Marion,

First the Y cable: Since the impedence of the 1/4 inch cable is higher than the three prong XLR, you will not find an adapter (Y cord) that will put both an XLR and a 1/4 inch (High Z) into one 1/4 male plug to go into your amp. But do not lose heart, there is a fix. HOSA makes a Y cord that has two female 1/4 inputs connected to one male 1/4 output plug, and this is the plug you need. If you already have an XLR type mic, you can purchase either a 16 foot cord that goes from XLR to 1/4 inch (Radio Shack #33-4010) or an XLR to 1/4 inch plug adapter/impedence matcher (Radio Shack #274-016).

If you do not have a mic, may I suggest the Radio Shack 33-3001, which comes with an XLR to 1/4 inch cord, and is the best kept secret in the mic world. It normally goes for around $80. but has been dropping in price over the years, and you can get one on sale for around $35. I use a lot of Beta 58s and 57s and with a windscreen, the RS beats them both on flute or soft female vocals. It will go direct to your HOSA "Y" and you can plug your guitar into the other leg of the "Y".

Now comes the tricky part. You will have to balance the input of the guitar pick-up with the natural input of your voice mike, since you have only one Y-ed input into the can amp. Since you cannot adjust the volume of your voice mic, bring it up in the amp volume (gain) until you like the sound and the volume. Then, using the gain slider on the guitar pick-up, put the guitar higher or lower in the mix, as you see fit.

If your guitar does not have a gain control for the pick-up (most likely passive) you might have to consider buying a pre-amp to boost or control the guitar volume, or consider the two input amp (which, after this, may be cheaper than all the adapters, etc.)

There are other options, such as the Morely A-B-AB selection pedal, but again the two input amp will probably come out cheaper in the long run.

Finally, the perceived volume of whatever amp you choose will be enhanced if you get it off the ground, and somewhere near the ear level of your intended listeners (a hospital bed-table works great). But do not put it behind you or feed-back will result. Good Luck!