Lightspeed with a Tube Output Stage

[bluegti]

I built a lightspeed attenuator and have been using it with a MyRefC amp with great results. I heard that the lightspeed is not a good match for use with a tube amp (not sure why... maybe someone can explain), but I decided to try going from my lightspeed to my bottlehead foreplay III to a tube amp.

I really like the attenuator and I really like the foreplay III, but together there was some additional magic. I can't say exactly what the difference was, but I liked what I heard.

Anyway, I was wondering how hard it would be to create a tube output stage for the lightspeed? I'm still learning about these things so I'm wondering if someone has any ideas of where I would start learning how to build this?

[georgehifi]

Originally Posted by bluegti

I built a lightspeed attenuator and have been using it with a MyRefC amp with great results. I heard that the lightspeed is not a good match for use with a tube amp (not sure why... maybe someone can explain), but I decided to try going from my lightspeed to my bottlehead foreplay III to a tube amp.

I really like the attenuator and I really like the foreplay III, but together there was some additional magic. I can't say exactly what the difference was, but I liked what I heard.

Anyway, I was wondering how hard it would be to create a tube output stage for the lightspeed? I'm still learning about these things so I'm wondering if someone has any ideas of where I would start learning how to build this?

The Lightspeed loves tube amps as they are usually over 50kohms input impedance, some one has told you a crock of s---. If you need a tube buffer for the Lightspeed for a low <50kohms input impedance power amp, then this is the best buffer I've heard, it is also low output impedance for a tube buffer 100ohms, it's origins came from the top of the line Tektronics tube oscilloscope and was the highspeed low output impedance buffer in it. It's called the (SLCF) Super Linear Cathode Follower.
Still the best buffer is no buffer if your systems allows it which yours seems to.

Cheers George

[sonidos]

Uriah Dailey headed an Austin, TX get together last summer and we heard some great sound through his LDR attenuator and the OddWatt Odd Blocks. We were mightily impressed and we still talk about that sound combo as being pretty much the best we heard. I know it left me drooling and thinking about buying some Odd Blocks in the future with an LDR attenuator.

[bluegti]

Looks like I need to try using the lightspeed without the foreplay as a buffer. I don't know why I didn't bother trying it.

Thanks George!

[georgehifi]

That is what I would do, as this way you have the potential for the most transparent and dynamic sound, so long as your tube amp has more than 50kohm input impedance, which most tube amps are.

Cheers George

[atmasphere]

Originally Posted by georgehifi

That is what I would do, as this way you have the potential for the most transparent and dynamic sound, so long as your tube amp has more than 50kohm input impedance, which most tube amps are.

Cheers George

The problem with this approach is twofold: 1st you are totally dependent on your interconnect cables to get a decent sound, and 2nd as you decrease the volume you will find it acts as an effective bass and dynamics filter too.

That's what a buffer can reduce or fix entirely, depending on the design. My rule of thumb is that if a passive running direct sounds better than active, then there is something wrong with the active.

[georgehifi]

Originally Posted by atmasphere

My rule of thumb is that if a passive running direct sounds better than active, then there is something wrong with the active.

That's why all buffers circuits sound different, as do all potentiometers, they are never as true to the source as no buffer or no pot at all.
Just plug your source directly into your poweramp/s with a very quite cd, this is the perfect match.
And this is what a properly implemented (impedance matched) Lightspeed will do for you, it will always sound more transparent and dynamic than any buffer or pot, as it is in effect just one soldered resistor in the signal path, with no featherweight wiper contacts.

Cheers George

[atmasphere]

Originally Posted by georgehifi

That's why all buffers circuits sound different, as do all potentiometers, they are never as true to the source as no buffer or no pot at all.
Just plug your source directly into your poweramp/s with a very quite cd, this is the perfect match.
And this is what a properly implemented (impedance matched) Lightspeed will do for you, it will always sound more transparent and dynamic than any buffer or pot, as it is in effect just one soldered resistor in the signal path, with no featherweight wiper contacts.

Cheers George

I play a line section that I have yet to see any passive beat, and there have been some serious comers. It is all-tube and has a direct-coupled balanced output.

[georgehifi]

By all means post up the circuit, this is what were all here for, DIY. Yet I bet you can still hear it in the signal path.


Cheers George

[atmasphere]

There's not much to it- its a Circlotron. I use 6SN7s for the tubes and run a servo to control DC Offset. I'll see if I can draw up a schematic.

It probably *does* have some sort of signature- but in that regard everything does. If you have enough output from your DAC, you don't need any gain in front for this thing to work.