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29th Mar 2014, 6:47 pm | #1 |
Retired Dormant Member
Join Date: Mar 2014
Location: Wolverhampton, West Midlands, UK.
Posts: 153
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A fun build preamp
Here is a preamp that I built for fun.
I wondered what I could do if I just bought low voltage DC into a preamp. This is what happened.. And yes the main question was how can I build SRRP and get isolation for the heater supply? What did I learn? Don't use low volt DC use low volt AC and transform it.. But it was good fun. However I achieved what I wanted with an inverter etc. And its only got a DC supply. Thinking back it was a moment of madness but that's the fun. Tubeglow. Last edited by Tubeglow; 29th Mar 2014 at 6:55 pm. |
29th Mar 2014, 7:10 pm | #2 |
Retired Dormant Member
Join Date: Mar 2014
Location: Wolverhampton, West Midlands, UK.
Posts: 153
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Re: A fun build preamp
The back of the preamp,
And the Vero board circuits. The B+ is 400V. Maida regulator and decade input selector with debounce. The prism on the top changes colour with input select. You know when you just want to build something different..LOL Glass tile with a sparkle on the front drilled for separate volume controls. Tubeglow. |
30th Mar 2014, 10:19 am | #3 |
Hexode
Join Date: Mar 2014
Location: Fareham, Hampshire, UK.
Posts: 482
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Re: A fun build preamp
Very nice build, Tubeglow. What tubes did you use?
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30th Mar 2014, 10:21 am | #4 |
Retired Dormant Member
Join Date: Mar 2014
Location: Wolverhampton, West Midlands, UK.
Posts: 153
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Re: A fun build preamp
I used ECC88.
EM80 indicators. Tubeglow |
30th Mar 2014, 10:24 am | #5 |
Dekatron
Join Date: Mar 2008
Location: Worthing, West Sussex, UK
Posts: 5,185
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Re: A fun build preamp
I love the use of the EM80's as VU meters, very smart!
Mark |
30th Mar 2014, 6:22 pm | #6 |
Retired Dormant Member
Join Date: Mar 2014
Location: Wolverhampton, West Midlands, UK.
Posts: 153
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Re: A fun build preamp
I guess most know how to do this,
however for those that don't here is decade counter input selector with debounce. You must fit 0.1uF ceramic caps direct across the chips supply rails. To decouple the supply.(direct on the chip base). It drives the relay input card. Just a simple push button to select. The circuit always defaults to input 1 which can be mute or what ever you think. Somebody might find it interesting. This is the circuit used in the preamp. Just for interest the type of cable used to couple components together is less critical if the cable is driven. If its not that's a different situation. Now here is a thought, could you make just a selector with a passive pre, well yes you can! The reset is not connected to pin 13. Its just good fun! Tubeglow. Last edited by Tubeglow; 30th Mar 2014 at 6:35 pm. |
30th Mar 2014, 6:47 pm | #7 | |
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Re: A fun build preamp
Quote:
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30th Mar 2014, 6:49 pm | #8 |
Retired Dormant Member
Join Date: Mar 2014
Location: Wolverhampton, West Midlands, UK.
Posts: 153
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Re: A fun build preamp
Ok no problem...You are correct!
I'm not talking audiophool cable. However you are still correct! Tubeglow. Last edited by Tubeglow; 30th Mar 2014 at 7:00 pm. |
30th Mar 2014, 9:59 pm | #9 |
Octode
Join Date: Apr 2009
Location: Aylesbury, Buckinghamshire, UK.
Posts: 1,522
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Re: A fun build preamp
Thanks TG, that's a handy little circuit, I may well use it on my next build.
I'd be inclined to use separate series resistors on the LED's to prevent the "off" LED's being reverse biased. Cheers, Rob.
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