2. amps-preamps
  3. 178789-1660

Troubleshooting Fosage Signature phono amp.

I'm looking for some ideas on what this odd, intermittent problem could be. As the pic shows, that toggle switch to left of the tubes(left channel on the opposite side) is the gain between MM & MC.The right channel cuts out from time to time and I can remedy the problem by switching it back and forth a handful of times.

When I "fix' the problem this happens-channel becomes microphonic. Slightest touch, tap or vibration on the deck of the unit, or shelf is heard. When this phenomena presents itself, the signal may cut out again but often just TOUCHING the toggle, the signal is RESTORED!

Support for this product is non existent. Impossible to get a schematic, so taking it to a tech is a crap shoot. I may have to try and contact the Foz directly.

The tubes are fine, and I have checked for obvious, loose connections.

I'm thinking toggle connection/circuit path of the board connector has some kind of continuity issue. 

The cable on the right side is the toggle, in the circuit pic.

There isn't much to this box, so I'm hoping to figure out what's going on.

Thanks in advance.

 

 

tablejockey
ozzy62's avatar
ozzy62
3,219 posts
 

As much as I loved the sound of the Fosgate, it was noisy so I moved on. I hope you can figure out your issue.

 

 

tablejockey OP
3,945 posts
 

"(I wonder if those copper tube sleeves might not be helping)."

4krowme-insight appreciated. I use the Foz WITHOUT the tube shields- never noticed them preventing extraneous noise.

Having a Sunday afternoon free, I poked around and disconnected/reinserted that white   cable that leads to the output jack. Not having pulled the board, I believe it interfaces with that switch on deck?

Since then, the Foz is playing fine. Something going on- perhaps a break in continuity and that move temporarily  "bridges " the open?

Also, I redressed that red/black cable on the same  channel. The wires had just 1 twist. Doing so  completely eliminated a slight hum that could be heard at 12:00 and higher. The Foz is nice and quiet now from the listening position-WIN!

"As much as I loved the sound of the Fosgate, it was noisy so I moved on."

Ozzy62-

Yeah, I get it. I believe it's the all tube topology which is a double edged sword-fantastic sonics, but depending on music genre and volume level, tube hiss will always be present to some degree-even with "premium"  tubes.

The unit  build is el cheapo! I'm not sure if it's a MIC product, or where it's  built. 

The sound presentation however, to my ears isn't bested by some of the usual tubed suspects up to the $4-5k range. They are quieter,  but only when the music stops. Had several side by side, then heard by the S.O. and her girlfriends. They heard the Foz as most convincing, as my ears do.

 

 

 

 

 

czarivey
5,946 posts
 

tube phonostages hiss and microphonic, because tubes cannot be that of a high gain especially for LOMC carts. also tube phonostages LOVE to EAT tubes FAST so checking tubes more frequent with tube tester than in poweramp is recommended. 

tablejockey OP
3,945 posts
 

"LOVE to EAT tubes FAST so checking tubes more frequent with tube tester than in poweramp is recommended."

czarivey-since you mentioned it, I'm don't test tubes. Just replace something if I notice the SQ amiss. Some of the tubes are as old as the unit-10 year

The NVO Spa would be a nightmare finding a microphonic tube!

I've wanted to try one of these, but they get scooped up quick and rarely on the used listings.

More to discover