D-LA2A Support Thread

[saint gillis]

Awesome! Do you use both hands to turn the gain knobs?

 

[frederickalonso]

Awesome! Do you use both hands to turn the gain knobs?

LOL :

 

[Rlucas41]

Hi Rlucas41

I never created a cart (s) since I bought the components little by little as money was flowing. I created and used this Excel BOM for the three units that I built so far, is not a cart per se but it contains all the mouser part numbers, you just can copy and paste, it's very complete with prices and everything (is not only the Mouser stuff but the complete BOM), It should be pretty close, I don't remember errors on it but be careful,  I'll leave this link a couple of weeks, I hope that helps.



https://www.dropbox.com/s/xvr7nroz63k0wg3/dual%20la2a%20marco%20bom.xlsx?dl=0

Cheers

Marco

Marco, Thank you very much!

Kindest regards,
Robert

 

[JW]

I'm curious what portions of the calibration I need to do again if I replace V1

(I went from a pair of 5751 tubes to two 12ax7's for V1 on both channels)

 

[alexc]

Very, very nice    Loving  the mci meters,  no doubt! I love my ones for sure.

 

[cdeboda]

Never got around to it so figured I'd do it now. Here are the pictures of my finished D-LA2A. She's a magnificent beast, for sure.

 

[cdeboda]

Some insides:

 

[cdeboda]

Some more guts and gore:

 

[cdeboda]

And finally, insides close up:

 

[JW]

Can I bump my last question a few posts back.

When replacing V1, do I need to re do the full calibration or just part of it?

 

[[silent:arts]]

When replacing V1, do I need to re do the full calibration or just part of it?

Nothing to calibrate with V1.

 

[JW]

Really? I don't even have to re do the stereo balance calibration? Sweet.  (I'm going 5751 tubes to 12AX7)

 

[ron_swanson]

Hi all,

First, apologies in advance for what may be noob questions.  First post of probably many going forward here. 

I've built a number of 1176 compressors and a couple of Pultec EQ's and done some guitar amp work over the years, but this is my first 'non-kit-in-a-box with full instructions build', so trying to learn as much as I can while doing as much detective (reading including most if not all of the pages within this thread) and as much homework as possible before asking questions. 

With that said... I'm well into my build of this silent:arts D-LA2A build...

Two questions:

1.) There's what looks like an indication for a diode printed on the PCB board sandwiched in-between the top of the relays and the audio input / output headers that I can't seem to correlate to the schematic or the parts list, nor does there seem to be any indication of what component is expected like other components are elsewhere indicated on the PCB.  Am I missing something on the schematic?  The parts list? Maybe a test point?  Something that a more experienced builder would know intuitively?

2.) My enclosure (Collective Cases) includes a 'on' power description as well as a hole for a power indictor light on the front panel for what looks like it would have been made for a 6.3VAC Fender type guitar amp socket and indicator lamp .  If so, in the tube guitar amp circuits I have seen,  it appears that power for this light usually comes from the tube heater power.  Is it ok to source the power for this lamp from one of the other heater lines or is that a bad idea?  If bad, what would be best practice in this case?    I'm using silent:arts PSU.

Thanks in advance!

Greg

 

[rock soderstrom]

Hi Greg,

1) This is a flyback diode for the coil in the relay.  https://en.m.wikipedia.org/wiki/Flyback_diode

cheers

 

[[silent:arts]]

1) D101, D102, D201 & D202 in the schematic, 1N4148

 

[ron_swanson]

Hi Greg,

1) This is a flyback diode for the coil in the relay.  https://en.m.wikipedia.org/wiki/Flyback_diode

cheers

Excellent!  Thanks for the link, rock soderstrom!

1) D101, D102, D201 & D202 in the schematic, 1N4148

Ah, now I see...  hidden in plain sight.  Also thrown off by the N14141 --> N14148 notation on the BOM. 

Thanks Volker!

No thoughts on powering the 6.3VAC power indicator lamp using one of the heater power supplies?

 

[andyfromdenver]

No thoughts on powering the 6.3VAC power indicator lamp using one of the heater power supplies?

You can tackle this one  ;D. 
Assess your Power Transformer (PT) heater current rating.
Assess the total current draw from the tubes heaters (data sheets).
Assess the current draw of a #47 bulb (150mA).
If you're within the handling, you can use it.

Best wishes,
Andrew

 

[ron_swanson]

You can tackle this one  ;D. 
Assess your Power Transformer (PT) heater current rating.
Assess the total current draw from the tubes heaters (data sheets).
Assess the current draw of a #47 bulb (150mA).
If you're within the handling, you can use it.

Best wishes,
Andrew

Thanks Andrew!

Assuming a 2A PSU spec, it looks like I would be slightly under the PSU specs...

PART      QTY  Ma        A      SUB AMP TOTAL
12AX7 2 300 0.3        0.6
12BH7 1 600 0.6        0.6
6AQ5A 1 450 0.45    0.45
#47         1 150 0.15 0.15

          TOTAL AMPS    1.8A

To be more clear, my question was meant to check if anyone thought adding a lamp to the heater power supply will cause any unexpected issues such as noise or would that be pushing the PSU too close to its specs?

Cheers,
Greg

 

[Rlucas41]

Opinions please... how important is it to buy a “matched” pair of T4B’s for use in stereo mode?

 

[[silent:arts]]

My original UREI T4Bs are not matched.