Preamplifiers using DHT

[square_wave]

I have been drawn into some discussions about the beauty of DHT type preamplfiers in recent times. This has happened many times now that I am tempted to try something in the near future. I really like the amplifier I have now but I am quite curious. When I do some R&D, this is what I see.

A summary :

Sound Quality Advantages​

• Transparency and Detail: DHT preamps are praised for their ability to reveal subtle nuances and micro-dynamics in music, offering a "see-through" clarity that indirect-heated triodes (IDHT) often lack.
• Natural Tonality: The direct heating of the cathode eliminates the intermediary cathode structure, resulting in a more organic, lifelike sound with reduced harmonic distortion.
• Euphonic Character: DHTs like the 45, 2A3, or 300B tubes impart a warm, rich tonal signature that many listeners describe as "musical" or "emotionally engaging.

Challenges and Trade-offs​

• Noise Management: DHTs are inherently noisier than IDHTs, requiring meticulous engineering (e.g., active bias systems, low-noise filament regulators) to achieve silent operation.
• Tube Selection: Only premium-grade DHTs (e.g., TJ Meshplates, NOS 45s) perform optimally, as microphonics and emission noise vary widely between tubes.
• Cost and Complexity: DHT preamps often demand expensive transformers, custom power supplies, and careful tube matching, raising both initial and maintenance costs

Forgive the clinical sounding summary. I got that from an ai tool that do research.

I am curious to hear experiences from people who have seen massive improvement with DHT type preamps in their personal systems.

 

[yogibear]

DHT pose a big challenge to make them dead silent. Doing that is an art and science.

DHT presents very natural and relaxed vocals. Intoxicating…

A well executed DHT preamp has the ability to completely transform your chain. SS components chain benefits the most.

However there are some triodes which ae considered to sound akin to DHT without hassles of DHT. Will be testing one soon in the driver stage of an amp.

DHT preamp crafted by me, Re084, rectified by DHT 1805.

 

[square_wave]

@yogibear , Thanks. That preamp looks lovely! There is a lot of talk about the beauty aspects of the DHT sound!

However, technically speaking ---- Are there any benefits in terms of transparency and resolving capability if you go the DHT way ? In case there is, can you elaborate on that a little. No pressure....Just whenever you find some time.

 

[Soulsatisfaction]

I have been drawn into some discussions about the beauty of DHT type preamplfiers in recent times. This has happened many times now that I am tempted to try something in the near future. I really like the amplifier I have now but I am quite curious. When I do some R&D, this is what I see.

A summary :

Sound Quality Advantages​

• Transparency and Detail: DHT preamps are praised for their ability to reveal subtle nuances and micro-dynamics in music, offering a "see-through" clarity that indirect-heated triodes (IDHT) often lack.
• Natural Tonality: The direct heating of the cathode eliminates the intermediary cathode structure, resulting in a more organic, lifelike sound with reduced harmonic distortion.
• Euphonic Character: DHTs like the 45, 2A3, or 300B tubes impart a warm, rich tonal signature that many listeners describe as "musical" or "emotionally engaging.

Challenges and Trade-offs​

• Noise Management: DHTs are inherently noisier than IDHTs, requiring meticulous engineering (e.g., active bias systems, low-noise filament regulators) to achieve silent operation.
• Tube Selection: Only premium-grade DHTs (e.g., TJ Meshplates, NOS 45s) perform optimally, as microphonics and emission noise vary widely between tubes.
• Cost and Complexity: DHT preamps often demand expensive transformers, custom power supplies, and careful tube matching, raising both initial and maintenance costs

Forgive the clinical sounding summary. I got that from an ai tool that do research.

I am curious to hear experiences from people who have seen massive improvement with DHT type preamps in their personal systems.

DHT is like if you are into then there is no other option which will make you satisfied.
Question is not only with preamp your entire chain must compliment DHT amp.
Then will only preamp will do may or may not be. Your power amp also plays a big role.
Noise and hum is more character of DHT amps and then what heater circuit you are going to use. Is it AC or DC.
I have amp where all DHTs are used. Driver tubes 45/2a3.
Above then what speakers are we planning to hookup with DHT. That will be a game changer.
If someone hooks up conventional box speakers then chances are you may miss what you are looking for.
Try and experience yourself whenever you get a chance and then you will become advocate of DHT.
It’s like using iPhone then you don’t look for options.
Hope I have understood your question and replied accordingly.
If you are in India and Bangalore sometime come and have experience at my place.

 

[captrajesh]

DHT is like if you are into then there is no other option which will make you satisfied.

If you are in India and Bangalore sometime come and have experience at my place.

Which DHT preamp do you have?

 

[yogibear]

Audio world can surprise you any time and change your high held beliefs. My own experience has been bizarre. And it comes from, (apart from occasional off shelf purchase), last three decades of DIY and now more than a decade of intensive tube world adventures. DHT on one hand gives you a very natural relaxed sound but that’s not the only option. I have played DHT with very high dB speakers, over 108dB of line array open baffles to simple triodes driving 88dB bookshelves.

So far have crafted and optimized three different tube preamp designs, DHT, and two with a single 6SN7, output transformer coupled and capacitor coupled. The latest being 6SN7 capacitor coupled, where each section of triode drive each channel. A single tube does it all. Th Sonics have been shocking and can stand up to best of DHT sound and much more. Imaging and soundstage is next to none with all instruments taking up their own place. Vocals have been the biggest surprise. Frequency response from 20hz to 80Khz with excellent gain and THD figures.

In amplification part, for me after experiencing tube 45, 300B and 2A3, nothing comes closer to EL84 and the beefy F2a smashes all the competition.

Next in line are two lower powered tubes, tube 46 and WE 349a amplifiers. Though I indulge in high powered SE amps only, above two are exceptions.

Just sharing my own hands on experience.

 

[AP@1992]

I have moved to a all DHT pre/power amplification. If the speaker is up to the task, this is one of the most beautiful sounding amplication money can buy. Low distortion. High resolution yet somehow sounding pleasant and musical.