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Low TIM, low distortion hybrid front-end
Low TIM, low distortion hybrid front-end
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Old 19th June 2014, 10:22 PM   #11
vzaichenko is offline vzaichenko  Russian Federation
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Quote:
Originally Posted by 5th element View Post
Don't start with valves, I've always been curious about the little glowing things used as a small signal front end >.< Trouble is I'd want them visible haha.
Right, watching the glowing tubes is fun )

Some time ago I came across a picture somewhere on the internet, showing an amp's front panel with two windows (left <-> right) and titles under those windows:

You look at tubes <-> Tubes look at you

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Old 19th June 2014, 11:21 PM   #12
still4given is offline still4given  United States
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Hi Valery,

Are you going to do Gerbers for this too? If it will be soon I would like to include them with the Low TIM order to save on shipping time and cost.

Thanks, Terry
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Old 19th June 2014, 11:33 PM   #13
vzaichenko is offline vzaichenko  Russian Federation
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Originally Posted by still4given View Post
Hi Valery,

Are you going to do Gerbers for this too? If it will be soon I would like to include them with the Low TIM order to save on shipping time and cost.

Thanks, Terry
I'll do my best to develop them over the weekend. Will keep you posted
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Old 19th June 2014, 11:40 PM   #14
still4given is offline still4given  United States
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Awesome!!!!
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Old 19th June 2014, 11:58 PM   #15
Ranchu32 is offline Ranchu32  Australia
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Valery, please add my name to the Gerber list - I'd like to order some boards too, once the design is worked through.

A few questions about the schematic:
- Can this work with lower voltages, or are the 70V rails needed for the valves?
- I know next to nothing about valves however looking at the datasheet for this device it states that DC plate voltage as 300V. Is an auxilliary power supply required?
- I don't see any rail filtering caps in the schematic. Have these been removed for Spice modelling - i.e. the actual schematic will have these components.
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Old 20th June 2014, 05:54 AM   #16
jerluwoo is offline jerluwoo  United States
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No one one seems to have mentioned that the output will be latched to the positive rail for the first 6 secs. or so after power up when the tube is not yet conducting. Need to have the heater supply power up about 10 secs. before the main power or something to that effect.
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Old 20th June 2014, 06:26 AM   #17
vzaichenko is offline vzaichenko  Russian Federation
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Quote:
Originally Posted by Ranchu32 View Post
Valery, please add my name to the Gerber list - I'd like to order some boards too, once the design is worked through.

A few questions about the schematic:
- Can this work with lower voltages, or are the 70V rails needed for the valves?
- I know next to nothing about valves however looking at the datasheet for this device it states that DC plate voltage as 300V. Is an auxilliary power supply required?
- I don't see any rail filtering caps in the schematic. Have these been removed for Spice modelling - i.e. the actual schematic will have these components.
Yep, you're in the list )

- Right, it would be not so good having less than 60V for the valves (actual anode voltage is even less than that)
- 300V is the maximum value, we are far below
- You're right, filtering caps are not shown for modeling purposes (they increase initial setting-up significantly) - I will add them to the final schematic
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Old 20th June 2014, 06:32 AM   #18
vzaichenko is offline vzaichenko  Russian Federation
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Quote:
Originally Posted by jerluwoo View Post
No one one seems to have mentioned that the output will be latched to the positive rail for the first 6 secs. or so after power up when the tube is not yet conducting. Need to have the heater supply power up about 10 secs. before the main power or something to that effect.
Absolutely right. I will test the actual time on a prototype. I use a microcontroller-managed soft-start and protection, so adding this function will not be a problem.

As a simplest solution, delay for connecting the speakers may be increased as required.
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Old 20th June 2014, 07:15 AM   #19
still4given is offline still4given  United States
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Seems a DC speaker protection circuit would take care of that problem.
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Old 20th June 2014, 07:18 AM   #20
vzaichenko is offline vzaichenko  Russian Federation
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Seems a DC speaker protection circuit would take care of that problem.
Yes, just may require a longer delay. We'll see how much longer...
I mean, it is normally combined with soft-start, providing delay before connecting the speakers at power-on
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Last edited by vzaichenko; 20th June 2014 at 07:23 AM.
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