Isoclean Fuse

Recently, I purchased an Isoclean fuse for my ARC VT100 MkII. The value of the fuse for the amp from ARC, is 6.25A / slo-blo type.

When ordering the Isoclean fuse the sales person informed me that Isolclean doesn't have the exact value of 6.25, so I should go up to the next fuse value of 7A (they either had a 6A or 7A).

When I installed the new fuse, what I noticed (and I don't know if this has anything to do with the new fuse) is that the bias of the amp dropped severly (from right at 130mV, down to around 88mV). After installing the new fuse I rebiased the amp but I couldn't get the amp back to 130mV. The best I could get was around 127mV, and this was with the trim pot turned up all the way. (Please note that all biasing was done after letting the amp warm up, with no music playing, for a minimum of 30 minuetes).

Just to check, I removed the Isoclean fuse and inserted the original fuse. Now, the amp showed a bias of 145mV, which I was able to lower back to the proper 130mV setting.

My questions are:

1) Is it OK to substitute a fuse value of 7A for one that is supposed to be 6.25A?
2) Would putting the 7A fuse in the amp cause the amp's bias problem?
3) Are there any other problems that may occur by installing the wrong value fuse?

Any remarks / recommendations that you can make will be appreciated.
Here's my advice. Don't spend $25 for a fuse.
Sometimes one should leave well enough alone. Isoclean fuses are not the answer to all future improvements, if any at all.
I know that they have a 6.3A because I bought 1 for my rowland amp. Ask them to order some for you.
IMO, the fuse had nothing to do with the bias level. NO, you should not put a higher fuse value than the original value.

I fuse does nothing except blow at specified value. Your ARC does not max out the 6.25A all the time..probable not even close. The value has been carefully chosen so if ever a short happens, it will blow before your internal components start to go.
Never use a fuse of a higher rating than specified. This is a recipe for disaster. Those people should have not even offered you a higher rating as I seriously doubt they'll pay for the repairs on your amp because the fuse rating had been too high. If they have a money back guarantee I'd take them up on it due to their ethics.
To Louisl, you should ask ARC if the fuse value directly affects the bias. I have not heard of this before, but I am not familiar with the ARC circuit. If you want to return the fuse I would be happy to refund your money. You may also want to ask ARC if you can use a 6.0A to replace your 6.25A.

To Genesis168, The 6.3A fuse is only made in the 5x20mm size. The ARC amp as well as most all US made electronics use the larger 6x31.8mm size.
A couple of comments. First, the only way I know of that a fuze can effect the bias is if it has a high enough resistance to cut the voltage from the power supply. It seems unlikely that a fuze would reduce the bias by over 25%. Something else is going on here.

Second, the MK II has 2 trim pots that need to be adjusted to set the bias, and it is an iterative process. Did you adjust both? Here is a link to an excellent treatise on how to bias this amp.
Since you are familiar with biasing, you probably know this already, but I put it here in case others may need it.

Third, I agree that you should not use a fuze of higher value than the manufacturer recommends, even though it is only marginally higher and would probably still protect the amp. The risk is just not worth it.
I encourage everyone to read the reviews and comments written below by the press.
What artistic audio is doing here is tantatmount to posting an advertisement. There is a separate section of Audiogon for such activity. Please refrain sir.
first of all, $25 for a fuse is insane. second of all, if the sales rep suggested you use a higher value fuse than you needed, then this company doesn't know s&%t about how a fuse works or what a fuse does. thanks for the heads up, i'll be 100% certain to not waste my money on this tweak.
Might I suggest using silver contact paste like Walker SST rather than wasting you money on the slower and inferior gold. The fuse is not unique here, only the gold plating...

Also keep in mind how many fuses you may have to protect you circuits. My Sony SCD-1 has three inside and one power, my Plinius SA-102 has four inside and two additional...

Silver treating these will do far more than one $25 fuse in one spot.
For the negative members responding to this posting I suggest you actually try the Isoclean Gold Fuse before you pass judgment on it's performance.

Also for everyone's information the only fuse that needs replacement is the main fuse that supplies power to your component.
Wow, I didn't intend to start a World War. Come on guys, lighten up a bit.

I'm a tweaker, and firmly believe that certain tweaks can help your system...not become something that it's not, but to improve on what's already there! I can tell you that I've spent much more than $25 for certain tweaks, haven't you? Some worked, others did nothing. Even though $25 for a fuse might seem insane, if it improves the sound, why not? Besides, Artistic Audio is trying to accomodate me by offering to refund my money!

After speaking with ARC, I removed the fuse from the amp (just to be on the safe side) and plan on exchanging it for one that will be a proper fit in my CD player. I'll let everyone know the outcome!

To Jadem6..I did clean the original fuse, and treated it with Caig's "ProGold G5 Contact Enhancer". It was an immediate improvement. I suggest everyone do the same!
Please stop the tasteless self promotion and advertising.
Artistic, I agree I should not pass judgement until I hear them. Perhaps you would loan them out to me as a trial, if I see the improvement, I will buy them, or you will agree to take them back if I find no benifit. If you look at my system posts, you will see I am a self proclaimed tweak freak, and am not usually a na-sayer.

How is it that only the power supply fuse needs changing? My Sony SCD-1 has three interior fuses that appear to be a part of the power supply circuitry. My Plinius SA-102 has two 10 amp fuses per channel as speaker protection. I assume the signal is passed through these, it would seem logical that they are even more prone to sonic quality than the power fuse.

I hope I read this as a non-attacking, non-judgemental post, in that I would like your input. I will let others judge your motives for posting, I was assuming it was to help educate...


PS I was serious about my offer to try them, please email me if you want to take me up on this.
I just applied Silver treatment to fuses in my poweramp and Monarchy DIP with nice results