Total Domination VFET (TDV) Amp (using 2SK2087C)

[rickmcinnis]

Rahul,

I am using the B- version of the TDV where you recommended 6.2K Ohms for the input load resistor - I am either using one of that value or 6.7K - I am wondering if one can go lower than that?

Over the weekend I thought I would see what happens when I replace what was a 2.5 uF DUELUND capacitor with one sized for a 2000 Hz high pass, .01uF. I have these great silver micas I got from Mr. Yazaki at SPEC CORP so that is what I inserted.

I figured instead of using the DSP box to do all of the frequency levelling the cap would take some of the attenuation load from the DSP. It does - I am able to eliminate half of the PEQs I was using and the resulting response is smoother.

So there are two questions - can you see any pitfall with an input cap of such a small value? I was thinking about lowering the value of the load resistor so I could use a larger capacitor.

It all sounds very good but on the odd occasion I hear a crack from one channel - only once last night. The levels are such that it is not a voice coil slapping the bottom of its gap and I cannot imagine it being a digital overload sound. I worry that it might be suspect soldering - which I will re-solder this evening.

Can you think of any reason this could cause distress with the TDV circuit and what effect would halving the load resistor have?

Do I need to consider power rating of this resistor? I am using a Texas Components Z foil - 0,7 watt.

At your leisure if you think this is worth the time.

Thanks,

 

[ra7]

You can go lower but the preceding stage should be able to drive it. I would say 4.7k is the general limit. Power rating is not so important.

With a smaller resistor, you need a larger coupling cap… this is before finishing morning tea

 

[rickmcinnis]

Thanks, Rahul. The point of lowering it so I could use a larger capacitor - I was worried the capacitor was too small.

Last night no funny noises so I will leave the values where they are - still need to re-solder just to be sure.

Take care,

 

[ra7]

That makes sense, then! Go for it, if needed.

 

[e_fortier]

Hi Rahul

Would you happen to have a graph of the THD vs. Output Power in watts ?

I made some progress on my monoblocs and my friend would like to also build it, he’s got lower efficiency speakers therefore was asking about the output power into 8 ohm. His supply would be 24Vdc biased at about 1.4A per your schematic on post no.26
I’m expecting about 15W but it would be nice if you could confirm.

Thanks
Eric

 

[ra7]

With 1.4A, I would call it a 10 W amp. At higher bias you get more power. Two or 2.5A it will do easily. I have it at 2.2A right now but with the bigger 193V choke. Hope that helps. Sorry, I don’t have such a chart handy ATM.

 

[e_fortier]

Thanks for the info. No need for a chart.

What’s your B+ at 2.2A ?

 

[ra7]

It has dropped to 20V but used to be 25V. Had to use the transformer for horsing around elsewhere. 20-25V is fine. 30V and 2 amps might be getting too much for the device even though it is quite large. On the THF51 and 2sk180, 60W might be fine.

 

[e_fortier]

Perfect, thanks Rahul 👍

 

[e_fortier]

Hi,

Just for fun, below are pics of my TDV monoblocs. Physically they are done, I kept the rugged industrial look, what’s left is the wiring. I’ve never heard a VFET/SIT so I can’t wait.
This design comes from the idea that I had some 0.44c/w heatsinks I wanted to use (6.5” x 6.5” x 7” high) so I managed to have the heatsink being the amp...nothing else needed except the power supply.
Each monobloc will be powered by a 24Vdc, 5A smps + Mark’ Filter.

Thanks to all who made this possible 👍

Older pic showing the top view

Eric

 

[pinholer]

Nice design! I like the industrial look. Form and function in harmony.

 

[Zen Mod]

Just for fun, below are pics of my TDV monoblocs.

Fugly!

 

[ElArte]

This design comes from the idea that I had some 0.44c/w heatsinks I wanted to use (6.5” x 6.5” x 7” high) so I managed to have the heatsink being the amp...n

Where did you get these wild heatsinks?

 

[ra7]

Fantastic! I want to say Fugly but ZM already did!

Many hours of joy ahead!

 

[e_fortier]

Where did you get these wild heatsinks?

It’s a member of Canuck Audio Mart who has a bunch for sale, each heatsink is $4 usd...

 

[PierreQuiRoule]

Just for fun, below are pics of my TDV monoblocs.

Very creative, Eric. I love it!!!

 

[von Ah]

Beautifully done! That’s classy-industrial, which is fitting for the Tokins. 😎

 

[Vunce]

Super cool TDV mono’s Eric!!
Wonderful job!

 

[e_fortier]

Hi guys

Tonight I have finally heard a VFET and I’m thrilled, the sound is not like what I’m used to, it’s very addictive. Thanks a lot RA7, excellent sounding amp.

p.s. I have a big thump when I turn off the DC side (24V) of the power supply via my switch in the front, am I the only one with that issue?

My closing sequence is: Power amp then pre-amp.

I think my sensitive full range probably skipped a heart beat, just like I did...lol

Thanks
Eric

 

[Vunce]

Eric,
Plug your smps bricks into a power strip with a switch. Leave your mono amp power switches on and use the power strip switch to turn them on and off. See if this reduces the thump.