John Curl's Blowtorch preamplifier part II

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Elaborate on didn't work correctly. I helped Mitch Cotter with a similar problem (if it's what I think). You need a turn on catcher for the Ib comp network (the one the user can't see). :D

4 issues,
1 Bingo you got it.
2 Unit did not servo to 0 volts dc.
3 Unit could be triggered to squeeg. (Unit impulse excited damped oscillations.)
4 RFI issues
 
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Well, you could flip it around if you're on 120vac mains with a dual 120vac primaries. In either event, you'd be in 'violation' of Menno Vanderveen's US patent # 6087822. This is used in the Torus conditioners from Bryston.
It worked quite well on the primaries of an overspecified r-core powering a dac.

Thanks for that patent. It requires bifilar windings! (Both coils are wound at the same time so the interwinding capacitance is higher, but the magnetic field is so close to the same.


jn, I would suggest to halt contributing, else Ed will be short of fingers, counting the variables affecting his FFTs for his article.:)

Ed
May I give you some more troubles? :D
Don’t count on “nominal” load for each trafo when you check for leaking fields. These fields ramp-up as soon as the waveform starts showing flat tops/bottoms.
There are really not many trafos I have checked which manage decent waveforms.

Start checking the waveforms with trafos unloaded. You’ll probably give-up soon.
Then feed the primaries from a Variac. Adjust variac for an output ½ of main’s voltage and start increasing it while monitoring the waveform and leaking fields of the trafo under test.

I bet a bottle of Ouzo that in most cases – and this doesn’t have to do with the type of trafo- reaching an 80-85% of mains voltage is the upper limit for nice waveforms and the rest.
Only then check effects of loading for each type of construction, operating each trafo at this upper input voltage.

George


Tomorrow I will have another day at the bench. So if there are any other testing request or suggestions get them in.
 
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Well, you could flip it around if you're on 120vac mains with a dual 120vac primaries. In either event, you'd be in 'violation' of Menno Vanderveen's US patent # 6087822. This is used in the Torus conditioners from Bryston.
It worked quite well on the primaries of an overspecified r-core powering a dac.

Wrong! This is a magnetic canceling circuit. "....so that high frequency harmonic distortion is magnetically canceled in the core of the transformer..." Makes for a clean transformer design.
But what I put up has been done for thousands of years or more. Not patentable. Anyone can and has used it.
It is shown to be used as a concept leading to others.... summing out of phase signals passing into and thru a transformer to cancel the unwanted.

Thx-RNMarsh
 
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George is right about reducing the drive. First thing I ask for in custom transformers is reduced core flux. Most commercial transformers run around 8-9 KG, which is as close to saturation as they can in practical terms. Dropping the drive has a lot of penalties- increased losses/lower regulation/bigger for the same VA rating but much less external field and much less mechanical buzz.

Off the shelf transformers don't offer that option. The best results I have had from Signal are their international flathead family, with the potted case. That would be worth getting an aluminium case for. Unfortunately the case would cost more than the transformer.

Do you have one of these? Item # EP-101A, AC Probe-Axial-20 mV on Magnetic Shield Corp. They show up on eBay for less. It makes the process much more deterministic and you can easily see where the fields are and which way they are going. It can be pretty depressing to see how little you can actually do with a given transformer and load.
 
jn, I would suggest to halt contributing, else Ed will be short of fingers, counting the variables affecting his FFTs for his article.:)

Ed
May I give you some more troubles? :D
Don’t count on “nominal” load for each trafo when you check for leaking fields. These fields ramp-up as soon as the waveform starts showing flat tops/bottoms.
There are really not many trafos I have checked which manage decent waveforms.

Start checking the waveforms with trafos unloaded. You’ll probably give-up soon.
Then feed the primaries from a Variac. Adjust variac for an output ½ of main’s voltage and start increasing it while monitoring the waveform and leaking fields of the trafo under test.

I bet a bottle of Ouzo that in most cases – and this doesn’t have to do with the type of trafo- reaching an 80-85% of mains voltage is the upper limit for nice waveforms and the rest.
Only then check effects of loading for each type of construction, operating each trafo at this upper input voltage.

George

Agreed, the manufacturers can save materials and get an even split between copper and Iron losses by running the transformer a little bit into saturation.
 
RNMarsh,
Isn't it funny how companies patent things that have been used and in the public knowledge base and the patent office doesn't catch that often anymore. I actually saw something in NASA Tech Briefs that was a new patent for something I had done years earlier and produced for a customer. I sent the person listed on the patent application a note about that and got absolutely no response. The patent was obviously invalid, but I bet they would try and protect it anyway. The patent office is a mess, they are not doing their due diligence anymore looking at previously patented material and publicly divulged information.
 
One quick trick question:

These are the psrr graphs of shunt regulator with different compensation.
Which one will sound better?
 

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No. It is indeed kV/m. For avionics, flying over ground based radars (peak field intensity 17 kV/m) and for broadcasting repeaters having the receiver in close proximity to the kWatts transmitter.

George
Um, that was a joke..clearly not a good one...

SRF cavities used in particle accelerators have higher gradients.

jn

edit: text from the ILC.. I hilite the salient point, that being 18 kilometers of 31 MV/meter. widgits.
http://www.linearcollider.org/ILC/G...--Superconducting-RF-cavity-industrialisation

Superconducting RF cavity industrialisation

Producing high gradient superconducting radiofrequency (SCRF) cavities that meet our demanding performance goals, are affordable and can be produced by industry represents one of the largest challenges on the way to making a solid project proposal for the ILC. The present 500-GeV ILC design requires about 18,000 nine-cell one-metre long niobium cavities (including spares) yielding an average operational field gradient of 31.5 megavolts per metre (MV/m). Although we can gain much experience from other projects (XFEL, Project X, etc) and from our own R&D programme, developing a worldwide capability to produce our cavities in industry represents an enormous challenge – one we need to address now. In that regard, a special satellite workshop on ILC cavity industrialisation was held in conjunction with the first IPAC meeting last month in Kyoto, Japan.

