Review of the Little-Dot MKIII Tube Headphone Amp/Pre-Amp

[Mike_TNT]

Originally Posted by ethebull

a) Normal / of no concern. LD matches the tubes electrically, glow brightness is not an indicator of balance or imbalance. The "burn mark" is called silvering, on the top of the tube. It's stuff they coat the inside with during manufacture. There's always variation.

b) Best practice is to turn off the amp when switching phones, waiting a few minutes, then proceeding. this might be overly cautious, but always do this when switching tubes, installing the jumpers, switching gain settings, or unpluging RCA's. Standard phono plug design is not very well conceived, but we're stuck with it. As the plug is removed or inserted, the circuit shorts +/- , which is pretty harsh on tubes and caps etc. Be kind to your new baby

Thanks a lot ethebull. I better stop abusing my baby's output before it's too late.

[ethebull]

Originally Posted by Mike_TNT

Thanks a lot ethebull. I better stop abusing my baby's output before it's too late.

U can get arrested for that in most states.

[Penchum]

Originally Posted by ethebull

a) "Standard phono plug design is not very well conceived, but we're stuck with it. As the plug is removed or inserted, the circuit shorts +/- , which is pretty harsh on tubes and caps etc. Be kind to your new baby"

E,

If the volume knob is at absolute 0 (full attenuation) there is nothing at the jack, correct? As long as this is verified first, you should be able to plug and unplug the headphones at will, correct? Please correct me if I'm wrong about this. I don't even remember when or where I learned this, but I do it like religion.

[ethebull]

Yes, you are correct P. Since the headphones themselves are a passive device, so long as the volume knob is 100% counterclockwise, the amp is safe.

My overly cautious style stems from years in pro audio. Is the device on the other end of this 1/4" jack vulnerable? You'd have to ask yourself every time... Old habits...

[batmanwcm]

Here's my story:

I received my MKIII but 1 of the power tubes was DOA. So I waited for the new power tubes to be shipped out and I never turned on the unit again. So no burn in.

Here's the problem:

I just received my replacement power tubes today. I put them in to the new MKIII. The gain is set to 3 and I start listening to it. The volume is extremely low on both channels. I increase the gain to 5 and the increase is minimal. I can pass the 2 o'clock position fine. Also, the left channel seems to be louder than the right channel. I'm using a Alessandro MS-1. Anyone know the problem?

Edit:
While burning in at the 11 o'clock position, I noticed the sound from my left channel stopped. However, the right channel became really loud. This was the kind of sound I was expecting to come of of the MKIII. I swapped the left power tube out and it returned back to the low volume.

[ethebull]

^ Let us know what you have.

phones, source, how they are connected, if you've checked source output settings... we need more info to be of help.

[batmanwcm]

Phones: Alessandro MS1's
Source: Winamp Lossless through PC using on-board audio line out.

It's connected through the 3.5mm jack to RCA cable that came with the MKIII. Output settings set to line-out.

I swapped it with the Sonic T-amp Gen 2 and it worked perfectly with that amp and headphone out.

[ethebull]

I'd start by checking the gain settings on the MK III. Turn off the amp and wait a few minutes. It could be confusion on the four switches in play here. To eliminate the gain as the cause of your problem here, set all four switches to "off". this will be max gain 10. Turn turn everythng on with the vol on the LD at zero. Turn up to 7-8 o'clock and report back.

Hope it works

[batmanwcm]

ethebull,

I did just what you said. Now there is sound coming from only the left channel. It's a lot louder now. I feel like this is how the MKIII should sound. But I'm not getting sound from the other channel.

[ethebull]

When I first got my MK III, I had the same problem for a minute. It looked and felt like I had inserted the headphone jack fully, but when I checked it, it clicked in another 1/8" and soved my problem

Start there, then recheck all connections (with the amp off!)

If that doesn't work, pull and clean the pins on the tubes, then reinstall,...

Report back

Good luck

[ethebull]

Also try swapping the RCA inputs

Install L to R and R to L. See if it's still no sound in the right earphone. This will eliminate your source as the problem.

[batmanwcm]

ethebull, I think you're right. I'm using the 3.5mm jack adapter to 1/4 jack adapter that was included with the MKIII. After wiggling it around, I heard the other channel kick in. Thanks, I'm off to buy a better adapter.

[batmanwcm]

Hey ethebull,

I just came back from the store. OK, I have finally isolated the problem. I have MS1's and IM716's. I now have two 3.5mm-> 1/4 jack adaptors. If I plug either headphones all the way in, in either adaptor, there is only sound coming from the left channel. However, if I pull out the headphone jack a little bit, I get sound coming from both channels. This is weird. Anyone know what is going on?

[ethebull]

Never have cared for stereo phono plugs.
Always hated using adapters for connectivity incompatibilities.
Problems arise all to often.

Glad you've isolated the issue though.

Enjoy the new amp and report back as it burns in

E

[batmanwcm]

Well the fact that I cannot plug in the headphone all the way doesn't really make sense. I get both channels full of sound when the plug is loose? It's like the issue you had when you realized that you didn't plug in your headphones all the way except the exact opposite is happening to me. Can anyone shed some light?