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Cheap Phono Preamp with tubes :)


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Did you ever wonder about products like this?  https://www.amazon.com.au/Douk-Audio-Vacuum-Desktop-Headphone/dp/B08R3S6MCR/ref=sr_1_1?dchild=1&keywords=douk+phono&qid=1611179028&sr=8-1

 

Let me be clear, I do not have one of these.  I just found it on Amazon, and it is a curious design, and VERY cheap (if it's any good).   Basically it's an opamp based phono preamp with a valve(tube) buffer and a headphone amp.

 

The headphone amp is a typical NE5532 opamp headphone amp.   It handles MM and MC and has a few loading options (don't know if you can combine them, but maybe). Three opamp circuit based onJRC2608 opamps (are these any good?).   Runs off 12V  and appears to have a voltage stepup circuit similar to Jim Hagerman's latest.

 

I have to say the circuit board looks quite neat and well made, but not sure about the plugin valve module idea though. 

 

Interesting toy or maybe even worth a try???

 

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I have heard many decent cheap opamp based phono but nevr hav a cheap and decent tube buffer. They all sound congested and overly warm. I think this one would be the same. If you need cheap stick with opamp only and maybe use battery to power it

Edited by mloutfie
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Just now, mloutfie said:

I have heard many decent cheap opamp based phono but never a anywhere decent tube buffer. They all sound congested and overly warm. I think this one would be the same. If you need cheap stick with opamp only and maybe use battery to power it

 

It's not that I need yet another phono preamp :)  I was just intrigued about this take on it.  Just thought I'd start a discussion to see what others thought.

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On 21/01/2021 at 9:13 AM, aussievintage said:

 

It's not that I need yet another phono preamp :)  I was just intrigued about this take on it.  Just thought I'd start a discussion to see what others thought.

 

Thanks for starting this discussion.  I am also curious what others think,  particularly user experiences of gear like this.   

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Interesting. Never seen anything like that before..... I don't really listen to LP's with headphones.... Or anything really for that matter. Still this is a first for me.

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4 minutes ago, MattyW said:

Interesting. Never seen anything like that before..... I don't really listen to LP's with headphones.... Or anything really for that matter. Still this is a first for me.

 

There are times I might like to sit on the deck and play a few records, but apart from the headphone aspect,   this is an intriguing looking device.  The electronics do look solid.  The basic idea of SMD opamps on a good circuit board has the potential to be a good low-noise phono preamp.  This one throws in enough gain for MC.  The addition of the tube buffers is, yes, a gimmick, but one many might want to experiment with given the interest in this type of thing before - thinking of the little bear  tube buffers etc etc.

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As someone whom has had no exposure or experience with tubes, I've found them to be intriguing. My local hifi store has the Project Tube Box DS2, which I've pondered over whether it would be worthy of purchase. 

 

So, in saying that, can one of the experienced members here give a rough idea of what the real world differences would be between the Project and something like what the OP has posted please? I imagine the Project would have a superior level of build quality etc, but would the signal path be basically similar to both in how it travels?

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39 minutes ago, mkaramazov said:

 

Thanks for starting this discussion.  I am also curious what others think,  particularly user experiences of gear like this.   

 

My experience has usually been fairly positive.  Nearly always get what I expected, and that being at least value for money.   The Jaycar phono I bought a couple of, and opened up and reviewed here a while back, is excellent value and  quiet and good sounding.

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4 minutes ago, Jebediah said:

As someone whom has had no exposure or experience with tubes, I've found them to be intriguing. My local hifi store has the Project Tube Box DS2, which I've pondered over whether it would be worthy of purchase. 

 

So, in saying that, can one of the experienced members here give a rough idea of what the real world differences would be between the Project and something like what the OP has posted please? I imagine the Project would have a superior level of build quality etc, but would the signal path be basically similar to both in how it travels?

 

 

It would be very interesting to compare.  The only hint I have is a reference that supposed, as I do, that the Project box is a hybrid, just like this one.      There's a good chance they are similar, even though there's almost a 10x price difference :) 

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3 minutes ago, aussievintage said:

There's a good chance they are similar,

 

Adding to my own comment,  the Pro-ject seems to use two  12AX7 type tubes, so 4 triodes.  There's scope for the tubes to be doing more work than just an output buffer.   

 

This compare to the cheapie up top - that uses a couple of small 6A2/6J1/6AK5 pentodes, most probably only output buffers.  More scope for tube rolling with the 12AX7s than with these.

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16 minutes ago, aussievintage said:

 

Adding to my own comment,  the Pro-ject seems to use two  12AX7 type tubes, so 4 triodes.  There's scope for the tubes to be doing more work than just an output buffer.   

 

This compare to the cheapie up top - that uses a couple of small 6A2/6J1/6AK5 pentodes, most probably only output buffers.  More scope for tube rolling with the 12AX7s than with these.

Thanks for this aussievintage. The Project (I imagine) obviously has features that the cheap unit does not, ie loading switches on the front for ease of use on the fly, plus the ability to connect two tables at once. 

But it certainly comes at a price difference as you pointed out.

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1 hour ago, Jebediah said:

As someone whom has had no exposure or experience with tubes, I've found them to be intriguing. My local hifi store has the Project Tube Box DS2, which I've pondered over whether it would be worthy of purchase. 

 

So, in saying that, can one of the experienced members here give a rough idea of what the real world differences would be between the Project and something like what the OP has posted please? I imagine the Project would have a superior level of build quality etc, but would the signal path be basically similar to both in how it travels?

I had a Little Bear unit that  used 3x  12ax7. Cheap, underdeveloped, fiddly heaps of gain but only MM capable. Needed to make up an internal ground etc. Almost mandatory to mod.

 

Also had the Project Tube b o x Ds2.

