Okay, thanks.
In technical data of Linn says output level is 0.5V, so, I made wrong conclusion. Further reading revealed that Line stage has 7dB gain, so it will do just fine with my CD output.
I am so much looking forward to evening listening hours (I have no neighbours, and familly is used to 🤣).
Thanks!
In technical data of Linn says output level is 0.5V, so, I made wrong conclusion. Further reading revealed that Line stage has 7dB gain, so it will do just fine with my CD output.
I am so much looking forward to evening listening hours (I have no neighbours, and familly is used to 🤣).
Thanks!
Excellent news!This is a good time to let people know that the output stage kits (for those with
their own TO-3 Vfets are close to done and will be shipping to the store shortly.
I have friends waiting. This amp, modest it may be, is a precious
I took up Mark’s challenge to ruin his Tuba-Filter with unnecessary and superfluous parts.
Notes:
Terminal block footprint for either 6.35 or the usual 5mm
4-pole cap on output
Heatsink part of the ground
Kemet R75G14100 1uF cap ESR 4.8mO
Potentially can use Wima DCLink 40uF at C4 and output
Bourns 3266W trimpot either 1K solo or 5K in parallel with 1.5K resister. I noticed this footprint is different than the one on Marks Tuba PCB
Notes:
Terminal block footprint for either 6.35 or the usual 5mm
4-pole cap on output
Heatsink part of the ground
Kemet R75G14100 1uF cap ESR 4.8mO
Potentially can use Wima DCLink 40uF at C4 and output
Bourns 3266W trimpot either 1K solo or 5K in parallel with 1.5K resister. I noticed this footprint is different than the one on Marks Tuba PCB
Attachments
This is a good time to let people know that the output stage kits (for those with
their own TO-3 Vfets are close to done and will be shipping to the store shortly.
Could Diyers with Vfet"s buy in the store and build Vfet amp with original Mr. Pass design front-end pcb's ?
This may have been covered before. I have a nice trafo I lifted from a broken Cambridge Audio amplifier. I was thinking of building a linear PS for this VFET amplifier
The amplifier had a power consumption of 250W printed on its back. The trafo looks to be around 250VA power rating.
I see the Meanwell has an output of 4.44A or 160W max. Could the trafo that I have be potentially suitable for this amplifier?
It has 2 x outputs of 29VAC, so if its suitable, I will need to step the DC output voltage down to 36VDC with some regulation
The amplifier had a power consumption of 250W printed on its back. The trafo looks to be around 250VA power rating.
I see the Meanwell has an output of 4.44A or 160W max. Could the trafo that I have be potentially suitable for this amplifier?
It has 2 x outputs of 29VAC, so if its suitable, I will need to step the DC output voltage down to 36VDC with some regulation
I would agree, 250VA is just within range of being able to drive two channels of a VFET amp.
Best to have a second chassis to make an external PSU. Without getting into the complexity of regulation, you could try a CLC filter in the second chassis with the power traffo, then separate RC filters for each channel inside the main VFET amp chassis. Something like 33,000 uF on either side of a Hammond 196Q2 (coils wired in parallel), followed by 0.2 Ohms feeding 15,000 uF to 30,000 uF per channel inside the VFET chassis. Adjust to get the voltage close enough. Depending on what you use for the rectifiers, you should be pretty close with what I've recommended. 37V is Ok, that's where mine is running these days.
Should sound really nice..
Best to have a second chassis to make an external PSU. Without getting into the complexity of regulation, you could try a CLC filter in the second chassis with the power traffo, then separate RC filters for each channel inside the main VFET amp chassis. Something like 33,000 uF on either side of a Hammond 196Q2 (coils wired in parallel), followed by 0.2 Ohms feeding 15,000 uF to 30,000 uF per channel inside the VFET chassis. Adjust to get the voltage close enough. Depending on what you use for the rectifiers, you should be pretty close with what I've recommended. 37V is Ok, that's where mine is running these days.
Should sound really nice..
Another query about this linear power supply.
I have the trafo, diode bridge and large caps all set up, Im getting almost 40VDC on each rail, so I need to drop about 3-4VDC on each rail.
I was thinking of using a LM317 & LM337 (with the appropriate resistors) on each rail - however these are rated at a max current of 1.5A each.
I see in Nelsons notes that each channel of this amplifier draws 1.6A at 36VDC.
Do I need to move to higher-current voltage regulation devices for an extra safety margin?
thanks again
I have the trafo, diode bridge and large caps all set up, Im getting almost 40VDC on each rail, so I need to drop about 3-4VDC on each rail.
I was thinking of using a LM317 & LM337 (with the appropriate resistors) on each rail - however these are rated at a max current of 1.5A each.
I see in Nelsons notes that each channel of this amplifier draws 1.6A at 36VDC.
Do I need to move to higher-current voltage regulation devices for an extra safety margin?
thanks again
Is the 40VDC with the power supply unloaded? The voltage will drop some with load.
Is your supply CRC or just C?
You can lower the output voltage by adjusting the R in a CRC filter. Increasing R to drop voltage will also improve filtering resulting in less voltage ripple.
Using Ohm's Law, V = I x R, and knowing the current draw is 1.6A, a 2 Ohm resistor will drop 1.6A x 2 Ohm = 3.2V
Is your supply CRC or just C?
You can lower the output voltage by adjusting the R in a CRC filter. Increasing R to drop voltage will also improve filtering resulting in less voltage ripple.
Using Ohm's Law, V = I x R, and knowing the current draw is 1.6A, a 2 Ohm resistor will drop 1.6A x 2 Ohm = 3.2V
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The LM317 would not be suitable for this application. If you feel the need to try a regulator, the LM1084 would be the one.
Either way, I will recommend a CRC or perhaps a CRCRC supply, instead of a regulator. My work with the ACA left me with the conclusion that even an LM1084 sounds inferior to a simple filtered supply. Using CRC or CRCRC, the R values may be adjusted to keep the output stage voltage from 36V to 36.5V or so. The current draw will be 1.6A or slightly higher. As others have mentioned, the PSU voltage will drop under full load.
Either way, I will recommend a CRC or perhaps a CRCRC supply, instead of a regulator. My work with the ACA left me with the conclusion that even an LM1084 sounds inferior to a simple filtered supply. Using CRC or CRCRC, the R values may be adjusted to keep the output stage voltage from 36V to 36.5V or so. The current draw will be 1.6A or slightly higher. As others have mentioned, the PSU voltage will drop under full load.
Thanks everyone, so it looks like I will be going with the resistor option; one 50W/2 ohm finned chassis mount resistor on each voltage rail.
At this stage, the powers supply is very simple: the trafo going to a bridge, then to a large 20000uF cap on each rail, centre tap from the trafo conencted.
At this stage, the powers supply is very simple: the trafo going to a bridge, then to a large 20000uF cap on each rail, centre tap from the trafo conencted.
Yes it was measured unloaded - to be exact I am measuring about 39.5VDC unloaded.
I thought the same thing about the voltage drop once the boards are connected, however, I figured I would experiment with resistors to see how much voltage drop I need (ie: start with 1 ohm). Just a bit cagey about connecting to the amplifier modules as is, as Im not sure what the max voltage is that I can feed them.
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