600:600 tranz in place of 10k:10k for LA2A Input ???

Sorry if this has been asked before but:

Will a 600:600 tranz work (Good) in place of 10k:10k with a 10k resistor added to the secondary of the 600:600 :?:
... or is there more to it?

I'm throwing together another LA2A & like using 1:1 (10k:10k) for the inputs.
The 600:600 trannys are from an old Yamaha boards Main & Aux/Buss outputs & are Tamara.
I'm going to try the Edcor 10k:600 for the output.

The last 2 LA2A's I built I used the JENSEN's which sound GREAT but wanted to try this out & save the $200+.

Thanks in advance.

If you are talking about adding the 10k in series with the transformer, surely this will be making a T pad with the 2 68k resistors ??

No, I think he's talking about putting 10K across the secondary. Is that right, Kevin?

It should work OK as long as the source impedance of whatever you're plugging into the LA-2A is 600 ohms or less. Try it out before drilling any holes.

But why not just spend 12 bucks and use an Edcor XSM10K/10K instead? The scavenged transformers you want to use are line output type and probably wouldn't work any better than the Edcor.

[quote author="NewYorkDave"]No, I think he's talking about putting 10K across the secondary. Is that right, Kevin?

It should work OK as long as the source impedance of whatever you're plugging into the LA-2A is 600 ohms or less. Try it out before drilling any holes.

But why not just spend 12 bucks and use an Edcor XSM10K/10K instead? The scavenged transformers you want to use are line output type and probably wouldn't work any better than the Edcor.[/quote]

Yes Dave, 10K across the secondary... I thought I read before about 1:1 trannys being just that & that the reflected impedance was determined by the resistor. Sorry, I still have some learning to do, that's why I'm asking.

I'll be using this MOSTLY with my 10k inserts on my console.

I also like the 1:1 instead of the 1:10 on the LA2A... to much step up for me.

I was going to ask about the Edcor's... I assume that the lack of "shielding" in not a problem?

It can be a problem with low-level inputs. But the transformers you were thinking about using are not shielded either, right?

As always I am contantly fiddling with my LA2a and I come from the school of..just try it! (as long as it is electrically safe, won't damage the unit)..Last weekeng I put a 5751 instead of 12ax7 at V1 and had an extra cinemag 2503 style transformer (with 50% ni) which I wired to the input as a 1:2 step up ,left the 10k termination resistor (reflects 2.4 k to the input)...I LOVE IT..is it absolutely correct? He!! no.. but it sounds GREAT... a frequency sweep shows no big lumps or bumps..I have driven it with 312's (bauman's 25*20), Forsell's, Hardy's and the Jensen Cascode tube pre from their site. Rather unscientfically I recorded a vocal using the same mic and pre with the modded and unmodded LA2a in the chain doing the same 5-10 db reduction...and I like the modded one (and so did 3 other engineers I played the tracks for..without telling them what was different about them)...I might put in a switch so you can choose between the Edcor 600:10K and the Cinemag 1:2..Much more aggressive with the edcor...smoother with the 2503..Give it a whirl...if it sucks you can change it...

Ray

600:600 was the original xfmr for the LA2, so whats the beef?

2503 will work, but might suck the bass out of a high source.

Not enuff pri inductance, but an experiment has proved once again to be better than a thousand theories, so give it a try.

10K;10: was a later Jensen mod to the LA2, as found in the white pages at the Jensen site.

600:600 was the original xfmr for the LA2, so whats the beef?

2503 will work, but might suck the bass out of a high source.

Not enuff pri inductance, but an experiment has proved once again to be better than a thousand theories, so give it a try.

10K:10K was a later Jensen mod to the LA2, as found in the white pages at the Jensen site.

Tamura 600 might have e=nuff balls with a Ni core to be called a 10K, at least the big ass one I took apart.

[quote author="NewYorkDave"]It can be a problem with low-level inputs. But the transformers you were thinking about using are not shielded either, right?[/quote]

No, They ARE shielded in cans.

The level shouldn't be a problem, I'll be driving it with a mic-pre, board inserts (10k) & sometimes maybe a DA converter.

