"Yuanjing" Gainclone 3886 - eBay amazing value ? - Page 3 - 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 22nd September 2009, 01:40 PM   #21
Cruzs is offline Cruzs  Indonesia
diyAudio Member
 
Join Date: Oct 2008
Default Another good looking ChipAmp board..

Hi all..

I'm a newbie and just wondering if anybody have information how to
contacts the owner of this web: www.hifizone.net

I'm really interested on their 3 good looking PCBs:
1. ALEPH3886 : http://www.hifizone.net/shop_view.asp?id=964
2. X-PP : http://www.hifizone.net/forum_view.a...4&view_id=1619
3. X-PT : http://www.hifizone.net/forum_view.a...4&view_id=1620

I mailed them many times but it seems they ignore me.. hiksz..

If anybody can't help me getting those stuff, I'd really appreciate.



Blessings,

- Cruzs -
  Reply With Quote
Old 22nd September 2009, 02:08 PM   #22
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Quote:
Originally Posted by Cruzs View Post
Hi all..

I'm a newbie and just wondering if anybody have information how to
contacts the owner of this web: www.hifizone.net

.......

- Cruzs -
1. IP issues - steal

2. same ?

3. seeing 30K as anode load for ECC83 make me laugh
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM
  Reply With Quote
Old 13th February 2010, 07:11 AM   #23
diyAudio Member
 
Join Date: Sep 2007
Send a message via Yahoo to linuxguru
Default Yuanjing LM3886 + NE5532 gainclone PCB

The kit may be dodgy, but the bare PCB is available and easy to assemble. I got one, and it's OK for the price. However, there are some issues with the design.

1) No star grounding. It uses two ground planes instead for the NE5532 and LM3886 sections, and the planes are connected at a single point. However, this is not good enough, since the main PSU filter capacitors are located and grounded on the NE5532 side, and the 7812/7912 regulators for the opamp supply are located and grounded on the LM3886 side. Significant ground-bounce issues are a certainty, and there's no easy fix for this.

2) No lifted ground for the input near the NE5532 - this is what contributes to the hum. However, this easily fixable with minor mods:

i) Remove the 10uF, 25V DC blocking cap for the feedback network for the input gain stage. Replace it with a 10 ohm, 1W metal-oxide resistor, mounted vertically as shown in the attached pictures. The upper lead of this resistor will be the lifted signal ground. The shield ground from the input connector is soldered to this lead (instead of being connected to the input terminal block), while the input goes to the terminal block as before.

ii) The input resistance from the non-inv terminal of the NE5532 gain stage is grounded at the lifted ground, not the PCB ground. This is done as shown in the attached picture - the resistor is (physically) diagonally bridged over another intervening resistor.

3) Lower frequency cutoff is too high. This is fixed by changing the values of the input resistance and feedback resistance to 47k instead of 22k. This changes the gain from 3.2 to 5.7, and improves the bass response for a given input capacitor.

4) The NE5532 opamp is not an optimal choice - it can easily be upgraded to a better opamp using 8-pin DIP sockets to permit rolling. I used an LT1208 lying around, but better choices are available - probably LM4562, LT1213 or OPA2134 will sound better.

5) Upgrade the DC blocking capacitors. I've used both Siemens MKL 2.2uF/630V and Pilkor MKP 1uF/275 VAC X2 with good results.

6) The bypass caps for the LM3886 are not close enough to the input pins. I soldered 100 nF MLCCs between +Vs and GND, -Vs and GND close to the pins on the bottom of the PCB.

With these mods, it sounds acceptably good for the price, but nowhere close to a decent audiophile-class gainclone like a Pavel Dudek or a Mauro Penasa Rev C.
Attached Images
File Type: jpg gc1_10x7.jpg (122.6 KB, 3250 views)

Last edited by linuxguru; 13th February 2010 at 07:14 AM.
  Reply With Quote
Old 13th February 2010, 08:30 AM   #24
diyAudio Member
 
Join Date: Sep 2007
Send a message via Yahoo to linuxguru
One other mod (optional): solder a 47p to 470p Styroflex or Silver Mica cap between the non-inv and inv inputs of the LM3886 on the solder side. This helps suppress some RF interference, as well as helps the LM3886 recover better from some kinds of clipping, as per the NatSemi Application Note. I used 68 pF, but the use of this cap is entirely up to the taste of the builder. You can omit it if the LM3886 is never going to be driven to clipping.
  Reply With Quote
Old 15th February 2010, 04:18 PM   #25
diyAudio Member
 
Join Date: Mar 2007
Location: California
Default Pre-assembled LM3886 success story

I have purchased from Ebay and used several China sourced LM3886 chip amps. They have all worked perfectly. I didn't check for star grounding or anything like that - it was just plug and play.

