Now for something different.
Two things came together recently .
I got a batch of brand new OPamps from BB, National and AD and i bought the new D.Self
book. I wanted to build his Precission Preamplifier since it came out in 1996 and to my surprise i found it unchanged in his new book.
I thought this could be an oportunity to try the new chips.
I enyoy a lot when other are doing good things and the Self design is clever and thourough. On the other hand he is dealing with the bipolar NE5534 that has input and ouput offset. To block all posible DC passes the signal is routed through no less then 9 high value elcaps and 6 foils ( plus a plethora of switches, potmeters and relays) until the tiny MC signal reaches the output. I do not want to start a discussion if that is audible or not but it created an unconfortable feeling in me.
I started to boil down the circuit to the minimum and by using Fet and servo technology plus leaving out the tonecontrol i could reduce the capacitor count to 3 foils in the subsonic filter. Actually i kept the subsonic filter because it is a good idea when you do not own a 10.000,-$ frontend with provision to clamp down the record.
It has the IEC extention build in with -3dB at 20Hz. That may be too agressive for some so i will experiment with the filter to find a maybe better compromise.
I am already building the MC stage. I did not use the Self design here. It is rather a very simple Phono Clone circuit with the twist that i can use a low value feedback resistor with the ADA4898-1. That comes in quite handy. I have build Phono Clones with the OP211 and AD797 that performed surprisingly well but making the feedback resistor smaller then 500 Ohm was not an option. With my Titan the gain was nearly 40dB and i had to reduce the gain at the output with a resistive devider. Not very elegant !
Two things came together recently .
I got a batch of brand new OPamps from BB, National and AD and i bought the new D.Self
book. I wanted to build his Precission Preamplifier since it came out in 1996 and to my surprise i found it unchanged in his new book.
I thought this could be an oportunity to try the new chips.
I enyoy a lot when other are doing good things and the Self design is clever and thourough. On the other hand he is dealing with the bipolar NE5534 that has input and ouput offset. To block all posible DC passes the signal is routed through no less then 9 high value elcaps and 6 foils ( plus a plethora of switches, potmeters and relays) until the tiny MC signal reaches the output. I do not want to start a discussion if that is audible or not but it created an unconfortable feeling in me.
I started to boil down the circuit to the minimum and by using Fet and servo technology plus leaving out the tonecontrol i could reduce the capacitor count to 3 foils in the subsonic filter. Actually i kept the subsonic filter because it is a good idea when you do not own a 10.000,-$ frontend with provision to clamp down the record.
It has the IEC extention build in with -3dB at 20Hz. That may be too agressive for some so i will experiment with the filter to find a maybe better compromise.
I am already building the MC stage. I did not use the Self design here. It is rather a very simple Phono Clone circuit with the twist that i can use a low value feedback resistor with the ADA4898-1. That comes in quite handy. I have build Phono Clones with the OP211 and AD797 that performed surprisingly well but making the feedback resistor smaller then 500 Ohm was not an option. With my Titan the gain was nearly 40dB and i had to reduce the gain at the output with a resistive devider. Not very elegant !
Schematic
Hi Joachim,
I can't find the schematic of this phonoclone headamp, can you post it please?
Thanks in advance.
Best regards,
Audiofanatic
Hi Joachim,
I can't find the schematic of this phonoclone headamp, can you post it please?
Thanks in advance.
Best regards,
Audiofanatic
I am just listening to it over my new headphone amp and inductive RIAA.
Input and output offset is nill so all is DC coupled. The inductive RIAA is very sensitive to even small offset but it works well.
Sound is quite transparent but i will listen more and will tel you.
Btw, quite fascinating to listen to vinyl over headphones.
Input and output offset is nill so all is DC coupled. The inductive RIAA is very sensitive to even small offset but it works well.
Sound is quite transparent but i will listen more and will tel you.
Btw, quite fascinating to listen to vinyl over headphones.
Yes, I miss listening to vinyl on my tube headphone amp run by salas' jfet phono stage!
