Thank you for the replies Ben & pinholer.
I usually run push pull, I haven't played much with single ended but I do like the sound of my MoFo's.
The reason I asked is because I'm planning on building a DC coupled THF51-S source followers with CCS, plus an active front end and global feedback, I'm trying to avoid chokes as I'd like to be able to pick it up when it's finished. I already have a bad back
I usually run push pull, I haven't played much with single ended but I do like the sound of my MoFo's.
The reason I asked is because I'm planning on building a DC coupled THF51-S source followers with CCS, plus an active front end and global feedback, I'm trying to avoid chokes as I'd like to be able to pick it up when it's finished. I already have a bad back
How could I miss this thread for all this time?! Great work Ben, I’ll study the details of your measurements and implementation for sure. Thanks for sharing the fruits of your knowledge with the community. There are always snippets and details from your posts that I pocket into my grey matter for future experiments and explorations ;-)
Best,
Anand.
Best,
Anand.
The reason I asked is because I'm planning on building a DC coupled THF51-S source followers with CCS, plus an active front end and global feedback, I'm trying to avoid chokes as I'd like to be able to pick it up when it's finished. I already have a bad back
Please let us know if you could successfully finish DC coupled version with CCS.
Toasty
Yes, and an oven.. We're building up a truck camper, and when I saw there was a "Turbo" mode on this, I couldn't resist (intended)
Yes, and an oven.. We're building up a truck camper, and when I saw there was a "Turbo" mode on this, I couldn't resist (intended)
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That may take a while, I was going to build a steam punk chassis, but decided the VFET chassis are much more elegant.
It's a variation on my power amp - Frank(enstein), I don't want to pollute the thread, If your interested, please forward your email by PM and I'll forward the schematic.
Sorry Ben, somehow I read the 193V numbers wrong...wouldn't want to suggest you use a lessor part!
BTW, I have a 193V that should be here in a couple of days to play with your topology.
Thanks again for your awesome explorations and sharing!
It is a matter of taste.... for me the sound of the choke was more powerful, sound is darker.
The change from resistors to choke using the same SIT is a fairly big change in sound.
But.... I did this around 2012 and I have to trust my memory.
But you can find similar impressions from other people in the old SIT threads from Mike (Michael Rothacher)
The change from resistors to choke using the same SIT is a fairly big change in sound.
But.... I did this around 2012 and I have to trust my memory.
But you can find similar impressions from other people in the old SIT threads from Mike (Michael Rothacher)
I'm curious if you can do the same to the BAF2015. I'm sure it works fine, just not sure if you connect the - side of the 1000uF to GND or to the Source. F6 has it connected above the lower Source resistor. 195T10 and watercooling....?
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I think it should work too. It seems to me that the connection should be to ground as the transformer secondary should be grounded. But someone that knows for certain should verify that.
The bias voltage will need adjustment as the choke will drop voltage and put a DC voltage at the source and affect the Vgs. Vgs=Vg-Vs so the gate bias voltage will need to be increased to offset the voltage at the source.
It will also affect the voltage seen by the zener and that may need to be a higher voltage. The Mosfet is an enhancement mode device whereas SITs are depletion mode. The the behavior will be different. I can't help you there as I haven't figured out the zener in my amp yet. With the zener in place, when I shorted the input, the Iq increased. With the zener out, shorting the input did not affect Iq. So the zener is out of my amp for now until I figure it out.
The bias voltage will need adjustment as the choke will drop voltage and put a DC voltage at the source and affect the Vgs. Vgs=Vg-Vs so the gate bias voltage will need to be increased to offset the voltage at the source.
It will also affect the voltage seen by the zener and that may need to be a higher voltage. The Mosfet is an enhancement mode device whereas SITs are depletion mode. The the behavior will be different. I can't help you there as I haven't figured out the zener in my amp yet. With the zener in place, when I shorted the input, the Iq increased. With the zener out, shorting the input did not affect Iq. So the zener is out of my amp for now until I figure it out.
