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DIT tube buffer?

post #1 of 43
11/23/06 at 12:25pm
Thread Starter 
Does anyone know of a really simple tube buffer that can be made, prefurably to use a cheap tube?
-greg
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post #2 of 43
11/23/06 at 2:12pm
DIT?

There are some simple tube buffers out there. The easiest/cheapest that comes to mind are the ones that are generally used with gainclones. Example here:
http://www.platenspeler.com/diy/amps...beclone_2.html
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post #3 of 43
11/23/06 at 2:23pm
i think the real question is how much power do you want this beast to make?

if you don't mind LOSING gain, you can use inverted triodes and have no output cap.
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post #4 of 43
11/23/06 at 3:10pm
Thread Starter 

DIY... my bad

I was planning on useing it between my source and my new reciever that will be powering my speakers. I would like to build it as well as be able to tayler the sound alittle. But im in no way looking for hi-fi. The system is deff low-fi, so it would just be for fun.
THanks for the suggestions so far, I'll look into them and I Would be intrested in any more suggestions.
-greg
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post #5 of 43
11/23/06 at 10:50pm
Thread Starter 
http://cgi.ebay.com/Tube-buffer-ampl...ayphotohosting
I was directed to this by a friend and it looks like it would work well. I was hopeing to go alittle cheaper but it looks like with the PC board it would be really easy.
I think that I might actually build this into the reciever and have the tubes sticking out of the top, so splice it in right after the RCAs from the source.
-greg
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post #6 of 43
11/23/06 at 11:02pm
I have the layout for the MF 10D but this kit has always held some appeal to me. http://www.audiodigit.com/?section=81 it sells for 80 euro. I haven't been to this site for a while so it figures that I never bought one . I found this brief review on it http://www.diyaudio.com/forums/showt...threadid=79695 . The ebay link looks interesting too..dB
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post #7 of 43
11/25/06 at 4:54pm
Bottlehead tube buffer sounds like what you need: http://www.audioasylum.com/forums/bo...es/115040.html
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post #8 of 43
11/25/06 at 10:04pm
Thread Starter 
Im going to buy one of the non populated boards from the ebay auction. It is suposidly an exact clone of the Musical Fedelity tube buffer. And I can populate it with high quality components for pretty cheap.
-greg
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post #9 of 43
11/26/06 at 3:20am
I assume that you've already bought your boards from ebay, but if not, I'd like to ask, "Do you need a buffer with gain?" If so, why?

If not, then I've got a unity gain tube buffer design that you might find interesting.
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post #10 of 43
11/26/06 at 3:35am
Thread Starter 
Well I havent bought the board yet. And I dont need any gain, just for coloration.
I am going to integrate this into my new old Pioneer SD-5200. Its a real basic reciever giving 10 wpc.
I'm intrested, enlighten me.
-greg
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post #11 of 43
11/26/06 at 10:54am
Quote:
Originally Posted by runeight View Post
I assume that you've already bought your boards from ebay, but if not, I'd like to ask, "Do you need a buffer with gain?" If so, why?

If not, then I've got a unity gain tube buffer design that you might find interesting.
I'm interested, too.
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post #12 of 43
11/26/06 at 5:52pm
So what you want is a tube stage with no gain that has high input impedance and low output impedance? Here's a simple buffer that will do this for you.

It is a basic cathode follower with some tricks. It has a CCS for the cathode load and uses a mosfet to bootstrap the plate. Normally a cathode follower has a gain of less than 1, but these two additions make the gain exactly 1. The THD should be negligible.

The PS should be easy to fabricate. The tube runs at about 4mA bias, so the PS needs to only supply 8mA at 200V and -25V.

I haven't built this, but I'm pretty sure that it will work as advertised. If you put a stepped attenuator in front of it it should make an excellent "active" attentuator with unity gain, high Zi and low Zo.

Gentlemen, if you decide to build this idea, I have one simple request beyond this point. I am very happy for you to build it and to share it and for anyone to make boards for it. I will offer as much assistance as I can to help with the PS and other aspects of a prototype. But I don't want someone to jump in here and start offering boards until we have finished the prototyping and have agreed that the design is far enough along for it to be committed to a board.
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post #13 of 43
11/26/06 at 6:23pm
Ooooo, that looks shiny, runelight. Look forward to hearing more about it in the future... I'll be looking for a simple tube buffer in 4 or 5 months and I dig 6922s! (I've actually got a pair of nice Amperex tubes that I think are somewhat wasted in my Tjoeb... love to give them a try in this puppy.)
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post #14 of 43
11/26/06 at 9:25pm
Here's a very simple PS that should work quite well for this buffer. Any decent 120V/25mA transformer will do.

This PS uses a voltage doubler to get both the B+ and B- voltages. Don't sweat the zeners here because I think that they won't hurt anything and they are easy to use regulation.

Let me know what else I can do.

Don't forget that you still need 6.3V/300mA for the 6922 heater. But this is easy too.
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post #15 of 43
11/27/06 at 1:19am
Thread Starter 
I think its awsome that you have gone and figgured this out, however, Im embarassed to say that this is slightly over my DIY head. Now with the Ohm changes I'm unsure if this is what I want, I basicaly just want to be able to color the sound with the tubes of my choice.
If this is going to help me do that then I am more than happy to read up and learn exactly what the heck your talking about. :P
And as i said thanks for coming up with all this.
-greg
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