Synergistic Red Fuse ...

Sunfire OEM AC Line Fuse is 10 amp / 32 V fast blow. I replaced with SR 10 amp, 250 V fast blow.

Lowrider, is the amp a Sunfire 300, as I was recalling? And does it say "MDA-10" for the mains fuse on the rear panel? Also, of course, a mains fuse would not be rated at 32 volts.

Best regards,
-- Al
 

Also, of course, a mains fuse would not be rated at 32 volts.

P.S: Unless perhaps a previous owner replaced the original fuse with a 32 volt automotive fuse, which might also explain why the fuse that was in there was a fast blow, rather than a slow blow which is what I’m pretty certain an MDA-10 is.

And if a previous owner had indeed replaced an MDA-10 250 volt slow blow fuse with a 32 volt automotive fast blow fuse, I would certainly not find it surprising that changing to a more properly rated fuse would make a transformative difference. And perhaps changing from the SR fast blow you went with to a slow blow would reduce the sonic downsides that you indicated resulted from the change.  As well as minimizing the risk that this expensive fuse will blow prematurely.

Best regards,
-- Al

Yes, Al, it's the Sunfire 300. On the back the Mains fuse says...
Line AC 12VAC, 50/60 Hz. The manual says 10 amp fast blow fuse.
It's quite possible the previous owner or a repair shop installed a 32 volt fuse.

I no longer use the Current Output since I bought Gallo floorstanders which only have one pair of inputs. (The Current fuse is a 5 amp Slow-blo MDL/Q). You have a great memory, as I did previously use a double-run to the speaker's upper and lower drivers.

I now use the Voltage Out since this is the standard output. As you know, the Current Output is for electrostats and tweeters. Due to the higher output resistance, there is less "body" or "slam" to the sound when used as a main output.

My impression is that the Gallo tweeters may be too revealing when using this fuse. It's the same result as when I tried the SR Black PC.
(I have even checked for correct speaker phase and polarity).

lowrider57:

What an interesting amp design from a real audio personality in Bob Carver. I will leave all the engineering to Al. This circuit is way more complicated than my thankfully simple SET amp circuits. 

Being you have an older amp , Al gives  very good advice in cleaning the fuse holders, power cord inlet, speaker ouputs and interconnect inputs. A good "spring cleaning" can be sonically very rewarding.

It sounds like the SR Black line of products are improving detail to a point that is not ideal for your system. That is my emotional response to my son's new 4K TV compared to my Panasonic Plasma TV. Too much detail that for me is distracting. He  loves the added detail.

The Isoclean fuse in my experience has a warmer, less detailed sound than the SR Black. Perhaps this or fuse or other fuses  that have gold in them would give you warmth but with less grain than the stock fuse.   

You may want to try one of the fuses offered by Music Direct. They are a fine company that has always honored their return policy.

Before ordering fuses from VH Audio or Parts Connexion be sure they accept fuses returns.

Audio Magic fuses are not normally returnable for a cash refund. At best one may be allowed store credit towards a future purchase.

When buying any product make sure to understand exactly what the terms of return are. 

Audio system enhancement and audio listening should be a rewarding and fun endeavor. I plan on having a very fun and rewarding session latter today.

David Pritchard