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 14th February 2012, 08:30 AM   #1
diyAudio Member
 
east electronics's Avatar
 
Join Date: Jan 2006
Location: Athens GREECE
Default 50+50 v rails

often while repairing amplifiers all boards need to be replaced .That is also a very common practice between professional amplifier that often and up in flames so since case/heatsink/trafo is available then a couple of boards will be a walk in the park to install

now from diy point of view there is a gozillion available schematics/boards for many applications and some of them come with detailed presentations and or extensive threads

One thing is missing though is Class AB amplifier with two transistor in the output but possible to operate in 50+50 volt rails

we ll know that 50+50 rails with only two transistors is risky and obviously out of SOA of any known transistor but on the other hand is common commercial practice to do that but with a Vi limiter installed .

In case i missed something and there is a schematic possible to operate one may please point it to me

on the other hand it seems that its a good time to clone any rotel or sansui that works under this principal and diy it all the way through

kind regards
sakis
__________________
SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
  Reply With Quote
Old 14th February 2012, 10:58 AM   #2
AndrewT is online now AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
I used Crimson Power amplifier modules.
CE1704 to drive 8ohms speaker from +-50Vdc.

I never blew up any of them.

They used a single pair of 2n3773, which are "only" 150W devices.

You could use one pair of 250W devices that are just as robust and considerably faster to easily get 100W into 8r0 and safely drive a severe reactance 8ohms speaker.
__________________
regards Andrew T.
  Reply With Quote
Old 14th February 2012, 11:46 AM   #3
ainrain is offline ainrain  Estonia
diyAudio Member
 
Join Date: Nov 2005
Location: est
Look at SYMASYM. AAK-s version was with 50v rails: My new SymAsym PCB design Rev_1.3
  Reply With Quote
Old 14th February 2012, 12:07 PM   #4
diyAudio Member
 
Idefixes's Avatar
 
Join Date: Dec 2003
Location: Mulhouse - Alsace
Send a message via ICQ to Idefixes
Nmos 200 from Quasi correspond to goal single paire of output mosfet and +/-50Vdc rail.

Nmos200 - Quasi's DIY Audio Site

Marc
__________________
website : http://audiyofield.wifeo.com/index.php
  Reply With Quote
Old 18th February 2014, 07:46 PM   #5
diyAudio Member
 
Join Date: Mar 2011
The V-I limiting makes a single pair of devices viable at +/- 50 Volts. I designed the Crimson modules to go into shutdown if the protection circuits operated for more than a few cycles. Some remanufactured PCBs are available.
  Reply With Quote
Old 18th February 2014, 07:56 PM   #6
tvrgeek is online now tvrgeek  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Md
Obsolete Toshiba Lateral MOSFETS. The DH-120 has 46V rails. Of course, without boosted drivers, the outputs only get to about 35V. Twin-die Exicons or Alfets. There used to be giant Motorola MJ somethings we ran as a power H at 46V, 20 Amps. Distortion will be high though.
  Reply With Quote
Old 18th February 2014, 08:20 PM   #7
effebi is offline effebi  Italy
diyAudio Member
 
effebi's Avatar
 
Join Date: Nov 2010
Location: Milan
Quote:
Originally Posted by east electronics View Post
often while repairing amplifiers all boards need to be replaced .That is also a very common practice between professional amplifier that often and up in flames so since case/heatsink/trafo is available then a couple of boards will be a walk in the park to install


kind regards
sakis
Well, Sakis, I have sometimes the same wish. (how strange eh ? )
Just a few weeks ago I had such need for a bass guitar combo 150w RMS /4 Ohm.
Before somebody starts to flame me, letīs say the original had only one pair BJT (and although going quite warm, it did not burn, problem was with the crazy front end/compressr/limiter). Maybe the wide case Sankens where original... or the huge heatsink where they were mounted plus the VI did their job.
But, looking for a ready to go 2 pair EF mono board for a plug-in replacement I did not find anything readily available . I believe the original DX Blame ST boards would do, but they are quite rare nowadays, at least here in EU.
Suggestions for a PROVEN, SIMPLE circuit with schematics , documentation AND PCB available are welcome.

Last edited by effebi; 18th February 2014 at 08:26 PM.
  Reply With Quote
Old 18th February 2014, 08:56 PM   #8
diyAudio Member
 
east electronics's Avatar
 
Join Date: Jan 2006
Location: Athens GREECE
Effebi for a bass application i would love to have a trace elliot amplifier working

To copy a schematic from those and produce a pcb will be a walk in the park

But if you have big sankens i will have to do some thinking and get back to you

Kind regards
Sakis
__________________
SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr
  Reply With Quote
Old 19th February 2014, 08:13 AM   #9
Aniket is offline Aniket  India
diyAudio Member
 
Aniket's Avatar
 
Join Date: Apr 2012
Location: Delhi, India
Hi,

Attached is the schematic of my next project, it's a low power version of my 250W amp which is working great.
2 output pairs @ +/-50V supply rails, good for ~120W into 8 ohm load.
I have designed the PCB also, which may be improved.
A number of substitutes could be used for the LTP and VA stages.

Regards,
Aniket
Attached Images
File Type: gif 100W PCB V2.GIF (320.2 KB, 322 views)
Attached Files
File Type: pdf 100W HIFI.pdf (39.2 KB, 61 views)

Last edited by Aniket; 19th February 2014 at 08:17 AM.
  Reply With Quote
Old 19th February 2014, 12:02 PM   #10
diyAudio Member
 
Join Date: Apr 2010
Location: Coffs Harbour, on the east coast
Quote:
Originally Posted by east electronics View Post
......One thing is missing though is Class AB amplifier with two transistor in the output but possible to operate in 50+50 volt rails

we ll know that 50+50 rails with only two transistors is risky and obviously out of SOA of any known transistor but on the other hand is common commercial practice to do that but with a Vi limiter installed .

on the other hand it seems that its a good time to clone any rotel or sansui that works under this principal and diy it all the way through....
Hi Sakis
There have been kits and PCBs available in the past for just one pair of output transistors but not now, modern transistors are cheap. Using 2 pairs TO3P or TO247 is no big deal. Only old designs like Quad 405 or NAP 140 meet your criteria and still widely available but they probably would need mods to sound good and stretch to 50V rails. There is the advantage of already having VI limiters on NAP140 PCBs, though. Symasym can be used with 50V rails by just amending resistors and a couple of transistors, if the boards come up for sale. They are certainly still available in Germany - check MBittner's site and links. SymAsym5 - Project

As we have discussed, those 50V rails can drop like a stone under load with many 1980s Japanese designs, so frying your output transistors is not as great a risk as some suspect. Often, power transformers were tiny, accounting for low power ratings considering the rail voltage. (e.g. only 70W/8R with unloaded 48V rails. I have a number of amplifiers like this with 48-50V rails but only ~150VA transformers and switched rails for 4R loads. However, I also have a stack of Marantz amps with normal transformers that always failed, taking out the protection circuits too - 1980s style absolute junk!

Your last option looks best to me though - at least you can lay out your own selected design with spacings, connectors etc. that would suit such a complete rebuild. You can still say that you have used a respected design to start with though. That's probably more important than the real sound quality for most clients, in my limited experience.
__________________
regards

Last edited by Ian Finch; 19th February 2014 at 12:05 PM.
  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
want to make 50-0-50 5 ampere mains transformer ravslanka Parts 9 3rd June 2008 11:25 PM
FS: SMPS 50-0-50 regulated DC Bent Swap Meet 7 25th August 2005 08:08 AM
PSU For sale SMPS 50-0-50 volt Bent Solid State 1 28th July 2005 10:06 AM
OPTI-MOS using 50-0-50 450VA TRAFO Calebay Solid State 6 6th February 2005 02:09 PM


New To Site? Need Help?

All times are GMT. The time now is 08:47 AM.


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