attenuating an LOD??? confused

[JeffS]

Hi All,

I have an iPod Touch that I finally got an LOD for. I have the SendStationg pocketDock. I noticed that the sound from the line out was much better than the headphone out. I'm running it through a Xin Mini-IV.

The only problem I noticed was that I barely turned the dial from 0 on the amp and the sound would almost instantly be about the most my ears could handle. I tried the internal tweaks of adding 75ohm (ety p->s) conversion that's built into the amp, and that didn't help (actually made the sound worse with the UM2s)

Out of curiosity, I grabbed an inline volume control that I had from Radio Shack. It's just one of those little lengths of cable with a thumb wheel in the middle to lower the volume of whatever you're listening to. I put that into the LOD, and then ran it into the amp. Lowered the volume from the LOD a lot, and this allowed the amp to get into it's zone, and really sounded nice.

I decided to measure it with my multimeter when I finally found what I thought was the sweet spot, and was shocked. The "sweet spot" came in around 475 Ohm. This could just be me, but isn't that a lot???

Here's the setup...
iPod -> pocketDock -> volume cable -> cardas hpi -> Mini-IV -> UM2

I haven't heard of anybody putting an attenuation cable between the LOD and the amp before. Is this normal? Is something weird in my setup?
Is this because the UM2s are extremely sensitive?

I figured, as a solution I'll just make a high resistance cable at a fixed resistance which will just simplify the setup a little. Is there anything weird
with this?

-Jeff

 

[mrarroyo]

No need to use an attenuator. First check that you do not have the DC-Boost feature in the Supermini IV on. If it is turn it off.

Next make sure that the gain jumper is set to low. If it is on high then set it on low.

Next you have two options. first see if you are using buffers, if no then you can use the built in P to S jumper to lower the output of the Supermini IV. If your amp has a buffer in the output stage you can remove and use jumpers to bypass that feature.

The picture below, the 4 pairs of jumpers allow you to customize sound. In the following picture, all the jumpers are at bypass (disabled) position. You can also see a buffer in place.

In the picture below, the positions of the jumpers set the Amp gain to 3 (or 8, on old versions) and enable Crossfeed. Impedance is set to low (bypassed) and Bass boost is bypassed (disabled). You can also see the jumpers to bypass the buffer.

 

[JeffS]

I've tried all the settings on my Mini, trust me. I've been rocking that lil' buddy since the III came out. I tried flipping the impedance switch but that actually degrades the sound quality of the headphones. It seems to remove too much bass, and thin out the sound quite a bit.

When I was running the amp from the hp out on the ipod, volume was good at about 50% that gave me enough play in the amp to adjust it fine.

Is this a problem with my amp that I haven't noticed before???
(please say "no", I can never get a response out of Xin and don't want
to be without an amp for months.)


-Jeff

 

[mrarroyo]

Another option would be using op-amps that have a lesser output. What op-amps are you using now? If the AD8397 you could go to the AD8616 and AD8656, plus you gain a longer battery life.

 

[JeffS]

I've been using the 8397, and occasionally flipping in the solid-tube.
Both have been yielding the same result.

I don't mind having to make a secial interconnect for use with this, I'm no stranger to a soldering iron. I'm more concerned that I've never heard anybody else on here seem to have this issue.

-Jeff

 

[mrarroyo]

I listen at very low volumes 60dB to 70dB and the Supermini w/o the DC Boost and driven by an iModded iPod worked fine in driving any of my cans. Occasionally when using IEM's I would switch the P to S. I have not read of anyone else w/ your issue. Good luck.

 

[brainsalad]

Just a thought, do you by chance have it plugged into a phono input?

 

[JeffS]

Quote:

Originally Posted by brainsalad /img/forum/go_quote.gif Just a thought, do you by chance have it plugged into a phono input?

???

The amp and dock in question only have mini connectors

-Jeff

 

[brainsalad]

Sorry, I miss read, you have a headphone amp. I thought you meant an integrated amp or receiver.