What makes a 600:600 different than a 10k:10k?
They're both 1:1... this always confused me
Is it more about how they "measure" frequency wise, under a certain load?

Thanks EVERYONE for helping. :thumb:

raysolinski,
Cool stuff man. I not afraid to try it, just want to understand a little better.

kubi,
...Which brings me to you... I'm still chewing on your math.

Maybe I am completely off. But I think 10k:10k will have more Inductace so it is ensured to be easyly driven by higher source outputs.
Is this right?
:?:

600 vs 10K is just an inductance issue.

Some old school sources will drive the 600, some new school stuff needs the 10K to avoid signal alteration.

Pick 600 ohms at 1 K CPS.

6 times 1000 (K CPS) times inductance (L) equals 600 ohms of inductive kick.

So L = 600/6000 = 100 milli henries enviroment for the source.

So if you follow the 1:10 rule , as opposed to the 100:1 rule for Crack, which was recently overturned by the Supreme Court no thanks to Justice Thomas, the "pubic hair on the soda can" guy, then you would want at least 10 times 100 mh equals

1 henry pri ind.

for 10K, just multiply 1 henry by 10,000/600 = you do the math.

[quote author="CJ"]600:600 was the original xfmr for the LA2, so whats the beef?
[/quote]
Well I'd like to set it up like the Jensen, which has an 11k across the secondary... so I assume it's reflecting 11k?

[quote author="CJ"]
10K:10K was a later Jensen mod to the LA2, as found in the white pages at the Jensen site.
[/quote]

This is what I used on my first 2 units & love it.. but never heard anything else.

Sorry CJ... I posted when you did.

I need do some research to learn how to measure inductance.

Is there a simple way or do I need special tools to measure?

EDIT-Found some good info from you guys... reading it now :thumb:

[quote author="NewYorkDave"] You can make it even simpler than that if you don't need to measure inductance in the presence of DC--and you don't, if it's for a Pultec circuit. Try this on for size:

[/quote]

Will this work for transformers?

Do I need to load the side not being tested?

Found this too, good info... still trying to get a grip on it but it helps. :green:

[quote author="NewYorkDave"]Oh, there's math for damn near everything in electronics. It's just a question of whether or not you choose to use it. Sometimes it'll save you some work, sometimes it's quicker to do it empirically.

With the secondary unloaded, frequency response will be down 3dB at the point where source impedance equals the inductive reactance of the primary.

Xl = 2piFl

If your source impedance is truly 600 ohms,

L = Xl/2piF = 4.77H for 3dB down at 20Hz.

In practice, you'd want your 3dB-down point to fall an octave or more below the lowest frequency you need to pass... In the case of full-bandwidth audio, that would be 10Hz. So a 4.77H primary wouldn't really be adequate for a 600-ohm source impedance. 10H or more is what you'd typically find in a high-quality 600:600 transformer.

But you must also take into account that with the secondary loaded, the reflected load impedance appears in parallel with the primary inductance. Which means that in the case of a 4.77H primary inductance and a 600-ohm source impedance, the loss at 20Hz will be greater than 3dB, the exact amount depending on the secondary termination.

This is an easy first approximation that assumes a resistive source impedance and does not take parasitics into account.

So, you can see why higher primary inductance is generally better, at least up to the point at which the copper losses and capacitance from the extra turns start to become a problem.[/quote]

OK... F*#k it.
My heads going to explode :shock:

I'm just going to hook it up & see/measure what happens.

Thats the best way.

I generally find a preponderance of bass to be a problem...maybe that is why i find the 2503 pleasing :thumb: ..I will grab an Edcor 10k:10k to see if I like that even more....Now If I could just get my new cascode tube pre to behave....

Ray

[quote author="kubi"][quote author="CJ"]600:600 was the original xfmr for the LA2, so whats the beef?[/quote]

The original LA2A had a UTC A-10 at the input, later a HA-100X. Both are 600:50k which is higher than 1:9.[/quote]

Kubi,

I think The CJ is talking about a LA2 which is different from LA2A

Kubi,

Just have a pic now,