Place output transformer next to mains transformer, good idea? (with pics)

[oldskool1]

Hey guys, I’m interested in buying the new clone of the EAR 825 eq. I have been talking with the builder, but I would like your help understanding some things about it.

In both units the mains transformer is very close to the output transformer. The original EAR, however, uses a toroid encased in metal (see pics). The clone uses an IE transformer with no case.

The builder says that they were able to: “achieved impressive results exceeding: Signal to Noise Ratio, reference to +4 dBu, 8Hz-40kHz: 95dB. It's amazing result BTW.”

I recently watched a video where EveAnna Manley details Manley’s upgraded switching power supplies and that it drastically improved their noise and hum performance. The Manley site quotes the Massive Passive’s signal to noise performance as -92db. This figure is worse than the EAR clone, despite Manley’s “This is Massive audio excellence which starts with this superior power supply. All lines are super-quiet in this low radiating high frequency design”

The EAR clone builder states that only input transformer placement matters, and that output transformers are immune to EMF. This is new to me. I really want to buy this thing, but I don’t want to get it and hear a ton of hum in the output, and have to send it back. What do you guys think? Should I start placing my output transformers right next to the Mains transformers in my new builds? You can browse the original thread on Gearslutz in the “New Product Alert” category if interested.

 

[ruffrecords]

the pics are very small

Cheers

ian

 

[oldskool1]

the pics are very small

Cheers

ian

Hi Ian, the pics are the same size as was posted by the builder. I wish I had bigger pics. On my computer I can magnify them in the GroupDIY pic viewer by pressing cmd + , which makes them legible. (I'm on a Mac).

 

[warpie]

The original pictures are larger actually. Since the manufacturer claims -95db SNR, it has to be -95db. Otherwise, he's lying. What is you concern exactly?

 

[oldskool1]

Since the manufacturer claims -95db SNR, it has to be -95db. Otherwise, he's lying. What is you concern exactly?

I want to buy this eq. My concern is that I don't want to buy this thing for $3200, only to find out that the specs are incorrect. I checked with the dealers, and I will have to pay a re-stocking fee if I return it, because it is a special order. Plus I'd lose the shipping both ways. Not great.

In my experience, having any audio transformers that close to the mains is a bad idea. Otherwise why did EAR use a toroid and shield it? My question is, does this look even remotely right, given that Manley goes to huge lengths to achieve better performance, and doesn't even match a unit with the output transformer right next to the mains?

 

[oldskool1]

The original pictures are larger actually.

Yes, you are right. Here they are in larger size. I originally dragged them to the desktop... I was not aware that this copies only the thumbnail size.

 

[john12ax7]

The EAR clone builder states that only input transformer placement matters, and that output transformers are immune to EMF.

That is a dubious claim, is that what was actually said? Note that you can get away with close proximity, it's not automatically bad. But it requires shielding or proper orientation (often 90 deg). Measurement and experimentation is needed.

I had owned a famous stereo eq a while black. There were only output transformers, no input. The right channel, which was closer to the power transformer, had very measurable higher output hum / noise induced from the power supply.

It's really up to the designer to verify everything works ok. There is no universal answer. Can you just ask for measured data? That would be easiest way to alleviate your concerns.

 

[oldskool1]

That is a dubious claim, is that what was actually said?

Not exactly, but it was implied by omission. I just wanted to make sure I was on the right track before I pushed the same question again to the guy even harder. I'll ask again.

 

[andia]

it looks like the IGS 825. why not ask @igs ?

 

[warpie]

The reason this clone uses IE transformer instead of toroidal is most likely because igs don't have toroidal winders and it's cheaper for them to use their own IE transformers.

I don't know whethet this affects the specs or not but since they claim SNR -95db, it should be -95db.

 

[Matt Syson]

Having been caught out by putting output transformers next to each other in 1982 I would suspect that the channel crosstalk figures are not that good. Yes it was tedious having to remount 24 transformers with double spacing! IF the mains transformer happens to nave been wound well it COULD possibly be OK (probably 60 Hz mains?) Did they specify what meter weighting curve was used for the noise measurement as some 'favour' gear that has significant LF noise (hum), an old trick from the 1970's which is why reputable manufacturers gave the results using several meter weightings and rMS or Q peak etc. Of course SNR will be 95dB below Plus 4dBu so actually minus 91dBu. Output transformers are NOT immune to external magnetic fields but whether it is a problem in any given setup is the next question. Stacking 2 Manley 1U EQs on top of each other gives hum because the mains transformer field radiation pattern gets disturbed. Using 'tricks' to get a decent pereformance is shoddy for what is 'mass production'. Quality has to be designed IN early on.

 

[Somkereki]

Hey guys, I’m interested in buying the new clone of the EAR 825 eq. I have been talking with the builder, but I would like your help understanding some things about it.

In both units the mains transformer is very close to the output transformer. The original EAR, however, uses a toroid encased in metal (see pics). The clone uses an IE transformer with no case.

The builder says that they were able to: “achieved impressive results exceeding: Signal to Noise Ratio, reference to +4 dBu, 8Hz-40kHz: 95dB. It's amazing result BTW.”

