Duelund conversion to DIY Helix Geometry Cabling

Question for the experts, would a Helix spdif cable sound good? Would one made using 18ga Neotech UPOCC on both signal and shield perform better than 16ga milspec on shield?

@ divertiti

I have made over 4 versions of the Helix SPDIF and with milspec cabling it still beats most cables but when you use OCC on both signal and ground; you have a world class cable...

Wig

Thanks Wig, what length do you make them? I heard it has to be at least 1.5m... and what rca plugs do you use? I have only the Klei absolute harmony rcas but not sure if they are good for digital

@ divertiti

Mines are right around 1.5M and are outfitted with KLE Silver Harmony based upon Williewonka extensive testing of the KLE plugs with SPDIF.

Wig

That's great to know, I only have 18ga unocc, do you think the shield/return needs to be thicker like 16ga?

@ divertiti,

I have only used what Williewonka has recommended; 16 Ga as the Neutral. Let us know what you think after complete burn-in.

Wig

@divertiti - WRT; Cable length...

Since many people on this forum have reported better results wit cables longer than 1.5 meters you migfht think it would be the case with all cables.

However, we are talking about the Helix geometry with KLEI Harmony RCA plugs

The RCA plugs are what makes any SPDIF cable sound better, because with those you can get great performance even with a shorter cable.

Then factor in the Helix Geometry and you have yourself an extremely good cable

I have used Helix cables as a SPDIF link with the harmony RCA’s at 2 meter, 1 meter, and 0.5 meter, all identical wire and plugs and I could not tell the difference.

My last SPDIF was in my system for around 2 years and was the 0.5 meter version with

1. Silver Harmony RCA’s
2. SIGNAL: 1 x 24 gauge Neotech solid silver with Teflon insulation
3. NEUTRAL: 1 x 16 gauge silver plated mil-spec wire

If I were to build one today, knowing what has been posted in this thread alone, I would probably fabricate as follows for the very best performance

1. KLEI Absolute Harmony RCA’s
2. SIGNAL: 2 x 18 gauge solid, bare UP-OCC twisted - inside a teflon tube
3. An optional cotton sleeve over the Signal conductor assembly (personal preference)
4. NEUTRAL: 1 x 16 gauge solid, bare UP-OCC with Teflon insulation
5. and make it the length that suites your application

The only other option that may make a difference would be to use 2 x 18 gauge bare UP-OCC solid silver for the SIGNAL wire

Alas, I have to rely on others like @wig , for their excellent feedback and observations regarding SPDIF cables because I no longer have them in my system

Hope that helps - Steve

@divertiti  - WRT:  I only have 18ga unocc, do you think the shield/return needs to be thicker like 16ga?

Unless you are specifically performing  comparisons of wire you would not notice any difference there "might" be. Any difference would be miniscule

UP-OCC wire is amazing stuff, so there would be very little if any difference between 16 gauge and 18 gauge when used for the neutral

Use the 18 gauge - it will sound fantastic !

Regards - Steve

@in_shore -
WRT...’

A question to anyone , has anyone tried Furutechs F1-50s NCF ends on their helix power cords ?

I would have to guess that by the lack of responses to your question, nobody has "invested" in the Furutech connectors.

I have tried a few brands of plugs and the silver plated copper from Sonar Quest provided the best sound on my system and to my ears.

The brands I have tried in order of preference...

1. Sonarquest Silver plated Copper
2. Vanguard Silver plated Copper - a very close second to Sonar Quest
3. Oyaide Gold plated deoxidized Phosphorus Bronze
4. Marinco brass
5. Wattgate brass

Furutech products are manufactured to the highest standards for extreme applications and they price them accordingly, but for Audio applications, I consider many of their products as "overbuilt" - i.e. it’s a bit like using a sledgehammer to drive in a thumb tack

But if expense is no object - go for it :-)

Hope that helps - Steve

As an update to my search for Chassis Mount 3 Pin Female XLR Connectors.
I have found a part with a PC OCC a (Alpha) as the main pin.
It is a Furutech FT-786F, this type of part gives added confidence to the route I am taking, it is not too expensive either, and only two are required to commence the new set up.

I have extended my search further to discover PC CCC Wire that miight prove useful in the Double Helix Power Cord Design.

