If you talk about my pic, there are 3 transformers:
top left: Clock & power,
bottom left: chopper n=1:32
bottom right: de-chopper
They are standard MACOM / Pulse Engineering SMD devices 0.5...500 MHz or so.
I had to modify the input transformer.
The preamp is not meant for audio, though it has no global feedback!
I'm trying how far I can push down the 1/f corner.
The CPLD generates the chop clock & delay to the de-chopper from a 100 MHz osc.
top left: Clock & power,
bottom left: chopper n=1:32
bottom right: de-chopper
They are standard MACOM / Pulse Engineering SMD devices 0.5...500 MHz or so.
I had to modify the input transformer.
The preamp is not meant for audio, though it has no global feedback!
I'm trying how far I can push down the 1/f corner.
The CPLD generates the chop clock & delay to the de-chopper from a 100 MHz osc.
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Beware you need the low Vcesat for that circuit, it usually come for free but then...
My resolution for 2018 is to build as many phono stages as I can that are considered
'wrong'. I have my transamp MM stage, this and also the balanced flat gain stage based on the AD524 I've mentioned before. There must be some other topologies out there that clearly show I don't care about the 'best'
'wrong'. I have my transamp MM stage, this and also the balanced flat gain stage based on the AD524 I've mentioned before. There must be some other topologies out there that clearly show I don't care about the 'best'
My resolution for 2018 is to build as many phono stages as I can that are considered
'wrong'. I have my transamp MM stage, this and also the balanced flat gain stage based on the AD524 I've mentioned before. There must be some other topologies out there that clearly show I don't care about the 'best'
The AD624 is better, it actually gets close to the 5534 sweet spot on noise for MM. I could send you a couple for Christmas.
I should have said AD524 'inspired' so the classic op-amp wrapped around a bipolar. Another of Wayne's experiments. Horrifies all those who think first gain stage should never go over 40dB. He never got beyond a lash up so I might go for a proper job with veroboard
A Low Noise Balanced In Moving Coil Preamp Using the ZTX851 - Pro Audio Design Forum
A Low Noise Balanced In Moving Coil Preamp Using the ZTX851 - Pro Audio Design Forum
OK, I used the 624/744 split RIAA that Walt and I published for years. When I switched to the Monster Alpha 1 MC I was surprised that the noise did not bother me at all and left it in.
Well it is always good to try stuff that has been abandoned in the past. '-) This circuit from 1981 is interesting, and is very quiet. Distortion? Yes, a bit.
You guys can try the grounded base design and hear what it sounds like for yourself, I have. Back in 1975 Mark wanted to 'improve' the original JC-1 design and we switched over to grounded base input for two new models: The JC-1AC and the JC-1DC that had more headroom (double the voltage compared to the JC-1) and was non-inverting. I got my first JC-1AC in 1975 (still have it somewhere) and was initially disappointed in the sound, it really did sound overdamped or 'underwater', so I got my tech to mount a switch so that inverting (common emitter) or non-inverting (common base) could be used easily. Of course the audio polarity would changed as well, but this was too early (1976) to take much note of. Listening to mostly direct disc records (Sheffield) with a Supex cartridge, Levinson JC-2 phono stage and Electrocompaniet power amp, we found the hi Z (100 ohms) to sound better. Go figure. Hey, it was my idea to use the common base input, and it didn't work out as well as I had hoped. Your listening experience may differ from mine. I know that VandenHul liked virtually zero ohm input and others still recommend it today. Because of this I originally added a summing type input in the original Vendetta SCP-1, (pre-preamp) in 1983, accessible by pins on the circuit board, but by 1990 when we came out with the SCP-2B, we weren't able to use this option, and 10 ohms became our minimum setting ever since. I know of no rational reason why the summing type input should not work, it just did not work for me.
As far as Mark Levinson is concerned, I really watched the change in him over the decades. When I worked with him up to the mid 70's he was an idealistic young guy who wanted to make the best sounding equipment that he could, and he was a great salesman for his products. He remained a great salesman, but his products changed over the decades, and now are ridiculously expensive or some sort of gimmick. I don't take him seriously anymore, enough said.
