UA 176 Output XFMR - need pri inductance

[CJ]

that makes sense, gapped transformers can vary a lot in their primary ind. if they build them quick.

UTC stands for You Take a Chance 

people do use gapped transformers for push - pull, the Fender Tweed DeLuxe with the Triad #108 is an example,

you do get a more linear core,  and it is more stable with age (magnetic aging will lower inductance over many years)

 

[bockaudio]

Yes, about 1989, Walter Sear taught me that the reputation of UTC had lead to the nickname (amoung the old guys then) "You Take Chances".
This is observed in real 670's, with UTC inputs, and is part of why I've never seen two identical channels in one. The input measurements vary. The Triads on the output however, identical.

 

[emrr]

Yes, about 1989, Walter Sear taught me that the reputation of UTC had lead to the nickname (amoung the old guys then) "You Take Chances".
This is observed in real 670's, with UTC inputs, and is part of why I've never seen two identical channels in one. The input measurements vary. The Triads on the output however, identical.

It's funny that's the experience, yet we have Rein Narma stating he picked the UTC A-26 OUTPUT transformer for use as an INPUT because it had the best balance with least problems of anything he tried.  Different question, in some ways. 

 

[Winston OBoogie]

I always wonder, is there some minimal gapping in a PP output that makes a good tradeoff against current imbalance and the response loss and distortion that comes with?  Probably not with 12BH7 levels of current.

Hey Doug,
most manufacturers don't seem to do this.  The exception I've found is Lundahl who do state that their push-pull transformers have a small gap to allow for some imbalance.  The inductance of these Lundahls that I've checked specs on seem to be in the 270H - 300H range.

 

[emrr]

Hey Doug,
most manufacturers don't seem to do this.  The exception I've found is Lundahl who do state that their push-pull transformers have a small gap to allow for some imbalance.  The inductance of these Lundahls that I've checked specs on seem to be in the 270H - 300H range.

Makes sense given the common catalog specs tend to say '0mA DC in primary'.  Hidden in my ? is whether there's any change in this as you graduate to power tube currents, or does core and wire size follow on as 'good enough'.

 

[Winston OBoogie]

Makes sense given the common catalog specs tend to say '0mA DC in primary'.  Hidden in my ? is whether there's any change in this as you graduate to power tube currents, or does core and wire size follow on as 'good enough'.

That question might be beyond my pay grade .
I suppose it depends on how much imbalance and how big a core.  Or what class the output runs in?  I can imagine that switching from one side to the other would be worse than a 'both sides always on'  class A.

 

[emrr]

Or what class the output runs in?  I can imagine that switching from one side to the other would be worse than a 'both sides always on'  class A.

Hmm.  Above mine too.    I immediately think that'd be analogous to having DC offset on an audio file, but maybe wrong. 

 

[CJ]

Nickel alloy is where you have to watch DC.

if you run a steel xfmr at 12 KG, you still have 18-20=8 KG to play with which should handle any DC imbalance,

but if you run a Nickel core at 2.5 KG, you only have 5-2.5 =2.5 KG for DC imbalance, 

remember that audio waves are not always symmetrical,  so there is always some type of imbalance going on,

also, ampere turns is amps times turns, so the lower the turns count, the less DC flux, and the same with current.

but if you have a lot of turns and a lot of current, then you have to watch the DC thing,

with a Nickel core you will have less turns to get the same inductance, so ampere turns will be lower than with a steel core so the reduced saturation level of the nickel will be somewhat compensated for by the lower turns, 

Nickel tends to saturate in a hurry once you reach the upper levels of the B-H curve which might be less pleasing than the more gradual slope of the silicon saturation line,

 

[Winston OBoogie]

Nice info CJ, thanks.

 

[emrr]

Thanks CJ

 

[bockaudio]

I measured 63Hy@100H in my 6003.
100Hy ea in the two coils of the Reichenbach 176 (multiple taps version).
The 176-b has no taps, fixed CV amp.

 

[CJ]

Thanks for that! 

do you know how much voltage your meter is putting out during the 100 H test?

 

[bockaudio]

1V but I can do two values lower if you want.
Interesting how the ONE spec we really want with audio xfmrs (100Hz inductance) is not on spec sheets.

 

[CJ]

do you have a signal generator and an ammeter?

 

[bockaudio]

I own a microphone manufacturing company.

 

[CJ]

well everybody knows that i just wondered if you want to do another different inductance test?

 

[Winston OBoogie]

Interesting how the ONE spec we really want with audio xfmrs (100Hz inductance) is not on spec sheets.

Even specifying recommended max source impedance with given response would help.  Nada listed for Cinemag, Jensen, Sowter...
Again, Lundahl - sometimes.

Anyway, thanks for the measurements.

Hey David, it's good you have a signal generator and ammeter

 

[abbey road d enfer]

Because inductance varies with frequency and level, there are so many answers to this basic question that it would congest the spec sheet, so manufacturers address those who paint by numbers by describing typical implementations, which is adequate 90% ot the time. It's only when we ask a little more than the basic role of converting voltages that these info are needed. Indeed reverse engineering is one of these circumstances.

 

[CJ]

yes plus everybody uses a different instrument for measuring inductance.  most DMM's, even 15 dollar meters from across the pond,  will give close results for volts and ohms, but not so for inductance meters.  they all seem different, Tektronix, Stanford Instruments, Gen Rad, Fluke,

so if a customer buys a transformer and measures it, and gets different results, he is going to call customer service so omitting that loose spec can save a lot of company time.

i think i see how this went down, Putnam built the 610 preamp with the 12 BH7a running single ended which requires a gapped transformer,  then he built the 176 compressor with the push-pull 12BH7a which does not require a gapped transformer, so he gabs the gapped transformer anyway and it has enough  inductance to work so he uses it, that is what engineers do, they grab stuff off the shelf that works then they use it.  because it saves time and money. and engineers are all about saving money.

good thing he only used 3 extra taps, i could not handle any more>

 

[abbey road d enfer]

good thing he only used 3 extra taps, i could not handle any more>

Phhhhew! How do you know which one is which?