• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

How to build a warm, smooth and sweet tube buffer

Now that you made a choice about using tubes there's a bunch of good tube preamps.My first choice would be a hybrid transistor+tube preamp so my second choice is Luxman cl 34.That's because it is NOT warm, smooth and lush, just the best all tube mm phono preamp you'll ever be able to build and the only design i found able to take a full 10V rms input signal without getting into hard clipping and that's not something you can get with any preamp , tube, topology.
Just try it and we'll talk later about what are the needed qualities of a phono preamp.
 
Last edited:
Warm, smoothest and most lush - I don't really think you want the audio preamp to impart its own sound qualities on your audio. I think you mean transparent, open or blameless. The hybrid approach will get you the lower noise input - maybe a JFET - valve cascode. Failing that something with an e88cc as first stage may be ok.
 
  • Like
Reactions: JMFahey
Do you have the parts list and build plan?
It's on merlins website.
However at closer look the board i was thinking of : 3-tube-riaa is replaced by
a 2 board set : 2-board riaa set The idea of 2 board might be easier to fit into compact designs and
in addition they already has a rca connector mounted.
I still have one of these boards in stock.
( as we both are discussing good phonostage projects i do not consider this threadjacking )
 
Well, I have decided that instead of putting anymore time, money and effort into improving a fatally flawed format, I am here to declare that I am really and officially done with digital playback for good.

I instead want to concentrate my efforts into building a warmer, more musical phonostage (with tubes of course). Any projects I should look at?
Get yourself a set of "Sound Practices" magazines. (But why are you blaming the format rather than, say your speakers or amplifier? See the discussions between Lynn Olsen and John Phelan, oh, 15 years ago)

P.s. by the way, the power supply is at least half of the circuit.
P.p.s see the example earlier on how to do RIAA passively. Feedback (think about slew rate vs noise sensitivity) is your enemy in the RIAA stage:
 
Last edited:
Lots of excellent suggestions. I would add a few things. One is hum with the RIAA curve having most gain at LF. Heaters DC and regulating the HT depending on design. Careful layout avoiding power supply hum, using isolated RCA connectors. Miller capacitance can also change the cartridge loading. Its quite difficult to get accurate RIAA equ over one stage due to valve tolerances if driven from a plate load due to variations in Rp. The noise figure of the stage after the RIAA must also be good in this case. Some approaches take an op-amp method with the RIAA placed in the feedback or a bit of both. If only feedback you need a lot of gain. I've never built one as I have no vinyl unfortunately but would have loved to.

Here's an audio research one with RIAA in feedback path.
https://www.bonavolta.ch/hobby/en/audio/ar_sp3.htm
 
Last edited:
OK, rather than trying to build the perfect audio warmifier on the first try, why not try a simple experiment to become acquainted with what the various distortions sound like?

One could take a simple cathode follower and play with its biasing. You could bias it so warm that it's on the verge of drawing grid current. That will distort the signal some (more or less, depending on bias point chosen).

Perhaps also employ a very large value grid stopper (10k ohms?), to vary the distortion characterstics.

You could use a choke input, tube rectified power supply. Go all-out old school. A single 12AU7, 6SN7 or similar twin triode could easily be powered from a small power transformer, a 6X4 rectifier tube, and a quite modest choke. Perhaps the higher impedance power supply is part of that 'vintage tube' sound.

I have found that some paper-in-oil capacitors have a 'rounding' effect on the sound. I picked up a bunch surplus back in the 1990s.

So, to sum up. design the triode cathode follower and its power supply to work with higher distortion than you'd normally aim for, and find out for yourself what the distortion sounds like. It could be just the thing to fatten up the sound from your digital source. Or you might find out that this is not what you're looking for.
 
Care to tell me why?
Because it has no answer.
You are craving for very subjective words which have no actual or direct technical (or real world) meaning.

Those are buzzwords used by sellers.

Let me give you an example:
Soap "should" be promoted based on their cleaning properties, do we agree?
As in: "XXX soap cleans better than others"
Sales were average.
Then a GENIUS Publicity guy (or con man? .... you decide) invented the concept of "BEAUTY soap" which if you think 5 seconds is NONSENSE.
Sales went through the roof. 😱

beauty soap.jpg


Beauty 2.jpg


Then others HAD to invent "9 out of 10 Cinema Stars use it" which again is nonsense, or , best case, irrelevant.
Again sales exploded.

s-l1600.jpg

Nowadays "salesmen" sell preamps, power amps, tubes, components, etc. with same sweet and enticing words:"warm - smooth - soundstage" - etc.

Forgive us Techs and in general people caring for REAL Audio advancement for not caring much about such vague "emotional" meaningless descriptions.

A preamp (or any magical component) can bring as much of those as Palmolive soap can bring Beauty to user, think about that.
 
This is clearly a problem on your end.

If you simply do not understand regular and very, very commonly used words, describing fantastic sound, beautiful music, delicious food, whiskey, beer or wine: you might start digging there.

🙂🤚
Forget wine, food, music, whiskey, or beer, we are talking electronic components and schematics here.
Looks like you are out of your field.

Unless manufacturers start publishing datasheets showing fantastic/beautiful/delicious graphs or curves, let alone equations calculating them.