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Old 10th January 2011, 02:00 PM   #1
webby is offline webby  United Kingdom
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Default Looking for a DHT Pre & Phono design / ideas please

Hi All,
Having read these resent threads:
#26 pre amp
WE417A Valve Preamplifier
Tube heaters AC or DC?

I would like to ask you gurus a few questions please....

If I understand the threads correctly, a DHT pre can provide a lower signal to noise ratio.
Could this therefore provide a solid basis for a high performance line level pre amp with a phono stage?
Maybe using these ingredients;

Salas shunt HV,
Ros coleman Regulators

But using more easily available components than the #26 valves?
I realise they may be a drop in performance, but I tried to find one of these valves, it was expensive.

What valves could be used, good, common type to allow changing within the same family of valves.
But still provide very good performance?
Does anyone know of any kits available?

Many thanks
Ian
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Old 10th January 2011, 02:31 PM   #2
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Hi Ian
DHT has more noise level than indirect heating tube and less gain but more emotional feeling and transparent. good for line stage with a out put transformer, 300B is the best in result if you don't think it is a waste.
Phono stage needs more gain,at least 2 stages of mid or high mu tube, 6922 in mu stage with a LCR RIAA filter is a hi-end quality design
cheers
tony ma
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Old 24th January 2011, 03:49 PM   #3
webby is offline webby  United Kingdom
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Thank you Tony ma.
What circuits or combination out there would you recommend?
I was hoping to build a single unit, thinking it might save building two separate power supplies?
Thanks
Ian
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Old 24th January 2011, 03:56 PM   #4
Bigun is offline Bigun  Canada
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Always good for a read... Direct Heating
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Old 24th January 2011, 04:36 PM   #5
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Quote:
Originally Posted by webby View Post
Thank you Tony ma.
What circuits or combination out there would you recommend?
I was hoping to build a single unit, thinking it might save building two separate power supplies?
Thanks
Ian
Hi Ian
Separated power supply always has the better sound only cost more, in line stage very simple you can use just same as a single end power amp's design but in 600 ohm out put and a DC filament power supply is needed if for DHT
Phono stage you can search for Shishido's design 6DJ8 with a 600 ohm LCR RIAA filter, this is a very Hi End design
cheers
tony ma
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Old 24th January 2011, 04:57 PM   #6
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Hi!

If you are on a limited budget, a DHT preamp is not the right choice IMHO.
If you are willing to spend the best possible parts a DHT preamp is great! If not you will get better results with IDHTs.

While phono circuits with all DHTs are doable (I've done that) it takes a lot of effort and it will be BIG!

Also I'd advice not to start with a DHT design if this is your first preamp. Better gain experience with some IDHT circuits first before you dive into the DHT preamp waters.

Best regards

Thomas
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Old 24th January 2011, 05:00 PM   #7
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Hi!

Quote:
Originally Posted by makaiyumtony View Post
Phono stage you can search for Shishido's design 6DJ8 with a 600 ohm LCR RIAA filter, this is a very Hi End design
No, it's not! It's among the lowest end circuits for LCR phono! It uses ugly large electrolytics as coupling caps. I also dislike the mu follower concept. More coupling caps and tubes in the signal path as necessary

Best regards

Thomas
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Old 24th January 2011, 05:03 PM   #8
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If you are looking at DHT small-signal amplification, go find Andy Evans. He has more experience in this area than anyone I know.

Poinz
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Old 24th January 2011, 05:34 PM   #9
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Originally Posted by Vinylsavor View Post
Hi!



No, it's not! It's among the lowest end circuits for LCR phono! It uses ugly large electrolytics as coupling caps. I also dislike the mu follower concept. More coupling caps and tubes in the signal path as necessary

Best regards

Thomas
Hi Thomas
I did try that circuit but I changed the cap to Solen, The sound not bad compare to most SS phono stage or tube with CR filter only, may be Tango's RIAA filter unit sound good, but now I already changed to WE437A SE to Tango's LCR unit with transformer coupling and 5876 pencil type tube in out-put section with transformer too
cheers
tony ma
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Old 24th January 2011, 05:38 PM   #10
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Hi Tony,

Yes I believe that it sounds better than most SS phono stages,but it won't reveal what is possible with LCR EQ.

I dissmissed Solens a long time ago BTW, did not like them at all.

I build my LCR phono stages all transformer coupled with tubes like EC8020, WE437, E810F, E55L, D3A, 6AM4

Thomas
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