[chalupa13]

Is there a better place to hook up the external aux input on this schematic? I connected directly to the 27 tube grid, but the volume is very low and I cant use the volume knob to control it. I'd be ok without using volume knob but would like to get better amplification somehow. Thanks.

[morzh]

What are you connecting exactly?

First of all, you have to use a capacitor in series.
Second, you need to introduce a switch that switches between the detector output and your source. Else what you have is having your detector output in parallel to your source which will:

1. Potentially introduce noise from the RF.
2. Shunt your source with the low 24 det tube impedance therefore reducing the input signal.

[chalupa13]

Connecting phone or mp3 player. I used 0.005uf cap and resistors to connect the input. Here is the actual connection.

[morzh]

Remove the detector tube (the one right before the 27 on the left), see if the volume goes up.

[chalupa13]

Nope, no change to the volume level. Pulled all of the 24s one at a time.

[morzh]

The values you use seem OK to me. I doubt raising capacitance to 0.01uF would make much difference: the impedance of the tube's input is very high compared to maybe 10kOhm at the low frequencies and 3kOhm at about mid-frequencies.
See if your iPod's output is sufficiently high (should be).
Or you could possibly see if your radio does achieve sufficient loudness as a radio what AC amplitude you develop at the 27's input (detector output) and, should it prove much higher than the iPod's, then you know what the problem is.

[chalupa13]

Radio itself gets very loud. Some stations are uncomfortable with loudness at 75%. I will check my phone headphone output but i'd imagine it should be more than 1v to drive headphones at lest at full volume.

[morzh]

Also for just shits and giggles, use one channel at a time, not both at once. Just for the unlikely possibility they are trying to cancel each other.

And when measuring the output of your iPod, measure it by itself first, and then on the #20 resistor, to see if something (can't imagine what that would be) brings it down.