"Yuanjing" Gainclone 3886 - eBay amazing value ? - Page 5 - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 19th February 2010, 06:24 PM   #41
diyAudio Member
 
barry.childs's Avatar
 
Join Date: Jun 2008
Location: Lostwithiel, Cornwall
Thank you, I will have a look. Regards Barry
  Reply With Quote
Old 19th February 2010, 09:17 PM   #42
diyAudio Member
 
barry.childs's Avatar
 
Join Date: Jun 2008
Location: Lostwithiel, Cornwall
I thought this looked interesting!
High speed power amplifier w/spk protection Goldmund ! on eBay (end time 02-Mar-10 16:39:33 GMT)
  Reply With Quote
Old 20th February 2010, 04:45 PM   #43
diyAudio Member
 
Join Date: Sep 2007
Send a message via Yahoo to linuxguru
Quote:
Originally Posted by barry.childs View Post
Yup, I saw that and the kit looked to be fairly good value. The schematic will only be provided if you buy the kit, though - that leaves no way to evaluate or simulate it before buying.

I took a look at the Naim NAP-140 schematic (apparently used on the EBay clones as well). It seems to be similar on the input side to the Self Blameless, and on the output side to the Quasi. It simulates reasonably well, but the choice of the output and driver transistors is important - it appears to do better in the sim with old 'slow' output transistors like the 2n3773. Some mods also have significant impact on sonics. It's probably a tweaker's paradise, but not recommended for reproducible 'build and forget' projects.

Last edited by linuxguru; 20th February 2010 at 04:52 PM. Reason: addendum
  Reply With Quote
Old 20th February 2010, 07:39 PM   #44
diyAudio Member
 
barry.childs's Avatar
 
Join Date: Jun 2008
Location: Lostwithiel, Cornwall
There's a lot of info on the pink fish forum regarding the naim clones, and it's all prety good, but like you say it's all about tweaking. I thought the goldmund clone was interesting just due to the amount of bits for the money. Iv'e emailed him to find out what the input voltage is, and what the out put was. I wouldn't want to spend a fortune on another power supply, especially not knowing if it is any good. How do you do these simulations, and what's your favourite amp? Barry
  Reply With Quote
Old 20th February 2010, 08:20 PM   #45
diyAudio Member
 
Join Date: Sep 2007
Send a message via Yahoo to linuxguru
Quote:
Originally Posted by barry.childs View Post
I thought the goldmund clone was interesting just due to the amount of bits for the money. Iv'e emailed him to find out what the input voltage is, and what the out put was. I wouldn't want to spend a fortune on another power supply, especially not knowing if it is any good. How do you do these simulations, and what's your favourite amp?
Just on a whim, I bought one of those Goldmund clone kits off EBay today - I have the remaining parts (output transistors, transformer, filter caps, etc.) to complete one prototype. The main attraction is that it's a single board unit, with the rectifier, filter caps and two channels all on one board - this helps reduce the cabinet wiring clutter a bit. It will probably take a couple of weeks to get here, and another month to completely assemble and test - let's see how it goes...

I use LTSpice for simulation. At the moment, the Quad current-dumping topology is my favourite discrete amp topology. BTW, there are Quad 405 bare PCBs as well as PCBs + inductors on EBay from seller 'tubeshunter'. I haven't tried it out, but it looks tempting. I can probably kludge my own current-dumping variant onto that Quad 405 board, but it appears to have only a TO-3 outline for the output transistors. Another issue is matching and alignment: In the Quad topology, low THD and good sonics are obtained only when the reactive bridge is precisely balanced, which requires some measurement/matching.

There are also bare PCBs for the JLH 1969 and 1996 Class-A circuits on EBay. However, Class A is too wasteful of power for continuous use in the tropics. Maybe a version with scaled-down rail voltages and something like 5W output might be worth looking at for a small bookshelf amp to drive 3" full-ranges.
  Reply With Quote
Old 20th February 2010, 08:39 PM   #46
diyAudio Member
 
barry.childs's Avatar
 
Join Date: Jun 2008
Location: Lostwithiel, Cornwall
Hi, Is that an Indian flag you have there? Funny you should mention Quad. My best amp i've had was a quad 303. I just sold a Naim nait 3 on ebay. I quite liked it but I needed the money to make my own. I am very interested to see what you think of the goldmund. I know the real ones sell for the price of a house in England! Do you know what transformer to use with that? I have a 160va 25-0-25 for the gainclone. Wondered if that was too small!. Iv'e been searching the web for anyone who has made the goldmund, but no luck. Regards Barry
  Reply With Quote
Old 20th February 2010, 10:09 PM   #47
diyAudio Member
 
barry.childs's Avatar
 
Join Date: Jun 2008
Location: Lostwithiel, Cornwall
Well, He only had 1 left, so I bought it. Sometimes you can't delay. And often when the manufacturers see a copy they sue, (and Goldmund are rich) so here we go. I'm looking forward to making it. Barry
  Reply With Quote
Old 21st February 2010, 05:36 AM   #48
diyAudio Member
 
Join Date: Sep 2007
Send a message via Yahoo to linuxguru
Quote:
Originally Posted by barry.childs View Post
Hi, Is that an Indian flag you have there? ... I am very interested to see what you think of the goldmund. I know the real ones sell for the price of a house in England! Do you know what transformer to use with that? I have a 160va 25-0-25 for the gainclone. Wondered if that was too small!. Iv'e been searching the web for anyone who has made the goldmund, but no luck. Regards Barry
Yup, I'm an Indian in Bangalore. Quick thinking on that Goldmund clone - it's a convenient board, if nothing else.

I received the schematics from the seller, and it is basically a cascoded FET-input LTP, driving Hitachi-topology VAS, driving a Self Type-II EF at the output. Almost the exact same thing has been attempted on numerous projects here at DIYAudio - in particular, several versions of Symasym use very similar topologies, sometimes with more elaborate cascoding in the VAS.

If the Goldmund clone sounds anything like Symasym, I don't think it will be a disappointment. The Hitachi-style VAS (and its sequels) are known to be both very detailed overall, as well as authoritative in bass. It's a capable circuit, hopefully the layout will do it justice. One can also upgrade the component selection if necessary.

A 25-0-25 160 VA transformer should be fine for both a gainclone and the Symasym/Goldmund. I plan to use a 24-0-24 250 VA EI-transformer that I have lying around.
  Reply With Quote
Old 21st February 2010, 12:24 PM   #49
diyAudio Member
 
barry.childs's Avatar
 
Join Date: Jun 2008
Location: Lostwithiel, Cornwall
If your in Bangalore and i'm in Cornwall I imagine there is quite a time difference. I wish my English was half as good as yours. Now you must not be too technical with me as I am a bit stupid when it comes to circuitry, but i'll do some googling and see if I can learn. I am looking forward to the kit coming. What output transistors would you reccommend. Barry
  Reply With Quote
Old 21st February 2010, 05:10 PM   #50
diyAudio Member
 
Join Date: Sep 2007
Send a message via Yahoo to linuxguru
Quote:
Originally Posted by barry.childs View Post
What output transistors would you reccommend.
It's hard to beat the Toshiba 2sc5200/2sa1943 pair - they're fast, linear, rugged and inexpensive. There are probably some Sankens that have better specs, but Sankens are also counterfeited heavily. You best bet is probably the Toshiba or its Fairchild clone, the KSC5200/KSA1943 pair, sourced from a reputed distributor.
  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
Mauro Penasa's My Reference 3886 "RevC" supra Chip Amps 6 1st April 2006 06:37 AM
LM3875/3886's "NC" pins really not connected? BJAMR Chip Amps 3 22nd March 2006 06:59 PM
Fullrange "Roland" drivers on ebay Dave Jones Full Range 1 5th July 2004 02:25 PM


New To Site? Need Help?

All times are GMT. The time now is 10:13 PM.


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