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Post by tonycamphd on Apr 27, 2014 20:04:22 GMT -6
unit7 that looks killer Paul! The shot of the face flipped open shows exactly what a clean job u did.
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Post by levon on Apr 29, 2014 3:04:55 GMT -6
Man, I wish I could build something like this. Looks gorgeous.
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Post by unit7 on Apr 29, 2014 13:58:20 GMT -6
Thanks for the kind words! But unfortunately, how clean this build ever was, it's not ready yet. I've powered it up, nothing seems to have been smoked, but I'm getting readings that are very off. The power section is spot on as is the BH7 tube, but the other tubes are very off (despite glowing nicely  ). I've checked and double checked resistor color codes/values and all seems ok. Next step will be to double- and triplecheck all wiring and unsolder resistors to check that they are ok. Re wiring I've already found one possible error that involves the Sowter output transformer. But before going on with that I'm waiting for reply from Brian @ Sowter just to get confirmed that I've read the Sowter data sheets properly. For a non transformer expert those data sheets can be a little bit vague. Meanwhile I still haven't got a delivery date from Canford on that VU meter so I've checked alternate options. IMS has this in stock:  It costs three times the plain Sifam VU + shipping, customs and tax ($250+) because it'll be imported from the US, but with my original looking chassi and the amount of time I've spent on this build perhaps I'll give the build this treat  |
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Post by wiz on Apr 29, 2014 17:11:42 GMT -6
great stuff..
cheers
Wiz
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Post by unit7 on May 1, 2014 10:19:56 GMT -6
Some progress... Got an email from Brian at Sowter confirming that the data sheets on their site graphically corresponds to the original LA2 1968 schematics. Now, Cayocosta's drawing at RecProAudio uses the original UTC transformers and those transformers have a lot more connections than the Sowters. For instance the UTCs have dedicated ground pins but the Sowters don't. Instead the Sowters are grounded by attaching them to the compressor chassi - at least that is what happened with mine. The result is that the wiring will be a bit different from the original and Cayocosta's build - and you have to make sure that the Sowter pins corresponding to the original UTC pins marked '10' (on both input and output xformers) are going to ground (in my case: grey cable on Sowter input xformer 1009e, and yellow cable of output xformer 1290e). I did this on the input xformer but, as mentioned in the previous post, missed it on the output xformer. It's fixed now, and the off the chart readings on some of the tubes are now fixed! I'm doing this build at home ('DARLING! Don't be afraid if the lights go out, it's just me testing this build!') so I have no good equipment for sending tones or measure properly. But I just plugged a mic in to test and the unit passes audio, no buzz or hum and that gain knob shows some muscles! After having it powered on for a couple of hours with speakers on and no issues, and occassional measuring of the tubes, I decided to plug in the T4B (Kenetek). This is the recommended procedure as the unit passes audio without the T4B installed and you avoid the risk of damaging the T4B if you measure the tubes and take care of issues before installing it. As mentioned I think I'll be better off testing and calibrating the unit in my studio, but during this test I wasn't able to get any audible compression. So I've contacted Kenetek and got some directions. I also read the GDIY LA2 thread and found some good tips. However I would like to install the meter and the last resistor first. The Mouser order is pending and could be as late as end of this month. And the meter.... I did cancel the delayed Canford order and went for the Teletronix meter from IMS instead! So perhaps you won't see more here for a few weeks. I'll be back as soon as there's any progress. Cheers! Attachments:
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Post by tonycamphd on May 1, 2014 10:52:26 GMT -6
great Paul, i'm glad you did the teletronics meter, your wonderful build deserves it like you said, keep us posted as you work it out!
