pass vs jeff rowland - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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 13th October 2001, 04:59 AM   #1
diyAudio Member
 
Join Date: Oct 2001
Location: .
pass labs use simple circuitry to give good results.
similarly jrdg use simple ic circuits in his power amps.would anyone here comment and explore its secret

[Edited by arthur on 10-12-2001 at 11:36 PM]
  Reply With Quote
Old 13th October 2001, 05:50 AM   #2
diyAudio Member
 
Join Date: Sep 2001
Location: Salt Lake City
I don't really know much about JRDG but I owned a pair of Boulder 250AE monoblocks a few yeaars back. They were built like a tank and based on the famous Jensen Op Amp. However, they always had a tinge of graniness to them that never went away, weather they were left on all the time or not. They ran very cool so I'm suspecting that they were biased in the class AB range. It seems like the driver stages developed more heat than the output devices did. Overall, my KSA-80B sounded way better as long as it was left on all the time. The old Krells will still give any modern amp a run for the money.
Am getting the parts together to build a pair of Aleph 1.2's. When completed I suspect they will be the best sounding amps I will ever own. My personal feeling is that with the advancements in high power semiconductors these days, the op amp has lost out and is no longer needed in the high end market. Simpler circuits with modern semiconductors are really hard to beat!
Mark Gulbrandsen
Salt Lake City, UT
  Reply With Quote
Old 13th October 2001, 01:32 PM   #3
diyAudio Member
 
promitheus's Avatar
 
Join Date: Jan 2001
Location: Germany
I agree that with todays semiconductors and designs opamps are no longer needed. They simply donīt sound so good anymore. Thatīs the reason there are a few good discrete transistor designs replacing opamps the last years.
  Reply With Quote
Old 14th October 2001, 06:08 AM   #4
diyAudio Member
 
Join Date: Oct 2001
Location: .
how do u feel the sound quality of the JRDG amp(model 8ti)
it consists only 2 stages of ic amplifications
is it easilier for our audio diyer?
  Reply With Quote
Old 14th October 2001, 04:16 PM   #5
diyAudio Member
 
Join Date: Sep 2001
Location: Salt Lake City
Well, I'd ahve to see the schematic before I could tell you. These I.C.'s could also be specially selected to achieve the high peformance that JRDG is known for. I for one would not want to build the Boulder 250's that I had, It was based on a discreet Jensen op amp and was quite complex. For the money that Rowland sells his stuff for and to find out that it is I.C. based really makes me wonder about them. Not that I'C's can't sound good. I guess the point is that if they were THAT good more designers would be using them. I can't remember the last time I saw an I.C. in a piece of high end audio gear's signal path. They are usually put to other tasks such as servo feedback, or power supply regulation.
Mark Gulbrandsen
SLC, UT
  Reply With Quote
Old 14th October 2001, 06:31 PM   #6
diyAudio Member
 
Join Date: Jul 2001
Location: Orleans, France
They are some limitations in integrated circuit design, by instance it's impossible to make a high quality resistor, or a very low resistance "wire". Usually, this limitations are surmounted by use of many transistors and sophisticated circuits. But the fact remains that results are not as perfect as desirable.

Better results can be achieved in "hand made" amplifiers because of the large choice of components and design, but the audible difference is only noticeable on very high quality equipements...

Regards, P.Lacombe
  Reply With Quote
Old 14th October 2001, 10:31 PM   #7
diyAudio Member
 
Join Date: Sep 2001
Location: Salt Lake City
I would have to assume then that you've stated the main reason that the Jensen op-amp was done discreetly, out of seperate parts. This would allow for eiminating the problems you mentioned. I think that if the Boulder had a higher bias output stage that it might have not had the graininess it did. Seems like all the remainder of the amp was all class A.
Mark Gulbrandsen
SLC, UT
  Reply With Quote
Old 15th October 2001, 10:36 AM   #8
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
What are you guys talking about? Rowland uses discrete transistors in his designs.And dozens of TO-3 cased output devices.I've personally met and worked with Jeff on one of his amplifiers. "Lack of overall or nested negative feedback eliminates time domain distortion. Each transistor individually tested and matched for optimum operating characteristics. The large number of high-speed bipolar output transistors provides uncompromising reliability and eliminates the need for electronic protection circuitry. A single voltage amplification stage utilizes field effect transistors(operating in transconductance mode), which increases low-level signal recognition. The absence of capacitors, inductors, fuses and protection circuitry throughout the signal path eliminates the adverse effects of these devices. A specially designed toroidal power transformer is supported by the substantial output stage capability. All critical circuitry is encapsulated in a thermally-conductive epoxy to ensure excellent thermal stability, mechanical integrity and to facilitate ease of service."







  Reply With Quote
Old 15th October 2001, 12:21 PM   #9
Helix is offline Helix  United Kingdom
diyAudio Member
 
Helix's Avatar
 
Join Date: Jul 2001
Location: UK
I don't mean to sound silly, but how can
"critical circuitry is encapsulated in a thermally-conductive epoxy" facilitate ease of service?
  Reply With Quote
Old 15th October 2001, 12:35 PM   #10
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
It's a little brick about 60mm square by 10mm thick.It just plugs in to the amp.Maybe that's what these guys are calling an IC?
  Reply With Quote

Reply


Hide 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
gainclone and jeff rowland miguel2 Chip Amps 65 17th January 2014 07:33 PM
Jeff Rowland Model 7 Please Help rebank Solid State 2 13th February 2009 10:44 PM
Jeff Rowland Model 5 itom Vendor's Bazaar 0 12th July 2008 03:06 PM
Jeff Rowland Model 1 Sandor Solid State 0 18th March 2008 11:44 PM
Jeff Rowland ben goh Analogue Source 0 14th May 2005 07:04 AM


New To Site? Need Help?

All times are GMT. The time now is 06:47 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright Đ1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2