Looking for a DHT Pre & Phono design / ideas please

[webby]

Hi All,
Having read these resent threads:
http://www.diyaudio.com/forums/tubes-valves/151421-26-pre-amp.html
http://www.diyaudio.com/forums/tubes-valves/180541-we417a-valve-preamplifier.html
http://www.diyaudio.com/forums/tubes-valves/116603-tube-heaters-ac-dc.html

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

 

[makaiyumtony]

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

 

[webby]

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

 

[Bigun]

Always good for a read... Direct Heating

 

[makaiyumtony]

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

 

[Vinylsavor]

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

 

[Vinylsavor]

Hi!

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

 

[Poindexter]

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

 

[makaiyumtony]

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

 

[Vinylsavor]

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

 

[makaiyumtony]

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

All the transformers ( step up, inter stage, and out put) in my phono is silver, and 4 power supplies one for each tube, how you thing of it ?
cheers tony ma

 

[Vinylsavor]

Hi Tony,

sounds promising
However the silver alone won't cut it. Important is the actual circuit matching of the tranaformers to the driving tubes and the LCR EQ.
I hope it sounded much better than the Shishido circuit, then it was worth the effort

Also separate power supplies for each tube is not really necessary, won't hurt either of course. I use separate LC decoupling with high inductance chokes per tube, which is as effective as separate supplies.

Best regards

Thomas

 

[makaiyumtony]

Hi Tony,

sounds promising
However the silver alone won't cut it. Important is the actual circuit matching of the tranaformers to the driving tubes and the LCR EQ.
I hope it sounded much better than the Shishido circuit, then it was worth the effort

Also separate power supplies for each tube is not really necessary, won't hurt either of course. I use separate LC decoupling with high inductance chokes per tube, which is as effective as separate supplies.

Best regards

Thomas

Thomas
All transformers were custom made by Electric Print Audio, is match to those tubes which I used and the EQ filter too and my next project is same style for a Studer A80's repro amp because we started live recording and try to make copies too
best regards
tony ma

 

[anubisgrau]

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

is there anyway to avoid that 47 uF caps on the signal path? i guess you refer to that as a weak point of a shishido circuit.

 

[Sheldon]

Here's one (phono at least). All DHT, not expensive.

http://www.diyaudio.com/forums/tubes-valves/169428-unholy-alliance-phono-amp-3.html#post2372139


http://www.diyaudio.com/forums/atta...99104-unholy-alliance-phono-amp-3a5-phono.jpg

Looks complicated, but not so much if you strip out the delay circuit. If your amp input impedance is 100k or so, the mu follower isn't needed either.

Sheldon