Presto K8 Radio Input

[tapesandtubes]

I've tried searching the forum for an answer but so far no luck...

Here's my problem:

I'm sending a line level signal into the radio input of my Presto K8. However, it's not coming through when I turn the volume over to the right hand side (record); when I turn the volume over to the left hand side (phono) I get sound as displayed by the meter -- but it sounds bad. Here's the kicker, when I touch the tip of the 1/4" jack to the screw-on mic connector, I get beautiful tone and level on the correct right hand side of the volume pot (record).

I've read through the manual and it says that the radio input has an input impedance of 25,000 ohms and should be connected to the "second detector" of your radio.

Has anyone has this problem, and found a solution? Do I need to send a powered signal to the radio input? I'm thinking that maybe I should just solder an old-style screw-on cable and use the mic input.

Thanks for your help.

[Jccc]

hello,

i use the radio jack for recording into the k8.
on the volume dial i have to set it to the phono side usually around the 2 marking.
i make sure the signal coming in isnt too hot or else it will be distorted.

I also watch the Volume Indicator and make sure the needle is bouncing around in the Green. its ok if it bounces out of it.

[tapesandtubes]

Thank you for your reply. That seems to be the same for me -- when using the radio input. However, I'm an uptight guy and a bit OCD when it comes to my equipment so I've been doing some research...

http://www.radioremembered.org/detector.htm

It appears that back in the the old days, Presto expected you connect the radio input (25K ohms) to the "second detector" of what would have been a tube radio (according to the manual). It's actually a small audio amplifier tube (see the article above). Which makes sense because other people have talked about connecting a headphone jack to the radio input.

So in order for me to use this as intended, I need to run a small mono amplifier signal, or a robust headphone amp into the radio input at 25K ohms. Whacky!

I'll keep working on it and report back...

[tapesandtubes]

Here's what I'll need to match the impedance...

http://www.atlasied.com/lt600-vc

[markrob]

Hi,

No need to match impedance here. You should operate in bridged mode. The driving stage should be a low enough output impedance so that it is able to drive the 25K ohm input that the K8 presents without loading it down. Since this is a pretty high impedance, it will be very easy to drive with most any modern solid state source. The only concern is the voltage swing required. You should be able to test this easily. Just plug in a source and see if you achieve full recording level.

Mark

[Jccc]

hello, i dont think you really need that thing to match the impedance.

i have my audio going through a Mackie 1202 mixer set with the proper levels and eq which are set to my liking and then the Mackie is going into the Radio input of the K8.

i just go out mono from the Mackie into the K8.

i have no issues with Audio level at all.

[tapesandtubes]

Thank you all for your replies. I'll do some more testing this weekend and let you know how it goes...

[tapesandtubes]

I got things working properly. I ended up soldering together a cable to run into the mic input. I'm getting good, clean levels. Thank you all for your help.

[tragwag]

great! nice photo too