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Post by pinkie on Jun 30, 2015 13:45:22 GMT
If I've understood it right Jez, the proper engineering solution would have been to supply a correctly specified transformer, when the DC offset would have been of no consequence. But given they hadn't a free DC blocker is an excellent solution. If there are any other significant benefits to avoiding mains DC, I guess I should look at fitting one further upstream of the rest of the kit. Whilst I didn't ask the direct question of Owen in those terms, I got the impression he didn't consider DC offset an issue that mattered (other than the transformer core saturation on the "wrong" transformer) Certainly all is silence in that corner of the room. The Benchmark is a silent device - both acoustically and electrically - and, critical for the case for the defence in the domestic discussion of whether to purchase one, can happily sit under the preamp instead of me insisting on keeping the Quad as far as way as possible - the SMPS power supply introduces far less noise into the environment. So its "tidier" - a slam dunk I feel!  |
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Post by Deleted on Jun 30, 2015 14:05:47 GMT
Many Bryston amps have mains DC blockers built in... I really liked and admired my 4B ST. I'm sure I will have another Bryston again at some stage. |
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Post by Deleted on Jun 30, 2015 14:54:53 GMT
If I've understood it right Jez, the proper engineering solution would have been to supply a correctly specified transformer, when the DC offset would have been of no consequence. But given they hadn't a free DC blocker is an excellent solution. If there are any other significant benefits to avoiding mains DC, I guess I should look at fitting one further upstream of the rest of the kit. Whilst I didn't ask the direct question of Owen in those terms, I got the impression he didn't consider DC offset an issue that mattered (other than the transformer core saturation on the "wrong" transformer) Certainly all is silence in that corner of the room. The Benchmark is a silent device - both acoustically and electrically - and, critical for the case for the defence in the domestic discussion of whether to purchase one, can happily sit under the preamp instead of me insisting on keeping the Quad as far as way as possible - the SMPS power supply introduces far less noise into the environment. So its "tidier" - a slam dunk I feel! That's not my opinion no. How over-specified should we make this transformer? All products have to be built to a set of engineering compromises that fit with the intended price point of the product. Mains transformers are generally the single most expensive item in a power amplifier and the recent huge increase in demand for copper from China has put up prices well beyond inflation in the last decade or so. In theory mains quality is the responsibility of the electricity supplier..... various laws have been enacted to help improve mains quality also. Do we really want a power amp to go from lets say £699 to £780 just for the off chance that a very few customers may have mains DC problems? The Bryston idea of a built in DC blocker is better IMO. Those who suffer from buzzing transformers are vocal about it but it needs to be remembered that for everyone having this problem there may well be hundreds who don't... |
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Post by Sovereign on Jun 30, 2015 16:37:14 GMT
I guess I should look at fitting one further upstream of the rest of the kit. Whilst I didn't ask the direct question of Owen in those terms, I got the impression he didn't consider DC offset an issue that mattered (other than the transformer core saturation on the "wrong" transformer) You would be better off fitting a DC blocker to the extension block that feeds the whole system. Removing DC from the mains is not simply the avoidance of toroidal core saturation. The toroidals I have made for me always have massively over spec'd iron cores which cannot saturate, however the fitting of a good DC blocker had a substantial benefit to the sound of my HIFI |
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Post by Deleted on Jun 30, 2015 16:47:50 GMT
I wouldn't expect any improvement to sound quality from either mains DC blockers or "over spec'd" transformers....
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Post by Sovereign on Jun 30, 2015 17:31:11 GMT
I wouldn't expect any improvement to sound quality from either mains DC blockers or "over spec'd" transformers.... Jez your totally correct, neither would I, neither would others in the know. But the difference was lovely. I didn't understand so two others also tried the same thing and reported the same very positive findings. I get my 13A DC blockers from Nick Gorham (longdog Audio) and he can't fully explain it either. |
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Post by Deleted on Jun 30, 2015 17:37:08 GMT
I wouldn't expect any improvement to sound quality from either mains DC blockers or "over spec'd" transformers.... Jez your totally correct, neither would I, neither would others in the know. But the difference was lovely. I didn't understand so two others also tried the same thing and reported the same very positive findings. I get my 13A DC blockers from Nick Gorham (longdog Audio) and he can't fully explain it either. Exactly the reply I expected  Carry on.... |
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Post by Sovereign on Jun 30, 2015 17:44:58 GMT
But the stars, moons, trees and blades of grass in the garden do have to all line up correctly for it to work.
