers just moved a lot - it didn't get progressively worse - it seems as though it was some kind of impedance mis-match or perhaps sending an "unregulated signal" to the amps was not okay with 'em? I dunno.

Yep.. running the IO direct quite simply, showed me a potential for my system I was previously unaware of. While the sound was worlds better, it still needed & had room for improvement since at the time I was running all stock (russian) tubes in the IO. I expect that running the right NOS tubes in the IO direct configuration would produce even better results.

If any one out there has the ability to run the phono direct to the amps - by-passing the volume, I highly recommend it for an eye opening experience. Nothing I have ever heard in audio has produced such massive gains. The difference in sound was quite honestly like comparing a clock radio to a "decent" system.

thanks Jazzdude, I have an email in to John Tucker

Yes, Bryan, Albert runs Soundlabs, so the "woofers" weren't pumping, but he had a feedback like sound coming out. It was frustrating, but he eventually found that there was something causing the IO to vibrate and cause this problem. In his case it wasn't subsonic, and maybe the excitation in your case is at a different frequency, but it might be solved in a similar way. With the amount of gain at micro signal levels in that IO, it doesn't take much to make something happen.

As far as your woofer pumping goes, it must be a signal or resonance of some kind. I'm sure the IO must have a relatively low output impedance of around 1k Ohm or maybe less. That should be just fine with the Lamms. Did you try running it with the tonearm leads unplugged? That would isolate the problem to either the IO or the turntable. I just have this gut feeling that it's not an impedance thing when going direct from the IO.

Glad I'm not butting in. :^)

Hello Petland. Regarding the RCA 5u4gb rectifier suppled. It will work- however it is a "directly heated" full wave rectifier and not recommended.I would consult Mick with regards to using it, Indirecty heated rectifiers[recommended] will prevent cathode stripping of the other tubes in the line.The sylvania 5v4g that you mentioned is a good rectifier especially when used in conjunction with the early gt versions of the sylvania 6sn7's. I don't know why the guy would send you a 5u4g.Perhaps that was in error for the other 5932. Enjoy. Cheers David.