300B amp project

[grovergardner]

See this thread for version #2:

http://www.diyaudio.com/forums/tubes-valves/128047-tips-comments-upcoming-300b-build.html

 

[Hun7er]

Thanks I like also delicacy

I already see Thomas Mayer amp and seems wonderful !

There is several combinaison

26 - 10y or 46 - 300b but costly with filament bias to get the best

alternative are 6n6p or EL84 or EL34

 

[grovergardner]

I was being a little loose with the term "delicacy"--I was picking up on your original post, in which you said you didn't want a thin sound. Anyway, I suggested two ideas that to my ears offer full, rich sound without sacrificing detail. If you want an all DHT amp like Thomas Mayer builds, it's very expensive but can be eextremely beautiful. But they are also relatively low-gain designs and will need a strong preamp.

 

[andyjevans]

I used to live in France (Ardeche) so you have my sympathies!

My own journey went through several 300B and 2a3 amps, PP and SET. The disadvantages for me were 3 stages, indirectly heated tubes and cathode bias with cathode bypass caps.

When I discovered the 4P1L I found solutions:
- 2 stages because the gain of the 4P1L is 10
- PSE output stage is equivalent to a 2a3 (bit more)
- ALL stages can be used in filament bias, so no cathode bypass caps.
- All DHT so very transparent sound with excellent timbre on acoustic instruments
- 4P1L is ridiculously cheap and very robust. You can buy a box full.

There is a thread on 4P1L SE and a few of us have built these since about 2012. I would not go back to 300B or 2a3. I use all Lundahl iron. I've built around 4 of them. The circuit is very simple but the PSU and filament supplies are quite complex.

 

[Hun7er]

Hi,

For me delicacy didn't translate to thin.

Thanks you

I was being a little loose with the term "delicacy"--I was picking up on your original post, in which you said you didn't want a thin sound. Anyway, I suggested two ideas that to my ears offer full, rich sound without sacrificing detail. If you want an all DHT amp like Thomas Mayer builds, it's very expensive but can be eextremely beautiful. But they are also relatively low-gain designs and will need a strong preamp.

 

[Hun7er]

Hi Andy,

My sympathies too I read a lot of your post on this forum and it's very inspiring and interesting with various shootout of topologies and OPT

If someone has an 26 or 201a - 10y or 46 - 300b schematic it would be very helpful.

I already have 4P1L - 4P1L - 300b

Thank you

I used to live in France (Ardeche) so you have my sympathies!

My own journey went through several 300B and 2a3 amps, PP and SET. The disadvantages for me were 3 stages, indirectly heated tubes and cathode bias with cathode bypass caps.

When I discovered the 4P1L I found solutions:
- 2 stages because the gain of the 4P1L is 10
- PSE output stage is equivalent to a 2a3 (bit more)
- ALL stages can be used in filament bias, so no cathode bypass caps.
- All DHT so very transparent sound with excellent timbre on acoustic instruments
- 4P1L is ridiculously cheap and very robust. You can buy a box full.

There is a thread on 4P1L SE and a few of us have built these since about 2012. I would not go back to 300B or 2a3. I use all Lundahl iron. I've built around 4 of them. The circuit is very simple but the PSU and filament supplies are quite complex.

 

[MrCurwen]

Ask for

1) gyrator and CCS fed DC filaments. This adds to the sound quality significantly; removes a lot of IMD and thus improves soundstage.

2) actively regulated B+. Greatly improves dynamics and especially bass quality. Have only a film cap (10µF or so) after the regulator. Greatly simplifies (makes cheaper) PSU preceding reg.

3) source follower driving the 300B grid. Greatly improves transient response. Makes the amp sound a lot 'bigger' than it is, and more 'fast'. Removes annoying sibilance from high register.

4) fixed grid bias. Very easily delivered by the source follower. No need to worry about bass performance or quality issues due to cathode bypass caps.

These things can be implemented to most traditional SE schematics easily. They'll however have your amp punching more than one class above it's weight class.

For best results, I would go even further, but your solder guy would probably talk you out of such things. =)