IGC LM3875 Testing in Bangkok - 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 12th August 2003, 06:12 AM   #1
CRM is offline CRM  Thailand
diyAudio Member
 
Join Date: Aug 2003
Location: BKK
Default IGC LM3875 Testing in Bangkok

Last week there was the IGC testing which set up in Bagkok by some members of Audio forum named "htg2". The IGC had been connected to drive Proac Response4(89dB, 8ohm, rec. amp power-> 50-500w).What happen then! the IGC was automatically shut off itself many times(I think it would be thermal shutdouwn function).
But the IGC manufacturer claimed that he had test one of his very special version IGC(with some special supply) he made for one customer who has Response4, and it can drive the Response4 with a dramatic performance. The IGC manuf. also commented that a testing system may have some problem of setting up with ground( he said all CD-Pre-IGC must be ground together, unless the IGC might not give a full power)
This brought to a big quarrel here.

So, KueiYangWang, Peter Daniel or any Chip-experts here
may I ask all you guys your opinion, can the IGC drive Response4 properly? A minimum rec.power for Response4 is 50w.
What kind of speaker should be suitable for IGC?
TIA
  Reply With Quote
Old 12th August 2003, 08:25 AM   #2
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Sawadee Khap CRM,

When you say that the ICG shut down do you mean that no sound came through or that the volume was reduced? When the thermal protestion cuts in, the volume is reduced but not cut off completely.

Can you tell us more about the set up the IGC was used with? Did you use a preamp and if so how long were the interconnects between the preamp and IGC?
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 12th August 2003, 12:51 PM   #3
Banned
 
Join Date: Mar 2003
Location: Lisbon, Portugal
Default Re: IGC LM3875 Testing in Bangkok

Quote:
Originally posted by CRM

So, KueiYangWang, Peter Daniel or any Chip-experts here
may I ask all you guys your opinion, can the IGC drive Response4 properly? A minimum rec.power for Response4 is 50w.
What kind of speaker should be suitable for IGC?
TIA
In MY experience, NO WAY!
With only 1000uf capacitance on the PSU you'll have a hard time to get a pair of speakers these days that play well with the GC.
With additional caps on the PSU, yes.

Go here, and read from post #74 to the end of the thread.

High-end preamp for my GC

Good reading.
  Reply With Quote
Old 13th August 2003, 03:24 AM   #4
CRM is offline CRM  Thailand
diyAudio Member
 
Join Date: Aug 2003
Location: BKK
Thanks Nuuk & Carlosfm
Fisrt let me tell you that I'm not the owner of that testing system and I didn't have a chance to joine them.
For the testing system as I know: source Sony SACD-SA1, Pre-Krell?, Power the IGC VS Krell(Model?), Speaker Response4, all interconnection and speaker cable Silver Lace. It is a very well set up in a room with acoustic tuning. (*the IGC used some fair size heat sink)
I said in my first post that the IGC had automatically turn off its operation( no sound to Response4) many times, after that it was turned on(by listener) to drive Response4 again. To my conclusion, I think the chip temperature may be too high then the Thermal shutdown function was activated to turn off operation, till the temp decreased below that critacal range so it could work again. At this point I have some more questions though!
After many rounds of Thermal shutdown, will the chip operate accurately? Where is the limit of the turn of Thermal shutdown function?
Or will the Thermal shutdown function work through all the life time of a chip?

