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catman

An initial review of the DIY Akitika PR-101 phono stage.

18 posts in this topic

G'day all, well it has been a somewhat interesting week and mostly because I completed successful construction of the Akitika phono stage, and whilst it is designed to be included into the larger Akitika PR-101 line preamplifier, I built the phono stage as a standalone stereo phono stage, powered by my existing DIY ESP P05B plus and minus 15 volt power supply.  Interestingly enough at least according to the phono stage circuit diagram 12 volt rails are used however 15 volt rails cause no problem and actually improves signal headroom somewhat.  Building this phono stage involved more assembly work than I had expected but was completed without any hassles....just a lot of soldering!

 

Assembly aside, how does it sound?  Very nice indeed.  I actually did a little op amp rolling after completion and it is my feeling that whilst the supplied NE5532's work and sound fine, the substitution of these to OPA2134's results in a smoother and more musical sound without any noise penalty, (but don't ask me why....I don't know).  I've actually done a head to head comparison against my DIY ESP P06 which reveals only a very subtle difference in sound quality and in fact in terms of treble 'openness' the P06 has the slight edge!  However the Akitika phono stage is a lovely sounding, smooth and detailed phono stage with on board capacitance loading and useful adjustment provisions.  Very neat!  

 

However the Akitika has one enormous 'plus' over the ESP P06, it is a very quiet phono stage, even at maximum gain (about the same level as the ESP P06).  How I wish that my ESP P06 was as supremely quiet!  The Akitika uses an interesting active Miller Loop circuit configuration to determine the (47 k) input impedance of the phono stage, suggesting a 13 db theoretical improvement in 'quietness', over the more commonly used 47 k 'termination resistor'.  Whatever the reason, the Akitika phono stage is unbelievably quiet.  Most impressive!  The designer of this phono stage certainly knows his stuff! 

 

This is a superb DIY phono stage for moving magnet and high output moving coil phono cartridges.  I love it!  Regards, Felix. 

Edited by catman
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THanks Felix, I may give that a go.

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Just ordered one.

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Finally got around to posting pics of the completed phono stage.

 

IMG_1539.JPG

IMG_1541.JPG

IMG_1542.JPG

IMG_1543.JPG

 

 

 

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Hmmm. What regulators does it use? Here's what I suggest:

 

* Dump the toroidal transformer and use an EI, C core or best of all, an R core transformer. 

*Use lots of capacitance after the rectifiers.

*A capacitance multiplier after that.

*Followed by LM317/337 regs.

*Bypass caps at the supply pins of the OP amps.

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19 hours ago, mloutfie said:

Is 30db boost mode enough for low output MC?

Not in my system, this is a MM only stage, for MC I have a Boozehound Labs Pre pre.

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15 hours ago, Zaphod Beeblebrox said:

Hmmm. What regulators does it use? Here's what I suggest:

 

* Dump the toroidal transformer and use an EI, C core or best of all, an R core transformer. 

*Use lots of capacitance after the rectifiers.

*A capacitance multiplier after that.

*Followed by LM317/337 regs.

*Bypass caps at the supply pins of the OP amps.

It uses 78xx and 79xx regulators, the supply is very basic to say the least, however when I built this cashflow was not very good. The supply is probably the best area to improve.

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43 minutes ago, Batty said:

It uses 78xx and 79xx regulators, the supply is very basic to say the least, however when I built this cashflow was not very good. The supply is probably the best area to improve.

 

Indeed. The M317/337 regs are a significant step up in quality. The transformer is one of the biggest problems I see. Toroidals have no place in phono preamps. 

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5 hours ago, Zaphod Beeblebrox said:

...... Toroidals have no place in phono preamps. 

 

Why is that Zaph?     Aren't toroidal's meant to have the smallest magnetic field therefore less likely to induce 50hz hum into a delicate circuit close by?

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Just now, Sierra said:

 

Why is that Zaph?     Aren't toroidal's meant to have the smallest magnetic field therefore less likely to induce 50hz hum into a delicate circuit close by?

 

Indeed, but they also couple VERY nicely to the mains. They have a very wide bandwidth and allow any mains bourne interference through. Obviously, the best option is an 'R' core transformer, mounted externally. 

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Thanks for that explanation Zaph ... good to know ... cheers!

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Posted (edited)

On 22/10/2016 at 10:45 AM, Batty said:

Finally got around to posting pics of the completed phono stage.

 

IMG_1539.JPG

IMG_1541.JPG

IMG_1542.JPG

IMG_1543.JPG

 

 

 

That looks like a huge amount of fiddly work. How long did it take?

Edited by Nap250

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a weekend

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