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Post by svart on May 2, 2014 7:38:06 GMT -6
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Post by unit7 on May 2, 2014 8:31:35 GMT -6
Thanks! Yes I've seen that. Those are not the Sowters I've been using though so my colors are different. But I had forgot all those voltage check points. Very good for extra reference! |
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Post by unit7 on May 2, 2014 17:45:12 GMT -6
Just a short report to tell you that I finally had a chance to set it up properly for testing, feeding test tones etc. It still sounds clean and healthy and the compression works! I'll test further when the meter arrives and deliver a final report. Then I will also shoot some really slutty pics and post here!
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Post by unit7 on May 9, 2014 17:05:06 GMT -6
Meter arrived today! The missing resistor will be two more weeks from Mouser and I decided Tantra DIY is not for me, I just can't wait longer! So I went to the main electronics supplier here called ELFA to buy...one resistor! (ok, grabbed some heat shrink tube too  . It's a metal film resistor so I guess I'll have to replace to the incoming carbon resistor eventually for looks and feel. Indescribable feeling to finally get that gorgeous meter in place!! Then powering up and see it moving, and trim it to zero. Then run some audio thru it and see it working. No doubt the most rewarding and proudest DIY moment of mine. First sung vocal to run thru the circuit: Johnkenn!!! (John did a vocal harmony for me this week). Compression action feels like a STA at really slow settings. Guess I will have to try other T4s eventually... I believe ADLs T4 is more grabby. Before testing in my studio it's hard to get a feeling for the tone of the unit, or how it will work in a context. Will let you know later. Some info about that meter for future builders: For illumination I chose the 'lightbox' option which can be seen also at Cayocosta's build. I chose it for a clean appearance. When packing the meter the guys at IMS noticed that the dial plate on this special Teletronix logo version is thin aluminium and they warned me that the backlit lightbox option wouldn't work very good. They were right. Some light reaches from the sides but not enough imo. Look at the UA reissue. It's lit with one bulb from above. Should be the way to go. But worse than the faint light is that the lightbox is too big for Androidtube's original style case. I could barely close the lid because the lightbox pushed the output XLR and the big orange drop C6. With hi voltage inside you don't want things touching. So illumination still remains to be solved. Will order some bulb holders shortly. Attachments:
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Deleted
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Post by Deleted on May 9, 2014 19:29:37 GMT -6
Great!
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Post by wiz on May 9, 2014 19:37:56 GMT -6
very VERY cool
8)
Wiz
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Post by tonycamphd on May 9, 2014 23:07:04 GMT -6
great job Paul, it looks fantastic with that meter! looking forward to your thoughts on it as you get to know it better.
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moatl
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Post by moatl on May 10, 2014 10:30:46 GMT -6
Hi Paul, I solely registered here so I can have a closer look at your build images (not possible as a guest) Great to see yours is coming along - too! Great job man! Also I see you figured out how to add the logo  The meter also looks great - pretty close to the Beede! I saw this morning you sent me a PM on GDIY concerning the lamp holder - the one I used in my build was taken from a broken API meter that I had laying around...but here's one from Mouser: eu.mouser.com/ProductDetail/JKL-Components/29MB-T/?qs=%2fha2pyFadui4J6bdSDgWk9zkem13ZIXXkSVirWTP9gukfFbHCsnfhA%3d%3dmaybe you can use the info there to find a similar one elsewhere or even at ELFA Good luck! Martin |
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Post by unit7 on May 10, 2014 13:20:19 GMT -6
Wow, thanks Martin! Nice with a compliment from the guy with one of nicest DIY LA2 I've seen. Everybody else: Check out Martin's build at groupdiy.com/index.php?topic=3278.2440(post #2455) P.S. Attaching that logo to the faceplate was really tricky... |
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Post by unit7 on May 13, 2014 12:28:45 GMT -6
Brought my new baby to the studio yesterday. I'm located in an old building and sometimes I've had issues with hum, so I was pleased to find that it is super quiet(!). Then played with it on a few different voices and acoustic guitars and compared to ADL1500, RI STA and TC Phoenix.
I got the feeling that both the input (saturation) and the compression detection is kind of sensitive and 'touchy', so it would make sense using a faster comp in front of this. Never tried that yesterday though.