Acrolink do a Speaker Cable.
I have done a few searches over the past week and have seen used cable for sale at a not too extorionate asking price.
Shipping and Import will be required on most I have seen if exporting to the UK.
The Wire is available in 10 AWG and 14 AWG.  

Correction to my Last Post
The Acrolink Wire is D.U.C.C  
From  my most recent use of D.U.C.C used both on a Full Solid State System and now my own Full Valve System.
D.U.C.C Wire has tremendous capabilities at separating a singer and instrument and exgtending a Soundstage.
Between CDT and DAC the old used cable is completely relegated.
Between SUT and Phonstage the whole presentation becomes much more real and the sense of honesty has been further reiterated. 

@williewonka Thanks Steve. I made a Spdif today using 2x18ga Neotech UPOCC (stock insulation) and 16ga mil-spec as neutral (will switch out when 16ga UPOCC arrives). I made it to be 1.27m long and it performs fantastically. So much so that it's not giving much ground to a Nordost Valhalla 2 spdif after A/B. Now on all my helix cables, there is an expansiveness to the sound at the expense of tonal density. That's the last area that I think the Nordost cable does better. I suspect the slightly looser density is due to the milspec wire so will report back when I switch out the neutral.

One thing I'm unclear on is how to coil the 16ga neutral if it is being created using the air tube method? If the bare wire is free floating inside the tube, how do you coil it with the drill?

Also one more question for @williewonka @grannyring and @wig , has there been a consensus on which sounds better:
1. Putting two bare UPOCC conductors in a twisted pair inside a single PTFE tube
or
2. Insert each bare UPOCC conductor into its own PTFE tube first then twist the two tubed run into a twisted pair?

@divertiti - RE:

One thing I’m unclear on is how to coil the 16ga neutral if it is being created using the air tube method? If the bare wire is free floating inside the tube, how do you coil it with the drill?

I’ve never made and "Air" neutral.

Personally for me, it poses too much of a problem inserting such a long wire into the teflon tube

The signal wire on my 9ft speaker cables took some effort inserting the wire

1. the wire needs to be as straight as possible
2. the tube has to be held as straight as possible

To coil it with a drill I would probably

1. cut the wire 2-3 inched longer than the tube
2. first tape the wire to the rod and then tape the tube to the rod
3. then wind as normal

I would select a tube that is just a little bigger than a single strand fo bare wire

RE: -

has there been a consensus on which sounds better:
1. Putting two bare UPOCC conductors in a twisted pair inside a single PTFE tube
or
2. Insert each bare UPOCC conductor into its own PTFE tube first then twist the two tubed run into a twisted pair?

Electrons have a propensity to stay within the physical boundary of each strand of wire and only "jumps" to another strand if the amount of energy being transferred exceeds the "capacity" of that strand (or a faster route to ground is provided).

The signal in Interconnects is "low energy" and using 2 x 18 gauge wire would probably result in very few electrons making the jump between the two strands.

For speaker and power cables I use a separate tube for each wire

For Interconnects I simply twist the wires together first and insert into a single tube. This allows for a little more "wiggle room" in order to to tighten the coil down around the signal wire in order to install the RCA housing without any difficulty.

But if I have to guess - having each wire in a separate tube would probably sound "MARGINALLY" better.

Hope that helps

Regards - Steve

@ divertiti

I have done the „outer“ coil as „airadotption“ using a 6mm Teflon tube on a 1.5sqmm wire on some power cords.
For further protection I did use an additional 10mm PVC tube over the Teflon tube, (PC at 230V).
It was easy to slide the wire into the PTFE tube, but the PVC tube had been a bit more difficult, but worked.
I used to twist the 2 outer wires (2x 15 AWG) together by hand at the same time.

The PTFE tube needs to be longer as the wire, as it shortens after  twisting.
However, I‘m not sure if it is worse the extra work. My concern is, stripping the insulation may damage (cut) the OCC wire and this may „eliminate“ some of the benefits. If one could get the OCC wire naked, I would probably do the Air-Adaption.

@mawe - try Parts Conenxion for "naked" UP-OCC

https://www.partsconnexion.com/occ6n-copper-hook-up-wire.html.

