• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Very basic question: What is a "DHT" preamp?

Status
Not open for further replies.
Jump to Latest
myleftear

myleftear

Member
Joined 2017
Paid Member
#1
Hi friends
As I once again surfed around (on the quest for whatever wonderful project came to light), I found "DHT preamp".
Many experts seem to casually talk about, but there seems to be no description of what a "DHT preamp" even is.

"Digital Home Theater Preamp" ?

Must be something much more, ahem, intricate!
Thanks for shedding light on this!
david
 
#3
DHT stands for "directly heated triode". These are the old style tubes that some prefer to use although they are somewhat noisy and/or microphonic and therefore difficult to use successfully. It is a matter of looks plus perceived sound quality that makes them coveted.
 
#5
FullRangeMan said:
DHT tubes have no filament to heat cathode, the Cathode is heated directly hence the acronym.
Very good sound tubes.
Click to expand...

Um, sorry… b-b-b-bûllsnot. You probably should have worded that as,

DHT = Direct Heated Triodes have ONLY a filament. It serves both as 'heater' and source of electrons. Most DHT tubes (all except antiques) have some variation on 'thoriated filament' as well. It was found early on that impregnating the filament wire with a high amount of thorium substantially increased emission (at a given temperature), thus allowing lower temperature filaments to do the job, and last far longer than untreated filaments.

The “sound” of DHT triodes can be as subtle as you care to design, or as substantial as you might creatively desire. That part is up to your design. The downside of DHT tubes, especially in preamplifiers, and very much especially in PHONO stages is that the naked filament wire unless run on a heavily regulated DC source, can pick up substantial hum from the A/C passing thru the filament wires.
_______

That's better. Hope it helps clear things up.

GoatGuy
 
Status
Not open for further replies.
Top Bottom