Leach describes three versions, common base, common base with current mirrors (aka "Hiraga") and common emitter. They all require either floating power supplies or isolation transformers.
The Hawksford version requires also isolation and floating power supplies, but has the advantage of a convenient insertion point for the RIAA network (a high output impedance junction, as in the Vendetta). As far as I know, this design idea (augmented by a fair amount of snake oil, following his deeply criticized AES paper http://www.essex.ac.uk/csee/research/audio_lab/malcolmspubdocs/J7 Fuzzy distortion.pdf ) was implemented in an obscene expensive MC preamp, manufactured by LFD Audio where he also works as a consultant.
They all have the advantage of zero current through the MC cartridge and the same practical disadvantage of the power supply/isolation. Hawksford recommended a 2V lead cell as a power supply!
Others tried to use some sort of photocells and a light source to implement the floating power supply; this would work for collector currents for up to 100-200uA, leading to very high current noise. From a noise perspective, the optimal collector current is Vt*SQRT(Beta)/Rsource. For Rsource=10ohm and Beta=100 it's 20mA!
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"and the same practical disadvantage of the power supply/isolation" - what means this?
I own the Hawsksford equalizer. Both versions, the expensive one with LOT´s of batteries and a version with conventional PSU. The big version is at LFD the second time to repair.
It´s not very relyable, at least my sample. So i claim a bit of competence concerning this design. I also have the circuit values and details but are not allowed to give them out. Of cause i could ask because the battery version is not longer produced. Two PHD´s and one professor have worked hard on that design so it has some credibility. I do not know what Malcolm would design today. It is over 20 years old and progress HAS been made.
Compared with syn08s designs they are not particular low in distortion but i like the sound very much. It´s very smooth with low fatique. My designs are more dynamic and have more drama but still i learned a lot from Hawsksforts approach, searching for elegant simplicity and listen to the subjective impact of component choices. A good cartridge produces ca. 1% distortion so hunting for extreme numbers
may not be the only way to good sound. Still i learned that it is a good thing if not at the expense of extreme complexity. I stand somewhere in between the two camps i identify here. For me subjective quality is as important as good measured performance. As i already stated i find Syn08s approach relevant and fascinating. That is the reason i am posting here. I really would like to have his bipolar design on my test bench and in my listening room. I see a lot of innovative thinking and have already learned a lot here.
It´s not very relyable, at least my sample. So i claim a bit of competence concerning this design. I also have the circuit values and details but are not allowed to give them out. Of cause i could ask because the battery version is not longer produced. Two PHD´s and one professor have worked hard on that design so it has some credibility. I do not know what Malcolm would design today. It is over 20 years old and progress HAS been made.
Compared with syn08s designs they are not particular low in distortion but i like the sound very much. It´s very smooth with low fatique. My designs are more dynamic and have more drama but still i learned a lot from Hawsksforts approach, searching for elegant simplicity and listen to the subjective impact of component choices. A good cartridge produces ca. 1% distortion so hunting for extreme numbers
may not be the only way to good sound. Still i learned that it is a good thing if not at the expense of extreme complexity. I stand somewhere in between the two camps i identify here. For me subjective quality is as important as good measured performance. As i already stated i find Syn08s approach relevant and fascinating. That is the reason i am posting here. I really would like to have his bipolar design on my test bench and in my listening room. I see a lot of innovative thinking and have already learned a lot here.
syn08, you have capacitors in the circuit, in the RIAA. I do not say that a LCR or LC version sounds better. It´s just another option i would like to mention. I have no own experience with those designs. What i have seen in the Van den Hul phono was that the coils were encapsulated, i think in ferite but i may be wrong. I can ask Jürgen Ultee if he can give me more details but he was quite protective.
Syn08, where are you ? It´s your thread and i would like to learn more what YOU think.
Syn08, where are you ? It´s your thread and i would like to learn more what YOU think.