I put the STA on mid attack and slowest release to get close to the same compression action. All the compressors I compared of course behaves a tiny bit differently but still imo in the same ballpark. Tone wise I feel, just as I've sensed a few times before, that the STA and Phoenix are very close. The ADL is a bit brighter and has more mids, and my DIY LA2 ends up somewhere in between, even with the fairly dark Mullard tube I've got installed.
I don't believe it will be my go to for vocals, as I like the Retro stuff better.. But for acoustics on the other hand this could become a new favorite!
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Post by tonycamphd on May 14, 2014 8:57:30 GMT -6
Brought my new baby to the studio yesterday. I'm located in an old building and sometimes I've had issues with hum, so I was pleased to find that it is super quiet(!). Then played with it on a few different voices and acoustic guitars and compared to ADL1500, RI STA and TC Phoenix. I got the feeling that both the input (saturation) and the compression detection is kind of sensitive and 'touchy', so it would make sense using a faster comp in front of this. Never tried that yesterday though. I put the STA on mid attack and slowest release to get close to the same compression action. All the compressors I compared of course behaves a tiny bit differently but still imo in the same ballpark. Tone wise I feel, just as I've sensed a few times before, that the STA and Phoenix are very close. The ADL is a bit brighter and has more mids, and my DIY LA2 ends up somewhere in between, even with the fairly dark Mullard tube I've got installed. I don't believe it will be my go to for vocals, as I like the Retro stuff better.. But for acoustics on the other hand this could become a new favorite! good stuff Paul! do you have a La3a? |
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Post by unit7 on May 14, 2014 10:08:39 GMT -6
Brought my new baby to the studio yesterday. I'm located in an old building and sometimes I've had issues with hum, so I was pleased to find that it is super quiet(!). Then played with it on a few different voices and acoustic guitars and compared to ADL1500, RI STA and TC Phoenix. I got the feeling that both the input (saturation) and the compression detection is kind of sensitive and 'touchy', so it would make sense using a faster comp in front of this. Never tried that yesterday though. I put the STA on mid attack and slowest release to get close to the same compression action. All the compressors I compared of course behaves a tiny bit differently but still imo in the same ballpark. Tone wise I feel, just as I've sensed a few times before, that the STA and Phoenix are very close. The ADL is a bit brighter and has more mids, and my DIY LA2 ends up somewhere in between, even with the fairly dark Mullard tube I've got installed. I don't believe it will be my go to for vocals, as I like the Retro stuff better.. But for acoustics on the other hand this could become a new favorite! good stuff Paul! do you have a La3a? Yep, but only the UA reissue |
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moatl
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Post by moatl on May 15, 2014 7:02:59 GMT -6
Anytime Paul! You didn't use trim caps as per the original, right? What values did you use at C4 and C14? I used the original Arco 465 one's there and did some sweeps to measure their effect on the frequency response. C4 adjusts the high frequency response of the entire unit and you really can adjust it a lot! C14 in combination with R23 adjusts the hf response of the compressor side chain circuit. So you really can go from having a slight HMF drop and a bump just after 10K before the roll-off sets in, to having a big bump at around 1K followed by a pretty intense roll-off above that. It's really crazy how you can shape the freq. response with all that. Especially for vocals you can get a real warm sound but still add some high end sheen! So it might be worth trying out different values there |
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Post by unit7 on May 15, 2014 13:19:21 GMT -6
moatl Thanks! No trim caps in mine. Went for 330pF on both C4 and C14. Didn't know that C4 is that influential. Sounds like a a spot for experimentation. So what happens with higher vs lower value choice of caps? edit: searched the la2 thread at gdiy and it seems higher values on c4 results in less hf roll off. so i believe i'll stay with 330pf for now...
