32ohms

[audiophileboss]

I have an extremely $ and phenominal sounding hi fi system the I will pair this amp up to. But when i test the amp(my system is in my room, i will build amp in basement) i will just use my iphone amd Iw as wondering if I could teat the amp with my HD 429.

Could you use a 32ohm phone for a test?

[Grainger49]

You can test with 32 ohm headphones but it won't sound as good as with the high impedance headphones the amp was designed for.  You might hear some distortion caused by the impedance mismatch. 

But it will tell you if both channels are working.  Keep the iPhone as far away from the crack as possible.  They emit noise that is picked up by the tubes. 

[mSummers]

How far away do you need to keep the iPhone?  I'm building my crack for my office which has an open seating layout (no cubicles, just desks) and is full of iPhones.

[audiophileboss]

Thanks for your help! But, how far does the phone have to be?

[Paul Birkeland]

Just turn on airplane mode if it's an issue.

-PB

[fullheadofnothing]

Also, it is not a problem particular to iPhones or Bottlehead gear. All cell phones create interference that can be picked up by audio gear in general. I actually hear it less with my iPhone than I used to, but that may have more to do with using a CDMA carrier as opposed to my older experiences with a GSM phone.

[monsterdonkey]

How far? I can't say with the Crack but here's my experience: My friends and I all use tube amps for our guitars. The resting phone noise will be picked up by the guitar if the phone is in your pocket. It's a kind of ticking sound.

My friend, who's wife is on call all the time, leaves his phone on top of his amp while we play just in case she calls. During normal operation we can't hear it but if he gets a call the disturbance created by the extra activity gets picked up through the amplifier. It blasts out a much louder screech then. That's about six inches away through half an inch of plywood and possibly some sort of shielding material.

If you mess around with what you can hear and where you'll be surprised by all of the radiation coming off that thing. It might make you reconsider which pocket you keep it in, but probably just across the desk from the amp would be sufficient. You won't want the amp too close to your monitor either.

Cheers

[Doc B.]

The magnitude of the problem seems most largely influenced by these things - the mu of the input tube, the distance of the phone from the device, the carrier used by the given cell phone, and the signal strength from the nearest tower.

If I set up a Tode, with its EF86 input tube running very high gain, in the listening room upstairs we have problems with some phones. The building is very well shielded with all metal siding and roof and the phone is constantly searching for signal with its attendant bleep da da bleep da da bleep - even though you could hit the cell tower with a rock from our back door (we are apparently below the radiation pattern, or that tower doesn't talk to our phones at all).

The solution is to set the phone on the railing at the top of the stairs where they are about 20 ft from the amp. With a Crack and its 12AU7 the problem will be much less severe.

[Paul Joppa]

I would expect that a small capacitor could be added to ground the grid of the input tube and improve the situation - though I haven't experimented with it.

[Grainger49]

He hasn't had a problem yet, I was just warning him.  I should have said any cell phone, iPhones are no better or worse than others.  But they are most often mentioned here as a source of interference.

[2wo]

for what its  worth, my 4G phone is less of a problem then my last 3g or whatever it was...John