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4P1L DHT Line Stage
4P1L DHT Line Stage
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Old 2nd January 2018, 11:27 PM   #1481
andyjevans is offline andyjevans  United Kingdom
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I have no microphonics at all with 4P1L, and also none with 2P29L. I doubt if it's the gyrator. I would suspect the chassis. All my amps have 4mm thick soft aluminium top plates. Same with sides, unless they're wood which is also pretty dead. None of the chassis ring when they are tapped. If I tap the 2P29L itself I get a low volume high pitch ring for about 15 seconds, and then it dies out completely. I have the 2P29L stage in a chassis of its own, which happens also to be quite heavy since it contains four 126C.

My solution has always been high mass. I don't use any suspension system - just mass to kill resonances.

What's your chassis like, what weight, and does it resonate when struck in any way?
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Old 3rd January 2018, 07:15 AM   #1482
mogliaa is offline mogliaa  United Kingdom
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4P1L DHT Line Stage
I agree with Andy. My 4P1L is very quiet, however in my case it took about 200 hours or so to reduce the microphonic noise. My chassis is an IKEA chopping board which is less than 8mm thick I guess.
With the 2P29L I have no microphonic noise whatsoever and there are several builders out there reporting similar results.
I'm guessing is the batch of 2P29L you have Barry? I can post you a pair of 2P29L for you to test if you want.
cheers, Ale
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Old 3rd January 2018, 09:27 AM   #1483
frentec is offline frentec  United Kingdom
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Hi Ale,
Thatís what I donít understand, I am not getting Microphonic noise from 4P1L! I have also been playing with PSU & my original one was based on the Siberian but rectification was with GZ33 & 2 Shottky diodes, so it was CLCRC, but changing the 220 R Resistor for a 10H choke made a huge difference. I guess I might change the whole setup for full Rectification now as well. As they say in for a penny in for a pound!
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Old 3rd January 2018, 09:30 AM   #1484
frentec is offline frentec  United Kingdom
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I will give it some thought regarding your offer Ale & a happy New Year
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Old 3rd January 2018, 03:58 PM   #1485
andyjevans is offline andyjevans  United Kingdom
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Quote:
Originally Posted by frentec View Post
Hi Ale,
Thatís what I donít understand, I am not getting Microphonic noise from 4P1L! I have also been playing with PSU & my original one was based on the Siberian but rectification was with GZ33 & 2 Shottky diodes, so it was CLCRC, but changing the 220 R Resistor for a 10H choke made a huge difference. I guess I might change the whole setup for full Rectification now as well. As they say in for a penny in for a pound!
I wouldn't worry about a hybrid or Graetz bridge - it's what I use most of the time since conventional transformers without a centre tap are usually cheaper and more available. I don't think it makes too much difference. What makes a difference for me is all polypropylene caps - I use ordinary motor run caps and nothing else in the PSU.
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Old 3rd January 2018, 04:32 PM   #1486
frentec is offline frentec  United Kingdom
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Hi Andy,
I totally agree & I use all polyprop also, they are also more reliable, I use hybrid also because of the lower expense to performance ratio, it's just the curiosity factor regarding performance, I also prefer AZ31 to AZ1 regarding rectifier Valves, I just think the AZ1 sounds veiled in comparison, in fact prefer the GZ33 to any of them.
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Old 3rd January 2018, 04:49 PM   #1487
Blitz is offline Blitz  Germany
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The biggest difference in my setup was in the psu:
1. Go from EI Transformer to Double-C LL1683
2. Go from one rectifier setup to true dual mono with two transformer
2a. Get rid of the normal chokes and use the special amorphous core chokes of 50ae...super-resolution...
3. Go from CRC for the coleman reg to LCLC
4. Use directly heated rectifiers, I like a lot the 5c3s black plate from the 50s for it unbeatable price/performance ratio
5. go away from bridge or hybrid and use classic fw with CT.
6. I am always using Mundorf tubecap, will test oilers in comparison next...sofar they have been always extremely slow in comparison.
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Old 3rd January 2018, 06:07 PM   #1488
frentec is offline frentec  United Kingdom
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If I'm not mistaken 5C3E should work as a near perfect drop in for GZ33, I already run Filament supplies clcrc, I will try a second choke I think, especially as so much has been stated here on the plus side.
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Old 4th January 2018, 10:18 AM   #1489
frentec is offline frentec  United Kingdom
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Quote:
Originally Posted by andyjevans View Post
I think Frentec and I are very much on the same page here. <snip>
I agree with Andy on the Iron used in Filament Supply, I've tried Lundahl in previous projects & found that 159Y's (750mA 0.6H) work well for here, followed by the cheap Epcos ones, (the type Ale recommends), You save yourself serious wedge here & for a fair result IMHO.
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Old 4th January 2018, 11:25 AM   #1490
frentec is offline frentec  United Kingdom
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Quote:
Originally Posted by mogliaa View Post
I agree with Andy. My 4P1L is very quiet, however in my case it took about 200 hours or so to reduce the microphonic noise. My chassis is an IKEA chopping board which is less than 8mm thick I guess.
With the 2P29L I have no microphonic noise whatsoever and there are several builders out there reporting similar results.
I'm guessing is the batch of 2P29L you have Barry? I can post you a pair of 2P29L for you to test if you want.
cheers, Ale
Hi Ale,

I would like to take you up on your offer with the 2P29L, from what everyone is saying, itís got to be worth it.
Thanks Barry
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