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moatl
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Post by moatl on May 16, 2014 10:24:23 GMT -6
Right, a higher cap value of C4 will result in a better HF response of the entire unit (lower value = more roll-off) I did some freq. response measurements and attached the graphs. There you can see what C4 does. I have to add that I terminated my LA2A with 604 Ohms on the output. the blue graph shows the freq. response without termination - all other graphs show different C4 values WITH termination. C14 and R23 decide how much of the signals HF is sent to the compressor side chain. the lower the cap value the more hf is sent to the side chain -> the more the gain reduction circuit reacts to high frequencies -> the more hf roll-off when compressing Also if I'm not mistaken r23 controls where the roll-off starts - and it can go as low as 1K (or just above 1K) at the same time I experienced a slight bump just below 1K. I also made some measurements while adjusting those two trimmers but unfortunately forgot to save them  Attachments:
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Post by unit7 on May 20, 2014 10:53:53 GMT -6
Probably the final chapter of nerdery of this thread - The meter lamp...As mentioned the 'Lightbox' option that Sifam offers is too big for this chassi. Sifam has another simpler and cheaper option too (called Festoon lamp type illumination kit) but I'm not certain it will fit either, and then add the super slow service from Sifam, at least for non major customers like me. The original LA2 has a hole in the faceplate for the screw that holds the lamp assembly. But I didn't want to drill that hole so I've been checking other options. For simplest possible solution I've been looking at two options to attach the lamp holder 1) On the backside of the meter there's a screw, probably for mounting the Festoon illumination kit 2) The brown plastic sides of the meter has holes. So I moved on and looked for a good lamp holder. For 6V lamps I found a lot of options in a format called BA9s. So I began looking for a BA9s lampholder with a suitable holding bracket that could be mounted directly to one of the options above. Found some interesting options made for pinball machines but nothing that would be good enough without some mod. So finally, after having no success with my swedish goto's I chose this at eBay ($6.95 from seller 'cqradiosupply'):  Then I started looking for miniature angle irons/brackets suitable. No success - too big/too thick metal. Ok, so what if find a suitable piece of metal that I could bend/drill for a good angle iron. Found this piece of bar made of brass for $2 (label says: K&S engineering, Chicago) 30cm long, 6mm wide and 0.6mm thick:  Then ordered a 6V/200mA (BA9s) lamp from Elfa, and an extra 12V in case the 6V would be too bright. So after deciding to attach the lamp holder to the plastic brown side of the meter, some metal work, bending, drilling, riveting etc this is the result:  Dang, I'm soon 50 but I was happy as a kid seeing that lamp glow! 6V works great BTW. Finally I've been back and forth about the level of perfectionism on the wiring management. There are one or two cables, and also a few metal film resistors that could be replaced to reach really good karma, but after mounting the lamp and using a few cable ties I think this will have to do!  As mentioned...I'm a happy DIYer tonight! |
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Post by jcoutu1 on May 20, 2014 11:22:30 GMT -6
Looks awesome.
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Post by unit7 on May 20, 2014 13:31:23 GMT -6
Ok...so four months later... There's a promotion video over at UA about their LA2 reissue where an interviewed employee mention the build time. I believe he says about 8-9 hours to build one unit, then says something like 'well it's actually more like 6 hours now, but I probably shouldn't mention that here'  Thanks to Christian Whitmore of Pro Audio Tubes for all the help!
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Post by tonycamphd on May 20, 2014 21:52:36 GMT -6
bravo! unit7 it looks great Paul! you should be proud of such an awesome build! |
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). I've checked and double checked resistor color codes/values and all seems ok. Next step will be to double- and triplecheck all wiring and unsolder resistors to check that they are ok. Re wiring I've already found one possible error that involves the Sowter output transformer. But before going on with that I'm waiting for reply from Brian @ Sowter just to get confirmed that I've read the Sowter data sheets properly. For a non transformer expert those data sheets can be a little bit vague.
. It's a metal film resistor so I guess I'll have to replace to the incoming carbon resistor eventually for looks and feel.
