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An open letter to Uli Behringer
Old 31st March 2013 | Show parent
  #121
Lives for gear
 
JohnRoberts's Avatar
 
🎧 10 years
Quote:
Originally Posted by Uli Behringer ➡️
Dear JR,

thank you for your comment.

We have responded to RadarDoug's concern about the potential defect of the transformer we sent him. We deliberately focused on the power consumption under no-load condition and the noise level, which he had reported.
Understood, but as I noted his original post appeared to also question the flux density.
Quote:
As demonstrated, the transfomer works exactly as designed but unfortunately the shielding and lamination got damaged during transportation, which led to the increased noise level. However all electrical specifications were met and the transformer was fully functional.
Indeed, I understand how large scale manufacturing works. Transformer design is pretty much a pass/fail exercise, adequate to satisfy safety agency concerns and power the product, unnoticed by the end user.

Subjective qualitative opinions about internal components invisible to the customer is not important in the grand scheme. What is important to value customers is doing the job for a price.
Quote:
If you or RadarDoug would like to take this to an independent lab and investigate further, we are more than happy to assist with all supporting documents.
I have no pony in this race, while not impartial I am trying to be an objective observer. If we have any disagreement still is is about what the customer complained about in his original post a couple months ago.

As I posted earlier in the thread it is the nature of value products for the transformer design to be "just good enough". While this may seem a sin to some here, it is a virtue to sharp pencil designers.


Quote:
The GMX212 guitar amp meets all power and safety requirements, is fully UL certified and comes with a 3-Year Warranty program.

The amp has been in the market for close to 10 years and with 100,000 sold units and basically no reported transformer failures in our RMA system, it is fair to assume that the design is perfectly fine. A quick google search has equally turned out no results.
Zero failures seems extremely good. I guess there should be at least one failure, but apparently this one was off your radar screen.

It is or should be obvious that if the transformer design was insufficient and routinely failing in the field, it would have been noticed long ago and corrected. Zero (reported) failures over 10 years suggests it is sufficient.
Quote:
Transformers are designed to specifications and not by "adding a bit more copper and windings". If RadarDoug feels his self-made transformer provides a better solution for him, we gladly accept his opinion and gracefully bow out of the discussion. However, we must state that the amp no longer meets compliance requirements and we as a manufacturer obviously cannot take any liability.
Yes, but transformer secondaries supply both voltage and current. Testing windings without load is like testing how fast a car goes while up on blocks with the wheels not touching the ground.
Quote:
I hope this answers all questions. Thanks everyone for contributing to this passionate and interesting discussion.

Warm regards

Uli
I am just trying to translate what is going on for people with less experience about such matters. It was your representative that opened this can of worms with detailed voltage measurements, that looked to me like a "blind them with science" defense. Lots of precision and detail but with limited significance (unloaded).

While a little slow to notice, you have gone above and beyond to respond fully after engaging. As I suggested before interpretation of even more detailed objective data requires experience probably lacking here. Further this is not an ideal forum for a fair critique of a value product subsystem.

Folks here are routinely replacing capacitors with film versions, and opamps with higher slew rate models in the pursuit of audio nirvana. Good luck pleasing this audience.

JR
Old 1st April 2013 | Show parent
  #122
Lives for gear
 
S2udio's Avatar
 
🎧 10 years
Quote:
Originally Posted by JohnRoberts ➡️
Testing windings without load is like testing how fast a car goes while up on blocks with the wheels not touching the ground.
JR
Avery valid point
As an industrial electrical/electronics engineer 35yrs + ( audio as well )
Not a transformer designer BTW...

All transformers that I have professionally tested must be measured on 0-25-50-75-100%
Loading via resistive / capacitve / loadbanks....phase /lead/lag variations
Measured Input / Output current / temperature....all monitored.
Also varied at 50/60 hz for 24 hr soak, and visual inspection.
Nastys are always audible ,and the above measurements always show why.
A Pass is only when all specs are met withinin the soak period.
I suspect most "consumer" transformers are only tested "off load"
Bad ones will occure.