Now we help Merlin tune it. JFETS go to Spain. Malaga is Costa Del Sol, but could not find one for Costa Brava. Sorry Merlin.
On the floor is my headphone amp. I posted it some time ago but i am still working on it.
It has 30mA class A and i whould like to bring it up to 100mA. There is also a kind of strange distortion when i crank it on the inefficient AKG701. Let´s see what i can do when i have my new measurement equipment for my home.
At work there is still a lot of construction going on and i expect to be back in my lab not before the end of April. That is also the reason i have a lot of time for my hobby.
At work i can not do much momentarily except setting up the soundroom for a party on friday.
It has 30mA class A and i whould like to bring it up to 100mA. There is also a kind of strange distortion when i crank it on the inefficient AKG701. Let´s see what i can do when i have my new measurement equipment for my home.
At work there is still a lot of construction going on and i expect to be back in my lab not before the end of April. That is also the reason i have a lot of time for my hobby.
At work i can not do much momentarily except setting up the soundroom for a party on friday.
That 701 is difficult. My neighbor has a pair and we made a single Mosfet buffer with CCS, like mini Zen, it was driving my Grados loud from CD level. AKG dead, would not bother. So I did a virtual ground to provide symmetric bcs it had just a single polarity 600mA reg, and boosted voltage gain by sticking an OPA in front. Only then the 701 woke up. That buffer was running hot bias.
Hanze Hifi ?
Hi Joachim,
To bad I didn't get your post earlier, in fact I didn't get it at all.
I was searching for an earlier post of you and read that you're in Holland today!
Are you visiting my friends, Jaap and Johan?
If yes, I would have done everything to be there to meet and talk to you.
Nevertheless Germany is not so far so maybe next time...........
Best regards,
Audiofanatic (José)
Hi Joachim,
To bad I didn't get your post earlier, in fact I didn't get it at all.
I was searching for an earlier post of you and read that you're in Holland today!
Are you visiting my friends, Jaap and Johan?
If yes, I would have done everything to be there to meet and talk to you.
Nevertheless Germany is not so far so maybe next time...........
Best regards,
Audiofanatic
(José)
Listening to phonstages and further work on the headphone amp.
I visited a friend and we listened to phono and also listened and measured my headamp
on an Audio Precission system.
We used my REGA turntable with Lyra Helicon on a Roxan stand.
First we listened to the High Z MPP with inductive RIAA and later we substituted the MPP
with the ADA4898 phonoclone.
Noise in both setups was no problem. The MPP dead quite and the Phonoclone had a low level of hiss that sounded like white noise, ear on the electrostatic speakers at decent volume. That ADA4898 has a very low 1/F corner frequency and is superior to the AD797 in that issue.
We both preferered the MPP slightly. It had a more robust and full sound. The Phonoclone was typical for circuits like that. Very fast and clean, maybe a little sterile but with very good resolution, fascinating in it´s own right. This is a very simple little project that you can build in one afternoon. If you want even less noise you can parallel
4 or 8 but that drives the price up ( that chips are not cheep) and a discreet stage can be made for that money.
It was very interesting to listen to and measure the headamp. I had constructed it without any measurement equipment just by common sence and listening and in fact it sounds just fine. We usen the Sennheiser PX200 that worked extremely well.
This is a great bargain when you want to try headphone listening without spending a fortune. Measuring it brought interesting results. We measured the Fet buffer, the linestage and the outputstage seperately. Clipping was at 7.5V RMS. That is loud enough for hedaphone listening but i am contemplating to raise the output for my hard to drive AKG701.
The Fet produced around 0.2% distortion, mainly second harmonic and very linear over frequeny. The compleet amplifier had an exponentially falling distortion profile.
A recipy for good sound in my experience. The shunt feedback voltage amplifier was of cause 100x better and the diamond buffer alone was also under 0.002% so it is posible to run that stage open loop as an option. If you are uncomfortabe with the Fet i designed a new version with OP buffer and servo that should have neglible distortion.
