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4P1L DHT Line Stage
4P1L DHT Line Stage
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Old 1st June 2018, 02:33 PM   #1541
shadowlight is offline shadowlight  United States
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Andy, do you have a schematic for it that you can share? I just picked up an amp which is balanced in so wanted to try balanced preamp. Right now I plan to use XLR to RCA adapter with my 4P1L preamp.
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Old 1st June 2018, 02:39 PM   #1542
andyjevans is offline andyjevans  United Kingdom
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Don't have a schematic - was a while ago and didn't last long. Had some sort of current sink using red LEDs, out of Morgan Jones. For balanced I'd use 01A in preference since the sound is better and the anode resistance doesn't matter so much.
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Old 28th September 2018, 12:24 AM   #1543
albertli is offline albertli  Canada
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Smile 4p1l line stage

I happily have my line stage finished today and it is singing for me at the moment. Luckily I don't come across any problems with noises and or microphonic, dead quiet. It sounds very natural with detail, warm and lush sound, sounds better to my 26 for a big margin when start. I have to let it break in for 100 hours before detail comment.
First of all I have to thanks Andy for his advices, Rod's guildence in converting the filament board and of course have to thank Ale for his design.
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Old 28th September 2018, 12:26 AM   #1544
albertli is offline albertli  Canada
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Forgot the picture.
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File Type: jpg IMG_20180927_134115.jpg (979.3 KB, 388 views)
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Old 28th September 2018, 05:31 AM   #1545
andyjevans is offline andyjevans  United Kingdom
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Great result! You've worked very hard on this build and it shows!
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Old 29th September 2018, 04:20 PM   #1546
albertli is offline albertli  Canada
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Quote:
Originally Posted by andyjevans View Post
Great result! You've worked very hard on this build and it shows!
Thanks Andy,
I'm planing the PSE amp at the moment. Could it be possible to put everything together instead of separate psu chassis. I run out of space.
Albert
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Old 29th September 2018, 04:47 PM   #1547
andyjevans is offline andyjevans  United Kingdom
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Quote:
Originally Posted by albertli View Post
Thanks Andy,
I'm planing the PSE amp at the moment. Could it be possible to put everything together instead of separate psu chassis. I run out of space.
Albert
I use separate chassis for everything - 6 in total! Just means I can change stuff about and mix and match. I experiment a lot.
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Old 29th September 2018, 09:45 PM   #1548
albertli is offline albertli  Canada
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Quote:
Originally Posted by andyjevans View Post
I use separate chassis for everything - 6 in total! Just means I can change stuff about and mix and match. I experiment a lot.
Good approach
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Old 16th October 2018, 06:04 PM   #1549
Vbenonisen is offline Vbenonisen  Norway
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A few days ago I did some inevitable browsing and came across Intact Audios filament modules intended for Rod Colemans filament boards. intact audio


Could someone comment on the effectiveness of this simple approach for use in a DHT preamp? Is this enough filtering for the filament boards? I feel it kind of defeats the purpose if one makes an extremely quiet DC supply and THEN uses the Colemans.


I like this common mode choke approach. It somehow feels right. But is it just for output stages?
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Old 16th October 2018, 06:22 PM   #1550
andyjevans is offline andyjevans  United Kingdom
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For all my Coleman regs I use choke input, just a Hammond choke of the right current capacity. This is particularly important for filament bias which needs to be uber clean. So no - I don't think a choke is "too much" and I think you need both the choke and the reg for best results. I believe Thomas Mayer uses just the chokes so that's his preference if that's still his current setup.

I've recently changed my preamp from filament bias to using SIC diode bias and this is probably less critical than filament bias, but since I like overkill and a good Dunker Factor I'll be leaving the chokes in, certainly for my daily listen setup. I haven't looked at SIC diode bias for my PSE 4P1L stage. It's possible but the diodes give me only 0.9v of bias so less practical for an output stage. For my 26 preamp I'm using 10 diodes for 9v plus a 120R resistor to give me a touch of feedback. Sounds very detailed indeed, and this is now my daily listen with 7mA current through the 26 and an amorphous plate choke. I haven't used 4P1L in a line stage for a while - I was using 01A or 2P29L until the 26 just "clicked" and came right with SIC diode bias like it had never done totally in other setups.

Last edited by andyjevans; 16th October 2018 at 06:29 PM.
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