Hi everybody
If I take a specific design of 6SL7 driver for 71A
Fixed bias and wish to convert the 6SL7 to 6sn7 what does it takes to change it by a resistors values and capacitors
The dac that I'm talking about is the following:
https://sw1xad.co.uk/products/sw1x-dac-v/
Best regards
If I take a specific design of 6SL7 driver for 71A
Fixed bias and wish to convert the 6SL7 to 6sn7 what does it takes to change it by a resistors values and capacitors
The dac that I'm talking about is the following:
https://sw1xad.co.uk/products/sw1x-dac-v/
Best regards
Certainly some resistor values will need to be changed. 6SN7s will also draw twice the filament current, which may or may not be a problem. The gain of the output will also drop considerably. Why do you want to swap them? That's a very nice and expensive DAC. I don't think it's a good idea to hack up the board. I would certainly consult the manufacturer before changing anything.
I'm interested in this myself and I'm guessing that it would be changes to the cathode and anode resistors. Hopefully those are through hole (unless you're good with SMT - I'm not yet, 🙂 ).
It looks like the manufacturer supplies this DAC with either 6SL7 or 6SN7, so they should know.
Edit: when you say fixed bias, do you mean the DHTs or the 6SL7s themselves? Typically 6SL/N7s are self biased via a resistor (or something like a LED) on the cathode, but AFAIK there's no reason not to measure the tube's current draw and use a small negative voltage to bias it. There would be a trimpot on the board to do that; it makes tube rolling harder of course.
Edit2: or maybe a CCS
It looks like the manufacturer supplies this DAC with either 6SL7 or 6SN7, so they should know.
Edit: when you say fixed bias, do you mean the DHTs or the 6SL7s themselves? Typically 6SL/N7s are self biased via a resistor (or something like a LED) on the cathode, but AFAIK there's no reason not to measure the tube's current draw and use a small negative voltage to bias it. There would be a trimpot on the board to do that; it makes tube rolling harder of course.
Edit2: or maybe a CCS
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Starting with a circuit that uses a 71A, and converting it to use a 6SL7, and then converting again to a 6SN7 might be out of the question.
In order to prove or disprove the possibility of decent performance . . .
A complete and accurate schematic of the DAC and tube circuitry is worth 1000 Words; Also that schematic will save 100 Postings to get a sure answer.
In terms of amplifying, the closest specifications of the 6SL7 and 6SN7 are the Gm of 1600 microMhos and Gm of 2600 microMhos, respectively.
The specifications of plate resistance, rp; and the gain, u, are both extremely dissimilar.
Any circuit that is optimized for one of those tube types, is certainly not optimized for the other tube type.
Sometimes Marketing trades off Optimum Performance for . . . Optimum Sales.
Just my opinions (and the old Marketeer that I used to be).
In order to prove or disprove the possibility of decent performance . . .
A complete and accurate schematic of the DAC and tube circuitry is worth 1000 Words; Also that schematic will save 100 Postings to get a sure answer.
In terms of amplifying, the closest specifications of the 6SL7 and 6SN7 are the Gm of 1600 microMhos and Gm of 2600 microMhos, respectively.
The specifications of plate resistance, rp; and the gain, u, are both extremely dissimilar.
Any circuit that is optimized for one of those tube types, is certainly not optimized for the other tube type.
Sometimes Marketing trades off Optimum Performance for . . . Optimum Sales.
Just my opinions (and the old Marketeer that I used to be).
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grovergardner
Thanks for your reply
However this dac V can also comes with 6sn7 version which is more expensive
More ever the manufacturer don't share much of values to interchange them,
Rockies 914
The 6SL7 is fixed bias by small battery but the 71A is auto bias
All the wiring is solder point to point and there is no pcb or no trim pot.
Thanks for your reply
However this dac V can also comes with 6sn7 version which is more expensive
More ever the manufacturer don't share much of values to interchange them,
Rockies 914
The 6SL7 is fixed bias by small battery but the 71A is auto bias
All the wiring is solder point to point and there is no pcb or no trim pot.
