API-Sowter Transformers

[3nity]

i'm a thick head or what?
Some transformers even Cinemag work well without Zobel... :roll:

 

[khstudio]

[quote author="CJ"]Kevin, thanks for the inductances.

Try doing it over again, only short the sec leads together.

Also, do not agonize over the input termination too much.
There are a lot of chassis out there that ring like heck and sound good.

A transformer that does not ring at all might actually sound flat compared to say, an ol UTC ring-o-matic A-10.[/quote]

I didn't know that... cool, good info. :thumb:

It's funny you say that because I feel the Cinemag (that didn't ring at all) sounded "Flat" & the Sowter sounds more alive & real... even with the Zobel. I haven't tried it yet without it.

Brian's response above supports what I basically settled on: 120pf & 5.1k ZOBEL but NO LOAD Resistor. I also tested the load resitors, like Brian, & it didn't do anything for the response... what it "Could" do for the "Reflected" response I don't know nor have I tried, YET.

I also talked to Pat late last night & he opened one of his API 312's with the Sowters installed & confirmed that his also used the original Zobel... I keep bringing Pat up because he's the one that told me that his favorite API 312's had the Sowter input's.

Thanks CJ & everyone for your help & advise! :thumb:

 

[khstudio]

[quote author="3nity"]i'm a thick head or what?
Some transformers even Cinemag work well without Zobel... :roll:[/quote]

All transformers are different!

It all comes down to how "picky" you are.

In the end, I just want it to sound GREAT but also work properly... sometimes these are 2 different things. :wink:

I like my Cinemag's both with & without the loading resistor... but settled with it installed.

The reason for all my posts & questions is because Cinemag tells you straight up HOW to set them up = with a 150k Load Resistor.
Sowter... no info or advise was posted on their site or given until now.

I'm sure others that are using the Sowters & care how their gear is set up will gain from this thread.

 

[3nity]

How are you liking those Sowters?? for me Cinemag are clean! OEP sound some dirty or very fat....

 

[CJ]

That is good that you have a 35 kHz peak, as the original I tested had a peak at 40 K.
Different cables and scopes can make up the difference.

Also, I do not use a db scale when plotting freqs, so that peak of mine on a dB chart would be smaller.

The reason your 150 K resistor does nothing might be due to the API circuit having some resistance at the input that is quite a bit lower than 150 K?

You can measure it, just put an OPhm Meter where thensec terms go.

It might depend on the gain setting also.

Been a while since I looked at that circuit.

 

[khstudio]

I'm feeling good about this now :green:

Thanks CJ. :thumb:

I was wondering about how the circuit (or Op-amp 2520, etc...) could effect things.

If I could just stop getting interrupted by people stopping by my studio I could get back to work... they're all gone now, so I'll get back to it.

Can you teach me something?

OK, you've got "overshoot" & "Ringing"

Is the Zobel for fixing one or the other... or BOTH?

Same question about the "Loading Resistor"?

(I do know that the Loading resistor is also there to set (reflected) impedance... BUT the question I always have is - How come no Load Resistor in the API using the 2622???

 

[khstudio]

You can measure it, just put an Ohm Meter where the sec terms go.

It might depend on the gain setting also.

Should the pre be ON or OFF :?:

I tested it turned OFF:

Cinemag, with 150k load = 2.25k

Sowter, NO Load, Zobel of 5.1k & 120pf = 1.3k

(NOTE - ALL channels are using Peters/Fabio's PP2520's)

 

[CJ]

Well, that is the sec resistance and that is the difference.

Either more turns or thinner wire.

OK, now unsolder one sec lead and do the test over.

We want to ohm out the board, not the transformer.

And did you do the shorted sec inductance test yet?
We need leakage. Must have Leakage.
The White Coats are all about Leakage.

 

[khstudio]

OK, now unsolder one sec lead and do the test over.

17.9 Meg ohm - Unit turned off

(you never said on or off & I don't want to f**k anything up, so...)

 

[khstudio]

And did you do the shorted sec inductance test yet?
We need leakage. Must have Leakage.
The White Coats are all about Leakage.

This is a PITA now that they're installed... I can check the Cinemags, if you want???
I'll be back.

BTW,,, I'm freakin lovin' the shit out of these Sowters :!: :!: :!: :green:

 

[khstudio]

And did you do the shorted sec inductance test yet?
We need leakage. Must have Leakage.

Cinemag sec shorted:

Pri 1 = 685 uH
Pri 2 = 1013 uH

I'm not sure what this tells you but your making me wish I did this to the Sowters... but it would be a bitch :sad:

 

[CJ]

OK, now connect the pri for max series inductance aka 600 ohms, or whatever.

No measure Leakage again.

I just measured my Melcors, they ohm out at 7.35 Meg and 2.45 Meg, depending on polarity, it is just cap leakage one way.

This Hinson Custom Cinemag is a 1:5 I believe.
Sec DCR is 1.24 K instead of stock 1.5 K.
It sounds great, but never had anything else in there to contrast.

 

[khstudio]

CJ,
I just got done a long session & haven't had a chance to do the test - Primary's connected.

Hey... do you ever check your PM box??? :razz:
Left a PM days ago.

I used my API 312 with the Sowters on tonights session & was able to do direct comparisons to the channels with the Cinemags.
Both are cool but the band enev agreed that the Sowter channels sounded more "Real"... the High end / Definition is also a LOT better.

The Cinemags still sound nice too... just different & not as "Full" in the low end.
In some situations I think they MAY be better. Like all this crap... I've got to put some time into them to really hear how they work in various situations, then I'll have a definitive opinion. :green:

So far, the Sowters are my new favorite in the API pre.