OEP vs Lundahl transformers in the 1176

[mnats]

[quote author="Brad McGowan"]Unless I'm mistaken the Mnats board calls for OEP A262A2E (or Lundahl). That's a mic input transformer, right?[/quote]
I've never heard it referred to as a microphone input transformer, nor have I seen a circuit that uses it as such. Perhaps Joe was referring to a different model, or there was some mix-up with the model numbers?

 

[matthias]

the pic looks like the converter is limited to 20k ??

 

[byoung]

that is quite a rolloff, I might have to try a switch in mine and see if I notice a big difference between the two values in everyday use. I'm curious now what the response of the lundahls is since I will be putting them in my next 1176.

 

[mnats]

[quote author="matthias"]the pic looks like the converter is limited to 20k ??[/quote]
I'm pretty sure it isn't the transformer doing that!!!
[quote author="byoung"]that is quite a rolloff[/quote]
Please note the scale, and the fact that the trace with the 1k load is 0.5dB higher than the 2.7k one. Half power is around 12-13k - not hugely dramatic, but maybe enough to get mistaken for the "sound of iron"?

 

[jensenmann]

Now you´re making me curious. I have to audition this on my G1176s.
:roll:

 

[JLM Audio]

I've never heard it referred to as a microphone input transformer, nor have I seen a circuit that uses it as such. Perhaps Joe was referring to a different model, or there was some mix-up with the model numbers?

The A262A2E is only suited to low input level as the OEP website states "the transformers are rated at 100mW at 300 Hz and 1mW at 30 Hz (less than 1% T.H.D.)". This translates to a maximum input level of -6dBM to get 1% THD at 30Hz. While the output amp of the 1176 can put out +21dBM. So if you use a 1:1 transformer that works out to a transformer that needs to be able to handle roughly 1W and if you use a 1:2 transformer the transformer will need to handle roughly 3W.

1mW to 3W is a big difference but this shouldn't come as to much of a surprise as the original 1176 output transformer is about 8 times physically bigger than the A262A2E.

 

[khstudio]

Wow... interesting. I guess this is one reason why they're so colored?

I just completed 2 1176's:

1 with Lundahl input & one 5532 IC input - both have OEP outputs. I prefer the IC input over the Lundahl. Also, compared to my Distressors they're VERY good with alot more character.

I think I'd like to try a different OT to see what happens... Thanks for the info JOE :thumb:

Kevin

 

[imo]

I'de have to say that i prefer my balanced in over my Lundahl input as well.
Ian

 

[khstudio]

[quote author="jensenmann"]Now you´re making me curious. I have to audition this on my G1176s.
:roll:[/quote]

Me too.

My first impression was I was loosing a little too much "air" on top... not bad but noticable.

Gonna try the 2.4k

Kevin

 

[khstudio]

[quote author="imo"]I'de have to say that i prefer my balanced in over my Lundahl input as well.
Ian[/quote]

They are BOTH balanced, just different methods of getting there.

I'm with you on the sound though. :wink:

What else is the Lundahl (input TX) good for if I take it out???

Kevin

 

[mnats]

[quote author="JLM Audio"]The A262A2E is only suited to low input level as the OEP website states "the transformers are rated at 100mW at 300 Hz and 1mW at 30 Hz (less than 1% T.H.D.)". This translates to a maximum input level of -6dBM to get 1% THD at 30Hz. [/quote]
Thanks for the information Joe! But I'm a little confused about one thing...doesn't 1mW @ 30Hz work out to 0dBm and 100mW @ 300Hz equal 20dBm? 10log (P/1mW)

Still waking up so don't shoot me if I'm mistaken...

 

[imo]

yes, of course.. i guess that would be a case of using shorthand incorrectly<G>
i meant transformerless balanced
Ian

 

[BradM]

Thanks for the plot Mnats. It's nice to be able to visualize things. I'm really suprised that nobody has found their 1176 with OEP on the output to be a bit dark sounding until now.

