khstudio
Well-known member
OK, I tried it & NOTHING Changed at all.
What now?
Should I try loading the input trannys PRIMARY with 10k?
LA2A with Edcor Transformers - PROBLEMS!!!
- Thread starter khstudio
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Help Support GroupDIY Audio Forum:
OK, I tried it & NOTHING Changed at all.
What now?
Should I try loading the input trannys PRIMARY with 10k?
there's always the chance it's a bad input trans. they've shipped me one transformer that was wired incorrectly; half primary to half secondary (x2). They sent a replacement pronto, so great service. I was happy with the outcome. but I digress.
have another input to compare?
have another input to compare?
khstudio
Well-known member
[quote author="emrr"]there's always the chance it's a bad input trans. they've shipped me one transformer that was wired incorrectly; half primary to half secondary (x2). They sent a replacement pronto, so great service. I was happy with the outcome. but I digress.
have another input to compare?[/quote]
I bought 4.
I'm going to check the resistance on ALL the taps of each one right now.
What kind of reading/value of resistance should I be seeing?
have another input to compare?[/quote]
I bought 4.
I'm going to check the resistance on ALL the taps of each one right now.
What kind of reading/value of resistance should I be seeing?
khstudio
Well-known member
INPUT TRANNY MEASUREMENTS:
XSM 10k:10k
Both Primary & Secondary read about 600 ohms across + & -
& about half = 300 ohms from Center tap to either side.
One thing I noticed, there is a LOT more mass to the windings compared to the 10k:600 OT's... is this normal?
XSM 10k:10k
Both Primary & Secondary read about 600 ohms across + & -
& about half = 300 ohms from Center tap to either side.
One thing I noticed, there is a LOT more mass to the windings compared to the 10k:600 OT's... is this normal?
khstudio
Well-known member
[quote author="emrr"]just try a different one in circuit.[/quote]
I just ran a test sweep thru JUST the 10k:10k tranny's & they look good. :?
No roll off or funny stuff.
I tried the one in my unit now & a new one, both the same... even strapped a 11k resistor across the secondary to mimic the circuit a little, no change.
DAMN.
They work fine out of the circuit.
Just to rule it out, I'll try a different one.
But I think the circuit is making the input tranz unhappy somehow.
I say this because, Un-Bal = No Problem.
I just ran a test sweep thru JUST the 10k:10k tranny's & they look good. :?
No roll off or funny stuff.
I tried the one in my unit now & a new one, both the same... even strapped a 11k resistor across the secondary to mimic the circuit a little, no change.
DAMN.
They work fine out of the circuit.Just to rule it out, I'll try a different one.
But I think the circuit is making the input tranz unhappy somehow.
I say this because, Un-Bal = No Problem.
khstudio
Well-known member
Tried - NEW 10k:10k Tranz didn't help... same high end role off.
Tried - swapping the Polarity like you said, no work.
Tried - increasing secondary loading from 11k to 22k, nothing.
Has anyone else actually used these on an LA2A?
Tried - swapping the Polarity like you said, no work.
Tried - increasing secondary loading from 11k to 22k, nothing.
Has anyone else actually used these on an LA2A?
khstudio
Well-known member
Today I tried a COMPLETELY different Input Transformer to see if the high roll off would go away & it did!!!
For the hell of it I tried these TAMURA 600:600 (1:1) instead of the EDCOR 10k:10k's.
NOTE: Don't pay attention to the LOW END BS going on, my main concern here is the HIGH END rolling off like it did with the EDCOR's on the input.
Here's a sweep of JUST the Tranny (Un-Loaded) just to show what IT looks like outside the circuit:
Here's a sweep going thru my LA2A. OUTPUT is Un-Balanced (No Tranny)
The Tamura is on the input & the Secondary is loaded with the same 10k.
Notice theres NO strange Bump in the low mids & NO EARLY HIGH ROLL OFF (starting around 700Hz or so)
Here's a repost of the EDCOR 10k:10k on the input & once again the output of the LA2A is Un-Balanced.