They carry most gauges suited to the Helix Cables

But I am still not certain whether the "Air" adaption on the neutral is worth the effort

Regards - Steve

Thanks for all the answers gents. @williewonka I'm on the cusp of ordering but not sure if the Parts Connexion nake UP-OCC would be up to the quality of the Neotech, have they been pretty much comparable to the sonics of the stripped Neotech?

@diertiti - UP-OCC is a process and to be able to use that particular "code" i would have to guess that it is very tightly controlled and therefore the quality is consistent across all brands.

I would also like to think that Parts Connecxion also has protocols in place when sourcing their products which would ensure product quality.

You could try calling Parts Connecxion and see if they can put your mind at rest

But - If you are concerned about the quality you should buy the Neotech wire

I have not tried it, but there may be others that have

Sorry I could not be more helpful

PC OCC (Purity Copper - Ohno Continuous Casting) is a Japanese design for a Wire and has been produced under a Patent and known as the name PC OCC.
This Wire is no longer produced by Furukawa and is maily offered by Furutech who purchsed most of the final stock.

UP OCC ( Ultra Pure - Ohno Continiuous Casting )
Is made under the same Patent but is from another juristiction as the Furukawa produced Cable.
UP-OCC has not been stopped as a manufactured wire, but has been upgraded as a design to be UP-OCC a  (Alpha)
This is a cryogenic treated version that Furutech have become involved with.

Furukawa today offer PC Triple C as the replacement wire for PC OCC and the crystal structure is different in the Triple C.
It seems to work well wit Nano Treatment as to Cryo Treatment.

D.U.C.C
Is the purist of the modern wires, it is very different in the crystal structure to PC OCC, through the Crystal alignment, which are even more aligned by a In House Treatment which is referred to as 'Stress Free'

The last of the five Ohno Continuous Casting patents was issued in 1991, so these patents are all expired and anyone can make this product without license. I don't know whether there are trademarks on the name though, which could survive well past the patents. 

The OCC process is fairly costly, particularly with higher gauge materials, since the length of wire that can be produced at one time is much shorter. It's hard to believe that all the product we see on the market that claims to be OCC, really is. I don't know how this could be verified, other than by the reputation of the producer.

UPDATE: regarding  Balanced Symetrical Amplifiers

A few weeks ago I posted some updates to my web site identifying some amps that would not sound their best if a regular Helix cable were used with them.

I have now posted an adaption to the helix design that should work very well with these amps

Please see this link for the details if interested
http://www.image99.net/blog/files/b4dd81de6d4c72aa5052e5692987a506-81.html.

This approach could be used with amps that employ a single ended design also if desired...

• takes a bit more fabrication effort
• but the wire may end up costing a little less

At present, this is just in the design stage, but a fellow Agoner will be trying this approach to see how it performs compared to a conventional speaker cable

Stay tuned :-)

Regards - Steve

The name of OCC is given the name of the Professor Atsumi Ohno who discovered the Manufacture Process, where a Long Crystal was produced with the Wire.

I would assume if a Wire is produced with a Crystal Structure that is within the dimension that is outlined in the criteria for a Wire to be called OCC, there might be some ground for a challenge to be made.

There might be Wires Produced today that have a Long Crystal that is outside of the original OCC Specification, but when compared to a OFC Crystal qualifies as a comparison for it to be to be called OCC without too much risk of being challenged, especially if produced outside of the juristiction of the Patents.

Out of Interest, are the Five Patents known to have a end product of a produced wire ? and I wonder who the additional producers might have been.      

So I just bought a newly-made helix power cable from one of the guys on Tube Owners Facebook group (I think he's on this forum too) for my Cayin HA-300. Previous power cable is a Morrow Audio MAP3.

It seems to be fine for the last 2 days, but today I'm hearing a strange high-pitch static hum, kind of a buzz hum at times when no music is playing. It's not affecting my VU meter, nor does it change in volume or goes away when I put the volume down to zero. I haven't heard this before, especially on my previous cable. What can be causing this?

@jambaj0e

Test it with a cheater plug and see if the noise goes away.

But it has been all the way to this afternoon when I listened to it before I went running. Then I didn't listened to my system until after I ate dinner and took a shower, and that's when the problem started.
Nothing was physically touched on my system other than the power button and volume, and no other new devices were plugged in.
Not the mention, my amp and Chord Hugo TT2 DAC are plugged into a PS Audio Power Plant 3 Ac regenerator.