I'm going to put a 3.3k loading resistor in mine so that I err on the side of more "air".

By the way--for any of you that want to try a bigger and different transformer on the output, I spoke with Will Shanks from Universal Audio at AES and he said that UA will sell anyone their output transformer or the proper FETs.

Brad

 

[mnats]

I think a lot of people found their 1176 with OEP "dark sounding". If you do a little search, a lot of folks love the sound of their 1176 with this dirty little transformer too. And many have commented on having plenty of gain with the OEP in there, so perhaps you'll need to evaluate for yourself if it's going to work for you based on how you are going to use your unit.

I'm going to put a 3.3k loading resistor in mine so that I err on the side of more "air".

Good idea - remember that the impedence of whatever you are driving will be in parallel to the load resistor on the output.

Please have a search of the many discussions about the various versions of the 1176 before ordering a transformer from UA or anyone else.

 

[Rob Flinn]

1mW to 3W is a big difference but this shouldn't come as to much of a surprise as the original 1176 output transformer is about 8 times physically bigger than the A262A2E.

The Lundahl is also quite small compared to the original

 

[BradM]

I've already soldered in the OEP so I think I'll live with it for a while before I even consider putting in something else.

I noticed that the Mnats board can be setup to run the output transformer as 1:1. How does that affect the tone or frequency response?

thanks,
Brad

 

[glide 1]

[quote author="Brad McGowan"]Thanks for the plot Mnats. It's nice to be able to visualize things. I'm really suprised that nobody has found their 1176 with OEP on the output to be a bit dark sounding until now.

I'm going to put a 3.3k loading resistor in mine so that I err on the side of more "air".

By the way--for any of you that want to try a bigger and different transformer on the output, I spoke with Will Shanks from Universal Audio at AES and he said that UA will sell anyone their output transformer or the proper FETs.

Brad[/quote]


Hi,

My imediate impressions of the OEP was that it was "dark" and seemed to roll off the highs quite a bit so i'de like to know if you did this (swapped 1k to 3k3 at R84), if so any notable differences? Also if anyone tried the 2k7 aswell, can you please comment. thanks

I'll be trying out tha JLM DC111 tranformer soon, will post when i get it going.

glide 1

 

[mkoz]

By the way, has anyone tried OEP Input and Lundahl Output configuration yet? Or did I miss it in this thread? Everyone seems to have tried the other way around (with dissatisfaction) but I can't see anyone having tried this one.

Anyhow, that's the configuration I'm going for. I'll also try to implement the servo motor controlled flexi-resistor sensor idea instead of FET that we talked about in a thread a few months back, on one of two boards I have in hand. I hope I won't have to cannibalize the board otherwise I'm gonna have to order another one from Mnats, which doesn't take too long to arrive, but I just don't want to miss the Christmas break. It's a great opportunity for more DIY. Keep fingers crossed.

Another by the way, it's a great grounding scheme Mnats, congrats. I wish you could spare more space for the PSU section though, you could move CR11-R38-R85-R86 group between Q10 and R87, and then move the TL071 stage a bit up into the place vacated by them and then spread out the big caps to fit in comfortably, but one of those things I guess. Still, it's a great job as the additional PSU board rectifies that problem easily :thumb:

Mach

 

[Lowfreq]

Yeah, I've done the oep input and lundhal output.

I've also made it switchable between the oep and the IC input.

I haven't had a chance to give it a really good run through on a session yet, but a with quick muck around, I found it nice on vocals.

I found it was smoother and stronger in the mids with the oep, which I liked on vocals, but If i was using it to squash a room mic with drums, I'd probably be more inclined to use the IC input.
But I haven't used it much yet, so who knows, I may like the oep there too.

I also fould it easier to distort my 1176 when using the oep while the IC would stay fairly clean as you crant up the input.

 

[gevermil]

Ive got that big old freed 1:1 on the out and it works well
the oep dose tend to break up when you crank it
What ratio is that A262A2E wired on the H version , 1:2 ?
ID like to try another freed 1:1 in maybe