If the modification is proprietary then I wouldn't try to change it myself. I'm not sure there would be any sonic benefit and you'll degrade the value of the piece.
That said, if you know what the circuit is, anything is possible. But I don't think any of us could guess what would be involved.
That said, if you know what the circuit is, anything is possible. But I don't think any of us could guess what would be involved.
6A3sUMMER
As I have mentioned there is a version of this dac with 6sn7 which is more expensive version
So I guess this baby can fly 😎
As I have mentioned there is a version of this dac with 6sn7 which is more expensive version
So I guess this baby can fly 😎
montana,
I think you are correct, my old Post # 4 was wrong.
I have since Edited it.
$$$ makes many things possible, but you will have an extremely tough time trying to convert the less expensive 6SL7 to a 6SN7 version.
At the very least, you need 2 (Two) complete and accurate schematics.
If you think you can $ave money by taking the 6SL7 version and converting it to a 6SN7 version, I hope you can succeed.
Time is $ money
Parts is $ money
Doing a conversion might be more: "Plug and Pray"; Versus doing "Plug and Play".
Good luck and happy listening.
I think you are correct, my old Post # 4 was wrong.
I have since Edited it.
$$$ makes many things possible, but you will have an extremely tough time trying to convert the less expensive 6SL7 to a 6SN7 version.
At the very least, you need 2 (Two) complete and accurate schematics.
If you think you can $ave money by taking the 6SL7 version and converting it to a 6SN7 version, I hope you can succeed.
Time is $ money
Parts is $ money
Doing a conversion might be more: "Plug and Pray"; Versus doing "Plug and Play".
Good luck and happy listening.
It will work.
I am glad you want to learn. I am not sure how much you already know.
But . . . you have to change just about Everything.
Plate current (more B+ current for the 6SN7, do not overheat the B+ power supply).
Bias voltage
Plate load resistance
The number of stages of gain that are required to get the gain you need.
Filament current (don't over heat a 6SL7 filament winding by putting a 6SN7 filament across the winding).
Making a tube amplify is one thing, making it perform well is another:
Gain, harmonic distortion and intermodulation distortion, maximum output signal voltage swing, frequency response, impedance that can drive the next stage, etc.
6SL7 u = 70; Gm = 1600 microMhos; Plate resistance, rp, 44,000 Ohms
6SN7 u = 20; Gm = 2600 microMhos; Plate resistance, rp, 7,700 Ohms.
Putting a 6SN7 into a 6SL7 circuit is just like:
Changing out a 4.11 ratio rear axle, and replacing it with a 2.0 ratio rear axle. The motor and the clutch will not like it.
Have you ever drawn a load line on the plate curves graph?
Do not forget to include the next stage's input impedance that is in parallel with the plate load resistor (at least the grid's Rg to ground).
I am glad you want to learn. I am not sure how much you already know.
But . . . you have to change just about Everything.
Plate current (more B+ current for the 6SN7, do not overheat the B+ power supply).
Bias voltage
Plate load resistance
The number of stages of gain that are required to get the gain you need.
Filament current (don't over heat a 6SL7 filament winding by putting a 6SN7 filament across the winding).
Making a tube amplify is one thing, making it perform well is another:
Gain, harmonic distortion and intermodulation distortion, maximum output signal voltage swing, frequency response, impedance that can drive the next stage, etc.
6SL7 u = 70; Gm = 1600 microMhos; Plate resistance, rp, 44,000 Ohms
6SN7 u = 20; Gm = 2600 microMhos; Plate resistance, rp, 7,700 Ohms.
Putting a 6SN7 into a 6SL7 circuit is just like:
Changing out a 4.11 ratio rear axle, and replacing it with a 2.0 ratio rear axle. The motor and the clutch will not like it.
Have you ever drawn a load line on the plate curves graph?
Do not forget to include the next stage's input impedance that is in parallel with the plate load resistor (at least the grid's Rg to ground).
6SL7 has a higher mu than 6SN7, as well as a higher plate resistance. It may not play well as a direct replacement for 6SN7.