@jambaj I have read about (and observed on YouTube) noises (i.e. hum) that do not change volume when the volume control is adjusted on tube gear. It can be due to the design of a specific brand of tube.

It is related to the actual "design" of the plates and heater within the tube. Sometimes changing the tube to another brand will fix this situation.

Unfortunately there is no way of knowing which brands will work

So far I have only heard of one other incident from an Audiogon member where a hum was observed on a tube power amp after installing a Helix power cable. But that amp had a lot of tubes, so trying to debug the issue proved to be a challenge, so the member just used his previous cable

Can you try

1. reseating the tubes
2. switching the tubes around

Do you have any different brands of tubes you can try?

I would try the old cable again - if the noise is still there then it might be due to a tube that is close to failing?

BUT - Why did this happen with the Helix Cable?

Unfortunately, component designers can push their designs very close to a "limit" to squeeze out every ounce of performance

• they do not know what components and cables you will be using with their product
• so changing something as simple as a power cable can cause issues. 

I have experience component failure once before after a braided power cable was used with it

• the root cause of that failure was in fact the speaker cables being used - not the power cable
• the new power cable allowed the amp to work more efficiently, which caused it to exceed a "threshold" and the amp failed
• once the speaker cables were changed the amp worked perfectly with the new power cable

Keep us posted on your progress

Regards - Steve

Here's a video of one of the tube related issues

Two Types of Tube Amplifier Hum and How to Determine the Source - YouTube

Regards

What Happens to the Audible Hum when the Morrow Audio MAP3 is put back into service ?

The hum is still there with the Morrow Audio MAP3 power cable. I've swapped out all the tubes, except the new issue Western Electric 300b tubes since I ran out of time.

This morning, I didnt get a noise for a good half hour, then it came back. This is on the old power cable. Sigh. I'm out if the house for the day, so I can't test things out anymore until tonight 

@williewonka it doesn't sound like either hums. Doesn't really sound like an electrical hum/buzz nor doed it stay in one frequency 

@williewonka last night I've also reseated the tubes, as well as swapped out all the tubes except for the reissue Western Electric 300b tubes because I ran out of time. Didn't change a thing. 

Is the Auduble Hum coming from Both Channels with an even volume,
or is a Single Channel Audible Hum ?

Ear to the Speaker time i'm afraid, to investigate this one. 

@jambaj - since...

• the sound is still there even with the Morrow PC AND 
• since it appears to be intermittent AND
•  since changing the tubes did not fix the noise

I am starting to think that some other internal component, like a capacitor, is starting to fail perhaps?

I think because of the symptoms you have described and the remedial actions you have taken so far we can rule out both power cables and tubes as being the cause of the noise

@williewonka it doesn't sound like either hums. Doesn't really sound like an electrical hum/buzz nor does it stay in one frequency

If the frequency is varying , could it be a source component causing the issue?

• does it still make the noise with all sources disconnected?

Also - How old is the  Cayin HA-300

Regards - Steve

So it's still making the buzz, and I turned off my Chord Hugo TT2 right away, and so it doesn't seem to be the source, nor can I replicate the sound through the TT2's headphone jack.

The buzz is also a lot quieter, so much so that I could barely hear it from the Tekton Lore Reference speakers, and it's just a bit there on my Audeze LCD-3.

But biggest thing I found is that it's only coming out of the left channel. I thought it was both, but I flipped the headphones around, and it certainly traveled with the left ear cup!

And if anything, the "buzz" kinda sounds like a mix of air out of a balloon and static noise.

  Consequently, that's also the channel that had the scruffy noises several weeks ago, but went away.

The buzz traveled with the we300b tube! I swapped them, and the weird noise traveled to the right channel! On both the headphone and speaker, the noise is now on the right channel, not left! Next thing I'll have to do is take the WE300b out completely.

Just swapped back to the stock TJ Full Music 300b tubes, and so far, dead quiet. Crossing my fingers that I’ve found the culprit, and that hopefully Western Electric can ship out a replacement. If this noise problem is no more, I’m both relieved and saddened.

