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Class D Switching Power Amplifiers and Power D/A conversion

A simple tube buffer to add to Class D build?
A simple tube buffer to add to Class D build?
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Old 24th April 2019, 07:56 AM   #1
Bill poster is offline Bill poster  Thailand
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Default A simple tube buffer to add to Class D build?

Hi guys,

Really need your input choosing components.

Money is tight this year, so decided to build a simple DIY power amp and have an electrician friend helping with build. Will use the volume control from streamer dac.

So I already bought 3e TPA3255 board, which requires around 500w and around 40v, or up.to 48v. It's good for 250w per channel before distortion starts rising rapidly.

I want to add a very simple, good quality tube buffer. I don't require volume pot.

After this I will decide on power supply etc. Thinking toroid, but if switching is viable, thats ok too.

Btw I saw this simple buffer on Jimmys Junkyard Just a moment...
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Old 24th April 2019, 08:08 AM   #2
Bill poster is offline Bill poster  Thailand
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I saw this little thing on fleabay. Happen to like those tubes, and this is compact w step up. Any guesses if ok?
TS1 6SN7 CV1988 B65 Tube Buffer Preamp For Car Audio Car HIFI W/ Voltage Step-Up | eBay

Last edited by Bill poster; 24th April 2019 at 08:21 AM.
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Old 24th April 2019, 08:53 AM   #3
Khron is offline Khron  Finland
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1) Why exactly does it matter what sort of amp this buffer goes in front of?

Assuming the answer is "it doesn't",
2) Doesn't this then not belong in this subforum?
But rather in https://www.diyaudio.com/forums/tubes-valves/
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Old 24th April 2019, 12:25 PM   #4
Bill poster is offline Bill poster  Thailand
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Quote:
Originally Posted by Khron View Post
1) Why exactly does it matter what sort of amp this buffer goes in front of?

Assuming the answer is "it doesn't",
2) Doesn't this then not belong in this subforum?
But rather in https://www.diyaudio.com/forums/tubes-valves/
1. posted in the class D forum is because its predominantly a Class D build.
And someone may know of a tube buffer which works well with class D
modules
2. most members here are seriously polite and helpful
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Old 24th April 2019, 08:02 PM   #5
Mark Tillotson is offline Mark Tillotson
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All that's needed is knowing what impedance it has to drive, at what level and headroom, stuff like that. There's nothing special about class D modules, they take a signal in like other amps.


Somewhere in my arsenal of electronic oddities I have a valve opamp, which I've been wanting a good use for, but it strikes me you could base a buffer on one of those Philbrick opamp circuits: http://www.philbrickarchive.org/k2-w_refurbished.pdf
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Old 24th April 2019, 09:59 PM   #6
russc is offline russc  England
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Your amplifier is very efficient, decent quality, has a high-ish input impedance.
A good quality buffer will add nothing (except needless expense/power consumption/complexity).
A poor quality buffer will add distortion which you may like.
But I'm sure you already know that.
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Old 25th April 2019, 05:56 AM   #7
Temaad is offline Temaad  Australia
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Hi, I agree with "russc" But if you really want a buffer, get one using the 6N2 valve. They are very good sounding & you can easily upgrade to the Russian Mil Spec 6NP-P spec valve which is very good indeed. Cheers
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Old 25th April 2019, 08:07 AM   #8
Bill poster is offline Bill poster  Thailand
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Thanks guys. I will check out that tube.
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Old 4th May 2019, 09:35 AM   #9
InOtIn is offline InOtIn
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Many Class D amps (Hypex, IcePower) do best with a balanced input. So if you will be designing a buffer yourself, consider making it a differential design (which I doubt you could find on eBay or Aliexpress).
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Old 4th May 2019, 07:45 PM   #10
Turbowatch2 is offline Turbowatch2  Germany
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There are very small, cheap pre amp PCBs on eBay and Ali. NE5532 OP-AMP HIFI Audio Preamplifier Dual Preamp Board for Bluetooth New | eBay

They use the NE5532 (probably fraud) and invert. You can easyliy modify them to amplify 1:1. Just feed the output of one side into the input of the other and you have an inverting buffer, for sub 2$.

Sound advantages of buffered inputs are not from tubes or fancy IC`s, but better matching the complicated impedance of some amp modules.

Never seen an symetric tube buffer on the usual channels.

Last edited by Turbowatch2; 4th May 2019 at 07:48 PM.
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