Fuses for the BHK Preamp

magister said I found that they didn't need as much break-in in the BHK 250 as the one in the BHK preamp did (no idea why).
Greater power draw?

Magister (et. al) what direction did you find worked best in the BHK Pre?


Yes, I am using all black fuses. With the SR logo, the R is pointing inside the BHK amp. I can’t comment since I don’t have a BHK preamp. I reversed the direction of my main fuses about a month ago and you can tell the sound is wrong immediately.


For those wanting to tweak...

(1) DMP - 1.6A (2) DS DAC - 1A (3) Powerplant P5 - 5A (4) BHK Pre - 2A

All are 5 x 20 mm slo-blo. Of note, these are the specs for the 120v models.

Welcome reports on results.

speeddeacon said Magister (et. al) what direction did you find worked best in the BHK Pre?
In my BHK pre, I have the writing pointing into the amp. I read some info, attributed to the people at Synergistic Research, that says: the fuses are directional, but you can't predict which way is better. So you need to try a fuse both ways when you first get it and go with the direction that yields more detail; let it burn in that way. I'm sorry, I don't remember where I saw that item, but it does match my experience, since I have the writing going in on the pre but going out on the BHK 250.

Do they state the direction of the writing reflects anything about the internal contents? The writing on the case may be random.

AFAIK SR makes no claim about the direction of writing having anything to do with the contents. It is, however, a way to keep track of which way you’ve got the fuse inserted.

I have the BHK Pre coming and have had great success in the past with aftermarket fuse, especially the Audio Magic SHD. Wanted to confirm the fuse rating - is it 1.6A or 2A ?

And where are they located, inside the tube access ?

Dev said Wanted to confirm the fuse rating - is it 1.6A or 2A ?
This is a bit confusing, since the manual shows a picture of back panel labelled 1.6A, but when my factory fuse blew I pulled it out and found a 2A; I assume the latter is what PSA is shipping now. See this thread for more discussion, including my own experience (very good!) with SR Black in the BHK.
rogerdn said And where are they located, inside the tube access ?
Fuse holder on the back panel.

Folks, for those who have used the SR Black fuses on the BHK 250, did you use the default 2AH and 10AH ratings or went one rating up?

I’ve used the Red in the BHK preamp with success and thinking of the black versions for the 250 but noticed some comments about going one size up with the black version.


I used the default size.

I upgraded today from the SRI Red to the SRI Black for my BHK preamp.

My initial thoughts are it’s a mixed bag. More detail and wider sound-stage but very bright and aggressive. I know the fuse needs at least 75 hrs to settle-in but I’ve never experienced that from a fuse upgrade before. The orientation has the writing pointing in to the preamp, just as the Red was. Hopefully it will settle down.

My other equipment is all PS Audio (PWT, DSD, BHK300) and WIlson Duettes. Any else experience this with the SRI Black?



If anyone is interested, VH Audio has the special until the end of August where you get 3 synergistic black fuses for the price of 2 (mix & match to your heart’s delight)



for anyone still following this thread re: the directional nature of the Synergistic Research Black fuses, here are my findings:

  • i went through each fuse on the signal path from top to bottom, and did the power rails as a set.

  • it was easy to tell on simone kopmajer’s that’s why (you go away) track. note how the piano notes’s musicality, the way one note floats from one to another in the intro versus how it can sound a bit disconnected between notes as if they were thudded in the way it was played.

  • preamp liked it the SR and fuse specs writing “in”. As if I am writing in the direction away from the preamp.

  • amp liked it the writing going “out” for the signal path

  • for the power rails though, i liked it going “in”

  • fyi, broke in for 92 hrs using a similar rig: https://www.youtube.com/watch?v=ud2n7Mut13s




OK, I have to ask: did you notice any difference in light quality with different fuses?

OK, I have to ask: did you notice any difference in light quality with different fuses?
A bit, when the person or child who touched the exposed uninsulated mains voltage leads lit up . . .

If I could insert a question into this string… I have to replace the fuse of my BHK preamp, and have decided to go with a Synergistic orange. The fuse has an end stamped “S” and another stamped “E/U.” The Synergistic website states: “The Synergistic Research Blue and Orange fuses should be installed with the “S” closest to the hot side of the fuse holder and the “R” closest to the Neutral side of the fuse holder.” QUESTION: Putting all this together, does it mean that the “E/U” end of the fuse should be facing toward the rear of the preamp, and the “S” end toward the inside of the preamp?

I’m pretty sure it has nothing to do with EU. It is the S and R of Synergistic Research under the logo on the body of the fuse.

I have two Orange SR fuses for the power input (the two fuses by the IEC connector) of my BHK 250. I have the “S” towards the inside of the amp.

I tried them with the “R” towards the inside of the amp, and found the sound to be lacking punch and openness.

With the “S” towards the inside of the amp, everything just seems more airy and open, and most importantly to me, there is more punch and slam.

Hope this helps.

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