I do agree with Carlosfm that with only 1000uF , the IGC cannot drive such heavy load like Response4. But let me ask a stupid question, what is the actual power rating of Inverted Gain Clone?
(supposing to use diff+- 35V) A non-inverted GC can give 56W into 8ohm, so from my guesstimation I think the IGC souhld give less power. Please forgive me, if I'd asked some "used to know questions and answers" here, I'm a newbie to chip. My current system is all tube diy, and some experience with headphone opamp and OPA548 power amp(as Ti suggested).
Thank you very much
  Reply With Quote
Old 13th August 2003, 06:15 AM   #5
diyAudio Member
 
analog_sa's Avatar
 
Join Date: Aug 2002
Location: Sofia
Quote:
so from my guesstimation I think the IGC souhld give less power
your guesstimation is wrong. and it sounds like it wasn't the thermal protection cutting in at all but something entirely different, possibly external to IGC.
  Reply With Quote
Old 13th August 2003, 07:59 AM   #6
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
I agree. I have heard the LM3875 when overheating and the sound level is reduced until the the temperature has dropped but it does no cut out completetely.

I have heard tales of oscillation, distortion, fuzzy sound or no sound at all but never of a chip amp playing and then stopping and having to be restarted.

How was this amp restarted by the listener? The only scenario that I can think off is that the amp has a resettable circuit breaker instead of fuses. Presumably the amp drew too much current and the circuit breaker tripped.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 13th August 2003, 08:52 AM   #7
CRM is offline CRM  Thailand
diyAudio Member
 
Join Date: Aug 2003
Location: BKK
Oops! I made a wrong interpretation.
I read turough the thread in the Htg2 forum again, I found that it was just clipping when playing loud with a PinkFloyd CD. But, of course a chips was overheating. Though, GC and IGC can give 50w+ it just meets the minimal requirement of Response4. Then the total system may perform at minimum level only. Anyway, as analog_sa said my guesstimation is wrong, so can someone confirm the actual power of IGC?
PS. the IGC amp in this testing has no AC switch and no fuse( it's the owner requirement to manuf.), cause the owner said switch and fuse may reduce sound quality, hmm!!! very pure IGC with some threat
Thanks
  Reply With Quote
Old 20th August 2003, 05:53 PM   #8
diyAudio Member
 
Join Date: Oct 2001
Location: Hong Kong
Send a message via ICQ to hatasa
Great dynamic provide with the 50W Gainclone for Respoense 4... What I can tell is impossible... few years ago I also own the Response 4, even with my MarkLevinson No.33 also not enough there..... Response 4 really a monster!!!

My Gainclone using the LM3875 also, but more caps at the Power supply. Tried on the Redrose Rosebud Speaker, PMC LB-1, Dali small bookself, Dynaudio Acoustic PPM monitor... Well, fair for the performance but you cant ask for lot of the bass there!
  Reply With Quote
Old 26th November 2003, 03:43 AM   #9
diyAudio Member
 
Join Date: Nov 2003
Location: thailand
Default 50W Gainclone for Respoense 4

http://webboard.rexdiythai.com/index...y;threadid=571
Attached Images
File Type: jpg dsc00040.jpg (30.1 KB, 303 views)
  Reply With Quote
Old 26th November 2003, 10:29 AM   #10
Account Disabled
 
Join Date: Apr 2003
Location: US
Default Re: IGC LM3875 Testing in Bangkok

Quote:
Originally posted by CRM
can the IGC drive Response4 properly? A minimum rec.power for Response4 is 50w. TIA

one way to go is to calculate the chip's maximum dissipated power under the datasheet condition. And use that figure to calculate the maximum output power under a 4ohm load.

My sense is that the chip will dissipate a lot more heat under a 4-ohm load for the same power output. In other words, to dissipate the same amount of heat under a 4-ohm load, the output of the chip is a lot lower.
  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
Electronics component store in Bangkok (Thailand)? dtektoni Parts 0 16th August 2008 12:40 PM
Testing myhrrhleine Subwoofers 3 18th March 2008 05:03 PM
Jello in Bangkok eduard Everything Else 0 20th July 2003 09:47 PM
Yello or Jello in Bangkok eduard Solid State 0 15th June 2003 05:05 PM
Hifi in Bangkok herm Parts 5 15th April 2003 08:08 PM


New To Site? Need Help?

All times are GMT. The time now is 01:18 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