Tube buffer

[Filterlab]

Ok, I fancy some of that creamy valve goodness and a valve amp will be no good for my speakers (impedance all over the place due to the ribbons and very unsensitive), so I thought about popping a tube buffer between my DAC and 8000a (used as a power amp).

Without spending a frickin' fortune, where do I begin? I don't want to get something that will ruin the clarity of my system obviously, all the same I don't want something that makes no difference.

Pointers please chaps.

[The Vinyl Adventure]

I have an x10d with a bunch of mods from rock grotto ... It works really well in my office system (currently pc - caiman - x10d - mini t - usher s520) it sorta takes an edge of without taking away detail ...

(spoke to why buy new ... Def being repaired)

[Filterlab]

Cheers Hamish! :)

[Marco]

Hi Rob,

Hamish's suggestion is good, but if you want something really special, bespoke, and which won't break the bank, then I'd speak with Nick Gorham, who posts here as 'lurcher'.

Nick's a superb equipment designer, especially when it comes to valve kit, along with Anthony TD. Either of them would make you a valve buffer, with superb results, so take your pick and send them a PM, and you'll end up with something way better and much more satisfying than any commercially produced design! :)

Marco.

[WAD62]

Another timely thread, this is about the third time I've been considering something, and an informative thread starts up on AoS...as if by magic ;)

As an electronics numpty I use a chap for my repairs etc, yesterday he stated that he was going to build a valve buffer, and would I be interested in one.

So after ascertaining what it actually was, I was very interested...however I have a few question for you chaps.

Where is the best place to put it?

His view was that it was best placed between a pre amp and a power amp, however my configuration is bi-amped, Audiolab DAX, Q pre-amp, SX power amp (tweeters), & P poweramp (bass).

Obviously if I put it between my pre & power I'll need two of them, and additional interconnects, would I still get the benefit from fitting it higher up the chain, between my DAC and Pre Amp, which would require only one, or perhaps only the 'bass' amp of my bi-amp setup? :scratch::scratch:

All tips gratefully received :)

[Stratmangler]

You could run a buffer just before a passive volume control (pot/stepped attenuator/tvc) and get rid of your preamp.
You could even put a source selector before the buffer.

The buffer ensures that your source sees a stable load, with none of the pain you normally get with passive attenuation.

My mate Colin (Toppsy) has a unity gain buffer before this signal gets to his TVC.
The buffer was designed by Nick (Lurcher).

[Ali Tait]

I too have a unity gain buffer built by Nick. It's a great bit of kit, adding real drive to the system.

[WAD62]

You could run a buffer just before a passive volume control (pot/stepped attenuator/tvc) and get rid of your preamp.
You could even put a source selector before the buffer.

The buffer ensures that your source sees a stable load, with none of the pain you normally get with passive attenuation.

My mate Colin (Toppsy) has a unity gain buffer before this signal gets to his TVC.
The buffer was designed by Nick (Lurcher).

My Q preamp is 'mission control' as it were, I need it to integrate my AV system into my stereo setup, and it's only 18 months old! :rolleyes:

So can I take it that putting it between my DAC and pre-amp is futile? :eyebrows:

Cheers for the replies chaps...

[Stratmangler]

My Q preamp is 'mission control' as it were, I need it to integrate my AV system into my stereo setup, and it's only 18 months old! :rolleyes:

So can I take it that putting it between my DAC and pre-amp is futile? :eyebrows:

Cheers for the replies chaps...

Between DAC and pre would be fine.:)

[lurcher]

Personally, I think a important question you need to ask yorself before adding a buffer is why you are doing it? And what you want from it? The answer to that question IMHO alters the type of buffer you need. IMHO the MF buffer is aimed at folk who want a little extra 2nd harmonic in their system. Nothing wrong with that, 2nd its almost entirly benign, and can counter the effects of higher order distortion elsewhere in the system.

I know the ideal system is one with no distortion, but that doesnt exist, and in the real world its better to find a solution that sounds good to you instead of making yourself suffer with a hair shirt low distortion system. As I said IMHO only. To do that job, using a circuit that adds some 2nd harmonic, but very little else is a good solution, possibly the best though not the chepest is a single ended triode driving a step down line transformer. A cheaper solution is a active loaded cathode follower.

Another more interesting reason you may want to use a buffer is to make the life of your source equipment simpiler. Most DACs have a op amp output, that despite being correctly described as class A, will very quickly move into B wen driving real loads. Adding a unity gain buffer with a high input impedance, low input capacitance and low as possible distortion will often work wonders here. Possibly the best though again expensive solution is a input transformer driving a balanced gain stage into balanced step down line out transformers. Though a good cheaper solution is what Ali has, an augmented cathode follower giving very low distortion without needing loop feedback, so low distortion and very low high order distortion.