Quote:
Originally Posted by JohnRoberts ➡️
Folks here are routinely replacing capacitors with film versions, and opamps with higher slew rate models in the pursuit of audio nirvana.
JR
Yup
Me for one...

Apart from many DIY pres and Comps Etc,Etc...
Three Modded DDX3216 Desks here,Op amps caps,Cabeling,and other minors
Sound great now..
Shame They were not developed a bit more and build/parts Quality improved .
And the 4 .. XR2000 Intelligates (all modded PSU's) are my go to Drum toys,
Luv em...
Have spares as well...and 2 dead ADAT1616's needing pic bins !

Uli ...its not all bad !
Old 1st April 2013 | Show parent
  #123
Lives for gear
 
JohnRoberts's Avatar
 
🎧 10 years
Quote:
Originally Posted by S2udio ➡️
Avery valid point
As an industrial electrical/electronics engineer 35yrs + ( audio as well )
Not a transformer designer BTW...

All transformers that I have professionally tested must be measured on 0-25-50-75-100%
Loading via resistive / capacitve / loadbanks....phase /lead/lag variations
Measured Input / Output current / temperature....all monitored.
Also varied at 50/60 hz for 24 hr soak, and visual inspection.
Nastys are always audible ,and the above measurements always show why.
A Pass is only when all specs are met withinin the soak period.
I suspect most "consumer" transformers are only tested "off load"
Bad ones will occure.
Not to beat this to death.. but no-load open circuit testing is standard practice to QA a transformer on the "transformer" factory floor, to confirm the production line used the right number of turns. At this stage of the transformer's life the other aspects of the transformer design like the core material and how much has been cast in stone.

Testing under load is generally just done by design engineering departments, not to confirm the build accuracy, but confirm that the design delivers enough power where and how it is needed. For power amplifiers in some markets, a 75W audio amplifier needs to put out the rated 75W after it's hot from running for hours. Transformer output voltage will trend down as it heats up because the temperature coefficient of copper wire resistance caused winding resistance to increase leading to larger voltage drop loss from IxR, and less output voltage. The only way to determine this is to run it until it gets as hot as it will and see how it hangs in.

There may be occasional spot checks to confirm component quality but problem production runs will usually reveal themselves on the factory before the assembled products get out the door, so transformers are not routinely tested 100% (other than for transformer primary insulation resistance with the final whole product hi-pot test).

The over-design, or marginal design of a transformer's output for a given application is somewhat subjective, and mostly invisible to the end-user so not good fodder for a public gear-fan forum like this. Perhaps of academic interest on a more design oriented forum.

Overall not very high on the list for things customers should worry about IMO.

JR

PS: I'm just telling you more than you want or need to know about transformers. Feel free to cut this class.

Quote:

Yup
Me for one...

Apart from many DIY pres and Comps Etc,Etc...
Three Modded DDX3216 Desks here,Op amps caps,Cabeling,and other minors
Sound great now..
Shame They were not developed a bit more and build/parts Quality improved .
And the 4 .. XR2000 Intelligates (all modded PSU's) are my go to Drum toys,
Luv em...
Have spares as well...and 2 dead ADAT1616's needing pic bins !

Uli ...its not all bad !
Old 1st April 2013 | Show parent
  #124
Lives for gear
 
S2udio's Avatar
 
🎧 10 years
Quote:
Originally Posted by JohnRoberts ➡️
The over-design, or marginal design of a transformer's output for a given application is somewhat subjective, and mostly invisible to the end-user so not good fodder for a public gear-fan forum like this. Perhaps of academic interest on a more design oriented forum.

Overall not very high on the list for things customers should worry about IMO.

JR

PS: I'm just telling you more than you want or need to know about transformers. Feel free to cut this class.
Absolutely .....No dispute intended

Just Observing.
Old 1st April 2013
  #125
Gear Maniac
 
Prick Up UR Ears's Avatar
 
🎧 10 years
Quote:
Originally Posted by patferdig ➡️
was an insufficient number of windings.

Secondary Wiring : S1
Input Voltage : 230V
Material Specification, Output Voltage at No load : 2X27.5 +/- 5%
Actual Measurement Value (V) : 2x25.773
Result: PASSED


Please let me know if you have any further questions.