That being said, this problem happened a day after I used the Helix power cable on my HA-300, so as a caution, I will NOT be using that cable, sadly, and will go back to my Helix cable. I can’t say for sure that there’s a direct correlation between

I do hope that I can get a refund for the cable...

@jambaj - It’s likely the problem would have occurred at some point in time, even with the Morrow Power Cable because it sounds like the tube was on the brink of failing

Tubes can be problematic at the best of times, especially when used in designs that operate right up to the boundaries of a tube’s limitations.

I’m glad you found the problem, but I do think it was an unfortunate coincidence that a failure happened at the same you tried the Helix PC

The root cause of the buzzing was the failure of a single tune on one channel. Had there been some sort of power cable related issue it could have impacted multiple tubes on both channels or even worse the entire component

One thing I have observed - Helix cables actually allow solid state components to operate more efficiently, resulting in lower operating temperatures. This is one reason I do not believe the helix Power cable contributed to your issue

One issue I had with my Chinese built integrated tube amp - they used the wrong transformer for the Canadian market - it was rated at 100v and not 120v and as a consequence the heater voltages were 20% higher than the tubes were expecting, so it quite literally "burned through" tubes ever 6 months.at $300 per set. The company didn’t even admit this was a problem when I pointed it out to them and refused to fix the problem. I had it rebuilt and sold it - never again

I now avoid Chinese built products like the plague - I don’t care how good the reviews are!

As for getting a refund on the Power Cable - The Helix PC is NOT the cause of the problem - therefore the builder of the cable is not really at fault here AND it is a custom build - not a stock item than can be resold.

If you want to get rid of it - perhaps one of the readers of this thread will buy it from you - anyone interested?.

Regards - Steve

Hmm.... So you think it'll be safe for me to use the Helix cable again on my system. I really would like to think this is a freak coincidence, too.

Also got this from Western Electric's email for support and RMA: "Based on the detail you've given us, you may have what we call a "leaker," or gassy tube. This problem can be quite difficult to detect during final inspection and sometimes goes for years without notice. "

@jambaj
As I said in one of the posts above,

Unfortunately, component designers can push their designs very close to a "limit" to squeeze out every ounce of performance

• they do not know what components and cables you will be using with their product
• so changing something as simple as a power cable can cause issues.

I have experienced component failure once before after a braided power cable was used with it

• the root cause of that failure was in fact the speaker cables being used - not the power cable
• the new power cable allowed the amp to work more efficiently, which caused it to exceed a "threshold" and the amp failed
• once the speaker cables were changed the amp worked perfectly with the new power cable

I am extremely hawkish on finding the root cause of a problem, because without knowing the cause, a permanent and reliable "fix" cannot be implemented.

In your case
- it appears to have been a simple problematic "tube issue"
- or was it? could there be something in the design of the amp?

When I experienced problems with my Chinese Tube amp

• I thought - "it must have been the tubes"
• when I suffered a second failure I went looking for problems with that amp
• I found reports it had been poorly constructed.
• I was lucky in that I found a technician that was very familiar with the problems related to my amp and fixed it for a reasonable fee

So, for me there are two questions...

1. am I confident the Helix Power cable WILL NOT be the CAUSE of any future issues? - and my answer to that is YES, I am very confident!
2. am I confident your amp will not suffer any further problems? - unfortunately the answer to that is NO!

Amps are extremely complicated when compared to a simple power cable there are tubes, transformers, capacitors resistors etc. any of which can go wrong
Factor in things like " a "leaker," or gassy tube" and it increases the probability for something to "fail"

I have had the Helix power cables on every single piece of audio equipment I own, for over 4 years, and to date - not one component has had any issues.

If I were in your position - I would have the amp looked at by someone that is very experienced with fixing tube gear. It might have been something as simple as a "leaker or gassy tube", but it could be something more serious.

When something fails - there is a very specific reason and sometime it is not what we might be suspecting.

In my case my amp had the wrong power transformer, underrated resistors/capacitors, and underrated PCB traces - all of which had no real impact on sound quality - the only issue - it destroyed tubes after just six months of use.

By contrast - a friend of mine is still using the same tubes for 35 years - his amp was a great design and it was well built.