A nine-cell one-metre long niobium superconducting ILC cavity
We have made substantial progress towards producing cavities in industry that meet our 35 megavolt per metre gradient goal for individual cavities in a vertical test, which will determine the main linac. We are preparing to make that decision over the coming six months and we have also developed a set of diagnostic tools that are enabling us to understand and sometimes fix cavities that do not meet the required gradient.
 

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Agreed, the manufacturers can save materials and get an even split between copper and Iron losses by running the transformer a little bit into saturation.

it used to be that parts, transformers included, were designed conservatively. Now it is often the opposite.... driven by competitive costs to get bids etc.

For transformers, a spec you can ask for is the xfmr's load regulation. Forget the VA etc... its all fudged numbers now. Without a reference to a standard... temp rise can be anything the mfr/marketing wants it to be for a given VA etc. Just ask for the load regulation number..... the lower percentge number, the better. It isnt fool-proof but will help a DIY'er get the best performance for his money.

-Thx-RNMarsh
 
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Joined 2005
RNMarsh,
Isn't it funny how companies patent things that have been used and in the public knowledge base and the patent office doesn't catch that often anymore. I actually saw something in NASA Tech Briefs that was a new patent for something I had done years earlier and produced for a customer. I sent the person listed on the patent application a note about that and got absolutely no response. The patent was obviously invalid, but I bet they would try and protect it anyway. The patent office is a mess, they are not doing their due diligence anymore looking at previously patented material and publicly divulged information.
USPTO is pretty much of a shambles, and of course there is no Patent Cop going around and enforcing against infringement. The examiners I suppose are doing the best they can. Some of the things I've seen lately are shockingly old, abundant prior art going back many years. Even with superb search engines, without a good knowledge of fundamentals and a good memory, coupled with years of wide-ranging reading, it is all too easy to miss prior art. Couple this with a lot of said art being proprietary and escaping as it were when someone leaves a given company, even though one is sworn to not use the knowledge/trade secrets.

I got a kick out of the early days at Harman Multimedia when a new employee joined, having headed up engineering at Labtech. On the day he arrived for his first day of work a huge file came via courier from Labtech's attorneys in essence declaring that he couldn't work for Harman. Among other things a former division head had signed an agreement and not told anyone about it, stipulating that Harman would never recruit out of Labtech (Harman in fact did not, the person responded to an ad). But things went to court anyway. At one point one of the examples cited by the plaintiff was some soundfield processing that Harman might now be able to use and thus damage Labtech's business blah blah. It was pointed out after a huddle by defense that Harman was licensing the stuff to Labtech!

Another trade secret was distantly alluded to in a sort of 20 questions game at one point with me, and I eventually figured out that it was thought to be terribly clever to drive woofers in a three piece powered system by using series inductors and taking the signals from opposing polarity outputs of the BTL amps, or a single arrangement where channels were driven in opposing polarity and the mid-high acoustical polarity corrected by flipping one loudspeaker. This was thought to have been a key bit of IP. How the inductor didn't add about as much cost as an additional amp channel was never clear to me, but I guess it all depends on how cheap the L was.
 
I`m serious

So am I.

Looking at a piece of a circuit in isolation from the rest of the system may be pedagogically useful but tells you nothing about its effect on overall performance of the system. Some time ago, someone asked about whether it was better to have a high PSR and high noise in the supply or low noise in the supply and low PSR. There was some debate, but no-one mentioned the possibility of good supply noise (but nothing dramatic, easy to obtain) along with good PSR (but nothing dramatic, easy to obtain) to end up with excellent system performance. Fun for dorm room style debate, but lousy engineering.
 
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it used to be that parts, transformers included, were designed conservatively. Now it is often the opposite.... driven by competitive costs to get bids etc.

For transformers, a spec you can ask for is the xfmr's load regulation. Forget the VA etc... its all fudged numbers now. Without a reference to a standard... temp rise can be anything the mfr/marketing wants it to be for a given VA etc. Just ask for the load regulation number..... the lower percentge number, the better. It isnt fool-proof but will help a DIY'er get the best performance for his money.

-Thx-RNMarsh

Richard, serious manufacturers have to work under a standard. In Europe this is usually EN61558 and it is very detailed.
As usually, it specifies the minimum acceptable. So you can see two trafos bearing compliance to the same std and class ect and one has the thickest laminations accepted for the specified temp rise and the other has thinner (and runs cooler under the same load).

Now, load regulation is an important electrical parameter. But as Demian wrote, a low number there, does not provide for minimisation of external fields. It is what one is asking for.

Martin, when you order a lot of trafos, you can arrange for extra winding with the manufacturer. Me and the rest, can not.
What I do? I go for a trafo with a higher secondary voltage and I wind extra primary turns myself.
Or I buy two trafos with double the secondary voltage and I wire their primaries in series.:)

George

EN61558
IEC60555
CISPR 11
 
RNMarsh,
Isn't it funny how companies patent things that have been used and in the public knowledge base and the patent office doesn't catch that often anymore. I actually saw something in NASA Tech Briefs that was a new patent for something I had done years earlier and produced for a customer. I sent the person listed on the patent application a note about that and got absolutely no response. The patent was obviously invalid, but I bet they would try and protect it anyway. The patent office is a mess, they are not doing their due diligence anymore looking at previously patented material and publicly divulged information.

Yet, they take an extraordinary amount of time for not doing what they should.
 
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