ruffrecords

Re: Redd 47 Mic Preamp
« Reply #60 on: January 10, 2019, 04:42:18 AM »
Ok, I have removed the boost switch and input xlr.  Noise is still steady. I have a sample of the noise but mp3 is not an acceptable attachment format. I can email it to anyone who is interested.
Thanks

OK so you are saying with no NFB is still squeals?

Why did you remove the input XLR? Try a test noise with the transformer input shorted.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'


mixguy

Re: Redd 47 Mic Preamp
« Reply #61 on: January 10, 2019, 10:19:51 AM »
Thanks Guavatone. I will check those components. I have to step away from this for a couple of days and go to work. I will report back on what I find.

mixguy

Re: Redd 47 Mic Preamp
« Reply #62 on: January 10, 2019, 08:06:29 PM »
I removed the input to make sure that the low cut, phantom power and pad portion of the circuit weren't causing this.

ruffrecords

Re: Redd 47 Mic Preamp
« Reply #63 on: January 11, 2019, 03:47:35 AM »
If this is a point to point build then it may be a layout issue. Check you don't have any input wires near output ones.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

dbonin

Re: Redd 47 Mic Preamp
« Reply #64 on: January 11, 2019, 10:12:55 AM »
Hes using the DRIP PCB. 
I just finished two of them but they are in the box for shipping tomorrow, so I no longer have my hands on them! 
I didn't add the phantom power to them, so can't speak to that.

Are you using the sowter xformers?

Double check all your ground connections for continuity to the case, triple check your wiring etc   - basic stuff, but  these things are extremely sensitive to stray flux bouncing around the case.   

When you can, take a few pics and post the links here.
Stand off to the side of the unit, out of the line of fire.  Flip the ON switch...  "Watch for flames and sniff for smoke."

mixguy

Re: Redd 47 Mic Preamp
« Reply #65 on: January 15, 2019, 04:29:13 PM »
Been looking it over and haven't found any obvious mistakes. I asked Drip Electronics if they had a picture of an unstuffed PCB  so I could check component placement but no reply yet.

mixguy

Re: Redd 47 Mic Preamp
« Reply #66 on: January 15, 2019, 04:30:06 PM »
More pics

mixguy

Re: Redd 47 Mic Preamp
« Reply #67 on: January 15, 2019, 04:30:46 PM »
Last pic

Re: Redd 47 Mic Preamp
« Reply #68 on: January 15, 2019, 07:09:45 PM »
I see some problematic areas. The unshielded wires from the  XLR and DI Ins are very suspicious for crosstalk with the  output (and the feedback/ gain selector part) of the amp, especially if you keep these cables so close together. This can lead to oscillation...and your cable management of the VU input wires is suspect number one for that. Don't forget, this is your (XLR) output and you tie it together with your inputs, all of them unshielded.

Nice build BTW!
« Last Edit: January 15, 2019, 07:58:34 PM by rock soderstrom »

mixguy

Re: Redd 47 Mic Preamp
« Reply #69 on: January 15, 2019, 10:17:51 PM »
Thanks for the compliment. I unhooked all the inputs and gain selector switch. Only thing I left was the output hooked up and the noise is still present at the same level.


alexc

Re: Redd 47 Mic Preamp
« Reply #70 on: January 16, 2019, 01:23:19 AM »
v nice  build  ...  love the drip layout  ...  classy.
I ping therefore I am

Re: Redd 47 Mic Preamp
« Reply #71 on: January 16, 2019, 04:25:59 AM »
Thanks for the compliment. I unhooked all the inputs and gain selector switch. Only thing I left was the output hooked up and the noise is still present at the same level.

 I am not sure if this is a good strategy. I would leave the basic circuit as it is. If your components on the PCB are the right ones than the problem is in the harness. Did you unhook those yellow-red VU meter cables at the XLR  in/out? Use shielded wire for the DI in and other sensetive parts of your amp. Seperate Ins from Outs.
« Last Edit: January 16, 2019, 04:33:21 AM by rock soderstrom »

mixguy

Re: Redd 47 Mic Preamp
« Reply #72 on: January 16, 2019, 01:47:48 PM »
All wires were removed. Output XLR is shielded and straight to PCB.

Re: Redd 47 Mic Preamp
« Reply #73 on: January 16, 2019, 02:09:26 PM »

 ;D

mixguy

Re: Redd 47 Mic Preamp
« Reply #74 on: January 16, 2019, 05:56:04 PM »
Ok, I checked some voltages at the test points and every thing is almost double of what it should be. Not sure what is causing this.