Preamp Deal of the Century

Hi Jazzdude,

Thanks for your effort. It certainly was informative and will help me in my selection of a preamp.

Received my NOS tubes the other day...
Tried them out on my Chardonnay this morning but ran into noise problem with the 6F6G.
Appreciate if anyone could offer some help/explanation.
I have also sent an email to our tube guru (Ecclectique).

First, these are the NOS tubes I am using:
- Bendix 6101
- Sylvania JAN CHS 6SN7WGT (3080/3430 uMHOS, 3255/3115 uMHOS)
- Brima 6F6G (black round plates; perfect matching pairs @ 3080 uMHOS)

I first replaced all the stock tubes with these NOS tubes, set gain switch at the back of the preamp to the 1st position (my preference is the 3rd position), volume set to zero, and turned on the power amp last. Quiet. Waited for a minute. Still quiet.
Popped in a CD and noticed immediately improvements in imaging and dynamics.
Half way through the first song, I increased the gain by switching to the 2nd position. Sounded better. Still quiet. When the song ended, I switched to the 3rd position. After about 20 seconds, there were soft popping sound coming from the speakers and it grew louder... they sounded like fireworks... pi pop pi pop pop pi pop). I immediately switched back to the 2nd position and the noise was gone!

Next I swapped out the NOS tubes with the stock tubes, one by one until I found out which tubes were giving problems. To my surprise, it was the Brima 6F6G! I thought it would be the 6SN7. Thinking that I could still enjoy music through the new tubes, I switched to the 2nd position. Unfortunately, this time around there was that same sort of noise, even at the 1st and 2nd positions.

I don't recall anyone in this thread having problems with their 6F6G.
Is the noise I am experiencing microphonics? Is there a workaround or way to eliminate this problem? Is it possible the tubes are faulty?
Why was it okay at first when switch was at the 2nd position?

Would appreciate very much if anyone could offer some pointers what I should do next.
Thanks in advance

Ethifi,

In my experienced, the problem you described should come from the Bendix 6101. I had the Bendix beforehand when I received my preamp and found out the same anomaly as you pointed out. As you increased the gain, the popping (like a motorcycle idling) and tube rush sound increases in proportionality.

The Syrah can use the Bendix, but the Chenin (as Mick told me long ago) cannot due to a small change in the PSU. Maybe the new Chardonnay incorporate this change also.

goodluck

When I wrote about the problem, the stock regulators were already back in place and there was no noise, even at maximum gain. Current setup (no noise): NOS rectifier, stock regulators, NOS 6SN7.
I also experienced no noise with this config: NOS rectifier, stock regulators, stock 6SN7. I have tried all combinations. Conclusion: as long as the NOS 6F6G are used, there was popping noise.

Ethifi, I was using a Syrah before and now I am having a Chenin. I found no problem with Bendix, GZ32 and GZ34 with Syrah but for the Chenin, only GZ34 can be used. I was probably the first or second guy to own a Chenin and the first guy to realise this noise problem. I even shipped the whole unit back to Mick for inspection. I am using Sylvania 6F6G but there is no such problem found. I would suggest you to try out a pair of Sylvania 6F6G and see how it goes.

Eddy