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Post by jandl100 on Aug 30, 2021 5:55:00 GMT
I've heard big floorstanding brothers of those "boom & tizz" standmounts at one of the Wigwam shows a few years ago.
I hadn't expected to like them at all, but actually I really enjoyed them on the rock music that was played.
I've owned Klipsch Heresy 2 and thoroughly disliked them, though!
____
The amplifier hum problem sounds like a grounding issue inherent to the design. Possibly some variation of system grounding wiring would fix it?
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Bigman80
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Post by Bigman80 on Aug 30, 2021 7:53:22 GMT
I've heard big floorstanding brothers of those "boom & tizz" standmounts at one of the Wigwam shows a few years ago. I hadn't expected to like them at all, but actually I really enjoyed them on the rock music that was played. I've owned Klipsch Heresy 2 and thoroughly disliked them, though! ____ The amplifier hum problem sounds like a grounding issue inherent to the design. Possibly some variation of system grounding wiring would fix it? I wonder if they actually have an earth connection? |
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Post by rexton on Aug 30, 2021 11:33:59 GMT
I've heard big floorstanding brothers of those "boom & tizz" standmounts at one of the Wigwam shows a few years ago. I hadn't expected to like them at all, but actually I really enjoyed them on the rock music that was played. I've owned Klipsch Heresy 2 and thoroughly disliked them, though! ____ The amplifier hum problem sounds like a grounding issue inherent to the design. Possibly some variation of system grounding wiring would fix it? I wonder if they actually have an earth connection? No idea maybe I've not been I them. Firebottle might be on the case. I may persevere after all |
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Post by rexton on Aug 30, 2021 12:15:28 GMT
I've heard big floorstanding brothers of those "boom & tizz" standmounts at one of the Wigwam shows a few years ago. I hadn't expected to like them at all, but actually I really enjoyed them on the rock music that was played. I've owned Klipsch Heresy 2 and thoroughly disliked them, though! ____ The amplifier hum problem sounds like a grounding issue inherent to the design. Possibly some variation of system grounding wiring would fix it? I wonder if they actually have an earth connection? No idea maybe I've not been I them. Firebottle might be on the case. I may persevere after all |
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Bigman80
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Post by Bigman80 on Aug 30, 2021 13:05:18 GMT
I wonder if they actually have an earth connection? No idea maybe I've not been I them. Firebottle might be on the case. I may persevere after all If I were you, I'd whip the case open and have a look. No harm looking |
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Post by rexton on Aug 30, 2021 17:27:19 GMT
Maybe tomorrow if I can find some allen keys.
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Post by rexton on Aug 31, 2021 19:23:25 GMT
OK, update, these are going back. I just can't be bothered trying to get these fixed, they should have worked from the beginning. 300b journey over before began.
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Post by macca on Aug 31, 2021 20:56:13 GMT
You could try a WAD 300B amp. Seems to always be one for sale somewhere. Not single ended though, if that's a deal-breaker.
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Post by antonio on Sept 1, 2021 2:16:33 GMT
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Bigman80
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Post by Bigman80 on Sept 1, 2021 5:31:17 GMT
OK, update, these are going back. I just can't be bothered trying to get these fixed, they should have worked from the beginning. 300b journey over before began. Whilst its sad that we won't get a perspective of what these can do, I think you're making the right decision. If they arent right, they aren't right. |
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Post by electronumpty on Sept 1, 2021 8:28:53 GMT
A bit shoddy that, shouldn't happen. I thought Nobsound were o e od the more reliable Chifi makes.
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Post by firebottle on Sept 1, 2021 10:14:29 GMT
Unfortunately with simple implementations of heater circuit for DHT's hum can be a problem.
Pity you aren't closer so I could have taken a quick look Andy.
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Post by gninnam on Sept 1, 2021 17:48:01 GMT
I think you are making the right move also with sending them back. Such a shame it ended this way  |
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Post by rexton on Sept 1, 2021 20:10:08 GMT
Ah well, Sh#t happens I suppose. I suppose it made for a bit of drama and entertainment. Thanks to everyone that helped me out.
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Deleted
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Post by Deleted on Oct 20, 2021 5:59:13 GMT
With regard to Nobsound 300b monoblocks with hum problems.
Change the 6h8c tubes to high quality 6sn7gt tubes and these fine monoblocks will be absolutely silent.
They're fantastic amps BTW
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Post by jandl100 on Oct 20, 2021 6:20:12 GMT
^ Damn, too late!  |
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Post by rexton on Oct 20, 2021 14:54:46 GMT
Long gone....
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Post by firebottle on Apr 4, 2022 11:58:30 GMT
I don't quite see how changing the small signal valve would make these amps hum free.
HOWEVER, there has been a development with these amps, a chap I know has bought them and he is dropping they round to me to have a look at.
I may start a new thread on the investigation and development, or just post it here.
