I built one while I was at technical college many years ago as one of the tutors had the service manual.
It's a very straightforward design by todays standards using carefully optimised "classic" voltage amplifier stages.
Hard to say in real terms how good it would sound today as back then I hadn't anything like the same quality of speakers or source components.
From all I have learned in the passing years on circuit design I would say that subjectively it would sound excellent.
It's a very straightforward design by todays standards using carefully optimised "classic" voltage amplifier stages.
Hard to say in real terms how good it would sound today as back then I hadn't anything like the same quality of speakers or source components.
From all I have learned in the passing years on circuit design I would say that subjectively it would sound excellent.
I have a modded ZD22/HD250 integrated amplifier in my garage. (It doesn't normally live in a garage, it's just we've moved relatively recently, and I haven't found a proper home for it yet).
It's modded, because the power stage (HD250 part?) was upgraded by my father years ago (actually, decades ago) with some Crimson Electrik boards, as far as I'm aware the preamp is unchanged though.
How does it sound? Well, very nice I think - although I have limited frame of reference. I've not really compared it to much. It's faired very well against a friend's audiolab 8000 kit - although we were enjoying the music more than comparing kit (and possibly unfair/uncontrolled tests because we weren't keeping speakers constant).
Anyway, I feed it with a CD player and DAC, and listen on either LS3/5As or Mission 751s, and I'm very happy with it (admittedly, thats with the power stage, I can't swap the pre amp for something else to compare).
It's modded, because the power stage (HD250 part?) was upgraded by my father years ago (actually, decades ago) with some Crimson Electrik boards, as far as I'm aware the preamp is unchanged though.
How does it sound? Well, very nice I think - although I have limited frame of reference. I've not really compared it to much. It's faired very well against a friend's audiolab 8000 kit - although we were enjoying the music more than comparing kit (and possibly unfair/uncontrolled tests because we weren't keeping speakers constant).
Anyway, I feed it with a CD player and DAC, and listen on either LS3/5As or Mission 751s, and I'm very happy with it (admittedly, thats with the power stage, I can't swap the pre amp for something else to compare).
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I've Got One
If you're interested; I have a ZD22 PreAmp. Due to it's age and lack of use I would say it is in non-working condition. It has been stored for years in my attic. It was a fantastic piece of gear till one day the power supply started motor-boating. Not being technical, I put it aside and bought a new ( hafler) preamp. The workmanship of that Radford is something special, lots of neatly done hand wiring. I never had the heart to get rid of it but I will now consider an offer to part with it if it would be going to a loving restoration.
If you're interested; I have a ZD22 PreAmp. Due to it's age and lack of use I would say it is in non-working condition. It has been stored for years in my attic. It was a fantastic piece of gear till one day the power supply started motor-boating. Not being technical, I put it aside and bought a new ( hafler) preamp. The workmanship of that Radford is something special, lots of neatly done hand wiring. I never had the heart to get rid of it but I will now consider an offer to part with it if it would be going to a loving restoration.
Hi, I try to build a clone of the preamplifier zd22 Radford, has anyone ever heard this?
I have already 'designed the master for printed circuits, but first I would like to hear some opinion.
greetings.
w w w . p c b - a u d i o . c o m
Hi !
have you completed your project ?
Maybe you already have it but I am attaching the schematics
http://www.acousticpsychos.com/Files/Radford-HD250-ZD22-int-sm.pdfhttp://www.acousticpsychos.com/Files/Radford-HD250-ZD22-int-sm.pdf
The line stage (fig. 12) by the way seems unecessarily overdesigned
There are 3 stages when just the first one (gain =3) should be more than enough
I like very much this stage
With a friend we tried to clone it ... just the stage called LINE INPUT AMPLIFIER
Of course we use a log pot instead of the linear one
I liked the sound much more than how my friend liked it
This kind of "minimalist" approach is what fascinates me
Kind regards,
gino
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ZD22 Radford Available
If you're interested; I have a ZD22 PreAmp with the multi-voltage tap AC input. Featured an excellent phono section too. Now, Due to it's age and lack of use I would say it is in non-working condition. It has been stored for years in my attic. It was a fantastic piece of gear till one day the power supply started motor-boating. The workmanship of that Radford is something special, lots of neatly done hand wiring lots of discrete Xistors. I never had the heart to get rid of it but I will now consider an offer to part with it if it would be going to a loving restoration. Make an offer.
If you're interested; I have a ZD22 PreAmp with the multi-voltage tap AC input. Featured an excellent phono section too. Now, Due to it's age and lack of use I would say it is in non-working condition. It has been stored for years in my attic. It was a fantastic piece of gear till one day the power supply started motor-boating. The workmanship of that Radford is something special, lots of neatly done hand wiring lots of discrete Xistors. I never had the heart to get rid of it but I will now consider an offer to part with it if it would be going to a loving restoration. Make an offer.
i would like to build the line stage in figure 12 but i think it has 180 degrees phase shift or i am wrong? so i have to add a n inverting buffer .can you suggest one based on transistor or jfet?
http://www.acousticpsychos.com/Files/Radford-HD250-ZD22-int-sm.pdf
http://www.acousticpsychos.com/Files/Radford-HD250-ZD22-int-sm.pdf
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