I don't know how some of you guys get these things to work correctly for input trannys in similar circuits... like ANALAG's Opto Comp, etc...? :?
Either you don't care what it looks like, your lucky, didn't actually sweep/TEST or I got a batch of strange or bad transformers which I doubt.
I hope all this BS helps someone... I'm ordering some JENSENS OR CINEMAG's for this LA2A ASAP.
For the hell of it I tried these TAMURA 600:600 (1:1) instead of the EDCOR 10k:10k's.
NOTE: Don't pay attention to the LOW END BS going on, my main concern here is the HIGH END rolling off like it did with the EDCOR's on the input.
Here's a sweep of JUST the Tranny (Un-Loaded) just to show what IT looks like outside the circuit:
Here's a sweep going thru my LA2A. OUTPUT is Un-Balanced (No Tranny)
The Tamura is on the input & the Secondary is loaded with the same 10k.
Notice theres NO strange Bump in the low mids & NO EARLY HIGH ROLL OFF (starting around 700Hz or so)
Here's a repost of the EDCOR 10k:10k on the input & once again the output of the LA2A is Un-Balanced.
I don't know how some of you guys get these things to work correctly for input trannys in similar circuits... like ANALAG's Opto Comp, etc...? :?
Either you don't care what it looks like, your lucky, didn't actually sweep/TEST or I got a batch of strange or bad transformers which I doubt.
I hope all this BS helps someone... I'm ordering some JENSENS OR CINEMAG's for this LA2A ASAP.
khstudio
Well-known member
BTW... I'm aware that this isn't a completely horrible sweep.
At most it's about a 2dB or so drift from "FLAT"
BUT... It not only bothers me, I like to take these opportunities to "Learn" about why this happens.
#2, share it with you guys so you are aware &/or can help... me or anyone else.
#3 to have a great piece of gear I can confidently put the lid on & make music without looking back.
At most it's about a 2dB or so drift from "FLAT"
BUT... It not only bothers me, I like to take these opportunities to "Learn" about why this happens.
#2, share it with you guys so you are aware &/or can help... me or anyone else.
#3 to have a great piece of gear I can confidently put the lid on & make music without looking back.
solder_city
Well-known member
you give up too easy, son :razz:
only one day and youre ready to throw in the towel and empty your wallet? come on, now
i will think this over and see if i can think of anything else to check/try
only one day and youre ready to throw in the towel and empty your wallet? come on, now
i will think this over and see if i can think of anything else to check/try
khstudio
Well-known member
Can someone suggest what size CAP I should put in line on the input to run it Un-Balanced:?:
I think the EDCOR on the output will be fine as long as I load it correctly.
Also,
I spoke with Doug Williams - emrr - today & he mentioned how the output cap & Inductance of the OT "Could" interact & "POSSIBLY" cause the LOW rise in the SUBs I posted earlier.
PLEASE don't quote Doug or Me on this because it was over my head.
If he, or anyone else knows & wants to explain how that works... feel free. :green:
I think the EDCOR on the output will be fine as long as I load it correctly.
Also,
I spoke with Doug Williams - emrr - today & he mentioned how the output cap & Inductance of the OT "Could" interact & "POSSIBLY" cause the LOW rise in the SUBs I posted earlier.
PLEASE don't quote Doug or Me on this because it was over my head.
