Hi All,
At the moment I use a Little Dot MK2 with a pair of KLH ultimate One headphones. While I love the cans they are a bit of a bugger to drive at 32ohms and can cause clipping when playing music that's a bit busy and loud.
To that end I fancy building my own amp that will drive them and have been looking at the schematic of the Darkvoice 336se for inspiration as I already own some nice NOS 6080s and 6SN7GTs.
My question is that I can see the output caps are 30uf per channel so would upping the values help to drive my 32ohm cans without clipping? If not, how would you go about it?
At the moment I use a Little Dot MK2 with a pair of KLH ultimate One headphones. While I love the cans they are a bit of a bugger to drive at 32ohms and can cause clipping when playing music that's a bit busy and loud.
To that end I fancy building my own amp that will drive them and have been looking at the schematic of the Darkvoice 336se for inspiration as I already own some nice NOS 6080s and 6SN7GTs.
My question is that I can see the output caps are 30uf per channel so would upping the values help to drive my 32ohm cans without clipping? If not, how would you go about it?
Hehe - I've spent a good year+ looking at this.
Probably the best option to reduce output impedance and current driving ability is to either (a) parallel output tubes, (b) add a solid state cathode follower.
If you go push-pull and use a mosfet cathode follower just consider when the switching occurs as this can change the output impedance as the different tubes and fets switch in and out. However this complicates the amp itself with phase splitting etc.
Using parallelled 6800 (ie both triodes are used for each channel) just check the combined capacitance of the grids as this will act as a low pass filter if there's any resistance ahead of the 6800. Adding a gate resistor also helps add low pass filtering.
In terms of output caps, for 32ohm you may want to increase to something like 2200uF to prevent low roll off.
Probably the best option to reduce output impedance and current driving ability is to either (a) parallel output tubes, (b) add a solid state cathode follower.
If you go push-pull and use a mosfet cathode follower just consider when the switching occurs as this can change the output impedance as the different tubes and fets switch in and out. However this complicates the amp itself with phase splitting etc.
Using parallelled 6800 (ie both triodes are used for each channel) just check the combined capacitance of the grids as this will act as a low pass filter if there's any resistance ahead of the 6800. Adding a gate resistor also helps add low pass filtering.
In terms of output caps, for 32ohm you may want to increase to something like 2200uF to prevent low roll off.
JMO, stop shoveling dung against the tide. Build Sheldon Stokes' Headphone amp. I have 1 and have used it with great pleasure in combination with low impedance Grado and Sennheiser "cans".
As the man said, it doesn't sound like "sand".
As the man said, it doesn't sound like "sand".
Class A and should you want there's always the option of putting a tube on the front end.. Actually having a hexagon of fet heatsinks with the tube in the middle...
John Broskie TubeCad Journal did an analysis of the dark voice circuit with improvements. There is a very similar circuit I think Bottlehead Crack? The darkvoice has generally gotten "meh" "dubious" "mixed" reviews from DIY builders, probably not worth it as shown. But I am planning a 6AS7 HPA someday, so adding this article to the research.
Cathode-Follower OTL and SIT FETs
Just to add - there is a follow up article for the “V8” parallel tube that shows that final circuit design (isolates each output tube).
Is that a different issue altogether or at the bottom of this one? Do you have a link?
More OLT Design
Here you go.
This is a paralleled output - look at each output tube. They are connected separately so the tube power can be tuned and equalised.
Here you go.
This is a paralleled output - look at each output tube. They are connected separately so the tube power can be tuned and equalised.
Have a look at this thread there's a discussion on this. The White Cathode follower is a good example.
6N3/6N6 headphone amp using PCB.
6N3/6N6 headphone amp using PCB.