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Post by pinkie on Jun 30, 2015 18:18:46 GMT
That's not my opinion no. How over-specified should we make this transformer? All products have to be built to a set of engineering compromises that fit with the intended price point of the product. Mains transformers are generally the single most expensive item in a power amplifier and the recent huge increase in demand for copper from China has put up prices well beyond inflation in the last decade or so. In theory mains quality is the responsibility of the electricity supplier..... various laws have been enacted to help improve mains quality also. Do we really want a power amp to go from lets say £699 to £780 just for the off chance that a very few customers may have mains DC problems? The Bryston idea of a built in DC blocker is better IMO. Those who suffer from buzzing transformers are vocal about it but it needs to be remembered that for everyone having this problem there may well be hundreds who don't... That makes sense and still fits with what I was told. If it is possible to achieve value with a more tightly toleranced transformer and dc blocker cost effectively than that is an equally viable path. I couldn't see how DC was going to be an issue elsewhere either so I won't rush to try. I may get some crystals from the rock shop near our new house, and align them with the ley lines under the amp, but not a DC blocker |
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Post by pinkie on Jun 30, 2015 18:20:11 GMT
But the stars, moons, trees and blades of grass in the garden do have to all line up correctly for it to work. James - we are long overdue for a cup of tea or something stronger, so if you want to bring a DC blocker built like a brick shithouse, we can see what it does in the Yalding ley lines. If only I could guarantee when the neighbours will be out.  |
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Post by Sovereign on Jun 30, 2015 18:24:09 GMT
Yes , I work from home so I'm free most days
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Post by Sovereign on Jun 30, 2015 18:25:24 GMT
But the stars, moons, trees and blades of grass in the garden do have to all line up correctly for it to work. James - we are long overdue for a cup of tea or something stronger, so if you want to bring a DC blocker built like a brick shithouse, we can see what it does in the Yalding ley lines. If only I could guarantee when the neighbours will be out. However my one DC blocker is built into equipment , so I couldn't just bring it on its own |
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Post by pinkie on Jun 30, 2015 18:33:34 GMT
Not this week James - but maybe next. Remind me. I can live without the blocker if you come here. Be good to catch up
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Post by Deleted on Jun 30, 2015 18:36:55 GMT
 I didn't have to wait long. It was in the post box all the time. Obviously there is a cover over the exposed side - I just took it off to photograph. And it works! (The buzz, and hence offset, was quite loud just now when I tried it). The subwoofer buzzes for about half a second while the capacitors charge, and thereafter is silent. I have to emphasise just how impressed I am with BK electronics, their products, and their customer service. Whilst I appreciate the engineering point Craig (and Owen) were making about the right answer being to design the product with a properly rated transformer in the first place, the sub-woofer is excellent, and BK have provided this solution FREE long after the original purchace, quickly and efficiently - and it works. I would recommend their sub-woofers unreservedly. And I fail to see how anyone can ask hundreds of pounds for a lead which essentially does the same job, with a couple of diodes and a couple of electrolytics. Unless you believe fat wire, and fancy plugs and connectors are essential. Back to put the carnage in the living room back and listen to the Benchmark a bit more (the weather was too lovely yesterday). I'm not sure the sub is going to be used in the 2 channel whilst the benchmark is a house guest - it wasn't missed yesterday. But I haven't really had a chance to listen properly and compare with the Quad. The amp is extraordinary - if only because it is so tiny and runs stone cold even thrashed! Strongly suspect that they have copied one of the circuits sound.westhost.com/articles/xfmr-dc.htm , almost certainly figure 8 Rod Elliott also says "Commercial use is prohibited without express written authorisation from Rod Elliott". Let's hope that such permission has been sought, if that box uses the design on the webpage (caps 4700uf, diodes 1N5404), or something that could reasonably be construed as similar. |
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Post by pinkie on Jun 30, 2015 19:15:24 GMT
I didn't have to wait long. It was in the post box all the time. Obviously there is a cover over the exposed side - I just took it off to photograph. And it works! (The buzz, and hence offset, was quite loud just now when I tried it). The subwoofer buzzes for about half a second while the capacitors charge, and thereafter is silent. I have to emphasise just how impressed I am with BK electronics, their products, and their customer service. Whilst I appreciate the engineering point Craig (and Owen) were making about the right answer being to design the product with a properly rated transformer in the first place, the sub-woofer is excellent, and BK have provided this solution FREE long after the original purchace, quickly and efficiently - and it works. I would recommend their sub-woofers unreservedly. And I fail to see how anyone can ask hundreds of pounds for a lead which essentially does the same job, with a couple of diodes and a couple of electrolytics. Unless you believe fat wire, and fancy plugs and connectors are essential. Back to put the carnage in the living room back and listen to the Benchmark a bit more (the weather was too lovely yesterday). I'm not sure the sub is going to be used in the 2 channel whilst the benchmark is a house guest - it wasn't missed yesterday. But I haven't really had a chance to listen properly and compare with the Quad. The amp is extraordinary - if only because it is so tiny and runs stone cold even thrashed! Strongly suspect that they have copied one of the circuits sound.westhost.com/articles/xfmr-dc.htm , almost certainly figure 8 Rod Elliott also says "Commercial use is prohibited without express written authorisation from Rod Elliott". Let's hope that such permission has been sought, if that box uses the design on the webpage (caps 4700uf, diodes 1N5404), or something that could reasonably be construed as similar. I think if you read it that is commercial use of the written material. You can't go and write a book on the subject and sell it and use that article or significant parts of it. I don't believe it is possible to protect the rights to a circuit idea (other than by patent). Especially not one that could be readily designed from scratch by a competent engineer. |
