D-LA2A Support Thread

[rfused33874]

Hey guys!
I finally sourced all the parts and have been studying this thread before I start.  I have a couple questions still--

I'm going to use different input and output transformers.  Cinemag CM-6104 (1:4) for the input, and Cinemag CM-2840 (5:1) for the output.  There was a post on here that suggested adding more feedback with this configuration by getting rid of capacitor C4 and reducing the value of R11 "a lot".

1- If I were to get rid of C4, would I put a jumper in its place?
2- Can anybody suggest a value for R11 that would be a good starting place?

 

[audiophreak]

as luck would have it , an A-10 came on Ebay the day after my last post and got it for a fair price , installed and calibrated now , just cleaning up wiring and will post pix soon !!

 

[[silent:arts]]

... There was a post on here that suggested ...

It would be easier for all if you link to the post you are referring to

 

[rfused33874]

Apologies!

Here is the post I was referring to:
https://groupdiy.com/index.php?topic=32677.msg834254#msg834254

 

[[silent:arts]]

If I understand correctly this mod is suggested by Cinemag (via email to someone else) explaining a mod for an extended frequency response if using one of their output transformers?
Are you unhappy with the frequency response?

 

[rfused33874]

;D I can't yet comment on the frequency response, I haven't started.  I should have been more clear...  I've sourced all the hard to get parts (transformers, pcb, etc), but before I placed an order for resistors/switches/pots I was hoping for some guidance on a starting place of R11 following that 'mod' since those were the transformers I have.  When I reached out to Cinemag I didn't get a response.  I'm OK with ordering a range of values and testing them, but what are reasonable values to reduce it to?  "a lot" doesn't mean much to me

 

[[silent:arts]]

Since you don't need this mod don't do it, unless you are unhappy or something doesn't work.
Build it without any mod first. otherwise you are lost if trouble shooting is needed.

 

[audiophreak]

Hello All ,
                  Finally got the second D-LA2A done and lid is on !!  I had a vision and wanted to go BIG , sooo  5U case Simpson 4-1/4" Meters and 3" Collins knobs !!    I had some custom PTs made to be used with multiple tube projects 220vac@100mA ,  2 x [email protected], 12vac@1A,45vac@80mA  and used one in this, DC heaters,  A-10's and A-24s , locking toggles , sounds awesome !!

  Thank You to [silent:arts] / Volker  and all who post and help us along , I have learned so much , and have so much more to learn  ;D

 

[smadge]

Hello all

This is my first post here I'm eager to join your community and learn from you.

I am wondering if somebody could help with my newbie problem.

I had both channels working perfectly for a few months but for some reason now my left channel passes a very weak (almost none) audio signal. With the volume cranked all the way up to full it passes a buzzing distorted signal. When I flick the bypass switch off, all the audio signal goes away - e.g. it doesn't just bypass the compressor, there is simply no sound  passing at all.

I also note that if I play a source on this left channel, the meter moves and the more I turn the compress knob, the meter compresses more strongly - i.e. the meter swings further.

Looking at the DLA2A schematic, given that the meter compresses the more I increase the compression knob, my guess is that the problem is somewhere after the T4B cell. I say this because I suspect the problem is not at the input stage but somewhere near the output.

I've tried switching T4B cells and tubes but no change occurred.

Could anybody offer me any advise as to where to start diagnosing this?  I had thought that maybe the problem was somewhere near the relay's given that when I flick the bypass switch no signal passes through at all. I'm just so confused!

Thanks very much

 

[hugo]

Hello all

This is my first post here I'm eager to join your community and learn from you.

I am wondering if somebody could help with my newbie problem.

I had both channels working perfectly for a few months but for some reason now my left channel passes a very weak (almost none) audio signal. With the volume cranked all the way up to full it passes a buzzing distorted signal. When I flick the bypass switch off, all the audio signal goes away - e.g. it doesn't just bypass the compressor, there is simply no sound  passing at all.

I also note that if I play a source on this left channel, the meter moves and the more I turn the compress knob, the meter compresses more strongly - i.e. the meter swings further.

Looking at the DLA2A schematic, given that the meter compresses the more I increase the compression knob, my guess is that the problem is somewhere after the T4B cell. I say this because I suspect the problem is not at the input stage but somewhere near the output.

I've tried switching T4B cells and tubes but no change occurred.

Could anybody offer me any advise as to where to start diagnosing this?  I had thought that maybe the problem was somewhere near the relay's given that when I flick the bypass switch no signal passes through at all. I'm just so confused!

Thanks very much

Did you check your heaters ?

 

[smadge]

Thanks Hugo. Just checked heaters and they seem to measure 6.3v at each pin

 

[audiophreak]

Possibly check inout/output xlr  Molex connectors and cold solders.

 

[[silent:arts]]

Since your bypass doesn't work correctly there is something wrong in your input / output wiring.

 

[smadge]

Ok Ive rewired inputs and outputs and its working now!! Thank so much

 

[g9builder]

I'm after some trouble shooting help!

One of my channels has stopped compressing. (well it well compress a max of 2db with the gain reduction knob turned fully clockwise and then a high pitched winning sound emits). I have tried swapping all of the tubes over along with the cell from the good channel but this makes no difference?!!

Has anybody got any idea what could be causing this?

I was assuming it would either be the cell or one of the tubes. It passes audio and the channel is super clean otherwise and works fine as a preamp.

Any thoughts anyone? I'm at a complete loss  :-\

 

[audiophreak]

The noise sounds like what I've heard described as Oscillation , ( although I've never ecperienced it ) put that in the search for this thread for possible causes

 

[hugo]

The noise sounds like what I've heard described as Oscillation , ( although I've never ecperienced it ) put that in the search for this thread for possible causes

the best to counter oscillation, in my dla2a experience,  is to take low gain tubes on v1 (12ax7wa-r from tad), to use 50klog pots in series with 50k resistors for gain...or even 25k log with 75k resistor...

 

[rfused33874]

Hello
Hoping for help matching this Cinemag wiring to Sowter

INPUT (drawing attached):
CM2570 brown =
CM2570 red =
CM2570 orange =
CM2570 yellow =
CM2570 green =
CM2570 white/red =
CM2570 blue =
CM2570 white =
CM2570 black =


OUTPUT:
CM2840 red = 8940 yellow
CM2840 brown = 8940 green
CM2840 yellow = 8940 grey
CM2840 orange = 8940 pink
CM2840 black = there isn't one (only 4 wires on CM2840) can I leave it open?


Thanks for any help!

 

[moybm]

Hi, thanks to this forum I was able to mount my stereo version of this compressor that is almost finished but I am missing some fianles details for the finish.

I have tried to search for several websites even the front 3U stereo as it appears in the attached photo, but I can not locate it anywhere and the one I would be interested in getting is this design.  :-\

Would anyone know where I can find this 3U size front?

The ones I find are not like this, I even asked on facebook and youtube to Tyndall Electronics (Prentice Tyndall) but I have not received a response.  :'(

A lot of thanks for your help. 

 

[darkus]

Hi!

Im having some issues with my D-LA2A I complited about two years ago. The amount of gain reduction is shifting by time. If I set it on my vocal buss for 5dB of compression, an hour later Im only getting 3dB and I havent touched the frontpanel settings. Output gain seems a tad quieter as well.  Any ideas?