If he, or anyone else knows & wants to explain how that works... feel free. :green:
khstudio
Well-known member
[quote author="solder_city"]you give up too easy, son :razz:
only one day and youre ready to throw in the towel and empty your wallet? come on, now
i will think this over and see if i can think of anything else to check/try[/quote]
I know I know :wink:
But when I throw some old 600:600 (small) tranny on there & it STOPs rolling off the highs, & looks pretty normal, it makes me feel like I'm waisting my time. (On the input at least)
Like I said, I don't mind the EDCOR on the output with the correct loading. :green:
only one day and youre ready to throw in the towel and empty your wallet? come on, now
i will think this over and see if i can think of anything else to check/try[/quote]
I know I know :wink:
But when I throw some old 600:600 (small) tranny on there & it STOPs rolling off the highs, & looks pretty normal, it makes me feel like I'm waisting my time. (On the input at least)
Like I said, I don't mind the EDCOR on the output with the correct loading. :green:
solder_city
Well-known member
did you do freq response sweeps with gain reduction disabled?
gotta minimize the variables
gotta minimize the variables
khstudio
Well-known member
[quote author="emrr"]I think these are straight gain measurements with no T4B installed.[/quote]
Doug is correct. :thumb:
T4B is NOT installed for ANY of these test.
Doug is correct. :thumb:
T4B is NOT installed for ANY of these test.
khstudio
Well-known member
Just wanted to post this info:
solder_city
Well-known member
the so called 'low end bs' is prob. the result of resonance between output coupling cap and output transformer. if you use 22uf as recommend for the jensen mod, that would probably solve that problem.
is the feedback for the amp stage taken from between the coupling cap and transformer? that can cause funky stuff too, its usually better to couple the feedback with its own blocking cap. im not familiar with the 'drip' version of the circuit and how it may differ from the original.
as for the high freq rolloff, im still not sure.
ps: using CAPS sounds like SHOUTING, comes off as ANGRY- just incase you didnt know. italics for emphasis are better :razz:
is the feedback for the amp stage taken from between the coupling cap and transformer? that can cause funky stuff too, its usually better to couple the feedback with its own blocking cap. im not familiar with the 'drip' version of the circuit and how it may differ from the original.
as for the high freq rolloff, im still not sure.
ps: using CAPS sounds like SHOUTING, comes off as ANGRY- just incase you didnt know. italics for emphasis are better :razz:
khstudio
Well-known member
[quote author="solder_city"]the so called 'low end bs' is prob. the result of resonance between output coupling cap and output transformer. if you use 22uf as recommend for the jensen mod, that would probably solve that problem.
is the feedback for the amp stage taken from between the coupling cap and transformer? that can cause funky stuff too, its usually better to couple the feedback with its own blocking cap. im not familiar with the 'drip' version of the circuit and how it may differ from the original.
as for the high freq rolloff, im still not sure.
ps: using CAPS sounds like SHOUTING, comes off as ANGRY- just incase you didnt know. italics for emphasis are better :razz:[/quote]
That's what Doug said about the cap & tranny... I will try it.
It would put an end to THAT issue.
The circuit is the same as the original LA2A, so Feedback should be before the cap.
BTW, don't mean to shout... I assume people get the idea I'm just accenting "importance" of certain words... it's much faster ti CAP... but I'll keep that in mind & tone it down. :wink:
is the feedback for the amp stage taken from between the coupling cap and transformer? that can cause funky stuff too, its usually better to couple the feedback with its own blocking cap. im not familiar with the 'drip' version of the circuit and how it may differ from the original.
as for the high freq rolloff, im still not sure.
ps: using CAPS sounds like SHOUTING, comes off as ANGRY- just incase you didnt know. italics for emphasis are better :razz:[/quote]
That's what Doug said about the cap & tranny... I will try it.
It would put an end to THAT issue.
The circuit is the same as the original LA2A, so Feedback should be before the cap.
BTW, don't mean to shout... I assume people get the idea I'm just accenting "importance" of certain words... it's much faster ti CAP... but I'll keep that in mind & tone it down. :wink:
An obvious thing that seems to have eluded us all. You are using the XSM series, which have worse response specs than the WSM series. I doubt you need the level handling ability of the XSM; even the WSM stuff has around 10db more headroom then the original UTC iron. Your response measurements with the XSM input are in spec. I'd try the WSM since you've already done so many comparisons.
