sound of 45 v. 205d v. 2a3 v. 300b for headphones

[rcavictim]

For a headphone amp the lowest noise floor is of paramount importance so I'd be thinking in terms of operating off gel cell batteries. When the unit is turned off the batteries can be switched to a battery charging circuit from the mains plug in and completely disconnected and floating from both sides of the mains while operational.

In addition to the DHT's you mentioned the 1619 is a DH tube with a 2.5 volt filament that may be of use here. It is a transmitting power pentode that looks like a metal 6L6. It can be also used wired as a triode. I have some NIB and have interest in experimenting with them someday when I have time. Steve Bench has found they adapt well to starved filament operation resulting in way reduced harmonic distortion when used as line and pre-amplifiers.

 

[Tweeker]

Direct heated filaments are best powered by three Oompa Loompas turning a Bakelite capstan.

 

[dsavitsk]

For a headphone amp the lowest noise floor is of paramount importance so I'd be thinking in terms of operating off gel cell batteries.

It's an interesing idea, but I'd rather use AC until I discover that I can't make it work.

So, back to that schematic:

is that correct, or do I have something wrong?

In addition to the DHT's you mentioned the 1619

Looks interesting (and cheap.) I'll add it to the list of tubes to try.

 

[byang]

205D not suited for headphone/pre-amp

I have built headphone/pre amp using 205D, 6em7 and 26.

here's my impression of the amps built with those tubes:
205D has very relaxed sound. However, very noisy and bottom end is missing.
6em7 has very hifi sound. good highs and lows.
26 was my favorite: best middle and warm bottom. High is very smooth.

forget about using 2A3 and 45 for pre/headphone amps . those tubes are one level below the 3 tubes above sound quality wise. They are designed for more power and sacrificed flat frequency response.

 

[andyjevans]

It doesn't surprise me that the 26 would come up top. It's my standard preamp tube. But I'm just as keen on the 4P1L in triode.

 

[farhun]

I'm currently looking into schematics and opinions about building a headphone amp out of #26 and 45(or 4P1L). The output should suit a range of impedances since I have one AKG Q701 which is 62ohms, and two beyer DT770s 300 and 600 ohms. These days I'm checking older topics such as "The all DHT SET Headphone Amp" and "#26 pre amp", both are quite long!

I welcome any advise, schematics, and insight.

I wish dsavitsk could share more insight about his experience with this hp amp he was building in 2006 too...