I recently watched a video where EveAnna Manley details Manley’s upgraded switching power supplies and that it drastically improved their noise and hum performance. The Manley site quotes the Massive Passive’s signal to noise performance as -92db. This figure is worse than the EAR clone, despite Manley’s “This is Massive audio excellence which starts with this superior power supply. All lines are super-quiet in this low radiating high frequency design”

The EAR clone builder states that only input transformer placement matters, and that output transformers are immune to EMF. This is new to me. I really want to buy this thing, but I don’t want to get it and hear a ton of hum in the output, and have to send it back. What do you guys think? Should I start placing my output transformers right next to the Mains transformers in my new builds? You can browse the original thread on Gearslutz in the “New Product Alert” category if interested.

I have been an electrical and sound engineer for 48 years. Unfortunately, I have encountered this error several times because the output transformer was placed close to the mains transformer. Recently, a friend of mine had a "custom made" guitar amp like this. Even in "standby" mode, the noise could be heard from the speaker. (In addition, the manufacturer has built in very small and dried-up electrolytic capacitors with loss of capacity. ) There are many such manufacturers. I already learned in the technical school before the university that this is not allowed! (I had very good engineering teachers with a lot of professional experience. I have been grateful to them ever since. I would doubt that signal/noise measurement result! I don't understand why he placed the transformers so close, when there would obviously be room to place them further away. I certainly wouldn't buy it! (Although the internal structure of the device is very nice.) In sound technology, there are basic rules regarding the placement of components.

 

[igs]

Please hold off on any judgments until Monday. At that time, I will sit down at my AudioPrecision station, measure the necessary parameters, and present the results. I cannot do this today because we are currently on a long May weekend and are not working.

The opinions expressed here are absolutely unfounded and harmful both to the IGS Audio brand and to the 825EQ product. Do you think that after being in the pro audio market for 20 years, we can afford to present a device for 3290 Eur that does not meet the highest studio standards? I don't think so.

 

[zonkers31]

Documented signal to noise ratios can be all over the map. Many manufacturers as stated above did not alway quantify how the measurment was made. Some measure it at maximum output before clipping etc. Also even unweighted measurments can have filters. I can make unweighted noise measurements with my Audio Precision with filters from 22-22k, 10-80K, 10-300K, or set 400hz as the low end. All these settings can change the SNR reading on some gear.
Well designed gear will change very little between these different settings. I've seen people throw output transformers in gear (especially DIY racked modules) and the spec will look ok at 22-22K, but show massive ringing in the high end set at 10-80K. Both 92db and 95db referenced to +4db are excellent specifications and for me would not be the determing factor in purchasing either one.

 

[oldskool1]

Hey IGS, thanks for your reply, it was me that started this inquiry. I was about to reach out to you directly after asking your dealer Nathan Eldred whether he could measure the first unit that comes in, but he said he didn't have the gear to do it and he suggested that I should email you and ask for more details. It wasn't my intention to damage the IGS brand. This purchase represents several months savings for me and I needed to be sure about it because it differs from the original in the areas mentioned. Now I wish I had emailed you first before asking the question here. But it is what it is, we'll know the answer on Monday.

The EQ looks great by the way, and I'm sure I'm not the only person who is very excited to get one.

 

[Graham Nystrom]

A couple thoughts, output transformers are way less prone to EMF, but not immune. Also eq is not doing 40-80dB of gain like a mic preamp, so shouldn’t the entire circuit be less prone to parasitic EMF?

In my builds, my toroids are mounted vertically on the back right off the chassis and the closest module (output transformer at the back) can’t be any closer than about 2”.

You can spin the toroid to get waaaaay different interference patterns, and find a quiet node. Also the quiet node for the box in question might push the field into track gear above or below.

Distance is my preference to using shielding, but there are plenty of designs that work great with an internal EI PT with no shielding. Like I’m sure this eq does. It was nice of IGS to pop in. Good luck y’all.

Graham

 

[vintageampfixer]

The mains transformer is at least screened which will cut down some of the field it radiates and the output transformer is slightly rotated, probably to reduce interference ... but no transformer can be completely immune to nearby field(s) so it's perhaps more likely the induced noise is far enough into the specified noise floor to make it unimportant ...

It's also feasible they de-specified to reflect noise levels measured in production rather than designing the product to meet the original brief.

 

[Tubetec]

Holger demonstrated the difference between on and off board PSU very clearly on one of his builds .

I worked on a Demeter preamp before ,
LT winding on the PT was open circuit ,
I put a call through to their office in the USA , talked to the man himself ,
he told me no matter what I replaced the original transformer with Id be left with hum ,
it had to be that exact part , in the end it was no longer available .

I subbed in a small extra transformer to supply the LT , but no matter where I placed it there was some extra residual hum audible . In the end I had to find the position of minimum hum and leave it at that .

Tele V series incorporated power, input / output transformers and chokes in a compact Danner enclosure ,to do this they needed very heavy duty mumetal screening around all the transformers , as well as careful positioning .

If you want lowest hum a seperate screened power supply is the way to go ,

 

[igs]

I want to express my gratitude to everyone for the insightful feedback and valuable advice. With your help, we adjusted the placement of the power transformer, moving it an additional inch away from the output transformers. As a result, we've achieved a dynamic range exceeding 112 dB at 1kHz, with a +24 dBu output. Thank you all for your contributions to this improvement! This forum community is awesome!