All things LA2a related

[emrr]

Right, here it is again, since it's lost many posts back:

[quote author="emrr"]
Here it is, the old PSU variation question, specific to the LA-2A. Getting into 'religion' territory.

Has anyone done (does anyone recall anyone doing) a build using a tube rectifier? Experience with sonic outcome; anything notable? Obviously require a change in power transformer for filaments, and to account for tube rectifier voltage drop.

Conversely, has anyone listened to circuit using an off the shelf regulated SS supply, like the Power One?

Thoughts?[/quote]

 

[emrr]

[quote author="emrr"] Somebody measure the sidechain gain![/quote]

Sorry if we're re-inventing the wheel here. 119 pages is a little tough to scan and remember.

Okay, CJ's voltage chart is back, and the sidechain does indeed look like 52 db gain. Looks like 29 db in the line amp with his 12AY7 mod. Assuming an input level healthy enough to achieve your desired max output, the sidechain should always be able to overpower the incoming signal and cause compression. At least 10 db's worth of compression, even if input low enough to need gain knob wide open.

This points out that if the 12AY7 does reduce line amp gain by any measureable amount, the unaltered sidechain can then deliver more compression drive than the stock 12AX7 line amp circuit.

 

[cannikin]

emrr or anyone

any chance you could email me CJs voltage chart?

Been waiting for the chart to move forward with my build.

my address:

c a l r e c AT mac DOT com

 

[emrr]

it's a link in his signature.

 

[codered]

[quote author="emrr"]

Conversely, has anyone listened to circuit using an off the shelf regulated SS supply, like the Power One?

Thoughts?[/quote]

May I ask the reason for this question?It is interesting because the power supply of my racked vintage ten73s just failed.The racking was done by a boutique racking company (upwards of $1000).When I pryed it open it was a Power One inside .If you remember the Altec discussion in Lynn's site,John Hall himself suggested using the Power One International series becuase of the humbucking transformer.

 

[emrr]

[quote author="codered"][quote author="emrr"]

Conversely, has anyone listened to circuit using an off the shelf regulated SS supply, like the Power One?

Thoughts?[/quote]

May I ask the reason for this question?[/quote]

Because people at times have near religious reactions to the perceived 'sound' of the 'type' of power supply used. And as much trouble as most people have figuring out PSU's (say you do a multi-channel build off of the same PSU), I'd expect someone to have 'cut out the middle man' and gone fully regulated. OR, taken the guitarist approach and insisted on a tube rectifier. I guess the answer is either 'no', or 'I'm not talking about it'.

Is this really so esoteric? No one's thought about it?

 

[nielsk]

I have used them on all of mine, they work great, and putting it outboard makes for a very low noise floor. The only problem is that the high voltage model was discontinued..

 

[emrr]

Don't scare me like that! All 3 International Power high voltage models are in the Mouser catalog that came this week. page 1925.

"ah yes, but THE SOUND is what he asked about, not whether it would work."

 

[nielsk]

Oops, I got the name wrong, I have the International Power (not Power One) supply, the IHB250-0.1 model. It is nice and small, with adjustable 250 volt 0.1 amp output, multitap input, but, no longer made... I will have to check out the Power One, what model # are you using?

 

[emrr]

they are the same company; same thing. It's in the catalog; do you know something the rest of us don't know, or are you just saying they're no longer made?

 

[codered]

Guys,

Any group projects I can use the high voltage PS on ?I'm planning on the LA2A & G9 in the near future.
The Power-One is built solidly plus you get the aluminum chassis.The one in the Neve rack was built in '05 and had Nichicons all around plus the heat-sinking is industrial quality.
When I saw the Power-one in the Neve rack I officially threw the power supply myth out ,provided it is a good quality regulated PS.How do I measure the ripple voltage? is there any standard for audio application for defining "clean PS".

 

[Bluzzi]

Other than some mystical reason why use a costly PS when the one in the LA2A is so cheap and simple?

jim

 

[nielsk]

last time I went to buy them, no one showed stock anywhere, I contacted the company and they told me they were discontinued...I found a place in California that had a few and bought what they had and I have not tried to get more since....maybe they were put back into production?
I just like a remote power supply, no induced noise issues, and it is so easy to do with these units.

