Aikido 12Vac line stage/pre-amp build & review

[MKG]

Super sketchy badly soldered & asking for a short test run was successful! Signal is passing through it to the amps and I can hear music. Sounds pretty good. Need to double check voltages and then get to work mounting it in the case, fabricating the front panel, and building & wiring the Nixie tube vu/peak meter driver board.
With no signal and the volume up it’s fairly quiet, but I can hear what sounds like some odd oscillation- it gets significantly louder if I touch the bare volume twisty part.
It reminds me of the sounds that an am radio transmitting theremin I built a decade or so ago made, so I’m guessing it’s am interference and hoping that it will go away when I do final wiring with shielded cable and properly ground things.
John sent me some coupling capacitors to make up for the initial shipping delay- I’m a little unsure where to attach them, can any of you give me guidance on this?

Side note- if you have music paused and turn the volume up to see how quiet your preamp is, remember to turn it down before you hit play. Thankfully I didn’t blow any tweeters.

 

[Lavane]

C3 on each channel should be your coupling caps. The big dark gray blocks in front of the electrolytic caps. Did he send a different value or a different brand?

 

[MKG]

Different value and brand. He sent these:
https://glass-ware.stores.yahoo.net/1uf1kcodupof.html

 

[Lavane]

What value are ones you installed?

 

[santa]

The white caps he sent you would be used in place of the gray caps (c3)
Obviously those wont fit on the circuit board.

 

[Lavane]

I'm guessing the gray caps are maybe .47uf? A couple of the Magnavox console amps I rebuilt had .047uf coupling caps. I replaced them with .1uf caps. It's commonly done to get a little better low end responce.

 

[Lavane]

The white caps he sent you would be used in place of the gray caps (c3)
Obviously those wont fit on the circuit board.

They do look a bit large. I've gotten larger caps to fit by putting shrink tubing on the leads and bending them around the ends of the cap. It's not pretty in some cases though.

 

[MKG]

Sorry for the long delay, life got in the way.
Those gray caps are 2.2uf 275vac.
I’m having a bitch of a time making my rear and face plates- I’m not good at making things pretty.
Gonna take a sanity break from those for a bit and build the driver board for the Nixie tubes.

 

[MKG]

And the white cde caps he included aren’t what I referenced above- they look just like it but these are .1mfd and the ones I linked to above are 1.0 mfd.
So I’m not quite sure where or why I would use them.

 

[MKG]

Driver board is done.
All that’s left now is double checking voltages on both boards, final wiring, drilling the chassis and mounting things, and finishing the front and rear panel.
I thought about hardwiring everything to the nixie driver board but decided to make it easier to remove.

 

[Lavane]

And the white cde caps he included aren’t what I referenced above- they look just like it but these are .1mfd and the ones I linked to above are 1.0 mfd.
So I’m not quite sure where or why I would use them.

Ya, maybe shoot them an email and ask.l before guessing.

 

[MKG]

Yeah, I should probably ask. I’ll shoot him an email. While I’m waiting for a response I’ll keep guessing.
Maybe they’re ridiculously large bypass caps?
Maybe I should brush up on (or properly learn) electronic theory.

 

[Lavane]

If you go to far with value changes with coupling caps you can really alter the freq. responce. On a couple of console amp pulls I replaced some .47uf for .1uf if I remember values right. It gave a better bottom end. But if you go too far you can start loosing some of the high end, it might sound muddy, etc.

 

[MKG]

Doing final wiring. Finally.
Using Mogami mic/line wire for signal wire because it was cheap.
Just need to finish the wiring and then it’s time to bolt stuff in place. Exciting!
My xtronic soldering station decided to die on me. I’ve got a stahl DSDS on the way, managed to ghetto rig my xtronic enough to limp through the rest of this build (I hope).

 

[Lavane]

I have a Stahl. I bought an extra iron. That way I can have the two tips I use most mounted and ready to use. If you don't let the iron cool all the way down first, you will destroy the tips trying to remove them. I haven't had any problems with the Sthal station. I did have one without the digital display die on me. But it was due to a cat chewing through the iron cable shorting it out. If you have cats they seem to like the smell of the iron cable and chew on them. I lost two irons before I started having to hange them up high when not in use.

 

[Lavane]

That power supply for the meters looks like the switching supply I bought. I found it for around $13. I saw the same supply listed as high as $60, crazy. I've been using the cheap shielded mic cable from Parts Express and it works just fine.

 

[MKG]

I have 10 cats (9 of them are rescues, most with some sort of issue- seizures, etc) and two mastiff-lab puppies. Sounds like a lot but other than them, only two humans live in our large 3 bedroom house on 3/4 of an acre.
They’re all indoor though, and I do my soldering in my shop.
But they definitely factor in to my choices of speakers and other gear to bring inside to the main system vs the shop system.

 

[MKG]

That power supply for the meters looks like the switching supply I bought. I found it for around $13. I saw the same supply listed as high as $60, crazy. I've been using the cheap shielded mic cable from Parts Express and it works just fine.

It’s a cheap regulated switching power supply I picked up for $5 on eBay. The screw down terminals are complete crap so I removed them.
I’m a bit concerned about the meters introducing noise into the mix, but we’ll see once it’s all assembled.

 

[Lavane]

Something in that high heat silicone covering is like catnip to them. I'll be watching to see how that switching supply works out.

 

[MKG]

My Stahl DSDS arrived. I was super excited- it’s the first non ghetto/cheap electronic tool I’ve bought. I’m pretty cheap and typically buy whatever deal I can find.
Some things are worth spending money on.
Anyhow, the desoldering gun works well. Holds a steady temp and sucks as it should.
The soldering iron started to heat up, hit 150 degrees, and then slowly started dropping.
I’m not sure if it’s the base or the iron. Either way, I sent an email to parts express and I hope they’ll make it right.
In the meantime I’m stuck with my xtronic.
Finished the build. Lots of noise.
With nothing playing there is a very loud hum. Once music is playing it drowns it out.
I’m guessing it’s my grounding scheme? Grounding is something I struggle with. It seems like it should be simple, but I just can’t grasp the concept.
I’m thinking my next step is a ground lifter.
I believe I’ve mentioned that I’m not good at pretty- I measure 3 times and cut or drill once but it always ends up being wonky.
I usually just go for functional- my previous builds have typically been bolted to a random piece of wood.