Let´s see how it sounds subjectively. 0.2% second harmonic does not sound like distortion though and one version could have a provission to switch betwen the Fet and OPamp and also between open and closed loop.
I also made a headphone output for the Self phono-linestage. I use the LME49713 that can drive 100mA in the outputsatge, so headphone listen should be posible with most models except the current hungry monsters like the AKG701.
I had a chance to listen to the new Sennheiser HD1000 today and was extremely impressed. The sound was 100% my taste. Clean, fast and punshy in the bass, open, uncoloured midrange and very good detain in the treble.
I visited a friend and we listened to phono and also listened and measured my headamp
on an Audio Precission system.
We used my REGA turntable with Lyra Helicon on a Roxan stand.
First we listened to the High Z MPP with inductive RIAA and later we substituted the MPP
with the ADA4898 phonoclone.
Noise in both setups was no problem. The MPP dead quite and the Phonoclone had a low level of hiss that sounded like white noise, ear on the electrostatic speakers at decent volume. That ADA4898 has a very low 1/F corner frequency and is superior to the AD797 in that issue.
We both preferered the MPP slightly. It had a more robust and full sound. The Phonoclone was typical for circuits like that. Very fast and clean, maybe a little sterile but with very good resolution, fascinating in it´s own right. This is a very simple little project that you can build in one afternoon. If you want even less noise you can parallel
4 or 8 but that drives the price up ( that chips are not cheep) and a discreet stage can be made for that money.
It was very interesting to listen to and measure the headamp. I had constructed it without any measurement equipment just by common sence and listening and in fact it sounds just fine. We usen the Sennheiser PX200 that worked extremely well.
This is a great bargain when you want to try headphone listening without spending a fortune. Measuring it brought interesting results. We measured the Fet buffer, the linestage and the outputstage seperately. Clipping was at 7.5V RMS. That is loud enough for hedaphone listening but i am contemplating to raise the output for my hard to drive AKG701.
The Fet produced around 0.2% distortion, mainly second harmonic and very linear over frequeny. The compleet amplifier had an exponentially falling distortion profile.
A recipy for good sound in my experience. The shunt feedback voltage amplifier was of cause 100x better and the diamond buffer alone was also under 0.002% so it is posible to run that stage open loop as an option. If you are uncomfortabe with the Fet i designed a new version with OP buffer and servo that should have neglible distortion.
Let´s see how it sounds subjectively. 0.2% second harmonic does not sound like distortion though and one version could have a provission to switch betwen the Fet and OPamp and also between open and closed loop.
I also made a headphone output for the Self phono-linestage. I use the LME49713 that can drive 100mA in the outputsatge, so headphone listen should be posible with most models except the current hungry monsters like the AKG701.
I had a chance to listen to the new Sennheiser HD1000 today and was extremely impressed. The sound was 100% my taste. Clean, fast and punshy in the bass, open, uncoloured midrange and very good detain in the treble.
The dirty details
Some visuals:
This picture shows prototypes of Joachims' line amp/headphone amp at the top, his very compact prepre consisting of a new hot opamp and one (yes, one) resistor at the left. The batteries that supplied power to the prepre can be seen at the extreme left (black bricks).
The RIAA preamp is in the metal box, supplied by LC Audio power. It has the inductive RIAA, and the two coils, in sowter xformer cases, can be seen external to the box.
To say it sounded great must be the understatement of the month.
jd
Some visuals:
This picture shows prototypes of Joachims' line amp/headphone amp at the top, his very compact prepre consisting of a new hot opamp and one (yes, one) resistor at the left. The batteries that supplied power to the prepre can be seen at the extreme left (black bricks).
The RIAA preamp is in the metal box, supplied by LC Audio power. It has the inductive RIAA, and the two coils, in sowter xformer cases, can be seen external to the box.
To say it sounded great must be the understatement of the month.
jd
Attachments
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