Well Jan, this is why I do not subscribe to your magazine. I didn't subscribe to the 'Audio Critic' as well.
Dick Burwen is a good engineer. However, I replaced virtually everything that he did for Mark Levinson when I worked with Mark from 1973-1976. This was Mark's decision, not mine. I only had design control of the JC-1 and the JC-2 in this time period, but my discrete designs went into the LNP-2 and the LNC-2 as well, although they started as Dick Burwen's designs.
Dick Burwen, at the time, used the SAME IC that I had selected for the Grateful Dead PA board back in 1970. This was the HA-911. He had the advantage of selecting them for various tasks, and in hindsight, this was a great advantage, as many units had xover distortion that could be measured with the special equipment that I finally got in 1974.
However, in the meantime, between 1971 and 1973, the Grateful Dead stopped using the IC based board and returned to their modified Ampex tube mixers.
In late 1972, I was again hired by the Grateful Dead to make the active electronics for their new sound system, 'The Wall of Sound'. I decided to make all discrete circuits using complementary symmetry jfet inputs and transconductance output that I had developed in the intervening time since I last worked with them. Sonically they were a success, and everybody was happy, but I had to get a number of them built, somehow. At this time, I fortuitously found Mark Levinson at an AES convention, and he and I decided to make some electronics together. So, along with the design of the JC-1, I commissioned Mark to build the discrete gain modules for the Grateful Dead. He did so, and was so impressed sonically with the result, that he wanted to build the JC-2 preamp based on these modules.
At about this time, Mark also loaned the Grateful Dead one of Dick Burwen's mixer designs for the stage monitors at the Watkins Glen event, and it went well with the crew, who liked its overall sound. However, they did NOT switch over to Burwen modules, OR buy the mixer from Mark Levinson.
Years later, after Mark and I permanently separated due to a royalty hassle, Mark used a number of aspiring designers that he could more easily control.
Much later, when Mark lost Mark Levinson Audio Systems, and formed Cello, he rehired Dick Burwen to make the excellent EQ, that is well known, even today.
Dick Burwen has always believed in op amps and their high feedback. I just don't agree with him on this. So be it.
Dick Burwen is a good engineer. However, I replaced virtually everything that he did for Mark Levinson when I worked with Mark from 1973-1976. This was Mark's decision, not mine. I only had design control of the JC-1 and the JC-2 in this time period, but my discrete designs went into the LNP-2 and the LNC-2 as well, although they started as Dick Burwen's designs.
Dick Burwen, at the time, used the SAME IC that I had selected for the Grateful Dead PA board back in 1970. This was the HA-911. He had the advantage of selecting them for various tasks, and in hindsight, this was a great advantage, as many units had xover distortion that could be measured with the special equipment that I finally got in 1974.
However, in the meantime, between 1971 and 1973, the Grateful Dead stopped using the IC based board and returned to their modified Ampex tube mixers.
In late 1972, I was again hired by the Grateful Dead to make the active electronics for their new sound system, 'The Wall of Sound'. I decided to make all discrete circuits using complementary symmetry jfet inputs and transconductance output that I had developed in the intervening time since I last worked with them. Sonically they were a success, and everybody was happy, but I had to get a number of them built, somehow. At this time, I fortuitously found Mark Levinson at an AES convention, and he and I decided to make some electronics together. So, along with the design of the JC-1, I commissioned Mark to build the discrete gain modules for the Grateful Dead. He did so, and was so impressed sonically with the result, that he wanted to build the JC-2 preamp based on these modules.
At about this time, Mark also loaned the Grateful Dead one of Dick Burwen's mixer designs for the stage monitors at the Watkins Glen event, and it went well with the crew, who liked its overall sound. However, they did NOT switch over to Burwen modules, OR buy the mixer from Mark Levinson.
Years later, after Mark and I permanently separated due to a royalty hassle, Mark used a number of aspiring designers that he could more easily control.
Much later, when Mark lost Mark Levinson Audio Systems, and formed Cello, he rehired Dick Burwen to make the excellent EQ, that is well known, even today.
Dick Burwen has always believed in op amps and their high feedback. I just don't agree with him on this. So be it.
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I would like to generate an list of 'upgrades' that the Vendetta Research series of phono preamps over 10 year period, or so.
