3 preamp to choose from - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 10th February 2002, 01:07 AM   #1
claudio is offline claudio  Italy
diyAudio Member
 
claudio's Avatar
 
Join Date: Feb 2002
Location: Italy
Talking 3 preamp to choose from

Hello, I need your precious advice on these 3 pre amp.
One uses nuvistor, the second is a very simple cascode and the last one is the Kaneda pre.Of the Kaneda pre I only need the line pre.
I will use the best components, so I would like to know yours advices.
Thanks.
Attached Images
File Type: jpg pre cascode.jpg (21.5 KB, 3918 views)
  Reply With Quote
Old 10th February 2002, 01:09 AM   #2
claudio is offline claudio  Italy
diyAudio Member
 
claudio's Avatar
 
Join Date: Feb 2002
Location: Italy
this is the nuvistor
Attached Images
File Type: jpg pre nuvistor.jpg (29.4 KB, 3620 views)
  Reply With Quote
Old 10th February 2002, 01:23 AM   #3
claudio is offline claudio  Italy
diyAudio Member
 
claudio's Avatar
 
Join Date: Feb 2002
Location: Italy
and finally the Kaneda
Attached Files
File Type: zip kanedaa.zip (35.3 KB, 1027 views)
  Reply With Quote
Old 11th February 2002, 02:07 AM   #4
diyAudio Member
 
Join Date: Feb 2001
Location: Columbia, SC
Nuvistors, aka "acorn" tubes, are pretty cool, but you'll need to make sure that you can get the tubes and the sockets if you choose to go ahead with that design.

Grey
  Reply With Quote
Old 11th February 2002, 02:38 AM   #5
diyAudio Member
 
Lisandro_P's Avatar
 
Join Date: Oct 2000
Location: Argentina
Send a message via ICQ to Lisandro_P
I've choosen the Kaneda for my preamp (a design a bit different than the one you posted; Mr. Kaneda has literally hundreds of preamp designs published). I needed RIAA and line preamplification, and like the approach he used.
  Reply With Quote
Old 12th February 2002, 08:03 PM   #6
claudio is offline claudio  Italy
diyAudio Member
 
claudio's Avatar
 
Join Date: Feb 2002
Location: Italy
I have found the nuvistor at the shop, pretty expensive though,but I never heard any pre using them, so I am not so sure about them.

About the Kaneda, does it sound good?Can you compare it to which other pre? Did you use substitute ( 2sa640 and 2sk240 are not easy to find)?

The cascode circuit is very simple: the fet is used to gain in current, the 2n2222a to gain in voltage; it is used in common base, so it has extreme linearity and wide frequency response.The 2 bd139 are used as impedence adaptor: using only one bd139 the output impedance is about 25 ohm, using 2 bd 139 the impedence is around 1 ohm.
The local retroaction is of 3 dB only.This circuit is very sensible to the quality of the components used.

What do you think about it?

Claudio
  Reply With Quote
Old 12th February 2002, 10:05 PM   #7
diyAudio Member
 
traderbam's Avatar
 
Join Date: Jan 2002
Location: Earth
Claudio,
A comment on the first circuit. It may perform better using fewer transistors. Being a pre-amp I assume it will be driving +/- 2V or so into >10kohms. This is a peak current of 0.2mA. For good margin let's multiply this by 10 to give 2mA. The circuit shown looks like the Q4 bias is some 20mA to 40mA - overkill?

Instead of using two beefy BD139s I think the circuit would sound better using a single gazelle-like transistor such as a BC549. It has typical hfe 520, ft 300MHz and 500mW dissipation. The value of the emitter resistor should set the bias to, say, 10mA. The output resistance would be <10 ohms - plenty low enough for a 10k load. This saves a couple of parts and reduces the number of distortion generators.

BAM
  Reply With Quote
Old 12th February 2002, 10:39 PM   #8
Banned
 
Join Date: Feb 2002
Location: Dallas,Texas
Default Preamps

The Kaneda preamp looks good. The matched Fet diff pair can be the 2SK389 in place of 2SK240. This a great sounding Fet pair and used John Curl and Passlabs. The bipolars can be Zetex ZTX450 and what ever the Zetex pnp comp is. The Zetex bipolars are used in several Hi End designs. Zetex also makes some wonderful small signal mosfets. (hint they are in one of Mr. Pass's
articles.) Another couple of small signal bipolars are the 2SC17775 and 2SC872. The 2SK170 are also excellent jfets and neat differential pairs when matched. All these are fairly easy to find in DigiKey or MCM electronics. Check out the jfet articles at
www.borbelyaudio.com also. I am fairly certain that that
the nuvisitorschematic has errors These are great devices but are TUBES. They are very microphonic. CJ use to use them in a MC preamp. The PCB was mounted on Rubber bands for isolation!! I read that tube was developed for the front end of high speed oscilloscopes.

H.H.
  Reply With Quote
Old 12th February 2002, 10:59 PM   #9
diyAudio Member
 
Lisandro_P's Avatar
 
Join Date: Oct 2000
Location: Argentina
Send a message via ICQ to Lisandro_P
Quote:
Originally posted by claudio
About the Kaneda, does it sound good?Can you compare it to which other pre? Did you use substitute ( 2sa640 and 2sk240 are not easy to find)?
I haven't built the Kaneda yet (right now i'm working in the case for my amp ), but it's reputed to sound excelent. I'll post the other Kaneda design i have; it uses only a cap in the feedback path for stabilization, the rest of the circuit is identical... i got these schematics from a website a good while ago, but lost the link.

BTW, i've simulated the Kaneda with "off-the-shelf" devices (BC546/556 for the bipolars and two 2N4393 for the dual FET), and, at least there, it performs ok. I also have trouble finding japanese semiconductors here, but i think any quality audio devices (motorola f.ex.) would work right.
Attached Files
File Type: zip kaneda_preamp_2.zip (20.1 KB, 661 views)
  Reply With Quote
Old 12th February 2002, 11:11 PM   #10
lohk is offline lohk  Europe
diyAudio Member
 
lohk's Avatar
 
Join Date: Apr 2001
Location: Northern Noricum, near the Limes
Some questions to your first design:

Doesn't the first transistor of the output darlington have to be a PNP device (like in the Hiraga Monster) ?

Doesn't the output capacitor have to be much bigger? ( I would use at least a 10uF electrolytic with a 100k resistor to ground, because I think small foils sound worse when you have a significant DC offset )

Did you design it actually ? Or build it ?


I like it, but I still have doubts...

Klaus
  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
Preamp Opamp what to choose Ted205 Chip Amps 15 2nd June 2011 03:14 PM
What amp to choose Arne Chip Amps 9 10th August 2007 09:51 AM
Help me choose please fighi77 Tubes / Valves 12 10th June 2007 01:35 AM
Which DAC should I choose? AudioAngel Digital Source 2 18th September 2004 11:39 PM
Which preamp to choose for my ECC88s? Andypairo Tubes / Valves 13 26th July 2004 07:44 AM


New To Site? Need Help?

All times are GMT. The time now is 04:33 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2