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Post by antonio on Apr 4, 2022 15:44:39 GMT
I would be very happy to see the outcome Alan, wherever you post it  |
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Post by rexton on Apr 4, 2022 18:32:16 GMT
Still, I yearn for a pair of these, so maybe! I'll have to see what Alan has to say about these. Maybe, just maybe, I might be tempted to bag a pair, lets see.... !
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Post by firebottle on Apr 5, 2022 12:01:54 GMT
Some progress today with these Douk 300B monons. I have traced out the circuit and it's fairly conventional with a couple of 'quirks' and one glaring design error. The construction is good, with decent iron in it.  The pcb is easy to partially remove to get at:  The glaring error was fitting a 250V rated capacitor on a 420V supply rail. I have replaced it with a 1000V rated capacitor, also tested the removed capacitor and it is already showing signs of change to its characteristics. if left this definitely would have failed at some point.  There was an additional link fitted to earth the driver valve heater supply in an effort to reduce hum and burble but it was still awful when listening. I have removed this and added a pair of resistors to create a virtual centre tap and this improved things but there is still hum.  The output stage, the 300B valve on its own, is pretty quiet as it has a DC heater supply. More investigation is need to ascertain where more power supply or heater supply filtering is required. I have looked at the published specification on line and the supposed signal to noise figure is a total joke! Also the input impedance is 25k ohms whereas the spec says 100K. Ha ha. More to come. |
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Post by macca on Apr 5, 2022 13:32:44 GMT
''Also the input impedance is 25k ohms whereas the spec says 100K. Ha ha.''
That might lead to some unexpected results.
Junk. Not fit for purpose. No idea what the attraction is.
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Bigman80
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Post by Bigman80 on Apr 5, 2022 13:52:58 GMT
''Also the input impedance is 25k ohms whereas the spec says 100K. Ha ha.''That might lead to some unexpected results. Junk. Not fit for purpose. No idea what the attraction is. I must admit to not seeing the attraction either. There doesn't appear to be much sophistication to the design, implementation seems poor too. I'd have no confidence in them at all. If you want valves, you need to spend carefully as there is a lot of tat out there. Good valve amps cannot be had cheaply. |
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Post by antonio on Apr 5, 2022 16:57:18 GMT
I'm looking for a good valve amp on the cheap  |
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Bigman80
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Post by Bigman80 on Apr 5, 2022 17:04:05 GMT
I'm looking for a good valve amp on the cheap You'll not get a good one cheap. It's not possible. Look for a Croft V. Still affordable and very good. |
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Post by rexton on Apr 5, 2022 18:47:05 GMT
Well looks I might have dodged a bullet, maybe, jury still out?
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Post by firebottle on Apr 6, 2022 10:46:56 GMT
With regard to Nobsound 300b monoblocks with hum problems. Change the 6h8c tubes to high quality 6sn7gt tubes and these fine monoblocks will be absolutely silent. They're fantastic amps BTW Well blow my socks off, this is absolutely correct. The supplied 6H8C input valves are absolute garbage, I'm guessing they have a really poor cathode/heater insulation. One of them worked for a short while then was just as bad as the other. I have borrowed some quality 6SN7 and these amplifiers are quiet. I have added some feedback to the circuit and these sound excellent. I know there are aficionados of Class A no feedback but I always find a little feedback is beneficial to performance. The bass response is very extended. I shall also fit an earth lift resistor to prevent any problems with earth loops, particularly as these are monoblocks and loops can happen easily. So in conclusion the two problems with these amplifiers are an undervoltage cap in the power supply and shite Chinese small signal valves. |
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Bigman80
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The HiFi Bear/Audioaddicts/Bigbottle Owner
Posts: 16,398
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Post by Bigman80 on Apr 6, 2022 11:38:44 GMT
With regard to Nobsound 300b monoblocks with hum problems. Change the 6h8c tubes to high quality 6sn7gt tubes and these fine monoblocks will be absolutely silent. They're fantastic amps BTW Well blow my socks off, this is absolutely correct. The supplied 6H8C input valves are absolute garbage, I'm guessing they have a really poor cathode/heater insulation. One of them worked for a short while then was just as bad as the other. I have borrowed some quality 6SN7 and these amplifiers are quiet. I have added some feedback to the circuit and these sound excellent. I know there are aficionados of Class A no feedback but I always find a little feedback is beneficial to performance. The bass response is very extended. I shall also fit an earth lift resistor to prevent any problems with earth loops, particularly as these are monoblocks and loops can happen easily. So in conclusion the two problems with these amplifiers are an undervoltage cap in the power supply and shite Chinese small signal valves. Have i Judged them too quickly? No, i don't think so. How do they compare to your 286 Al? |
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Post by firebottle on Apr 6, 2022 13:47:23 GMT
 On test now, surprisingly good. |
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Post by macca on Apr 6, 2022 14:36:22 GMT
They do look pretty funky but if I wanted a low powered amp that couldn't drive a fly out of a window I'd just buy a twenty quid Sanyo off of eBay.
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a quick look on ebay and what do I find, 