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Post by pinkie on Jun 30, 2015 19:19:52 GMT
Since there are several competent engineers here - can anyone help with yet another hum problem. And very probably a ground loop problem. The problem is my pickup on my new acoustic guitar into my M-audio fast track ultra. If the guitar is resting on a chair the hum is bad and touching the cable sleeve and or the strings has no effect. If I pick the guitar up and rest it on my lap, and touch the cable sleeve the hum is greatly attenuated. Touching the strings and the cable sleeve it disappears. How do I fix this? (Laptop and M-audio are both powered by 2 wire dc from power packs and have no direct ground connection to true earth Where is the loop?  |
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Post by Stratmangler on Jun 30, 2015 19:53:21 GMT
Since there are several competent engineers here - can anyone help with yet another hum problem. And very probably a ground loop problem. The problem is my pickup on my new acoustic guitar into my M-audio fast track ultra. If the guitar is resting on a chair the hum is bad and touching the cable sleeve and or the strings has no effect. If I pick the guitar up and rest it on my lap, and touch the cable sleeve the hum is greatly attenuated. Touching the strings and the cable sleeve it disappears. How do I fix this? (Laptop and M-audio are both powered by 2 wire dc from power packs and have no direct ground connection to true earth Where is the loop? Can you get sound out of the M Audio unit with the laptop disconnected? If so, does the noise issue manifest itself then? |
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Post by pinkie on Jun 30, 2015 20:21:35 GMT
Since there are several competent engineers here - can anyone help with yet another hum problem. And very probably a ground loop problem. The problem is my pickup on my new acoustic guitar into my M-audio fast track ultra. If the guitar is resting on a chair the hum is bad and touching the cable sleeve and or the strings has no effect. If I pick the guitar up and rest it on my lap, and touch the cable sleeve the hum is greatly attenuated. Touching the strings and the cable sleeve it disappears. How do I fix this? (Laptop and M-audio are both powered by 2 wire dc from power packs and have no direct ground connection to true earth Where is the loop? Can you get sound out of the M Audio unit with the laptop disconnected? If so, does the noise issue manifest itself then? I'm going to play again tomorrow - just got stung by a bee trying to get in the studio. Maton pickups seem to have a bit of a reputation for hum - its under warranty. Disconnecting the laptop from the mains (not) but using it just off its battery rather than its power pack made no difference. The issue seems to be I need a ground point for the guitar. I have had the same issue with electrics but run a ground wire from the effects board to the chassis of the Fender. I guess putting an earth wire on the screen of the jack would fix it (one wire from the earth pin of a safety mains plug, wrapped round the shield on the cable). I might try that - but its clutsy I'll have another fiddle tomorrow. |
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Post by Stratmangler on Jun 30, 2015 20:46:38 GMT
I'm going to play again tomorrow - just got stung by a bee trying to get in the studio. Maton pickups seem to have a bit of a reputation for hum - its under warranty. Disconnecting the laptop from the mains (not) but using it just off its battery rather than its power pack made no difference. The issue seems to be I need a ground point for the guitar. I have had the same issue with electrics but run a ground wire from the effects board to the chassis of the Fender. I guess putting an earth wire on the screen of the jack would fix it (one wire from the earth pin of a safety mains plug, wrapped round the shield on the cable). I might try that - but its clutsy I'll have another fiddle tomorrow. What I was really asking is does the M Audio interface work with the USB cable disconnected from the laptop? I have an EMU0404 USB recording interface, and it works fine on its own, does ADC/DAC conversions (ie I can throughput sound) and drives headphones without a computer connected. I'm just trying to establish whether there's noise breakthrough adding to the problem. Your bootstrapping earths together might well be the cure required for your issue. I noticed an annoying very low level hum t'other day whilst listening on headphones - I ended up dressing the power cable to the EMU so that it didn't come into contact with the USB cable. I was hearing 50hZ hum over the USB to EMU. Dressing the cables sorted my problem. |
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Post by pinkie on Jul 1, 2015 5:41:02 GMT
I'll investigate tonight or maybe Friday (when a friend is coming round with his guitar). I don't think decoupling the laptop will stop the hum though now I've thought it through unmolested by nesting bumble bees (I thought they weren't aggressive). I was fazed by wasting hours wondering which configuration settings I had wrong when I first tried to set up the recording equipment because I couldn't get any input from the Shure SM57 mike I was using first, only to eventually test the mike and find the cable had broken (teenagers!). I had an issue when I first tried the Maton Messiah in our PA a month or so ago, but it cleared when I moved the internal condenser mike which is part of the AP5 pickup. However, the PA almost certainly has a chassis safety ground whereas none of the equipment last night does. So I guess the strings and pickup are acting as aerials and need a path to earth. My hand touching the return of the pickup via the guitar cable sleeve obviously makes that path to earth. (who would have thought my body could provide a sufficiently low impedance path to earth to silence a loud hum, whilst sitting on a chair on a carpeted floor, when an "expert" (sic) on this forum once told me I would need to stand in a metal bucket filled with water to be at risk of electrocution from faulty wiring plugged into a balanced mains unit) Bloody 'lectricity  Edit: (first version cut too many corners) |
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Carry on....