They look like this (below) and can be sourced from several vendors. Just search LM3886 in the Electronics>Home Audio>Amplifiers category. I would avoid the "all in one" boards that have on board PS.

Click the image to open in full size.

-Charlie
  Reply With Quote
Old 15th February 2010, 04:23 PM   #26
diyAudio Member
 
Join Date: Sep 2007
Send a message via Yahoo to linuxguru
That little unbuffered one is probably ok, within the constraints of its topology. Could you post its schematic, if you have one? I'd like to see if a lifted signal ground is implemented.
  Reply With Quote
Old 15th February 2010, 05:50 PM   #27
diyAudio Member
 
Join Date: Mar 2007
Location: California
Default schematic is from Datasheet

Quote:
Originally Posted by linuxguru View Post
That little unbuffered one is probably ok, within the constraints of its topology. Could you post its schematic, if you have one? I'd like to see if a lifted signal ground is implemented.
If you are referring to my post, the schematic is pretty much straight from the LM3886 datasheet. There is no muting switch, it is permanently connected to be "on" (no muting). There is a 1 ohm series resistor on the output, which I plan to replace with a link or the parallel resistor/inductor.

-Charlie
  Reply With Quote
Old 18th February 2010, 03:23 PM   #28
diyAudio Member
 
barry.childs's Avatar
 
Join Date: Jun 2008
Location: Lostwithiel, Cornwall
I bought one of these Yuanjing boards, and i'm quite pleased with the results. I think I will try linuxguru's mods though. I would like someone to explain the pre-amp. Is it a buffer and pre? Should the pot go where the jumpers are or are they just for bypassing the pre. I changed the op-amps for 4562's and it is much better. In fact it sounds very good, although bass is lacking. I considered getting a Pass B1 buffer and not using the op-amp, would this be an improvement? Any help would be appreciated. Cheers Barry
  Reply With Quote
Old 18th February 2010, 03:38 PM   #29
diyAudio Member
 
Join Date: Sep 2007
Send a message via Yahoo to linuxguru
Quote:
Originally Posted by barry.childs View Post
... I would like someone to explain the pre-amp. Is it a buffer and pre? Should the pot go where the jumpers are or are they just for bypassing the pre. I changed the op-amps for 4562's and it is much better. In fact it sounds very good, although bass is lacking. I considered getting a Pass B1 buffer and not using the op-amp, would this be an improvement? Any help would be appreciated. Cheers Barry
The pre-amp is a 2-stage amp, consisting of a gain of 3.2 stage, followed by the jumper block, followed by a unity-gain buffer. I used the jumper block for a dual-ganged pot, but you can just jumper it (actually, you need to jumper it or use a pot to get any sound at all). The jumper just connects the output of the gain stage to the input of the unity-gain buffer.

To improve the bass, increase the input and feedback resistances to 47k (from the 22k shown). That will change the gain to 5.7, which doesn't hurt. Also consider larger-valued input caps (say 3.3 uF or 4.7 uF) if you can fit them.

To remove the 50/60 Hz hum, use the lifted-ground mod that I showed earlier - it will get rid of about 95% of the hum, and the remaining hum is not noticeable.
  Reply With Quote
Old 18th February 2010, 04:03 PM   #30
diyAudio Member
 
barry.childs's Avatar
 
Join Date: Jun 2008
Location: Lostwithiel, Cornwall
Thank you Linuxguru for you extremely quick reply. I will do these mods tomorrow as I have to go to the pub now! Do you think it is beneficial to put the pots where the jumpers are or is it just personal preference? I'll get back tomorrow after the mods are done. Thank you very much for your help. Barry
  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 05:37 AM
LM3875/3886's "NC" pins really not connected? BJAMR Chip Amps 3 22nd March 2006 05:59 PM
Fullrange "Roland" drivers on ebay Dave Jones Full Range 1 5th July 2004 01:25 PM


New To Site? Need Help?

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