Scott is right about choosing input ultra noise bipolars for this application (virtual zero volt operation between the base and the collector) Some quality parts will NOT work well, for example the Hitachi complementary pair that I found to be the best overall devices for low noise that I have ever found. However, the Rohm devices should work OK, and the Fairchild PE8050-8550 worked for me with the SOTA headamp in 1979-82 or so period. Perhaps these devices are still available, but be wary of this problem with early saturation with some device types. I have seen it with a curve tracer so if you have access to one.
You guys can try the grounded base design and hear what it sounds like for yourself, I have. Back in 1975 Mark wanted to 'improve' the original JC-1 design and we switched over to grounded base input for two new models: The JC-1AC and the JC-1DC that had more headroom (double the voltage compared to the JC-1) and was non-inverting. I got my first JC-1AC in 1975 (still have it somewhere) and was initially disappointed in the sound, it really did sound overdamped or 'underwater', so I got my tech to mount a switch so that inverting (common emitter) or non-inverting (common base) could be used easily. Of course the audio polarity would changed as well, but this was too early (1976) to take much note of. Listening to mostly direct disc records (Sheffield) with a Supex cartridge, Levinson JC-2 phono stage and Electrocompaniet power amp, we found the hi Z (100 ohms) to sound better. Go figure. Hey, it was my idea to use the common base input, and it didn't work out as well as I had hoped. Your listening experience may differ from mine. I know that VandenHul liked virtually zero ohm input and others still recommend it today. Because of this I originally added a summing type input in the original Vendetta SCP-1, (pre-preamp) in 1983, accessible by pins on the circuit board, but by 1990 when we came out with the SCP-2B, we weren't able to use this option, and 10 ohms became our minimum setting ever since. I know of no rational reason why the summing type input should not work, it just did not work for me.
As far as Mark Levinson is concerned, I really watched the change in him over the decades. When I worked with him up to the mid 70's he was an idealistic young guy who wanted to make the best sounding equipment that he could, and he was a great salesman for his products. He remained a great salesman, but his products changed over the decades, and now are ridiculously expensive or some sort of gimmick. I don't take him seriously anymore, enough said.
Scott is right about choosing input ultra noise bipolars for this application (virtual zero volt operation between the base and the collector) Some quality parts will NOT work well, for example the Hitachi complementary pair that I found to be the best overall devices for low noise that I have ever found. However, the Rohm devices should work OK, and the Fairchild PE8050-8550 worked for me with the SOTA headamp in 1979-82 or so period. Perhaps these devices are still available, but be wary of this problem with early saturation with some device types. I have seen it with a curve tracer so if you have access to one.
Following on from your comment yesterday about the availability of low Rbb bipolars with low 1/f knee,I thought it might be a good time to offend the high voltage folded cascode mob with this blast from the past. This is Richard Lee's improved Leach MC headamp from 1981
A Flat Moving Coil Preamp Using Paralleled Amplifiers - Page 4 - Pro Audio Design Forum
I would copy the schematic but don't want to upset Richard and lots of good stuff over on Wayne's forum for people with an open mind so worth a visit
Is this Richard Lee's out of southern Calif? LA? If so, his sister called me a couple years ago. He died.
THx-RNMarsh
Nah this one is (or was a few months ago) happily enjoying retirement in Australia. He posts here sometimes as kgrlee
You can get pretty good litch on TT's these days. Combine this turntable with a linear tracker and the Dynavextor 17DIII and you will be somewhere. But honestly I am not sure accuracy of a cartridge is the pure ideal if the record noises become too prominanent. Then again I am not listening to the SNR etc, I judge the sound of the music, not groove noise etc. And thus far vinyl is still better. Besides just like the guy posted a month or more ago, according to mastering and mixing engineers vinyl sounds more like master tapes, even indistinguishable, compared to digital.
Monaco Turntable v2.0 | Grand Prix Audio
Monaco Turntable v2.0 | Grand Prix Audio
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