It's a real one with proper build quality  and adjustment flexibility as expect erd from  x10 the cost.

Tubes are output circuit but changing does change the sound.

 

Lost it in the fires. Replaced it with the non tube Phono box version.

 

They're not even comparable.

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28 minutes ago, eman said:

Lost it in the fires. Replaced it with the non tube Phono box version.

 

They're not even comparable.

I'm sorry to hear you were affected by the fires mate. 

 

So just to clarify, you found  the Tube Box to be superior in sound to the regular Project Phono Box?

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42 minutes ago, eman said:

Tubes are output circuit but changing does change the sound.

 

Interesting, so , did they parallel two triodes on each side or something?

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20 minutes ago, Jebediah said:

I'm sorry to hear you were affected by the fires mate. 

 

So just to clarify, you found  the Tube Box to be superior in sound to the regular Project Phono Box?

Sorry  I was not clear there.

I meant the Project Tube unit was much better than the cheap LB one; as expected by the price.

I wouldn't put the Projetc tube box in the 'cheap phono' range. That's why not comparable.  It's a real one.

15 minutes ago, aussievintage said:

 

Interesting, so , did they parallel two triodes on each side or something?

I have no idea about tube details, but it can be widely found online that they are in the output stage.

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12 minutes ago, eman said:

 

I have no idea about tube details, but it can be widely found online that they are in the output stage.

 

 

Actually I don't think so.  I found this

 

" the 'headamp' is a low-noise J-FET stage with the first triode in cascode, leveraging a substantial 70dB overall gain.there's even a second tube gain stage between the two halves of the passive network. Thus the maximum gain available to the user is +65dB, just about spot-on for the vast majority of sane MCs. Furthermore, Pro-Ject is smart enough to ensure the Tube Box DS2's compatibility with likely partnering amplifiers by buffering its output, not via the triodes, but with a solid-state Burr-Brown op-amp'."

 

 

So we should not be comparing it to the cheapie at the top at all.  Turns out it is quite different.  Just as well, given the price tag.

 

 

 

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1 hour ago, aussievintage said:

...

 

1 hour ago, aussievintage said:

 

....

So we should not be comparing it to the cheapie at the top at all.  Turns out it is quite different.  Just as well, given the price tag.

 

 

 

Regardless of exact technical  details my conclusion was the same.

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25 minutes ago, eman said:

 

Regardless of exact technical  details my conclusion was the same.

 

Quite so.    It also goes to show that what is posted online "widely" is often complete  rubbish.

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On 21/01/2021 at 10:57 AM, aussievintage said:

Interesting toy or maybe even worth a try???

Not worth a try.  I have wrestled with phono pre-amps for a long time.  The fundamental problem is the combination of (1) the phono signal is tiny; and (2) valves are noisy.  To get a goody is difficult and expensive.  

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10 hours ago, SL1200 said:

Not worth a try.  I have wrestled with phono pre-amps for a long time.  The fundamental problem is the combination of (1) the phono signal is tiny; and (2) valves are noisy.  To get a goody is difficult and expensive.  

 

Can't agree.  I make my own valve based phono amps, and when done right, VERY hard to beat.  DC heaters, good shielding etc etc, standard practice for instrumentation amps, will deal with all the noise "problems".

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12 hours ago, SL1200 said:

Not worth a try.  I have wrestled with phono pre-amps for a long time.  The fundamental problem is the combination of (1) the phono signal is tiny; and (2) valves are noisy.  To get a goody is difficult and expensive.  

 

1 hour ago, aussievintage said:

Can't agree.  I make my own valve based phono amps, and when done right, VERY hard to beat.  DC heaters, good shielding etc etc, standard practice for instrumentation amps, will deal with all the noise "problems".

 

Do you make an MM tube phono stage, av ... gain 40-44dB?  Or is it an MC phono stage ... gain 60-66dB?

 

Duc (r.i.p.) made an absolutely wonderful-sounding tube MM phono stage (40dB gain) ... but, in several comparisons I did over the years, even this had a higher level of background noise than my MC 'Muse' phono stage (62dB gain).

 

A tube MC phono stage is best done IMO as a hybrid - using a jfet gain stage first off (to raise the signal to MM levels) ... and then use tubes for the MM section.

 

Andy

 

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16 minutes ago, andyr said:

Do you make an MM tube phono stage, av ... gain 40-44dB?  Or is it an MC phono stage ... gain 60-66dB?

 

Duc (r.i.p.) made an absolutely wonderful-sounding tube MM phono stage (40dB gain) ... but, in several comparisons I did over the years, even this had a higher level of background noise than my MC 'Muse' phono stage (62dB gain).

 

A tube MC phono stage is best done IMO as a hybrid - using a jfet gain stage first off (to raise the signal to MM levels) ... and then use tubes for the MM section.

 

To start with, I fully agree,  just put a head amp or transformer in front of a good valve phono is you want MC.

 

Measuring and comparing a valve phono for "background" noise is problematic for a few reasons.  Firstly I will always contend that if you can't hear it in normal use, then the noise is plenty low enough. 

 

Secondly, if you fret about low noise you can't even hear,  I could tell you about military and industrial preamp designs that achieve lower noise than you would ever need.  For example, they put the valve in a tight metal box inside the main metal box of the main amplifier, well away from everything else, mounted on rubber,  and fed nothing but DC into the inner sanctum of the valve.  If you want low noise, you can do it, but modern practice is to put the valves on show, with not even a can on them.  Quite a bad idea for those paranoid about noise.   I compromise by putting a can on the first triode at least.

 

Thirdly,  I  hand select for low noise and best performance.  The variability between valves makes testing of one example only fairly meaningless.  When you say it had a higher background noise, did you only try only one set of valves?  How were they shielded?

 

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