Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

Richard Lee's Ultra low Noise MC Head Amp
Richard Lee's Ultra low Noise MC Head Amp
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 8th October 2019, 10:06 PM   #1591
sonnya is offline sonnya  Denmark
diyAudio Member
 
sonnya's Avatar
 
Join Date: Oct 2001
Location: Denmark
If the short is the same. For voltage and current... Lets say 12.5ohm.. (~1mA emitter current 2x parallel)

Then there is no difference.. I totally agree... And you should not be able to hear any difference and even if the channel is inverting. (both channel in phase of course)
__________________
Mirand Audio amps and Dac's - SALES - OPAMP BASED PREAMP + OLED bundle - 40%
Preamp OPAMP based + OLED Display + LPS V2.1 PSU: 304 - Discount 204
  Reply With Quote
Old 9th October 2019, 03:02 PM   #1592
billshurv is online now billshurv  United Kingdom
diyAudio Member
 
billshurv's Avatar
 
Join Date: Mar 2014
Richard Lee's Ultra low Noise MC Head Amp
Sutherland Engineering Little Loco phono preamplifier | Stereophile.com


Another nearly $4000 current mode phono stage! I note he puts the active components on the underside of the board so you can't see how simple it is
  Reply With Quote
Old 9th October 2019, 04:08 PM   #1593
Mark Johnson is offline Mark Johnson  United States
diyAudio Member
 
Mark Johnson's Avatar
 
Join Date: May 2011
Location: Silicon Valley
Richard Lee's Ultra low Noise MC Head Amp
Ron Sutherland is also big believer in thiiiiiiick PCBs. The farther apart the two copper layers are, the better he likes it. Is that an inconsistency?
  Reply With Quote
Old 9th October 2019, 04:31 PM   #1594
billshurv is online now billshurv  United Kingdom
diyAudio Member
 
billshurv's Avatar
 
Join Date: Mar 2014
Richard Lee's Ultra low Noise MC Head Amp
hey at least he has gone SMT other than the goofy great load resistors which kind of scream 'no you don't want to change gain'. Does seem pricey when a parasound JC3+ is a grand less, and even that is 2500 more than I would proabably spend on phono stages... Although the parts budget is stacking up.



I should note here I do not think Ron is a bad guy. And he has chosen a hard way to pay the bills.
  Reply With Quote
Old 9th October 2019, 09:17 PM   #1595
syn08 is offline syn08  Canada
diyAudio Member
 
syn08's Avatar
 
Join Date: Aug 2005
Location: Toronto
Default I was wrong

Indeed, the Aluminum Polymer caps are worse than regular, good quality electrolytics.

I took a #375, installed sockets for the 7 caps and swapped lots of Al polymer and electrolytics, measured the noise input shorted. Attached is the result, the regular electrolytics (type below) and the worst of the Al polymer devices I was able to get. These Al polymer are all over the place regarding noise (both in noise level and corner frequency), they can be as good as the regular electrolytics, but are certainly much worse on average.

Fortunately regular Panasonic electrolytics are available to replace directly the Al polymer in the $375 layout:

4xdecoupling: 3300uF/6.3V ECA-0JHG332 DigiKey P5511-ND
1xpower supply: 2200uF/6.3V ECA-0JHG222 DigiKey P5510-ND
2xoutput 1000uF/6.3V ECA-0JHG102 DigiKey P5509-ND

However, this is an interesting engineering exercise only, the excess LF noise was not audible (I tried hard).

The ZTX devices have a noise corner frequency around 12-15Hz, which makes sense.

With the Panasonic electrolytics, the noise of #375 (input shorted) is around 0.3nV/rtHz, down to 20Hz.
Attached Images
File Type: jpg caps.jpg (342.3 KB, 136 views)
File Type: jpg IMG_2142.jpg (871.0 KB, 135 views)

Last edited by syn08; 9th October 2019 at 09:23 PM.
  Reply With Quote
Old 9th October 2019, 10:38 PM   #1596
billshurv is online now billshurv  United Kingdom
diyAudio Member
 
billshurv's Avatar
 
Join Date: Mar 2014
Richard Lee's Ultra low Noise MC Head Amp
Quote:
Originally Posted by syn08 View Post

However, this is an interesting engineering exercise only, the excess LF noise was not audible (I tried hard).

.

Surely that sums up this entire thread . No-one needs 300pV/rtHz front ends for sane phono setups.
  Reply With Quote
Old 10th October 2019, 06:43 AM   #1597
Rod Coleman is offline Rod Coleman  United Kingdom
работник
diyAudio Member
 
Rod Coleman's Avatar
 
Join Date: Jul 2004
Location: Warwickshire UK
Richard Lee's Ultra low Noise MC Head Amp
Quote:
Originally Posted by Mark Johnson View Post
It was Horowitz and Hill who shined a spotlight on the very low measured noise of the Zetex transistors. Zetex themselves, and their new corporate owners (Diodes Inc) just call it a medium power high current transistor. There's no mention of noise anywhere on the datasheet. There's no guarantee its noise will be the same from unit to unit, or from week to week, or from fab to fab.

