[silent:arts]

Re: D-LA2A Support Thread
« Reply #1920 on: March 13, 2019, 04:30:33 PM »
You are puzzling me. How do you recognise increased gain in a channel not passing signal?


Holger

Re: D-LA2A Support Thread
« Reply #1921 on: April 06, 2019, 01:45:06 PM »
Another one: built around an old Weston 862 meter. Currently I'm using Kenetek's here. I/O TX are Carnhill 9k6:600.The meter has a sticker marked 1966 on it. The 5V PSU went crazy when connecting the meter bulbs so I used a little 5V MeanWell SMPS for relays and meter illumination. Knobs are 40mm dia. Fat looking guy...





[silent:arts]

Re: D-LA2A Support Thread
« Reply #1922 on: April 07, 2019, 02:52:36 AM »
Nice as always - only one but big meter as always - a true CLAßEN.

This will be used in the Röhren(Rein)Raum at the Krässemaschinenwerke Hamburg?

Holger

Re: D-LA2A Support Thread
« Reply #1923 on: April 08, 2019, 02:42:53 PM »
Nice as always - only one but big meter as always - a true CLAßEN.

This will be used in the Röhren(Rein)Raum at the Krässemaschinenwerke Hamburg?

;-) yes...

dmp

Re: D-LA2A Support Thread
« Reply #1924 on: April 08, 2019, 02:51:39 PM »
It's my understanding that LA2A's run very hot gain-wise by nature and running them with the gain above 7-ish or so can / will result in artifacts.  Mind you, I don't have past hands-on experience here as this is my first hardware LA2A.  I have read within this forum and on the Interwebs suggesting that this is 'normal' behaviour, so at this point I haven't worried about any of that.    If I remember correctly, some of the 'fix' included swapping the 12AX7 out for lower gain tubes.  Honestly, at a gain setting of 7 the signal is WAY too hot for anything I'd ever use or want.  The signal is very distorted at those levels and not in a pleasant way IMHO.

If others here have contrary information to add here, a little help / input would be appreciated.

Be that as it may be, I'm interested in actually testing here.  So I undertand.... when you turn the gain up above 7 or so, you get an oscillation at 18KHz with no audio signal being input?   If so, I'll give this a test when I get a few minutes and report back.

I have to go back and look into it again, but my recollection is that with peak reduction way up and the gain way up, we got this ~18kHz noise. We were running a track into it at the time .
I made mine with Jensen 1:1 line in transformers which works really well (unless you want to run mic signals into it).  The gain is needed in this configuration when compressing heavily.

Eliani

Re: D-LA2A Support Thread
« Reply #1925 on: May 03, 2019, 04:09:32 PM »
I haven't gon through the whole thread yet...  ::)
But the BOM to dropbox link is broken on the first post...
Is anyone willing to share his.. mutch appreciated
"Iron Projects" at Eli-Audio.com

QNote

Re: D-LA2A Support Thread
« Reply #1926 on: May 09, 2019, 07:29:41 PM »
I haven't gon through the whole thread yet...  ::)
But the BOM to dropbox link is broken on the first post...
Is anyone willing to share his.. mutch appreciated

See Page 89 in this thread.  I have an updated link there, along with other resources.  New theory and troubleshooting videos in just a few weeks (I shot one of them yesterday).

BOM Link:  https://www.dropbox.com/s/2xky62b30ccsvfw/D-LA2A_BOM_QNS.xlsx?dl=0
« Last Edit: May 09, 2019, 07:54:40 PM by QNote »

weiss

Re: D-LA2A Support Thread
« Reply #1927 on: May 09, 2019, 09:01:51 PM »
Another one: built around an old Weston 862 meter. Currently I'm using Kenetek's here. I/O TX are Carnhill 9k6:600.The meter has a sticker marked 1966 on it. The 5V PSU went crazy when connecting the meter bulbs so I used a little 5V MeanWell SMPS for relays and meter illumination. Knobs are 40mm dia. Fat looking guy...

where do you always find them?
i only come across these way overpriced meters for several hundred bucks..  :o

https://reverb.com/item/11073137-1950-s-weston-electric-model-862-vu-meters-vintage-bakelite-with-black-panel-free-shipping
« Last Edit: May 09, 2019, 09:04:56 PM by weiss »

Holger


groselicain

Re: D-LA2A Support Thread
« Reply #1929 on: August 25, 2019, 03:39:57 PM »
Had this sitting on my shelf for over two years now and decided to finally finish it yesterday. I've gotten the left channel running perfectly, but the right channel has issues. I've checked it against the left channel with the eye test and all seems to be correct, but I really might be overlooking something. Right channel meter doesn't register audio on output, but it does zero on gain reduction. Output pot works fine, gain reduction does not introduce compression—only distortion in the last 25% of its throw. Stereo linking is switched off, the stereo adjust is wide open. I've switched all tubes and T4Bs from left to right to no avail. Here's a list of voltages at test points:

  • 99.6
  • 1.137
  • 209.4
  • 108.9
  • 1.204
  • 227.5
  • 111.1
  • 274.3
  • 19.59
  • 52.69
  • 84.2
  • 0.846
  • 5.48
  • 167.3
  • 96.3
  • 365.4

Any help is so appreciated.


groselicain

Re: D-LA2A Support Thread
« Reply #1930 on: August 27, 2019, 08:59:38 PM »
I didn't post pictures just because I felt certain there's no discrepancy between the two channels, but would it help if I did?

scott2000

Re: D-LA2A Support Thread
« Reply #1931 on: August 27, 2019, 09:05:00 PM »
Quote
I felt certain there's no discrepancy between the two channels,

The voltages above are for both channels?

groselicain

Re: D-LA2A Support Thread
« Reply #1932 on: August 27, 2019, 11:29:37 PM »
No sir, those are voltages for channel two only. I omitted channel one since it’s operating properly. Should I post them as well?

groselicain

Re: D-LA2A Support Thread
« Reply #1933 on: August 29, 2019, 05:05:29 PM »
Closer view of PCB

groselicain

Re: D-LA2A Support Thread
« Reply #1934 on: August 29, 2019, 05:56:13 PM »
Looks like my first picture got messed up in the upload. Sorry for the rat's nest, I had intended to wait to ziptie the wiring until I had everything sorted. It might be worth mentioning that when I pass audio through the malfunctioning side, it gets louder when I remove the T4B. Is that a clue to anything? Thanks so much.
« Last Edit: August 29, 2019, 06:41:29 PM by groselicain »

scott2000

Re: D-LA2A Support Thread
« Reply #1935 on: August 29, 2019, 07:41:08 PM »
Any links to what the test point voltages represent?

Quote
No sir, those are voltages for channel two only. I omitted channel one since it’s operating properly. Should I post them as well?

groselicain

Re: D-LA2A Support Thread
« Reply #1936 on: August 29, 2019, 10:01:40 PM »
This is what I was working with.

[silent:arts]

Re: D-LA2A Support Thread
« Reply #1937 on: August 30, 2019, 05:55:45 AM »
I've switched all tubes and T4Bs from left to right to no avail.
Check the side chain tubes heater voltage.

groselicain

Re: D-LA2A Support Thread
« Reply #1938 on: August 30, 2019, 12:24:00 PM »
Check the side chain tubes heater voltage.
Same on both channels 1 and 2,.
« Last Edit: August 30, 2019, 12:27:54 PM by groselicain »

scott2000

Re: D-LA2A Support Thread
« Reply #1939 on: August 30, 2019, 12:32:25 PM »
What's the voltage on the working channel at ?? TP 10 out of curiosity.... bulb??

All the tubes  in right places???


 

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