1. SCP-1, no feedback, solder-plated, FR-4, input stage only.
2. SCP-2, EQ added in second stage, gold plated, Nomex board material
3. SCP-2A Improved power supply, fully floating (no center tap), much bigger caps.
4. SCP-2B Made non-inverting, added 47K optional input load, Holco resistors in RIAA.
5. SCP-2C Replaced set of mos fets for jfets in second stage, ten times measured distortion improvement.
6. SCP-2D Substituted high speed soft recovery diodes for standard diode bridges.
7. SCP-2T 1% Teflon caps from same manufacturer substituted for RT Polystyrene caps.
Where are the tweaks?
For the record, there have been no 'upgrades' to the CTC Blowtorch over the lifetime of the product.
1. SCP-1, no feedback, solder-plated, FR-4, input stage only.
2. SCP-2, EQ added in second stage, gold plated, Nomex board material
3. SCP-2A Improved power supply, fully floating (no center tap), much bigger caps.
4. SCP-2B Made non-inverting, added 47K optional input load, Holco resistors in RIAA.
5. SCP-2C Replaced set of mos fets for jfets in second stage, ten times measured distortion improvement.
6. SCP-2D Substituted high speed soft recovery diodes for standard diode bridges.
7. SCP-2T 1% Teflon caps from same manufacturer substituted for RT Polystyrene caps.
Where are the tweaks?
For the record, there have been no 'upgrades' to the CTC Blowtorch over the lifetime of the product.
John,
Did i read once you made a updated custom version of the external power supply for the SCP -2 using power supplies similar to the Blowtorch with something like a CLC input - 317/337 with shunt regulator second stage. Or was I sniffing the flux remover too long....... Or is that the long lost Vendetta SCP 3?
Did i read once you made a updated custom version of the external power supply for the SCP -2 using power supplies similar to the Blowtorch with something like a CLC input - 317/337 with shunt regulator second stage. Or was I sniffing the flux remover too long....... Or is that the long lost Vendetta SCP 3?
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That's OK, I'll comp you one.
Yes, I once saw an opened Cello Audio Palette (actually Mark L showed it to me) designed by Dick and it was build from lots of individual modules based on opamp-type circuits.
Then again, Dick also successfully designed and build a magnetometer to measure the moon's magnetic field from a probe in orbit, to mention just one of his accomplishments....
jan
Now that we have the 'mods' taken care of, what about 'tweaks'?
That is difficult to list each and every change that I have made in my part selection and fabrication techniques, but I can give a few examples.
In 1970, I freely used SN60 solder, doorbell wire, ceramic caps, and carbon resistors.
I mostly designed with bipolar transistors, as jfets were undeveloped, but I did use fully complementary differential input stages.
When Mark Levinson and I started to work together, in 1973, he introduced me to FR-4 circuit board material, SN63 eutectic solder, polycarbonate coupling caps, Teflon wire, and 1% metal film resistors throughout the design, not just the feedback resistors. I contributed complementary differential input jfets, complementary self biasing jfets at the output, small mica caps, and transconductance preamp outputs.
We still used no gold plating on our connectors.
Matti Otala gave me the idea of less feedback, more open-loop bandwidth. (more later)
That is difficult to list each and every change that I have made in my part selection and fabrication techniques, but I can give a few examples.
In 1970, I freely used SN60 solder, doorbell wire, ceramic caps, and carbon resistors.
I mostly designed with bipolar transistors, as jfets were undeveloped, but I did use fully complementary differential input stages.
When Mark Levinson and I started to work together, in 1973, he introduced me to FR-4 circuit board material, SN63 eutectic solder, polycarbonate coupling caps, Teflon wire, and 1% metal film resistors throughout the design, not just the feedback resistors. I contributed complementary differential input jfets, complementary self biasing jfets at the output, small mica caps, and transconductance preamp outputs.
We still used no gold plating on our connectors.
Matti Otala gave me the idea of less feedback, more open-loop bandwidth. (more later)
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Now, where were we? Oh, yes, 1974. This is when I found problems in the high quality volume control pots that Mark Levinson was using. He had to change the brand and the loading.
A true measurement of ceramic problems, using a modified Tek 577 curve tracer, and a realistic bandwidth estimation of MC cartridges.
Not much changed until 1978 or so, when Dick Marsh brought out the potential problem of DA in caps. Then we tried to servo, rather than use coupling caps for future products. This led to direct connection of all stages from pre-pre-amp through the power amp (no coupling caps).