You can also use the same sort of buffer after a passive volume control to make a preamp, the buffer allowing the source to avoid the load of the following equipment. However the problem here is the volume control. I have yet to hear a blameless pot, every time I replace a pot with a stepped attenuator the improvement is not subtle.

The final place a buffer can work well is driving a transformer volume control. Often these are great sounding things, but unless they are driven well themself, can sound slow and a bit pedestrian. Again in that case a unity gain buffer will decouple the souce from the input side of the transformer to good effect.

Again, all IMHO, and while I agree the simple passive soultion should be the best, but in practice never seems to work out that way.

[The Vinyl Adventure]

Personally, I think a important question you need to ask yorself before adding a buffer is why you are doing it? And what you want from it? The answer to that question IMHO alters the type of buffer you need. IMHO the MF buffer is aimed at folk who want a little extra 2nd harmonic in their system. Nothing wrong with that, 2nd its almost entirly benign, and can counter the effects of higher order distortion elsewhere in the system.


so does that equate to what i am hearing when i say
"it sorta takes an edge of without taking away detail"

the stock x10 sounded odd to me, from memory it was to "loud" the mods i did seemed to get rid of that ... but i suppose the mods just change the character as opposed to the circuit...

[WAD62]

Another more interesting reason you may want to use a buffer is to make the life of your source equipment simpiler. Most DACs have a op amp output, that despite being correctly described as class A, will very quickly move into B wen driving real loads. Adding a unity gain buffer with a high input impedance, low input capacitance and low as possible distortion will often work wonders here. Possibly the best though again expensive solution is a input transformer driving a balanced gain stage into balanced step down line out transformers. Though a good cheaper solution is what Ali has, an augmented cathode follower giving very low distortion without needing loop feedback, so low distortion and very low high order distortion.


Cheers for the replies Nick and Chris...I think I understood Chris's answer a little more ;)

Nick this may be like communicating with a 5 year old for you, until yesterday I didn't even know what a valve buffer was, never mind why I wanted one :)

So if I was to go for a valve buffer between my DAC (Audiolab DAX, I'm pretty sure it's an op amp output:eyebrows:), and my pre amp what would give me the best 'low cost' results? The 'unity gain buffer' you mentioned? :scratch:

[lurcher]

so does that equate to what i am hearing when i say
"it sorta takes an edge of without taking away detail"

the stock x10 sounded odd to me, from memory it was to "loud" the mods i did seemed to get rid of that ... but i suppose the mods just change the character as opposed to the circuit...

Yes, there may also be a small element of the HF response being a tad down, taking some of the HF energy away shifting the balance towards the lower end. But not losing detail as that is more about 10kHz and lower.

Its also likely that what you are hearing is the source output stage having a nicer time of it.

[lurcher]

Cheers for the replies Nick and Chris...I think I understood Chris's answer a little more ;)

Nick this may be like communicating with a 5 year old for you, until yesterday I didn't even know what a valve buffer was, never mind why I wanted one :)

So if I was to go for a valve buffer between my DAC (Audiolab DAX, I'm pretty sure it's an op amp output:eyebrows:), and my pre amp what would give me the best 'low cost' results? The 'unity gain buffer' you mentioned? :scratch:

The simpilest and effective buffer IMHO would be a cathode follower, but make sure you use a active load (CCS), the valve "sees" the load in its cathode just as much as it would if it was in its anode, but that fact seems to be often ignored. That shape of circuit is nice and simple, but will need a output DC blocking cap, so the quality of the cap becomes vital. To avoide needing a input cap as well, I would add complexity and use a split rail power supply to avoid having to use a extra cap on the input side.

SRPP shapes are the flavour of the month again it seems, but IMHO they fall more in the "add 2nd harmonic" camp, and normally provide more gain than is wanted.

If you want a buffer with gain the Aikido is a great circuit to consider.

[WAD62]

The simpilest and effective buffer IMHO would be a cathode follower, but make sure you use a active load (CCS), the valve "sees" the load in its cathode just as much as it would if it was in its anode, but that fact seems to be often ignored. That shape of circuit is nice and simple, but will need a output DC blocking cap, so the quality of the cap becomes vital. To avoide needing a input cap as well, I would add complexity and use a split rail power supply to avoid having to use a extra cap on the input side.

SRPP shapes are the flavour of the month again it seems, but IMHO they fall more in the "add 2nd harmonic" camp, and normally provide more gain than is wanted.

If you want a buffer with gain the Aikido is a great circuit to consider.

Cheers for the reply Nick, I'll get my mate to act as an interpreter...'bag on the head', 'mayonnaise' etc., 'gain or no gain', I don't think I need any gain :doh: