Mono 300B SE Amplifier

[JPS64]

Starting today.

To understand: new DHT supply (thread in this forum).

HV supply from french LED magazine.

No electrolyt capacitors (customer can choose the type).

Try to find the best choice: Mundorf, WIMA MKS4, EPCOS MKP).

CMC tube socket, AMTRANS resistor, MILLS resistor.

Power components on top side.

Reduced cabling.

Any suggestion?

Attachments: first 3D View...

[JosM]

I have build a SE 300B monoamp by myself using Sowter "potted" output transformers and Sowter powertransformers with very good experience. For my brother I have build a SE 300B monoamp using ae-europe output and powertransformers, also with good experience. Mundorf caps are well.

[Green77]

I just finished my 300 amp. Used Mundorf Supreme but change them to Mundorf Supreme silver/oil just for test... IMO it was a big diffrent in sound..to the better

[JPS64]

The coupling capacitor between 6SN7 and 300B is silver/oil grade. The other ones are today WIMA MKS4 and EPCOS MKP DC Link. No electrolyt capacitor for the moment.

I am try to understand the design of Rob Coleman DHT Gyrator/Current Sink for physical implementation on this board.

[tomchr]

Schematic?

[JPS64]

This weekend the HV power supply and the heather supplies (prepared for RC´s DHT Heather design).

I try to publish the schematics beginning next week...

[JPS64]

Heather 6SN7: Salas low voltage regulator?
DHT 300B: Rob Coleman DHT Heather?

Or LiFePO4 Batterie pack (16Ah) as voltage source on f+ and adapted current sink on f-?

Meanwell COTS charger allowing rapid charging!

[kmaier]

It's not clear what, if any, design goals you have for such an amplifier. Have you given any thought to performance specifications, i.e., s/n ratio, freq. response, output power, distortion limits, etc.... or even a circuit topology? I'm not trying to rain on your parade, but you seem to be grasping at ideas for pieces of an amplifier and see what everyone thinks will work best. Having a set of (practical) design goals seems a logical starting point, otherwise you're going down a path of "designed by committee".

Regards, KM

[Palustris]

"The coupling capacitor between 6SN7 and 300B is silver/oil grade."

If I were starting to design a new SE 300B power amp, the last circuit topology I would choose would be to cap couple the driver tube to the grid of the output tube. The very best sounding most revealing capacitor is NO cap. Don't even consider cap coupling; direct coupling is an order of magnitude better.

The reason is not just because a capacitor doesn't sound as good as no capacitor; just as important is the fact that the 300B starts to draw grid current way before the grid reaches 0V. To get the best from the 300B you have to have a low DC path to ground so that grid current doesn't upset the bias of the tube causing distortion. At the very least, if you insist on cap coupling you will need a grid choke.

I would suggest either the monkey/DRD topology or stacked supplies as in the Komuro 300B.

[tomchr]

Originally Posted by Palustris

The very best sounding most revealing capacitor is NO cap. Don't even consider cap coupling; direct coupling is an order of magnitude better.

I second that opinion. Here's my schematic: DC coupled 300B idea - request for comments

I've made tweaks since then and will update the schematic eventually. Currently, I'm working on the power supply for it. I've had it running on lab supplies and it sounds very good to my ears. You can use any high-mu triode, I just dropped a 5842 in there as I had simulation models for it. If you don't mind the lower sensitivity, you can even use a 6J5 or half a 6SN7 to drive it.

~Tom