Dick Marsh introduces ground planes to audio. I first used it in JC-80 preamp.
Resistor quality came under consideration. I settled on Roderstein Resista resistors.
Cap quality as well. I settled on Reliable RT polystyrene capacitors.
And so it goes, as we are about 30 years behind at this point.
A true measurement of ceramic problems, using a modified Tek 577 curve tracer, and a realistic bandwidth estimation of MC cartridges.
Not much changed until 1978 or so, when Dick Marsh brought out the potential problem of DA in caps. Then we tried to servo, rather than use coupling caps for future products. This led to direct connection of all stages from pre-pre-amp through the power amp (no coupling caps).
Dick Marsh introduces ground planes to audio. I first used it in JC-80 preamp.
Resistor quality came under consideration. I settled on Roderstein Resista resistors.
Cap quality as well. I settled on Reliable RT polystyrene capacitors.
And so it goes, as we are about 30 years behind at this point.
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I'm working on that.
BTW, it's not a 'mag', I beg you pardon??
It's a 'bookzine'
jan
Apologies. Call it what you will, I still want it!
That was also Dick's approach to the perfect microphone, I try to cover both sides, all FET class A and lots of feedback.
Well, what have my associates and I found to improve audio electronics during the last 30 years?
First, audio cables have improved in both design and connector quality. This led to better and tighter RCA connectors that became available.
About 30 years ago, Vendetta Research first started as a side project. The improvements over the next 10 years (more or less) were mostly incorporated in Vendetta products, as previously listed. Also, I learned that I could not even use Tantalum or aluminum caps as power supply bypass caps directly located near active audio circuits. This was a big surprise, but I accept it, even today.
We experimented with connector construction. Dick Marsh and Walt Jung got me looking in this direction. Holm's book on contacts, and J.Whitley's articles on contact design in AMP application notes were very revealing. This lead to experiments including copper silver gold interfaces compared to copper nickel gold, as well as heavy gold directly over copper.
Wire experiments were made, and to my surprise, a Teflon based high voltage coax cable that was used extensively at LBL, and subsequently I used at Humphrey Instruments as high voltage control wiring, sounded LOUSY when hooked up as an audio interconnect. Go figure, but this was an example to me, of 'reverse expectations' i.e. it looked good, it was available, it had a good 'story' YET it sounded lousy. Go figure.
Experiments with Corcom and related RF, AC line filters were attempted and often rejected by serious listeners. What was going on?
Finally, toroid power transformers were found to have too much coupling capacitance, and we looked for alternatives such as classical E-I and D core for critical applications.
(more later)
First, audio cables have improved in both design and connector quality. This led to better and tighter RCA connectors that became available.
About 30 years ago, Vendetta Research first started as a side project. The improvements over the next 10 years (more or less) were mostly incorporated in Vendetta products, as previously listed. Also, I learned that I could not even use Tantalum or aluminum caps as power supply bypass caps directly located near active audio circuits. This was a big surprise, but I accept it, even today.
We experimented with connector construction. Dick Marsh and Walt Jung got me looking in this direction. Holm's book on contacts, and J.Whitley's articles on contact design in AMP application notes were very revealing. This lead to experiments including copper silver gold interfaces compared to copper nickel gold, as well as heavy gold directly over copper.
Wire experiments were made, and to my surprise, a Teflon based high voltage coax cable that was used extensively at LBL, and subsequently I used at Humphrey Instruments as high voltage control wiring, sounded LOUSY when hooked up as an audio interconnect. Go figure, but this was an example to me, of 'reverse expectations' i.e. it looked good, it was available, it had a good 'story' YET it sounded lousy. Go figure.
Experiments with Corcom and related RF, AC line filters were attempted and often rejected by serious listeners. What was going on?
Finally, toroid power transformers were found to have too much coupling capacitance, and we looked for alternatives such as classical E-I and D core for critical applications.
(more later)
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Of course there is no other branch of electronics or instrumentation that has needed any progress in the last thirty years. As far as I can tell not a single major change in component composition/material science or conductor/contact metalurgy was driven by the audio industry.
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What about XLR connections, were they available then?
What about TRS connections, were they used since the beginning of 20'th Century?
An externally hosted image should be here but it was not working when we last tested it.
Audio industry Scott was a driving force when cinema and radio were major forces of propaganda. It's all about political and economical power.
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