Elab LA2A - Build thread

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moybm

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Jul 6, 2012
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Hi, I'm following this thread because I find it very interesting, also because I have decided to mount this project. So far I have two doubts:

The first is that I've seen that there are 2 listings of components from different websites, one is from Mouser and one from Digikey ... are they both the same?

The second is that I am trying to find out which vacuum tubes to use, I see that the project needs 4 but I do not know where I would have to ask.

Thank you very much in advance, I hope to be able to contribute interesting content.

Greetings.
 

Deepdark

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moybm said:
Hi, I'm following this thread because I find it very interesting, also because I have decided to mount this project. So far I have two doubts:

The first is that I've seen that there are 2 listings of components from different websites, one is from Mouser and one from Digikey ... are they both the same?

The second is that I am trying to find out which vacuum tubes to use, I see that the project needs 4 but I do not know where I would have to ask.

Thank you very much in advance, I hope to be able to contribute interesting content.

Greetings.

Mouser and Digikey are electronic parts sellers. Both cards are somewhat indentical, but with the available parts both offers.

Which Vacuum tube to use is pretty suggestive and highly dépendent upon your budget. I'd say V1 could something like Mullard, Tung-sol or any other good brands. Try to put the best one at this positions for better noise response.
 

moybm

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Deepdark said:
Mouser and Digikey are electronic parts sellers. Both cards are somewhat indentical, but with the available parts both offers.

Which Vacuum tube to use is pretty suggestive and highly dépendent upon your budget. I'd say V1 could something like Mullard, Tung-sol or any other good brands. Try to put the best one at this positions for better noise response.

At first thank you for your reply.
My question regarding vacuum valves is somewhat more technical. This is my fourth project I am building (formerly 1176, Api, compressor bus stereo) but this is the first with vacuum valves. As far as I know for the integrated circuits of for example 8 pins there are many different types and functionalities but for example for vacuum valves being 9 pins ... are they all of the same functionality?

Thank you very much, greetings
 

Deepdark

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moybm said:
At first thank you for your reply.
My question regarding vacuum valves is somewhat more technical. This is my fourth project I am building (formerly 1176, Api, compressor bus stereo) but this is the first with vacuum valves. As far as I know for the integrated circuits of for example 8 pins there are many different types and functionalities but for example for vacuum valves being 9 pins ... are they all of the same functionality?

Thank you very much, greetings

What you want to know is the exact use of each valve or the technicals behind each of them? You could always take a look at the data sheets. Basically 9 pins tube here are dual triode. 2 heaters, 2 anodes, 2 cathodes and 2 grids as well as a center heater connection.
 

moybm

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My doubt is that I have no references of which vacuum valves to choose as the starting example for each of the sockets. :-\

Could it be worth to the 9-pin model 12ax7?

Or E88CC for the 7-pin?


It's just to take some as an example.

Thank you very much  :D
 

Deepdark

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V1 and v3 are 12ax7, v4 is 6aq5 (7 pins) and v2 is 12bh7. Look at the schematic it's all noted there. As for the brand and all, it's up to you.
 

moybm

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Hi again, I have another doubt regarding the components:

In the list that appears of Mouser there is a main transformer that for what I observe is 115 volts but in the same web you speak of a toroidal transformer that in its primary has two inputs of 115 volts, as I am from Spain here the network Electric works at 220 volts, then I understand that in the mouser project that transformer I will not need it?

Thanks  :D
 

Deepdark

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moybm said:
Hi again, I have another doubt regarding the components:

In the list that appears of Mouser there is a main transformer that for what I observe is 115 volts but in the same web you speak of a toroidal transformer that in its primary has two inputs of 115 volts, as I am from Spain here the network Electric works at 220 volts, then I understand that in the mouser project that transformer I will not need it?

Thanks  :D

Hi

The toroidal I spoke about is the Antek one. Dual primary coil so you can strap them for 220v operation. If you plan using a Hammond power transformer already available at mouser or digikey, use one that has a dual primary coil, too.
 

adam_f

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Aug 8, 2016
Messages
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Hello, just collecting parts for this build and I've got a couple of questions...

Will this meter work in place of the hairball one?

http://www.canford.co.uk/Products/58-383_SIFAM-AUDIO-LEVEL-METER-AL39WF

Also is there much audible difference between using the toroidal power transformer or the Hammond 369JX?

Thanks!

Adam
 

andyfromdenver

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Athens, GA
adam_f said:
Hello, just collecting parts for this build and I've got a couple of questions...

Will this meter work in place of the hairball one?

http://www.canford.co.uk/Products/58-383_SIFAM-AUDIO-LEVEL-METER-AL39WF

Also is there much audible difference between using the toroidal power transformer or the Hammond 369JX?

Thanks!

