Search found 117 matches

by greenmanhumming
Thu Oct 28, 2010 8:06 am
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 171922

Re: BAN Build Thread

I couldn't get the whistles to show up on the scope well enough to see a voltage or frequency. I have bought new boards and rebuilt the BANs using some new parts and some retrieved from the old boards and all works fine now! I used low temp lead/tin/silver solder and socketed the input transistors a...
by greenmanhumming
Sun Oct 10, 2010 10:03 am
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 171922

Re: BAN Build Thread

I'll check the power supply with the scope tomorrow, tho I think I have done that before and not found anything.
by greenmanhumming
Sun Oct 10, 2010 10:00 am
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 171922

Re: BAN Build Thread

I might have done the 10x the wrong way around I think I divided by 10 when I should have multiplied so tru figures much larger. I'm using the smaller Jlm switching power supply. With some extra filtering too. Actually I suspect the audible whistles and the steady supersonic oscillation may be unrel...
by greenmanhumming
Sun Oct 10, 2010 6:33 am
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 171922

Re: BAN Build Thread

i should add it reads about 10mv on pin 1 of the first chip, and 5mv on pin 1 of the second chip.

the other side of each chip is something similar but lower level.
by greenmanhumming
Sun Oct 10, 2010 6:23 am
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 171922

Re: BAN Build Thread

on the worse affected side theres an oscillation at pin 2 of the first chip of 3mv and pin 2 of the second chip of about 2.5mv, and about 5.5mv at the output. thats measured with the x10 on the scope probe so the actual readings were 10x that. wavelength looks on my scope like about 1.2uS - about 80...
by greenmanhumming
Sun Sep 26, 2010 11:18 pm
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 171922

Re: BAN Build Thread

maybe it is the damaged board. there must be either a lost connection somewhere or my jumpers are causing the oscillation.

weird that its the same on both boards though, if it is the boards.

i replaced the input 47pF with 100pF - no change.
by greenmanhumming
Sun Sep 26, 2010 9:11 pm
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 171922

Re: BAN Build Thread

going back to BC549 made it worse.

played around with the grounding, changed things but didn't eliminate it.

stumped.
by greenmanhumming
Sun Sep 26, 2010 8:03 pm
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 171922

Re: BAN Build Thread

I have shortened the legs on the (socketed)LM394 - no chnage. I have increased the ceramic caps near the LM 394 to 100pF, that reduced the level of oscillation but it's still there. how big can I go? does this tell us anything? I will try going back to different transistors, as I never noticed this ...
by greenmanhumming
Thu Sep 23, 2010 9:58 pm
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 171922

Re: BAN Build Thread

I replaced the pots with 10k $US10 stepped attenuators from ebay, they work great and have cured the channel imbalance. (although my gain controls now work in reverse, since reverse log attenuators were not available, i'm living with it in the name of mental flexibility!) I still have (audible) osci...
by greenmanhumming
Mon Sep 06, 2010 11:12 pm
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 171922

Re: BAN Build Thread

thanks that's some things to look at. yes the board is a mess, there are a couple of jumpers i put in to connect stuff that had been disconnected due to broken traces. however as far as I can tell it is now connected correctly, but i may have missed a connection. i suspect the quieter channel is onl...
by greenmanhumming
Sun Sep 05, 2010 10:23 pm
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 171922

Re: BAN Build Thread

I seem to be having multiple problems with my BANs possibly since changing to LM394, and fitting IC sockets to the input transistor holes for easier swap out. but some of the problems may have been pre-existing. * one channel is louder than the other, this is partly pot mismatch, but not entirely. *...
by greenmanhumming
Sun Aug 29, 2010 12:36 am
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 171922

Re: BAN Build Thread

I'm also getting frustrated with the cheap 10k reverse log pots, I'd like to reoplace them with a stepped attenuator, but reverse log attenuators are not to be found, I could build one, but getting the right resistor values could be tricky. how about a kit? or can you use a linear attenuator with a ...
by greenmanhumming
Sat Aug 28, 2010 6:58 pm
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 171922

Re: BAN Build Thread

Is the signal to noise or other performance degraded by this effect? All my mics are transformerless except the ribbons and the one 414 mentioned and most only output signal one one pin.
by greenmanhumming
Sat Aug 28, 2010 7:53 am
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 171922

Re: BAN Build Thread

I don't have a schematic for the BANs. I have just plugged in 2 C414s identical in every way except one has an output transformer and the other doesn't - it has pin 3 grounded through a cap. the 414 with the output transformer is significantly louder than the other on the BAN, but when plugged into ...
by greenmanhumming
Mon Aug 23, 2010 8:58 pm
Forum: JLM Audio Kits
Topic: JLM 60Watt Power AMP Kit
Replies: 255
Views: 301587

Re: JLM 60Watt Power AMP Kit

OK, thanks, I figured the AMP wouldn't be loading it much.

I've used a separate 48v supply as I want to keep the phantom to spec.