Zu Soul Superfly

I changed a couple of variables in my system and gave the Dynaco another shot and I'm actually liking it a good bit more. I kept my reference ICs on my pre1 to F1/TWO.2 and threw on a "magwire" IC between my pre's second outs and the Dynaco and a pair silver speaker cables--(Grover SR, an old version I still have on hand) between the Dynaco and Souls and I've gotta say, its sounding great.

More balanced, lush and musical and very dramatic sound. I think I will keep this sucker as its matted to my extra cables anyway. Whether you believe some in cables or not or just consider them tone controls, this was a move towards what I was looking for in many respects. Interestingly I think I prefer how my digital sounds with my SS amps and analog with the tubes.

I'm very excited to have the option of switching between what I consider very good solid state and nice sounding tubes at will and without cluttering my living room.

As Phil stated in previous posts, the Superflys let you REALLY see the difference between different amplifier's presentations. That said, this will probably conclude my amp rolling for at least a little bit. I'll report back when I get the JFETs in my F1 though.

Time to go enjoy some music.

Gopher:

I mentioned to you on 7/06/2010 about upgrading your F1 to the F1J. I've read here since that you are going to do so. One potentially huge difference (problem?) for you, especially if you are using a tube pre: the input impedance for the F1 is 100K ohms single-ended and the F1J is 15K ohms (note at www.firstwatt.com under products it says 100K and 10K respectively, clicking on F1J it says 15K single-ended). Rule of thumb (from conrad-johnson): pre output impedance < 10% x amp input impedance, i.e. your pre must be less than 1500 ohms or you will probably lose some of the low-end frequency. You might want to send an email to Nelson Pass at nelson@passlabs.com and discuss this, especially if your pre has an output impedance greater than 1500. I'm anxious to hear what you think of the Soul/F1J combo, if and when you finally upgrade.

Regiggey,

Thanks for the concern. I asked my dealer who in turn asked the designer of my preamp and he said the following:

"I do not have the spec. of this F1J machine, but I guess it should be some SS power amp. The MM Pre has a cathode follower output stage, it should push this F1J fine."

A lot of the tech talk is lost on me, but I am concerned now reading this rule of thumb as the published specs are of my pre are:

Input Impedance: 100K Ohm
Output Impedance: 700 Ohm

Hmm, I already bought the damn Semisouth R100s and got an audio buddy to agree to do the update for me... Is this likely to be a poor match?

The rule of thumb is 10:1, that is, the input impedance is 10x the output impedance between the two components. I've also heard the rule of thumb is 20:1, but hey, it's a rule of thumb right, so the truth is probably somewhere in the middle, somewhere between 10:1 and 20:1.

MM Preamplifer has 700 ohms output impedance
700 ohms * 20 = 14Kohms
F1J amplifier has 15Kohms input impedance

14K < 15K

So you should be good.

Gopher:

You will not have a problem. Your are telling me that your pre output is 700 ohm which is less than the critical number of 1500 ohms for the F1J. 10% x 15000 ohms = 1500 ohms (F1J input single-ended impedance is 15K ohms (K=1000) or 15000 ohms. 700 ohms < 1500 ohms, so you will have no problem. Now, I'm assuming that the person who will be updating your F1 will be doing what Mr. Pass does when he updates a F1. To be safe, have your guy contact Mr. Pass via email and discuss it with him.