Adam

Hi Adam!  The meter you linked to is a suitable meter. It differs in size from the Hairball and possibly the illumination voltage required (all can be addressed in your particular build i'm sure)

Toroid transformers have a significant advantage in that they minimize flux radiation to nearby recievers (aka your output transformer). However, placement and testing/listening for hum is key, and the Hammond can be placed for no hum interference too.
See my thread "sinatra sings my way" for a method of listening for transformer interference.
The construction stage is your one chance to orient your transformers right, for a no-regrets, quiet build. I strongly suggest people take the extra time and effort to ensure they are not picking up hum from the PT, especially if they are using an un-shielded OT, IT.

Hope that helps!

Andy
 

adam_f

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Aug 8, 2016
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Thanks for your reply Andy, I've ordered the toroidal PT.

I'll give your method for listening to the hum whilst positioning the OT/IT a go, to make sure I get the quietest spot.

With the meter - I think the lamp is 12v AC,  but I've only got the 6.3v heater supply. What's the best way to generate the 12v? Do I need another smaller transformer?

Or maybe there is another meter which would be easier to integrate? I just chose that one because I can get it easily in the UK.

Thanks in advance!
 

andyfromdenver

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adam_f said:
With the meter - I think the lamp is 12v AC,  but I've only got the 6.3v heater supply. What's the best way to generate the 12v? Do I need another smaller transformer?
The unfortunate sticky-wicket being that the 6aq5 only accepts 6.3V otherwise could do heaters in series...sigh.

I've never looked at a meter upclose, so someone else will have to advise. But the "best" way to my way of thinking would be to get a 6.3V bulb, or hack in something 6.3V appropriate. It would be cray to add a PT just for that circuit.

Go LED VU meter! lol, then you could justify another txfr :)
just kidding, btw. , but that's what's in mine now and I love it.

I only briefly looked at the sifam meter page, when parts sourcing, but it seemed like there was a 12V lamp and a 6.3V lamp option, but I could be way wrong.

I know if you search around groupdiy, someone has addressed this :)

Andy

p.s. and to add: Cool project Deepdark! I like the separate power supply board idea and the DC heater for V1 :)  I'm sure the results are very nice.
 

moybm

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Hi andyfromdenver!

I write because I am having certain doubts with some components and in particular with some resistances and condensers. According to the plate indicates in its description the values ​​of the components to be welded.

When I made the request to mouser use the link that comes in the first post and of the components that have come to me some resistors are not the exact values ​​that appear inscribed in the plate, like for example: the 5 resistors of the power supply according to the inscription Its value is 820 ohm to 1w and in the order of mouser come 5 resistors of 910 ohm to 1w.

Or two capacitors C13_1 and C13_2 appear as 510pf and 470pf and in the list of mouser are 2 capacitors of 500pf.

Or C12 is not comming in the list of mouser.

and some more differences.

I need find these components exactly?

Thaks :)
 

adam_f

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Aug 8, 2016
Messages
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Hello,

the 1000v 2a bridge rectifiers listed in the mouser BOM are on backorder. Will this 800v one do the job?

http://www.mouser.co.uk/Search/ProductDetail.aspx?R=2W08G-E4%2f51virtualkey61370000virtualkey625-2W08G-E4

Thanks!
 

moybm

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Jul 6, 2012
Messages
40
That component is the same but it is manufactured to support up to 800v, ​​the voltage you are going to work will be far below so you should be worth the same.
 

adam_f

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Aug 8, 2016
Messages
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moybm said:
That component is the same but it is manufactured to support up to 800v, ​​the voltage you are going to work will be far below so you should be worth the same.

Great that's what I thought. Thanks!
 

adam_f

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Aug 8, 2016
Messages
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Just finished my LA-2A build using Elab's PCBs. Worked first time! Super quiet, zero hum and beautiful tube thickness and smooth compression. For anyone who's interested I used Tung-Sol 12ax7a's, a Philips 12bh7a and a GE 6aq5w, Antek power transformer, Sowter 1449e input and 1010a output transformers, and it's the DIY-racked case.

Cheers!

Adam

IMG_0106.jpg


IMG_0090.jpg
 

Rufus

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Jul 6, 2014
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Miami
I am posting my here to see if someone could help me to bring my Elab La2A kit to life....  every time I turn on the compressor the fuse blow up; I had unplugged the secondaries connection and I even rebuild  the primaries connection out of the box dutch taped the secondaries , and the fuse in the IEC keeps blowing up?  - before paying a professional to check my connections could some one please help me? ...
 

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adam_f

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Aug 8, 2016
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Hi Rufus,

I can’t see your diagram right now on my phone, but I did have a similar problem with the Antek power transformer. I found it blew fuses even disconnected from the circuit all together. I did a bit of googling and decided it was probably in rush current. Anyway, I tried a 1A slow blow fuse (as listed in the Opto 6 BoM) and this solved the problem. Maybe give this a try?
 

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