D-LA2A Support Thread

[justinheronmusic]

Just wanted to note some changes I have made to my build. I recently swapped out the big 10uf 630v Solen for a Sprague 10uf 500v Electrolytic. I'm using RCA long plate 12AX7s and RCA for the 12BH7 and 6AQ5. Souter in, Carnhill Out.

After letting the Solen burn in, I couldn't help but to notice a sort of raw feeling to the top end lingering. Not quite a spitiness, but a little too much "zing". At first I thought it was because I was using all carbon comp resistors, and they were leading to an unpleasant distortion. This sort of raspy response is welcomed on bass, but on vocals it wasn't as flattering. I was originally going to use the Spragues for my D-AOC build, but decided to leave that build as more modern, and the LA2A as more vintage. I swapped the Solen for the Sprague...

The difference is subtle, but it's there for sure. The Sprague really warmed up the compressor and gave it a more balanced feel. The syrupy weight is there. The top end feels like honey. It definitely feels warmer overall.

In retrospect, had I kept the Solen, I would have opted to use Sovtek 12AX7LPS or Gold Lions in the 12AX7 positions to balance the top end. The RCA tubes don't feel as "round" to me without the Sprague Electrolytic, but more obtuse. I am sure the Solen would also be a good fit for JJ tubes as the top end is already pretty veiled with those tubes. I would hypothesize that if I were using UTC transformers, or just a different combination of transformers, that might also come into play with what tubes and coupling cap to use.

Anyways, just something to think about. There aren't many people talking about that particular capacitor and the affect it has on the overall tone, so I thought I would chime in.

Happy Soldering!

 

[saint gillis]

Here's our boy,
  - case and panel from DonAudio
  - T4Bs from Electro Chronic (https://sites.google.com/site/diypartsstore/catalog/new-t4b-opto-el-panels) (very good stuff )
  - Sowter transformers
  - power transformer from AudioPhonics (for people in Europe you can order a custom toroidal transformer with voltages of your choice for a reasonable price)

  It's a stereo unit, all point to point wiring, thank to everybody in the forum for the good infos and for the rewritten schematics!  I wanted to try point to point wiring because I was curious about it and liked the old school style, I would say that it's a pain in the ass compared to using PCBs but on the other hand it's a kind of fun, well now that it's done if I had to give my advice I d say go for PCBs if you want to make it stereo because it's starting to make quite a lot of components.

  The noise floor is somewhere around -80/-75dbs, I have a bit more of 2nd and 3rd harmonic on the right side because it's closer to the transformer I guess, I'll try some mu metal sheets

  Here are some pics :
https://www.facebook.com/subcontinental/photos/a.1021647097852962.1073741827.480347595316251/1617253451625654/?type=3&theater

https://www.facebook.com/subcontinental/photos/a.1021647097852962.1073741827.480347595316251/1617253498292316/?type=3&theater

https://www.facebook.com/subcontinental/photos/a.1021647097852962.1073741827.480347595316251/1617253478292318/?type=3&theater

 

[saint gillis]

And I forgot to say.. it sounds awesome! especially on vocals but eveybody knows that

 

[JW]

I'm planning to skip the relays. So, no need for the IC. What should I be doing with those associated Torriod secondaries? Just float them? Or should I connect them to the board without the IC. (That doesn't seem like it would be the best) But what do I know?

???

 

[audiophreak]

Hello All,
              This may be a silly question but , I'm using a different PT that has a single 220vac 100mA secondary , do I connect the two leads to the HT connectors ( 1 &4 )  ? or do I need a bridge rectifier ? 

Thanks in advance

 

[[silent:arts]]

I'm planning to skip the relays. So, no need for the IC. What should I be doing with those associated Torriod secondaries? Just float them? Or should I connect them to the board without the IC. (That doesn't seem like it would be the best)

Don't populate D3-D6 and connect it to the board. You don't need C5-C8 either.
This way it is floating and out of the way.

 

[[silent:arts]]

I'm using a different PT that has a single 220vac 100mA secondary , do I connect the two leads to the HT connectors ( 1 &4 )  ? or do I need a bridge rectifier ?

You do need a bridge rectifier.

 

[audiophreak]

You do need a bridge rectifier.

Thanks !!    This looks right according to the schematic , but dont want to blow anything up , does this look correct ? 

 

[maq3396]

Happy Saturday all,

After staring at the pcbs and transformer sitting on my shelf for a while I would like to start this build.

Some time ago I read through his entire post but don't recall seeing any huge changes in terms of the original components.

If I order parts from the BOM from Azone (on page 1) will I be in the ballpark or are there some substitutions that I should consider?

Thanks
Mac

 

[ChrioN]

A part list would indeed be useful

 

[desol]

I chose to go with original opto's and inputs. I wouldn't worry too much about it and worry more about layout and wiring, etc.

 

[audiophreak]

Hello All,
                I seem to remember a schematic or PCB graphic with parts placement that had reference voltages on it , can't seem to find it now , does anyone have that ??

 

[Foots]

It looks like the webpages that had the BOMs have expired. Does anybody have the lists that they can post? Thanks!

 

[Foots]

Has anybody used the Hammond 369JX transformer for this build? I just ordered the PCB from Volker and am wondering if I should have him add the ps transformer before he ships to me.

Thanks!

 

[[silent:arts]]

If I googled the specs for Hammond 369JX correctly it would work with one channel without Relais Bypass, but not for two.

 

[Foots]

I'm gathering the parts for this project and can't wait to start! I found this video on YouTube (link below) and have a question I'm hoping somebody here can answer. Aside from a couple full kits, this will be my first build on my own.

http://youtu.be/M-lXJtmLrd8

It looks like this builder has done some kind of mod to switch the attack between fast/slow, but I only see one T4B for each channel. Anybody know how he accomplished this? I did find the mod for 2 T4Bs/channel, but this looks different. I've tried to reach out to the builder with no luck so far. Does anybody recognize the case? In his video comments, he mentioned Collective Cases and I've reached out to them. No response yet. [edit: Collective Cases says it's not theirs. I ended up ordering one from another vendor]

Thanks folks! I'm really looking forward to this project!!

 

[JW]

Okay,

I fired mine up with just V1 and V2. I'm getting 390VDC after diode rectification. Around 350 after the 4.7K 2 watt.

For 120VAC here in Oregon, US. I have the rondo primaries connected two yellows to mains hot, and two whites connected to mains neutral.

It should be down to 275V after the 4.7K 2 watt resistor. So I'm about 75V over here. Is this likely because the side chain tubes aren't in the circuit yet? Or is it possible I wired the rondo primaries wrong?

I've checked and re checked the Rondo secondaries and they're correct (though I am floating the orange wires because I'm not using the relay circuit)

Also, I listened to both channels (still with only V1 and V2, no t4 or sidechain tubes) Ch. 2  seems to be working well, ch 1 is pretty nasally and distorted sounding. Probably a separate issue but I want to make sure first that I have the primaries for the power transformer correct and figure out how to get the B+ voltage down.

 

[[silent:arts]]

Your PSU transformer is wired correctly.
With only 4 instead of 8 tubes the voltage is higher.

 

[maq3396]

What have people been doing for their front panel and enclosures?

I have found offerings from Don Audio and Collective Cases (Dandeurloo)

Any others out there that I am missing>

Thanks
Mac

 

[[silent:arts]]

Designing your own looks better and is more DIY  8)

https://www.frontpanels.de
http://www.schaeffer-ag.de/en/
http://www.frontpanelexpress.com