Regards,

Pat Ferdig
VP, Care
MUSIC Group
27.5 +/- 5%

gives 27.5 V +/- 1.375 V => 26.175 - 28.175V

how can 25.773 pass the test?


Just saying
Old 2nd April 2013 | Show parent
  #126
Lives for gear
 
JohnRoberts's Avatar
 
🎧 10 years
Quote:
Originally Posted by Prick Up UR Ears ➡️
27.5 +/- 5%

gives 27.5 V +/- 1.375 V => 26.175 - 28.175V

how can 25.773 pass the test?


Just saying
Awkward, but not a smoking gun. Clearly a disagreement between the no-load voltage and spec, if measured and posted accurately, either measurement, specification, or "PASSED" are not in agreement. If Pat does not walk back his posted measurement, or posted specification, it looks like a miss as presented.

Even a small voltage miss does not mean that the transformer would not function in the product to the market's general satisfaction. Not to be a broken record about this but no-load voltage tells me little about actual in circuit transformer behavior. FWIW mains voltage varies a lot more than +/- 5% so that nominal AC voltage spec is not an absolute output voltage pass/fail circuit requirement, but a target based on the transformer's simple turns ratio to confirm just than and nothing more. Rectified, with actual reservoir capacitors, and loaded DC voltage is what matters to the circuit behavior.

We should not ignore that there are large numbers of this SKU in customer's hands and reportedly problem free. This may just be an insignificant error, so don't read too much into this one discrepancy.

Stuff happens. And I repeat this is inside baseball not easily appreciated by general audiences. An objective critique of the design may be hard to find as even design engineers form opinions.

JR

PS again perhaps TMI about transformers...
Old 3rd April 2013 | Show parent
  #127
Here for the gear
 
🎧 5 years
Quote:
Originally Posted by Prick Up UR Ears ➡️
27.5 +/- 5%

gives 27.5 V +/- 1.375 V => 26.175 - 28.175V

how can 25.773 pass the test?


Just saying
Sorry for the misquoting of the information. I have validated the data with our quality team and here is a little more information that was provided based on testing of 230v and 240v. I hope this clears the confusion:

Secondary Wiring - S1
Material Specification
Input Voltage - 240v
Output Voltage at No load - 2X27.5 +/- 5%
Range - 26.125~28.875
Actual Measurement Value (V) - 26.86
Result - OK - within range

Secondary Wiring - S1
Material Specification
Input Voltage - 230v
Output Voltage at No load - 2X26.35 +/- 5%
Range - 25.033~27.668
Actual Measurement Value (V) - 25.773
Result - OK - within range
Old 3rd April 2013 | Show parent
  #128
Lives for gear
 
Radardoug's Avatar
 
🎧 10 years
Pat,
Did you test your quieter transformer for circulating current with no load?
What was the actual current value you got in both cases?
Old 14th April 2013
  #129
Lives for gear
 
🎧 10 years
This thread is getting tiring, why are people trying to 'nail' a company over a cheap transformer in a consumer-grade guitar amp that will probably last the 3 years of its warranty period.

The response from the manufacturer has been admirable compared to most, this is obviously not a common fault, and I think they should be allowed to move on.
Old 15th April 2013 | Show parent
  #130
Lives for gear
 
JohnRoberts's Avatar
 
🎧 10 years
Quote:
Originally Posted by londonengineer ➡️
This thread is getting tiring, why are people trying to 'nail' a company over a cheap transformer in a consumer-grade guitar amp that will probably last the 3 years of its warranty period.

The response from the manufacturer has been admirable compared to most, this is obviously not a common fault, and I think they should be allowed to move on.

The way to move on and let it fade away, is by NOT posting new comments.

This thread was quiet for a week, before you bumped it back to life.


JR
Old 15th April 2013
  #131
Lives for gear
 
1 Review written
🎧 5 years
My 2003 Mazda has a misfire. I think the President of Mazda motor company should comb the internet looking for me calling him out to explain this outrage.
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