One last thought - WRT the comment you received from Western Electric

I would write to "The Tube Store" and ask them the same question and see what they say.

www.thetubestore.com - Your online source for audio vacuum tubes.

I purchased all my tubes from them and they ensure all the tubes they send out are in pristine condition. You might want to try tubes from there in future - just a thought :-)

Regards - Steve

One last thing - I have compared the the LCR measurements of the Helix cables to some other cables - and they are basically "Goldilocks Cables" - i.e. not too firm and not too soft :-)
- i.e. Their measure values were in the "middle of the pack"
- from a zip cord cable
- to Stock Cables from Bryston and Naim
- and custom cables made from Furutech wire and DH Labs bulk wire.

Some people will postulate that the Coil "must" cause some issues
- IT DOES NOT!
- the Helix Coil is he NEUTRAL and so is basically at zero volts

The Helix cables have been "vetted" by some very experienced audiophiles from around the world and to this day, not one person has expressed any concerns about the design

I hope that provides some level of comfort

Regards - Steve

So I actually had the Cayin HA-300 for a year and 5 months, and two months ago, my one of Psvane ACME 300b tube flashed white and resulted in a -20dB drop on my right channel. Turned out it fried a wire-wound resistor. This was the first time I've had issues with the amp, and that's with fairly heavy use of my amp since it's connected to my computer, so I'd use it 6-10 hours sometimes (something I've stopped doing since I got the amp repaired)

I took it in to a local tube repair guy who's actually part of Westerex (division of Western Electric). He swapped out the resistor per the factory schematics, tested the amp and said everything worked out and he said the amp is in great condition.

Since then, eEverything was working fine with the stock tubes until I replaced it with the Western Electric 300b, and this time, it's the left channel tube that caused problem, and it followed the tube when I made the channel swap.

So far yesterday night and today, I haven't experienced the noise issue that came from that WE300b tube, and it looks like they'll replace it.

So yes, I have had the tube repair guy look into my amp to make sure everything was going well and he said the rest of the amp outside those replaced resistors was in good condition.

Good News, That your investigation of the Hum was located on one Channel Only and the Swapping over of the Tubes in the Channels showed the Hum problem had migrated to the opposite channel.

This is one of the benefits of using Valves in a System, by following a couple of Simple Preparation Rules, Valves can easily be exchanged.
Trouble Shooting to discover if a Problem is within a Valve, or if the Issue is Upsteram or Downstream from the Valve can be proven relative easily.

The Downside of using Valves in a System is that if a Third Party measuring device is not used to confirm the condition of a Valve, the use of the Valve is a done at ones own risk.
I have had 60 Year Old Valves give a reading that Measures beyond Factory Spec, and Brand New Valves that do not offer a reading to produce a Measurement.
   
The Speedy Access that you have to the Tube EE is a very valuable assistance, when there is a raised concern.

From a personnal viewpoint, especially after the reassurances being offered about the Helix Cable to support your inquiries.
I would put the Helix Cable back into Service and assess its usage for the Benefits that are bing Perceived.  

@jambaj - I don't want to worry you, but regarding 

So I actually had the Cayin HA-300 for a year and 5 months, and two months ago, my one of Psvane ACME 300b tube flashed white and resulted in a -20dB drop on my right channel. Turned out it fried a wire-wound resistor.

and 

He swapped out the resistor per the factory schematics, tested the amp and said everything worked out and he said the amp is in great condition.

If a wire wound resistor fails it is probably because it is operating close to it's upper power handling limitations. Which implies the components selected by the designers may not be best suited for the task.

Simply replacing the resistor to "factory specs" might result in the same problem occurring further down the road.

My technician "upgraded" to resistors that could handle the actual load with ease, because he felt the designers were "pushing the limits" of the resistors they had originally selected

I think if I were in your position, especially since the amp is on for prolonged periods, and especially since you had an issue with the Psvane tubes as well - I might want to get a second opinion, i.e. before something else happens

Regards - Steve

@williewonka
I have been in direct contact with Cayin’s engineer in China, and have even forwarded some of your questions and concerns, too. For example, in regards to the wire wound resistors:

" As for your question on the wire-wound resistors such resistors are designed and chosen to protect the amplifier. Such resistors will burn first if there were flashing tubes which can cause extreme high current. If without such protection the extreme current will go to the Power Transformer directly and burn the Power Transformer. Please kindly note."