I still want to know if a terminal board "build" layout has ever been posted.... I am building another unit and could probably make it prettyer, the last on most of the components are on the tube sockets (it actually works pretty well, but servicing it will suck...)

 

[Bluzzi]

Hi nielsk,

I've built 2 now and have absolutely no hum at all. Even if you put a PS out of the case the high voltages are still present inside and those are the ones you have to watch out for. Usually moving a wire or 2 will remove any noise induced.

Of course an outside PS will not make things worse.

jim

 

[emrr]

[quote author="Bluzzi"]Other than some mystical reason why use a costly PS when the one in the LA2A is so cheap and simple?

jim[/quote]

If you're building a two channel, the regulated off the shelf version would come in cheaper I bet. $46 for 100 mA 265VDC.

Again, not my question really. It's just one of the options. I'm more curious if anyone's done one with tube rectifier. The difference in PSU sound isn't really 'mystical', though the circuit its feeding matters a great deal as to whether there's significant perceived difference. Again, as many opinions as there are about it, I'm surprised no one's tried it.

 

[SSLtech]

Ah, but to build one with a regulated power supply and to discover that there's no particular improvement is the fastest way to shut up those who would claim that there IS a difference, so you never hear about it...

...and those who say that there's no compelling sonic reason to use a reg. PSU willnever build one because... well, there's no reason to, so far as they see.

So the only people who INSIST that there's a huge difference are those who have never built one yet...

...yeah, you know... the EXPERTS! :wink:

Keith

 

[emrr]

So true, so true. Looking for claims of hard evidence only. None to be had. I'm not expecting claims of 'substantial difference', but one never knows. For example, as many people as have complained about hum problems, not one person has put in a DC filament system just to see if it helped with the bottom end of the noise floor? In 120 pages of commentary? Yes, technique, technique, technique, I know. All in the layout.

it's another set of tests like you've done with iron, Keith.

it would only require:

1) an LA-2A
2) the urge to explore the nuances
3) a regulated PSU, a soldering iron, some test leads, and the ability to do the swap-out for observation.
3) the tube rectifier option is a little tougher, but you've all done crazy things with test leads, right? Different power trans and rectifier socket, probably a whole little 1920's looking mock-up on wood. Maybe one that sparks some when the dust gets too deep.

I lack #1 on the list.

people build what's safe; the clone. trying to find the few who've dared to experiment with the options in question.

I'm just gonna have to shut up about this, and leave y'all alone. :roll: :wink: :guinness: :green: :thumb:

 

[Bluzzi]

Doug you are looking for opinions or confirmation of improvement to the audio quality when using external regulated PS. I don't think you are going to get any.

Hum? what hum? Not many have complained about hum. If so then its the wiring not the PS, I insist on this. I'm really stickly about noise floor and my 2 LA2As are dead quiet! And believe me I'm not the best P2P wirer.

As you see the ones that have built them are quite happy with the stock PS section. It would seem that looking at the schematic that that PS section would inject some hum into the circuit but it doesn't in reality.

jim

 

[emrr]

As I said before, I'm really more interested in the tube rectifier version, but threw out both of the directions one could go.

I would expect anyone to be happy with a properly implemented power supply of any variety.

If you read the first 30-50 pages, there's lots of hum problems going on. I almost never have hum issues in my builds. But it seems a more common thread here. I have shit-tons of antique high gain gear that's quiet as a mouse with AC filaments; I know the deal on this.

Maybe this is my job to try all variants. First off I'm thinking tube rectifier, all octal tubes (oh hell, maybe 5 and 6 pin types), and nothing but bathtub style oil caps. :green:

Right.

I said I was done. :wink: :thumb:

 

[nielsk]

All mine have fully regulated DC filament supplies...not having compared mine to any others on the bench, I can't tell you if there is any difference, but they work great. I have been able to lower the noise floor in power amps by doing this.
My approach to anything has always been: take advantage of all knowledge and developed practice available to prevent any problems from occuring in order to not have to solve them, and I have seen plenty of noisy tube gear in my day.
In my understanding (limited, albeit) the "advantage " to tube rectifiers is the voltage sag adding a "compressed" sound, unlikely to happen in a non power amp application....(and we are talking about a compressor here)a disadvantage is the cost...unless you have a box full of rectifier tubes