All things LA2a related

[Scenaria]

PIX!

I love looking at how each of you wire em up.. they all end up a little different..

congrats

:guinness:

 

[Butterylicious]

What is the going rate for T4B's, and where to get them dang thangs?

 

[CJ]

Anywhere from 180 from UA, or down to 99 from a JBL sale they had a while back, also check the black market, or build your own.

I have can/board assemblies so all you need to do is solder in the EL panel and LDR cells. Where do you get those: You can mill around here:

www.vacuumbrain.com

cj

 

[Butterylicious]

I love the cardboard box test equip. I once built a DI box into a cigarette package in one of those sound check crisis situations. It stayed like that for ages.

 

[AnalogPackrat]

Cardboard chassis rule! My ASM-1 is still in a flip top shipping box. I really need to rack that thing. Got my Bloo "done" and started testing (no tubes, no T4B). B+ looked good, but no neon happiness. Found a cold solder joint on the turret that linked over to the neon. Zapped it. Neon is now on.

B21: 390V (@ C7A)
B20: 383V (@ C7B)
A1: 60V (@ neon lamp)

I think I'm good to go for step 2 (with tubes). But first I need a :sam:. <kssst> Ahhh. Wish me luck...

Oh, and congrats to Tom and thanks to sleepingtiger--the RatShack cable was easier to use on R2.

Back to the bench...

AnalogPackrat

 

[Bluzzi]

[quote author="CJ"]Anywhere from 180 from UA, or down to 99 from a JBL sale they had a while back, also check the black market, or build your own.

I have can/board assemblies so all you need to do is solder in the EL panel and LDR cells. Where do you get those: You can mill around here:

www.vacuumbrain.com

cj[/quote]

What a beautifully detailed page!

Do you still need a source for the octal housings? I found one and I could dig it up if you need. Let me know.


Jim

 

[CJ]

Thanks, Jim!

If you have a link for octal suff, by all means put it up and I can put it on the page.

cj

 

[Bluzzi]

OK, I'll look for it and post it here tomorrow.

Jim

 

[AnalogPackrat]

OK, tube test went well, inserted T4B, no smoke. Adjusted meter. Poked around for some other voltages just for sanity. Found a couple of odd things. The output of the 12BH7 White follower is only at 87VDC (I have grid stoppers on it). Then looking at the feedback line I only get 16V at the top of R22 (supposed to be 27V). Is this close enough? I'm going to try an audio test and then pack it for the night.

Thanks to Scenaria (and anyone who helped--SSLTech? CJ?) for putting this kit together. When my wife gets back to CA with the digicam I'll try to get some pics posted somewhere. CJ's page with Cayocosta's diagrams were also a big help. Oh, and all the photos (TheDug, SSLTech, Fum) made wiring routing a whole lot easier. And I'd like to thank the Academy...

:sam: :guinness: :grin:
Analog Packrat

 

[Butterylicious]

There's a NOS Urei T4B on evilBay. 140 clams buy chit now.

 

[AnalogPackrat]

Well, it works...almost. The pots I used for Gain and Peak Reduction are nice sealed NOS units I got at a local surplus joint. Either I wired them backwards or they are reverse log taper. Funky taper. Like nothing for the 30-40 degrees then BANG it's up to 30k. I'll be swapping them out for Plan B. The only other thing that is strange is that my meter shows nothing on either of the output monitoring settings, yet I'm getting output (and plenty of it with my gain pot turned down :shock: ). Will check tomorrow. Must be something silly on the connection to the output trafo.

Analog Packrat

 

[CJ]

The EL panel in a UREI T4 has to be spent by now, unless it was someones paper weight.

 

[Bluzzi]

CJ

I found the URL for the relay cases and sockets!

http://www.lineelectric.com/accessories/index.html

Ask Bill Harris for pricing. I think the socket and housing will come to below $2.00.

There are several sizes. Some are transparent some opaque if I remember correctly.

I found them when I was thnking of building a T4B. I decided to wait until I had the LA2A made with an original one first.

Jim

 

[CJ]

Thank's Jim! It's now on the T4 page.

cj

 

[Bluzzi]

Glad to make a contribution! I get so much here.

Jim

 

[Tom]

Here are some pixs of my new Bloo.

I plan on performing some tests over the weekend, but my first impressions are quite favorable.

The 10uf output cap C5 is a Solen polyprop cap I picked up at parts express.
http://www.partsexpress.com/pe/showdetl.cfm?DID=7&PartNumber=027-568

I think that the 30uf and 40uf filter caps C7a-d are a little big. In retrospect, I should have taken the time to look for smaller footprint caps.

Otherwise, everything went together fairly smoothly. This was my first tube project, and first project of such magnitude. It took me about 15 hours or so start to finish. Without this thread, I'd still be scratchin my head as those 1k grid stoppers were just the ticket to get my unit functioning. Cheers

Any suggestions or comments would be much appreciated. I look forward to my next project...which will have to wait until I do some recording!


Best regards

Tom

 

[Scenaria]

nice work!

and yea.. it seems like everyone keeps trying to squeeze in those atoms :green:

 

[AnalogPackrat]

Woo hoo! Found my stupid wiring error on the meter switch and replaced the goofy surplus pots with new PECs from DigiKey. Ran a signal generator into the Bloo while monitoring in/out--everything looks good. The meter seems to behave and there is a slight difference in the compress & limit settings when sweeping amplitude.

Time for some real audio tests. Thanks again for the kit, the photos, and the pointers...I'll try to post some photos next week when my wife gets home with the camera.


AnalogPackrat :green:

 

[cannikin]

Thats funny I just swapped out my crappy pots for PEC's, Nice pots makes the unit feel so much better.. :grin:

 

[AnalogPackrat]

Yeah, the PEC pots aren't too shabby. My audio testing last evening was frustrated by DAW interfacing troubles :evil: . This is the first time I've tried to run outboard gear with my Firepod and Sonar. It was not fun as neither has particularly great info in their manuals for this. Anyway, I got some real audio (acoustic guitar and vocals) piped into the Bloo and compared it to the Sonitus compressor plug-in's pseudo LA2A emulation. No comparison. The plugin introduces some weird AM artifacts when the signal is near the knee. The Bloo blew it away--silky smooth. :thumb:

For fun I inserted Voxengo's SPAN (spectrum analyzer) plugin on the Bloo return channel to have a look at the noise spectrum. Ignoring the local bumps it has a smile shape with more noise near the bottom and top. The biggest offender was 60Hz (and harmonics), but even that wasn't bad at reasonable gain settings. Here's an (incomplete) tabulation of some of the local peaks at various gain settings (average level was maybe 6dB down from the peaks). Note that is includes any noise from the Firepod's line inputs as well.

          Gain 0      Gain 30%         Gain 50%
f (Hz)   noise(dB)    noise(dB)        noise(dB)
60        -91           -83              -75.5
120       -91           -93              -76
540                    -102
1000                   -103
4350                    -94
6240                    -90              -86
15000     -90           -86.5

I'm going to take some more numbers with the front panel open to see how much of the AC leakage is coming from the proximity of the GR switch to all the AC stuff on the right side of the chassis. Probably not too much since it drops 15dB at low gain...must be the heaters. Not much I can do about that. Anyway, it's pretty dang quiet.

Analog Packrat