So in that way, these wire-wound resistors (different from the other resistors I've seen inside based on the factory photos. They're the gold one sitting underneath the pink Takman transistors in between the 300b sockets here: https://7review.com/wp-content/uploads/2018/08/CAYIN-HA-300-2.jpg)

@jambaj - Thanks for taking the time to reach out to the engineer

So basically - the designer of the Cayin amp has elected to use a "sacrificial resistor" as a circuit protection device

And here was I thinking that’s what fuses were for.:-)

But seriously, I have also looked into this further and it appears there is no right or wrong way, just a choice made by the amp designer

QUESTION: Should a resistor be "used in place of a fuse" ?

• some believe fuses should be used to protect the circuit
• others believe fuses degrade sound, so using a resistor for this purpose is an "acceptable risk" in order to achieve the best sound quality possible
• Some designers use purpose built breakers

Here an interesting thread on Agon that discuses a similar topic
Tube Amp - Output Power Fuse Protection | Audiogon Discussion Forum

So which "design" does a person choose ?

1. If "flashing" is a rare occurrence, then selecting amps like the Cayin you are hedging your bets that it will "likely" never happen, but if it does - you accept the risk and pay for the repair each time, but sound quality will be optimum, however, the more you use it "the more likely" it is to happen
2. OR - you select an amp that uses a fuse/breaker to protect the circuit, in which case you "may" suffer some sound degradation

It’s a similar style of "choice" I recently made...

• My previous Naim amp was very good, but the power supply Caps only last around 10-12 years before failing - it wqs designed that way - mine failed and that repair was around $400 and took about 4 weeks
• Other amps - like my current Bryston, comes with a 20 year warranty - so it will likely not fail, and possibly go on to run for even longer.

For me - I do not like being without the "hub of my system" for any length of time, so I replaced the NAIM with the Bryston.

My choice, but I now have peace of mind in that the design: does not rely on components that WILL fail (i.e. the capacitors)

In my case - it is guaranteed that the caps WILL fail at some point
In your case - it was just an occurrence that may never have happened

One thing for sure - we now understand the design approach used in the Cayin, the problem that only "may" occur and the outcome, which is of great value going forward..

Regards - Steve

@williewonka oh there are 2 fuses inside the amp too 

UP-OCC bare copper wire from Parts Connexion vs. other sources

I have just installed 2 x 14 gauge (effectively 11 gauge) solid signal wires made from the bare UP-OCC copper from Parts Connexion in my speaker cables - each wire is in it’s own Teflon sleeve, with a gentle twist.
The neutral conductor is 10 gauige stranded, silver plated Mil-Spec

OCC6N Copper Hook-Up Wire (partsconnexion.com)

My previous cables had a 2 x 16 gauge bare Neotech UP-OCC signal wire, twisted together inside a single Teflon tube
The neutral conductor is 10 gauige stranded, silver plated Mil-Spec

The quality of this wire appears to be the same as the Neotech or VH audio wire - just without any insulation, so it is perfect for building the Helix IMAGE (Air) variant.

Auditioning the new cables revealed a slight improvement in dynamics, but all the other metrics were too close to discern any improvements regarding image, fine details and clarity.

• I figure this is due to the larger gauge and also using a Teflon tube for each of the two wires, in place of two wires in a single teflon tube

The wire seemed noticeably stiffer than the the 14 gauge neotech wire I had used on my power cables, which requires a little more effort when fabricating the cables.

One other thing I tried was using the 2 x 14 gauge wires as the neutral conductor (but NOT coiled), just to see if there might be an advantage
- this revealed more details, faster dynamics, but I felt the resulting sound was too "analytical" and overly "crisp" for my own personal taste.

The one strange thing of note on Parts Connexion web site - all other gauges of this wire were "price/foot", but the 14 gauge was "price/meter".

Using this wire for the Helix IMAGE (Air) saves a significant amount of time spent removing the insulation from Neotech and VH Audio UPP-OCC wires
- well worth while :-)

Hope you find this useful

Regards - Steve

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Thank you Steve - I cannot say enough how I appreciate the time and efforts you have put into everything!