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Helix as an amp for real guitar cab - it works!


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Maybe this tip can be helpful for some midnight home players.
I have noticed that Helix headphone amp has plenty of power, took a look at manual and found out that it has 12ohms impedance. So I connected 8ohm guitar cab to headphones output and disabled  Cab/IR blocks. It works and sounds as it should! Like 1-2(?)W amp. Even too loud when you don't want to disturb your neigbours. I like it even more than when connected line to fx return of my tube amps set so low. There is no coloration and EQ curve already emulated in amps models but definately the speaker is as real as could be and the feeling of monitoring through real guitar cab is "that feeling".
Now i have to solder TRS to TS jack cord to bridge L/R power and lower impedance to 6ohms.
Try this at your own risk of course ;)

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11 minutes ago, zolko60 said:

So I connected 8ohm guitar cab to headphones output and disabled or Amp/IR blocks


Why disable the amp block.... CAB and IR I understand, but I'd be leaving an amp in place. 


12 minutes ago, zolko60 said:

Now i have to solder TRS to TS jack cord to bridge L/R power and lower impedance to 6ohms. Try this at your own risk of course ;)


At your own risk is right! Those are two small mono amps, they will not necessarily combine to make 6 ohms. Unless you have knowledge from L6 that this is 100% safe without damaging the unit, I wouldn't suggest trying this. I'd just use a standard speaker cable which would pick up on one side of the headphones.


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Cab (not Amp) - corrected.
So I am wating for bridged impedance value and "knowledge from L6 that this is 100% safe without damaging the unit" while playing my favorite speakers ;)
Maximum headphone amp power at some load impedances was the casual thing stated in specs. But I can haven't found specs for Helix LT nowhere. :(

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7 minutes ago, zolko60 said:

Yes I did, but don't try this at home until some Line 6 approval! :D
BTW: Speaker is speaker. Headphones have speakers so guitar cabs have them too.


You're right... speakers are speakers. If each side of the headphone jack is 12 ohm (and known to be true) I'm pretty sure an 8 ohm or 16 ohm speaker would be safe. Speakers don't draw power, they just take what they are given so they won't hurt the Helix. 


Just to clarify, my only concern with your previous post was when you thought you would "bridge" the left and right side of the headphone output. That sounds risky to me without approval from Line 6. 

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10 minutes ago, zolko60 said:

Are you aware of amps that do not lower impedance while bridged?


What would you expect if you combined the outputs of a pair of Fender Twins into one speaker. Would you consider trying that?

The same principle applies with a headphone amp. It is two separate mono amps... albeit, much lower power than a Twin :) 


Power amps are not always designed the same way when it comes to bridging.... and not all power amps can be bridged. That is the only reason I am suggesting that it might be in your best interest to check with Line 6 before creating a cable to bridge the L/R together. 

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If they want they can always show  in this thread. I am not willing to bother customer support with my insane "amp from nothing" project :D Reading of paralleled amplifiers it seems to me that shorting T with R is safe enough. 
Anyway, for my midnight playing needs I have enough power right now. Nobody can tell me now that using headphones or monitors is not what I hear using a real cab;) What I can do is even compare sound of amps I have to their Hx models at bedroom levels. It really interests me however if use of some other amp at the same volume would really be beneficial.
BTW: I was always a problem to get cranked tube power amp sound at bedroom level. Even today a good reactive load box costs 1/3 of Helix LT.

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I have consulted this with my friend. He says shorting R amp to the ground is not safe (when TS is used). So TRS to TRS cable is proper connection.
When paralleling, his advice is to use 0,1ohm, 1W "current sharing" resistors or to short T and R at the speaker TS side. To be sure both amps deliver the same signal it is good idea to place some mono DSP block before output (e.g mono volume).
I found some confirmation on yt:

I have submitted to ideascale the idea of publishing some specs of Helix to get to know the wattage of the headphone amp. If somebody is interested, please vote.

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  • 3 weeks later...

I took a tech supp ticket for headphones amp wattage. Unfortunately they seem not to have such a spec, so I have asked my friend, HxF user over the ocean to measure it for me.
He got whooping 1/4W for 8ohm load (for one side).
Connecting Celestion V30 100dB speaker to that wattage gives 94dB SPL at 1m (3 feet) distance.

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