I made significant progress today. Most of the signal stage wiring is done. I could finish it up in about half an hour, but there are two little blockages in my path; one due to a supplier problem, one due to me.
The first problem was with my parts supplier. I ordered some 1.0µf film coupling caps with long straight leads. When the parts arrived, they were the right capacitors except they had short crimped leads meant for PC board mounting. Well, a quick call to my supplier and they are sending out the right parts, but it means another few days delay.
The second problem was my mistake. When I ordered the volume control I had already drilled the chassis with a 3/8″ (9.5mm) hole. Unfortunately, I did not pay close enough attention and ordered volume controls with an M8 bushing instead of a 3/8″ bushing. The hole is just too big for me to use them. I have a bunch of potentiometers with the proper bushing size. Unfortunately the lowest resistance of the lot is 100kΩ. So I had to order the proper size and I have to wait for them as well. It might be several days before I can finish up this project.
Here’s what the signal stage looks like.
It’s a little cramped but everything is in position and the layout is acceptable. The socket at the top is the two gain stages; “right channel” on the right, “left channel” on the left. The lower socket is the two cathode follower stages. All I need now is the volume control and the two output capacitors and I’ll be able to finish up the preamp. I’m eager to get started testing this little unit.
I let you know when the unit is complete.
As always, questions and comments are welcome.
Another place to check is Parts Express.
They have ganged audio taper pots for less than $3.00 each. The selection covers the range from 1K to 1 meg. I’ve used them for years. They have a nice feel, no noise, each section is fairly well matched to the other section. Not at all bad for what they cost.
I have always admired your layouts. In fact, I now employ the same ground bus approach in all projects. I used to be one messy maker. No longer a fan of star grounds (with exceptions).
Wiring here looks plenty neat. I suppose I would dress a lead here or there if it seemed prudent.
Did you say you were going to use an Alps pot for volume? I’ve been bad and too often use what I have in the parts pantry…lots of dual gang pots in a variety of values, but they’re almost all salvage pulls. I don’t think I need to explain why that’s a gamble. I need to stock some new stuff, but Alps aren’t that cheap. Must be something between the salvage pull and Alps.?
Nice work here.
Here’s a hint on volume potentiometers. The best value I’ve found is actually a dual 100kΩ pot from, of all places, RadioShack. They sell this little pot for $4.99 USD. These are actually high quality APLS potentiometers made in Japan. I have found them to be smooth, accurate, long lasting, and quality performers year after year. I always keep a bunch in a parts bin for all kinds of projects. (I have five in my parts bin right now.) They take a 9/32″ mounting hole and because they’re small, they fit well in tight chassis.