Skiers who venture "off piste", away from the marked trails, are on their own.

Medical doctors who prescribe medications "off label", to treat conditions other than the ones the FDA has approved the drug for, are similarly on their own.

It may also be true that designers who use a transistor (or its vendor supplied .MODEL) "off datasheet", are similarly their own.

For a larruping good time, telephone Zetex's application engineers and ask them for a better SPICE model which is less inaccurate when modeling noise. Expect to be asked about the volume of Zetex parts you have purchased this year & will purchase next year. That's how they prioritize their time.
H&H may have widely publicised the low-noise performance of some of the Zetex transistors, but the firm have tried to draw attention to it, at least in their home territory (here in the UK) for many years. The attached Design Note on Moving Coil amplifiers is from their Application Book in the 1990s. Note in particular the adjective 'reproducible' on low Rbb.

The Zetex medium power transistors have low Rbb by design, and actually they have been remarkably consistent over decades of production. I suppose that Diodes could radically change the process to suit another fab, but the designs as they are give outstanding combinations of high Hfe and saturation performance at high current, and if they spoil this, the relatively high price points of Zetex parts would no longer be tolerated.

It's not just the types tested by H&H that have super low noise - many parts in the 7-series (ZTX7xx and FZT7xx) PNP and 6-series NPN have good performance too.

I can't speak for the Zetex that is now run by Diodes, Inc., but I can say that the Ferranti (who designed the first ZTXs) of the 1980s and Zetex PLC of the 1990s had staff who were remarkably helpful, and I learned many arcane points about transistors from them.
I liked the old firm so much at that time that I designed a CCFL backlight converter for our Handheld PCs with and all-Zetex semiconductor BoM, as a tribute.
Attached Images
File Type: png ZETEX-LN-MC-AN.png (90.8 KB, 136 views)
  Reply With Quote
Old 10th October 2019, 07:34 AM   #1598
Hans Polak is online now Hans Polak  Netherlands
diyAudio Member
 
Join Date: Mar 2005
Location: Blaricum
Quote:
Originally Posted by billshurv View Post
I will be interested to see if you leave the head amp in there after the tests...
Overload margin of my MC phonoamp is 30dB over the audio frequency range.
This is now reduced by 15dB with the inserted Head Amp.
Not sure if this step back is something to disregard.

Hans
  Reply With Quote
Old 10th October 2019, 08:03 AM   #1599
billshurv is online now billshurv  United Kingdom
diyAudio Member
 
billshurv's Avatar
 
Join Date: Mar 2014
Richard Lee's Ultra low Noise MC Head Amp
Well will be interesting to see if you hear anything with hot tracks.
  Reply With Quote
Old 10th October 2019, 01:06 PM   #1600
syn08 is offline syn08  Canada
diyAudio Member
 
syn08's Avatar
 
Join Date: Aug 2005
Location: Toronto
Quote:
Originally Posted by Rod Coleman View Post
Note in particular the adjective 'reproducible' on low Rbb.
Rbb is always reproducible; for a switching transistor, the designer tries to keep Rbb as low as possible, to minimize the saturation voltage. The price for having low Rbb is in general lower beta, at least in a standard process. Zetex found a sweet spot between saturation voltage and beta, with low noise as a byproduct.

There are essentially 3 noise sources in a bipolar device, Rbb, the collector current noise (or base, if you prefer SQRT(2qIb)) and the excess (shot, flicker, telegraph, GR) noise. The last component is LF and each excess noise generation mechanism is characterized by a coefficient, a power exponent for frequency, or the noise corner frequency, if you prefer. Physically, these excess noise sources are essentially determined by the manufacturing process cleanliness. Change the fab and the LF excess noise may blow the device noise performance off the chart, and that with a no (or minimum) impact on the switching device data sheet performance.
  Reply With Quote

Reply


Richard Lee's Ultra low Noise MC Head AmpHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
ultra low noise regulators wtnsmk Power Supplies 26 2nd May 2019 03:12 PM
ultra low noise power supply and low noise amplifier ambrosia168 Power Supplies 8 13th October 2017 02:43 PM
Matching a 1970's receiver with these Richard Allan Loudspeakers? (Richard Allen) gearu Full Range 9 23rd September 2014 03:36 AM
Ultra Low Noise - Ultra Low Impedance - Ultra big Problems! Stefan0815 Analog Line Level 2 14th January 2014 06:01 AM
Ultra low noise filters tiroth Solid State 14 21st May 2002 10:19 PM


New To Site? Need Help?

All times are GMT. The time now is 04:47 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki