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Educational Learn and Listen Class – Phono Stage Design Basics, By Ori Mizrahi-Shalom
May 21, 2022 @ 10:00 am - 3:00 pm$10.00
This will be a two-part experience (there will be a separate announcement for those members who only want to participate in the listening session and not in the class):
- A class on the design basics of phono stages from 10:00 to 11:30 AM PST
- Lunch – there are several locations for lunch nearby
- A listening session of a number of different sub-$1000 phono stages from 1:00 to 3:00 PM PST
This event will be held in-person in San Jose.
The class is a fast-paced semi-technical class that will introduce you to phono stage design in general, followed by a technical analysis of some phono stage implementations. The idea is to develop a deeper understanding of design techniques utilized in each unit and then assess to yourself in the following listening session how it influences the sound (if at all). This is the first “learn and listen” event for SFAS. Attendees will be asked to fill out a survey to decide if this format is suitable for future events. The class will take approximately 90 minutes.
The listening session will include several DIY and kit phono stages and two relatively inexpensive commercial phono stages for an opportunity to hear, or not hear, differences in phono stage designs.
PHONO STAGE CLASS TOPICS:
1) vinyl-recorded signal levels at audio frequencies, RIAA recording curve
2) signal levels of MM and MC cartridges, loading
3) Noise in amplifiers: thermal, 1/f, power supply, external EMI pickup
4) low-noise considerations for the input stage, characteristics of the passive and active components
6) reducing power supply hum, series and shunt regulators, PSRR
7) Implementing RIAA playback curve: passive vs active vs hybrid
8) Hagerman Cornet tube schematics, compare to EAR 834P schematics
9) Luxman EQ-500 tube schematics (simplified)
10) Muffsy PP3 kit schematics (op amp)
11) LT1115 Application Note (opamp biased into class A)
12) Boozehound kit schematics (super simple JFET)
13) Pass DIY Pearl III (yes, not II – you’ll know why after this class…)
14) RIAA with DSP EQ
WHO SHOULD ATTEND:
First you should be interested in technical details of electronic gear. Attendees are expected to know the basics of tubes, transistors and op amps as used in amplifier circuits.
If you’re not a tech or engineer, we have some homework assignments for you by clicking on the links below to the YouTube videos:
How diodes and triodes work: clip 1 00:00-11:00 and 23:34-26:13 and clip 2 (full)
Triode structure, grid effect on plate current 1:07-6:46
Cathode-bias Triode amplifier circuit 22:25-24:06 and 26:14-28:45
It takes a few hours to study this material, so please take it seriously and schedule a few days to go over the topics. Last minute charlies most likely won’t make it.
Due to time constraints and the extent of material covered, there will be no basic explanations of the prerequisite topics during the class.
WHY YOU SHOULD ATTEND:
We are trying the “learn and listen” format as one way to spice up SFAS events. Some members are not interested in technical topics and that is absolutely fine. Those people probably should skip this class. The class is for those who are technically-inclined and want to know more than vague and shallow descriptions in magazine articles. You will not get an engineering degree but you should know a lot about phono stages after attending this class. We hope that technical excellence translates into better sound and you will be able to assess that claim to yourself. Specific to this event, the class also discusses several kit units that you can build. It’s good to know what’s inside before you drop the cash…
Listening Session Description:
Intro: 10 min
Main Phono Units:
- Jim Hunton’s PASS DIY PEARL II, separate power supply with shunt regulators, Dayton foil/film caps, DC servo. ($800 total, 20 min main focus)
- Hagerman Cornet tube phono stage, including tube rectifier, added zener shunt regulation and NOS tubes. ($800 total, 20 min main focus)
- Ori’s simple phono stage (proprietary design) with shunt regulation and battery supply. ($NA, 10 min quick demo)
Reference Commercial units:
- iFi Zen: entry level opamp-based ($179, 10 min quick demo).
- Luxman EQ-500 ($6,695, NOS tubes, 20 min)
A special attraction is the power amp: We will use Tony Chipelo’s personal Music Reference RM-10 mkI (designed by the late Roger Modjeski) for this event. It is a unique design that extracts 27 WPC from a pair of EL-84 tubes by utilizing a 700V supply while keeping the power dissipation within spec. A new version of the Music Reference RM-10 mkII will be available soon, so this is a preview of an amp in the making.
Closing discussion and replay tracks 30 min
- classic Jazz, instrumental: Georgia – Teddy Edwards Quartet – Timeless SJP139
- pop, male vocal: Wild World – Cat Stevens – AM SP4519
- pop, female vocal: Riahnon – Fleetwood Mac – WB MSK2281
- classic Jazz, instrumental: Ebony – Jack DeJohnette/Cedar Walton/Ron Carter – LimeTree MLP0021
- cassical, piano solo, instrumental: Chopin nocturnes – Tomas Vasary, piano – Deutche Gramophon 136486 stereo
- classical, orchestral: Rachmaninoff/Symphonic Dances – Kiryl Kondrashin conducting the Moscow Philharmonic – Angel/Melodia 40093 Stereo
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