Fokin Distortion Measurements Part 1
I started to measure the Fokin amps the other day and realized that it was not as simple to do as I thought. Since I have 103dB sensitive speakers, I do not need a lot of power to get them loud. As a follower amplifier the Fokin does not have any voltage gain. Because my Luminaria preamp has enough voltage output to drive the amplifier and speakers to good volume in my room, I did not include a voltage gain stage in the Fokin.
For distortion measurements I have a low distortion 1000 Hz oscillator that outputs a maximum of 2.5Vrms. Since 2.83Vrms into 8 Ohms is 1 Watt, the oscillator by itself cannot even drive the amplifier to 1 W output into 8 Ohms. That does not even take into consideration that the voltage output of a follower amplifier is slightly less than the voltage input.
I first thought of using my ACP+ headphone amp/preamp for voltage gain but it only has a gain of 9dB (2.8X) which would give 7.0Vrms. However, 7.0Vrms is beyond the capability of the ACP+. Furthermore even if possible, 7.0Vrms would get about 5W out of the Fokin.
So Plan B was to use the Luminaria. It has a gain of 7X so a maximum of 17.5Vrms may be feasible. In reality I found out that 17.5Vrms exceeded the capabilities of the Luminaria. It can do 7X at a lower input voltage, but the 7X 2.5Vrms output was at its voltage output limit and thus also outputted a very high level of distortion.
So here are the harmonic distortion measurements. I have included 1W measurements of the ACP+/Fokin and Luminaria/Fokin for comparison. The ACP+ has much lower distortion than the Luminaria and that is reflected in the measurements. I believe the Fokin has lower distortion than the ACP+ and Luminaria and I will try to show that in my Part 2 post. I have only shown measurements up to 10W output because right now I do not have a voltage amplification stage that can output the voltage to drive the Fokin to 25W output. More to come on that.
So the following measurements of the Luminaria/Fokin combination show what my speakers see and hopefully for the most part what I hear.
Stay tuned for Part 2.
I started to measure the Fokin amps the other day and realized that it was not as simple to do as I thought. Since I have 103dB sensitive speakers, I do not need a lot of power to get them loud. As a follower amplifier the Fokin does not have any voltage gain. Because my Luminaria preamp has enough voltage output to drive the amplifier and speakers to good volume in my room, I did not include a voltage gain stage in the Fokin.
For distortion measurements I have a low distortion 1000 Hz oscillator that outputs a maximum of 2.5Vrms. Since 2.83Vrms into 8 Ohms is 1 Watt, the oscillator by itself cannot even drive the amplifier to 1 W output into 8 Ohms. That does not even take into consideration that the voltage output of a follower amplifier is slightly less than the voltage input.
I first thought of using my ACP+ headphone amp/preamp for voltage gain but it only has a gain of 9dB (2.8X) which would give 7.0Vrms. However, 7.0Vrms is beyond the capability of the ACP+. Furthermore even if possible, 7.0Vrms would get about 5W out of the Fokin.
So Plan B was to use the Luminaria. It has a gain of 7X so a maximum of 17.5Vrms may be feasible. In reality I found out that 17.5Vrms exceeded the capabilities of the Luminaria. It can do 7X at a lower input voltage, but the 7X 2.5Vrms output was at its voltage output limit and thus also outputted a very high level of distortion.
So here are the harmonic distortion measurements. I have included 1W measurements of the ACP+/Fokin and Luminaria/Fokin for comparison. The ACP+ has much lower distortion than the Luminaria and that is reflected in the measurements. I believe the Fokin has lower distortion than the ACP+ and Luminaria and I will try to show that in my Part 2 post. I have only shown measurements up to 10W output because right now I do not have a voltage amplification stage that can output the voltage to drive the Fokin to 25W output. More to come on that.
So the following measurements of the Luminaria/Fokin combination show what my speakers see and hopefully for the most part what I hear.
Stay tuned for Part 2.
