OEP vs Lundahl transformers in the 1176

[khstudio]

Which versions are you using for IN/OUT? Are they the same???

I just ordered a pair of A262A2C...
I'm assuming the "C" means with the can :?: anyone know?

Thanks,
Kevin

 

[matthias]

I tried oep at the output but I finally used lundahl and the original 1178 transformers

the resistor is r84, if I'm right...
can't remember the value.. sorry..

 

[khstudio]

[quote author="khstudio"]Which versions are you using for IN/OUT? Are they the same???

I just ordered a pair of A262A2C...
I'm assuming the "C" means with the can :?: anyone know?

Thanks,
Kevin[/quote]


How about you mfdu?

 

[astrovic]

[quote author="mfdu"]here in melbourne, trannies are usually six foot tall, wearing wigs and skirts and makeup and answering to the name "craig" or "verity".
but that's all good.



chris.[/quote]

Need help with something, sweetie? :wink:

Hmm, I'm a Chris from Melbourne too - sounds like I'll have to change my name. I might go for Craig...or Verity :shock:

[quote author="matthias"]if you use the oep you have to alter the value of the 1k resitor between "+" and "-" after the transformer, otherwise the frequency range looks like an eq [/quote]

I'm with mfdu - I've gone OEP in and out and haven't done this. Sounds great to me, but I've got nothing to compare against (I haven't tried the electronically balanced input yet).

But is this resistor change something I should be factoring in?

Chris/Craig/Verity

 

[astrovic]

[quote author="khstudio"][quote author="khstudio"]Which versions are you using for IN/OUT? Are they the same???

I just ordered a pair of A262A2C...
I'm assuming the "C" means with the can :?: anyone know?

Thanks,
Kevin[/quote]


How about you mfdu?[/quote]

Looks like you're right - have a look at the datasheet on farnell, which says "This range of transformers is also available with the Mu metal screening can fitted and may be ordered by replacing the suffix 'E' with the suffix 'C'"

 

[Brad McGowan]

[quote author="matthias"]if you use the oep you have to alter the value of the 1k resitor between "+" and "-" after the transformer, otherwise the frequency range looks like an eq
then you can make serious comparisons between lundahl and oep[/quote]

Can you please elaborate on your statement about the frequency response? R84 is the load resistor for the output transformer. So I'm guessing that we might want to make it 2k4. The spec sheets has "optimal load impedance = 600/2.4k" which I think means for parallel/series connections. Can anyone confirm this?

thanks,
Brad

 

[Brad McGowan]

Anyone?

 

[mnats]

[quote author="Brad McGowan"]Anyone?[/quote]
In a way, I know what you're saying - if someone throws something out there it would be nice if they would tell the whole story.

On the other hand, when did DIY become wait for someone else to do it?

Here's just a quick and dirty test I did: I put a 10k pot on the secondary of the OEP, fed a test signal in at a mid-frequency to set a reference output on the 'scope. Then I cranked up the test frequency to 20kHz and futzed with the pot and output gain until it gave the same output voltage from about 1k to 20kHz. When I measured the value of the pot I got 2.77k.

2.4k gave -0.6dB down at 20k

1k was -4.93dB down at 20k

All of you who dig the sound of their OEPs on the G1176 be honest now - what value are you using?

 

[byoung]

All of you who dig the sound of their OEPs on the G1176 be honest now - what value are you using?

Inquiring minds want to know :grin:

 

[enthalpystudios]

dont have an oep on my input... *But* mnats, i'd really be curious to know where the rolloff begins on the oep, say where its hitting -2 or -3 with a 1k resistor.

20k is higher than many really think about, i think (!)..... its way up there.

if the rolloff is slow, and starts way down at 16k, that could def. make for a 'vintage' or 'smooth'-ish sound.

 

[Lowfreq]

I've only been using mine for vocals, and I'm just using the 1k, just coz I'm a kinda paint by numbers kinda guy. :wink:

But I haven't felt the need for any more high end out of this comp. It may be a different story if i also used an input tranno, but I'm pretty happy with this configuration. I've used Nichicon HE's for the electros too, which seem pretty transparent, so thats probably helping.
But like I've said I've only used it on vocals so far.

Actually for a while there i thought it was killing some of the low end outta the vocals, until i did a mix without using plugins, and realised it was my crap ITB mxing skills. :roll: I blame myself, not the equipment. ha ha

 

[mich]

The roll off with the r84 as 1k starts at 5kh and is -6db at 20kh.

you can just leave out this resistor for better response.unless u like what u hear.....

 

[enthalpystudios]

yeah that is a real slow rolloff than.

very vintage ;]

but still, something i'd probably rather do with a LPF

 

[mnats]

[quote author="mich"]you can just leave out this resistor for better response.unless u like what u hear.....[/quote]
By 'better response' I guess you don't mean square wave:

 

[Brad McGowan]

Thanks for the follow-up guys. I would try some different values myself, but I don't even have mine built yet...I'm still awaiting parts. I like to at least have a plan ahead of time.

To continue the discussion about this transformer... I asked Joe from JLM Audio what he recommended for a load resistor after seeing this:

http://www.jlmaudio.com/Neve%20transformer%20info.htm

Joe responded to my email:

"I would neve use this mic transformer or any mic transformer as a output transformer as it can only put out -6dBM at 50Hz. For the transformer to be used as a output transformer it should be able to handle +18dBM to +24dBM so it can drive a pro A/D without saturating. Because this transformer would saturate so much at normal levels it has a good chance of blowing up anything solid state that is driving it. So a little bump in the frequency response it the least of your worries "

So my question is this: if this transformer is such a a bad choice for an output transformer then why was it chosen for this application? Is this a case of "in practice" vs. "in theory"?

thanks,
Brad

 

[Lowfreq]

I'm keeping on eye on this one.

I'm sure there'll be a few varying opinions on this.

Thoughts Jakob? Mnats?

 

[Michael Tibes]

[quote author="Brad McGowan"]
"I would neve use this mic transformer or any mic transformer as a output transformer as it can only put out -6dBM at 50Hz. For the transformer to be used as a output transformer it should be able to handle +18dBM to +24dBM so it can drive a pro A/D without saturating. Because this transformer would saturate so much at normal levels it has a good chance of blowing up anything solid state that is driving it. So a little bump in the frequency response it the least of your worries "
[/quote]

He is talking about the A262A2E, isn't he? I wasn't aware that it is a mic transformer, is it really distorting that early? Maybe that's the colouration many people here liked about it?

Michael

 

[gyraf]

I've used the OEP 'A2E only in the G9/diy - and at least in that application, it works very well - frequency response and all.

Use the transformer version recommended - and be ware of possibly mis-label'ed OEP transformers - I've had these at a couple of occations (though it may have been a Farnell-mess-up). Double-check your winding resistances against the manufacturer's specs to verify the type you have at hand.

Even though the different OEP transformers looks alike, they behave very differently in-circuit..!

Jakob E.

 

[Brad McGowan]

Unless I'm mistaken the Mnats board calls for OEP A262A2E (or Lundahl). That's a mic input transformer, right?

Brad

 

[byoung]

I'd really be curious to know where the rolloff begins on the oep, say where its hitting -2 or -3 with a 1k resistor.

20k is higher than many really think about, i think (!)..... its way up there.

if the rolloff is slow, and starts way down at 16k, that could def. make for a 'vintage' or 'smooth'-ish sound.

anybody have the ability to do a frequency response chart for both ways? It would be interesting to visualize.