Synergistic Red Fuse ...

I suspect it might be best to write failures like this off to, "that’s the way the cookie crumbles." 🍪 Failure to obtain expected results can occur - and have occurred - for just about every device ever conceived. And these failures to achieve expected results often generate a certain amount of angst and confusion, especially when they occur for something that's got a lot of buzz going for it. 🐝 Like the Black fuse or the new Blue fuse. There are many perfectly good reasons why these failures can occur; and those reasons have been thoroughly covered by your humble scribe ad infinitum.

geoffkait ...

The new BLUE fuses are so good in my system that its hard to believe that someone can install one and not hear the difference over a stock fuse. Perhaps the fuse is defective? Try another fuse? Hidden agenda? What??

Frank

I have to a agree with Frank’s last post. Given the pedigree of @veerapaneni components, i am finding it hard to understand as well. I was able to hear immediate improvements over a stock fuse in my system.

May be he was expectating improvements equivalent to those that comes from a equipment upgrade :-)

Whoa! Hey, that’s exactly what they said about the Black fuse when a couple regulars reported hearing nothing on these very pages. (Say, whatever became of Mapman, anyway?) No matter how many audiophiles go bananas 🍌 over one thing or another you don’t have to look too far to find somebody who doesn’t hear a gol durn thing. It happens all the time. That’s why controversial audiophile thingamabobs abound. Maybe the dude got a dud. 😛

Joe (Jafreeman), yes, the reason I asked about the subs is that connecting a sub to the outputs of amplifiers that are balanced or bridged or monoblocks can be tricky, and I’ve seen a lot of posts here in which people have described doing that in an incorrect manner, at least from a theoretical standpoint. Although in many cases the results are still reasonably good, due mainly to the happenstance of the internal grounding configurations of the sub and the amp.

And in the case of your particular sub the issue is further muddled by inconsistent and misleading statements in the manual, which I found at this link:

https://relsupport.zendesk.com/hc/en-us/article_attachments/115015632767/REL-ST-Series-Manual.pdf

In various places the manual refers to using the sub’s balanced input for amps having balanced outputs or differential outputs or bridged outputs, or various combinations thereof. And in at least one case it refers to "differential output (bridged mode) amplifiers," which is completely misleading.

In this case, since it is a fully balanced amp it has a differential output, and the amp’s negative output terminal therefore has a full amplitude signal on it. By connecting the sub’s ground wire to that terminal you are creating a path for that full amplitude signal to the sub’s circuit ground, then through some unknown but probably low impedance within the sub to the sub’s AC safety ground, then through the AC wiring to the amp’s AC safety ground, then through some unknown but probably low impedance within the amp to the amp’s circuit ground. In other words, not quite a direct short of that full amplitude output of the amp to the amp's circuit ground, but a connection of that signal to the amp's circuit ground through what is likely to be a relatively low impedance. Which depending on the particular impedances that exist between circuit ground and AC safety ground in the sub and the amp might degrade sonics, cause hum, or even damage the resistors that probably connect those two grounds in each component.

The right way to do it is stated on page 18 of the manual:

For differential amplifiers using two subs, one for each channel: connect red to positive; yellow to negative; and black to chassis ground; plug the Speakon into the balanced high level input (Bal Hi Input).

The "chassis ground" connection can be to any screw on the chassis of the amp, assuming that paint doesn’t interfere with the connection.

As I indicated, compared to what you are presently doing there may or may not be all that much difference sonically, depending mainly on the internal grounding characteristics of the sub and the amp. But this is the right way to do it.

Finally, when you try this you may find (depending on the design of the sub’s balanced input circuit) that the output of the sub increases by 6 db, and if so you’ll have to reduce its level setting correspondingly.

Getting back to fuses, regarding your mention that...

... the front-panel display on each amp now reads at 120-121V, whereas at lower fuse ratings, the line voltage was at around 117V. The operating range of the ARC 210’s is 105V-130V.

That’s certainly surprising, but what I can say with certainty is that if the 7 or 8 amp fuses were dropping 3 to 4 volts, not to mention 3 to 4 volts more than the 10 amp fuse is dropping, while conducting the more than 3 amperes the amp draws even when idle, the fuse itself would be dissipating (consuming) upwards of 10 watts of power, converting it to heat, and promptly melting. Therefore I suspect that either the line voltage has changed, or the fuse holder has loose or corroded contacts, or the meter on the amp is erratic, or some combination thereof.

Best regards,
-- Al