All of the above to avoid the use of a capacitor in order to ensure input device bias current through the mc is zero or effectively non-existent seems to me to be a questionable tradeoff. If I look at your front end amp Syn08, I see 4 active devices before we get to the opamp where the real gain is being done. That means noise in my book. Better to spend the money on a good cap and a low noise high gain input stage in my view. You have a lot of $'s tied up in that front end PSU as well, to say nothing of the big expensive and bulky caps.
Take a second look. The gain that matters for the noise performance is before the opamp.
Ah, you are counting the RIAA network as well.
Creating a RIAA network using inductances only is very simple. In fact, it's a direct synthesis exercise that can be done starting from the standard RIAA network and performing Z->Y jw->1/jw substitutions. However, I strongly doubt the results can be made better. As "bad" as caps can be, coils (in particular cored) are much worse in terms of Q, parasitic elements, etc...). And much more expensive to build at high precision and matching.
I agree. I would not do it with coils. In fact i work with coils since 40 years but for speakers. Yes i build my first circuit when i was 11. Jürgen Ultee is trained as an HF engineer and i trust that he found a solution. Anyway when i can get my hands on the phono stage i will measure it and listen to it. He build one of my analysers and he is no bullshitter.
i ALWAYS listen first and when it sounds great and measures bad i like to know the reason why. i am a professional designer so i do not have to please myself alone but also have to work agains hard competittion and some magazines have good measurement equipment. so when it measures bad i have a problem. i am very dependent on opinion by opinion makers to make some money for my little family and living in germany got really expensive recently so i try to balance my janus head between the listener and music lover i am ( i play decent guitar and compose, sing and even produce our own little band) and what the market expects from me. i listened to more sytems than you can imagine, i travel the globe since 25 years (also many times to sweden) to please do not call me stupid. I give my best and try to remain the enthusiast i always was since i heard the first klipschorn and quad electrostatics when i was 15. i think i belong to the good guy´s often to my monitary loss.
Joachim,
my attitude is purely academic. It has not been my intention to express opinion in other respects. Stuff like the Hiraga design is not commercially rewarding. The purpose of specification is to empower the audience in their choices, constituting convincing but for the sound quality irrelevant arguments. You can`t say to people, look, the distortion is very high, but that´s why it sounds so good. It´s also pretty useless to explain how much harder is to accomplish good sound than low measured distortion.
my attitude is purely academic. It has not been my intention to express opinion in other respects. Stuff like the Hiraga design is not commercially rewarding. The purpose of specification is to empower the audience in their choices, constituting convincing but for the sound quality irrelevant arguments. You can`t say to people, look, the distortion is very high, but that´s why it sounds so good. It´s also pretty useless to explain how much harder is to accomplish good sound than low measured distortion.
Sometimes designs sound good in spite of the measured distortion, other designs sound bad, even though they measure well with the STANDARD measurements that we generally make. It is quite possible that we are not measuring the more important deviations from the ideal, with our present test equipment.
Global negative feedback seems to be one of the worst problem makers. Yes, it reduces measured distortion, but it adds something more subtle, hard to measure, yet the human ear hears it well enough. That is what is being ignored here, and why subjective inputs seem contradictory to measurements.
Global negative feedback seems to be one of the worst problem makers. Yes, it reduces measured distortion, but it adds something more subtle, hard to measure, yet the human ear hears it well enough. That is what is being ignored here, and why subjective inputs seem contradictory to measurements.
100% wrong and, funny enough, this comes straight after you mentioned about using NFB in your new designs.
I would prefer, if possible, to confine this kind of crap in the BT thread.
My NFB consists of a resistor between the base-collector junction, in order to lower input Z. It works, it is relatively noiseless, and has an open loop bandwidth over 20 KHz.
I don't use it much, anymore, either, but it is a useful approach. to get VERY LOW input impedance without undue attenuation of the phono cartridge source output.
Yours, if I may be so bold, consists of adding an IC to a perfectly good input stage and feeding back lots of feedback to the input.
I don't use it much, anymore, either, but it is a useful approach. to get VERY LOW input impedance without undue attenuation of the phono cartridge source output.
Yours, if I may be so bold, consists of adding an IC to a perfectly good input stage and feeding back lots of feedback to the input.
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