[ricksc]

I've finally completed my bugle! By Jim's recommendations (and my own calculations) I set the gain to 50db so that I would be close to the maximum voltage swing at the inputs of my computer's sound card - so that I could use all the available bits when recording my vinyl to CD. Unfortunately,  the gain is just a bit too much. It depends on the record of course but most of the time I  am seeing more clipping than I am comfortable with.

Jim had mentioned using an external attenuater. What would this be exactly? A resistor - of what value? What about replacing the gain controlling resistor in the bugle with a pot? Where do I get high(er) quality pots that don't cost a lot?

A side note: I initially plugged the bugle into a line input on my trusty old kenwood receiver - the sound was horribly muffled, thought I had messed something up. Eventually I figured out that I might be overdriving the kenwood. I wired the bugle straight into the CardDeluxe in my computer - much better.

[GarMan]

Rick,

A voltage divider consisting of two resistors inbetween the Bugle and soundcard should work to attenuate the signal.  Just make sure the resistors are selected to keep the input resistance of the soundcard at the same level.  If you're familiar with L-Pads in speakers, the concept is the same.

For example, if your soundcard has R(in) of 100K, a 50K in series and 100K in parallel with the soundcard will reduce the output voltage by half, while keeping the 100K R(in).

BTW, when you plugged the Bugle into your Kenwood, did you plug it into the CD or Tuner input, or the Phono input?  Your receiver may already have a phono amp, and plugging in the Bugle into the Phono input would double equalize the vinyl recording.

Gar.

[hagtech]

Your best bet is to reduce the gain on the Bugle to match your sound card's input.  Keep in mind, with a 5mV cart, you'll get peaks five times greater in music.  That's probably why it clips.  My recommendation is to always run with the lowest gain you can live with.  

For an output pad, don't worry about the sound card.  You need much lower impedances so you don't roll off the highs.  And do this at the receiving end of the cable.  Like Garman says, two resistors will do the trick to make a voltage divider.  I'd go with a 10k series into a 1k load.  That drops plenty of gain while keeping bandwidth high and loading on Bugle to a minimum.

jh

[ricksc]

I've been trying more and more records with the 50db gain and it seems that there are really only a couple that clip a lot. Many that clip only 5-10 times on a side and some that don't clip at all so I'm thinking the gain is about right. I may still build an attenuator as per your suggestions (thanks) but the long range plan is to build a single ended to balanced converter with just a little bit of adjustable gain and roll the Bugle back to 40 at that point. (The sound card  has balanced inputs).  We'll see if I ever get that far. Kits like the Bugle, with PCB"s are much easier and more fun.

(GarMan - to answer your question - When I had the bugle plugged into the Kenwood it was an input marked 'Video' - not phono. But its good to check me on things like that).