[Ben777]

I recently purchased an Antique Sound HB1 Headphone Amp for about $250. It is a hybrid amp with two tubes, and I am exploring the tube mystique. So I plug my iPod into it and listen with Grado headphones (SR80 and RS1). At first it sounded bad, but I was told to let the tubes 'settle' or 'burn in'. They did get better after a while. Now the problem is that it doesn't seem to be amplifying! It sounds the same whether I plug by headphones into the HB1 or directly into the iPod. Can anybody explain this mystery? By the way, the volume control on the HB1 does work, so I know there is not just a wire from input to output. Also, I have the volume all the way up, of course. Does your HB1 definitely amplify? Does it give a clearly noticeable "tube" sound not provided by your source? Thanks.

 

[kramer5150]

Is the line out on your source variable? If so turn it up. Some "line outs" I have used were level controlled by the volume knob, or set in in the players system settings.
Switch sources to a home CDP deck and see if the problem persists.
swap interconnect cables maybe?
Is that amp variable bias? If so make shure the tubes are getting optimal bias voltage.
Make certain the amps power supply (wall wart or integral) is not defective.
Is the amps gain set low?

Could be an impedence mis-match between the amp and source. If the amp is presenting a high impedence to the source it will "perceive" a low line level.

?????

Garrett

 

[Ben777]

Quote:

Originally Posted by kramer5150 Is the line out on your source variable?

Thanks Garrett. My only source so far has been the iPod that I mentioned before, and that was turned all the way up. As I said, the Grado headphones sound the same whether plugged into the HB1 tube amp or into the iPod. In other words, the amp is amplfiying with a gain of 1! I got it by FedEx from the manufacturer via an online vendor, so I can only hope it is biased right. I don't know where I would even find someone to bias it, other than sending it back to the manufacturer. I suppose there may be some impedance issues between the iPod and the amp, but I expect a 'headphone amp' to work with the ubiquitous iPod. Hmmmm. I wonder what the impedance of an iPod output is?

I do have a good CD player at home, so I guess I'll go to the trouble to undo the cables and test the amp with it. And it didn't even occur to me that the power supply might be defective. It a big black brick separate from the amp.

Anyhow, it doesn't seem that anyone here has used an Antique Sounds tube amplifier. They do make some expensive and nice-looking amps, but that doesn't guarantee quality. If anyone has had success with the HB1, please tell us about it. Especially if it has a gain > 1 ! Thanks.

 

[Ben777]

Quote:

Originally Posted by Ben777 I do have a good CD player at home, so I guess I'll go to the trouble to undo the cables and test the amp with it.

I performed the experiment, and here are the results, if anyone is interested.

The issue is: when I plug my iPod directly into my new Antique Sounds HB1 tube amp and listen with SR80 Grado headphones, the volume is the same as if I listen with the Grados directly to the iPod. In other words, it doesn't seem as if any amplification is happening.

Now when I listen with my headphones directly to an old Sony CD player through the line out, the sound is weak.

When I plug the CD player into the HB1 amp, and listen with the Grados to the amp, the sound is strong again. So with the CD player, amplification is occurring.

This is as you would expect. What I am wondering is why the much stronger power out of my iPod doesn't either blow the amp or cause massive distortion. Maybe there is some limiting circuit built into this amp, which is very simple, has only two tubes, and costs only $250.

I note that the volume control on my iPod also works when it is plugged into the HB1. If I turn the volume down very low on the iPod, it gets very soft coming out of the amp. This is rather puzzling, since the weak CD line out signal gets amplified a lot.

Any ideas?