Go Back   Home > Forums > Live Sound > Instruments and Amps

Instruments and Amps Everything that makes music, Especially including instrument amps.

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 11th February 2006, 04:03 PM   #1
amperex is offline amperex  United States
diyAudio Member
 
Join Date: Feb 2005
Location: MI
Default Another IC OP Amp question....

Getting down to 'fine hairs', are ICs in the same family like tubes? Usually an Amperex 12AX7 with short plates sounds the same in the same circuit. Changing to an RCA short plate 12AX7 will sound different. Yet, both share the same part number.

Are ICs with same part number from different manufactures sound different in the same circuit? How about a late 1990s IC vs a 2005 IC from same manufacture? Identical sonics?

What brings up the question is using power transistors over the years. Same part number has an HFE that will vary from say an HFE of 20 to a HFE of 150. Kind of like jumping from a 12AU7 to a 12AX7, yet the transistor shares the same part number.

Apparently, solid-state has huge variances in manufacturing. I assume ICs are much closer tolerance. But, I still wonder about the ICs as mentioned above.
  Reply With Quote
Old 11th February 2006, 04:22 PM   #2
poobah is offline poobah  United States
diyAudio Member
 
poobah's Avatar
 
Join Date: Nov 2005
Good question,

I do know that in some cases popular chips are redesigned because the newer processes allow for smaller transistors and therefore less silicon. I'm not saying that is a bad thing. There are many parts that carry the old base number (with a few new letters appended) that have vastly improved characteristics... LM324XXXXX comes to mind.

  Reply With Quote
Old 11th February 2006, 04:54 PM   #3
diyAudio Member
 
Tube_Dude's Avatar
 
Join Date: Mar 2002
Location: Aveiro-Portugal
Default Re: Another IC OP Amp question....

Quote:
Originally posted by amperex


Are ICs with same part number from different manufactures sound different in the same circuit? How about a late 1990s IC vs a 2005 IC from same manufacture? Identical sonics?

Yes...identical sonics , because op amps unlike tubes use heavy feedback and can't be used open loop as tubes... and the feedback help to make differences to vanish .

Quote:
What brings up the question is using power transistors over the years. Same part number has an HFE that will vary from say an HFE of 20 to a HFE of 150. Kind of like jumping from a 12AU7 to a 12AX7, yet the transistor shares the same part number.

Yep...but in the transistor , even if the HFE change , the output impedance will be roughly the same (in common collector configuration ), unlike a change from a 12AX7 to a 12AU7 where the change in output impedance is drastic .
Quote:
Apparently, solid-state has huge variances in manufacturing. I assume ICs are much closer tolerance.
Not so!...But as ICs can't be used without feedback , they behave almost ideally , at last , on paper...
__________________
Jorge
  Reply With Quote
Old 11th February 2006, 05:02 PM   #4
testlab is offline testlab  United States
diyAudio Member
 
testlab's Avatar
 
Join Date: Dec 2005
Location: Grand Rapids MI
When it comes to transistors, they can vary in spec from manufacturer to manufacturer. In the case of JEDEC (2NXXXX numbered devices) devices parameters were assigned but, there is no absolute rule that says a device with that number has to meet all of the specs. A little different for the Japanese transistors since the numbers are assigned to the manufacturer.

In the case of IC's the same is roughly true. The differences are usually due to circuit topologies. For instance, a 1458 opamp from 3 different manufacturers, can have completely different layouts from each other. They are also dependent on the photolithography resolution(usually in uM or nM), that the manufacturer is using. Packaging material variations can also play a part as well.

Revisions to the die making process usually force revisions to popular devices. Most translate well but everybody has there klinkers.

Also be aware that, when reading the datasheet on a device, what is not in the data is as important as what is not. An example of this is the TL072. At the top they state a really attractive GBW and slew rate. Elsewhere in the document, you see that this is for small signal conditions with a 5 volt rail. Performance decreases considerably with +/- 15 volt rails, and even more with large signal response. This is no surprise since all amplifiers have reduced performance with large signal response. But, to those unfamiliar with the finer point of amplifier behavior, dissapointments may occasionally arise.

The upshot is, read the datasheets carefully and question any specs that seem to be to good to be true. Datasheets are ultimately written by marketeers, not engineers. Understand your critical design parameters. Look for things like voltage and current self-noise, large signal reponse, unity gain stability and, single supply stability.

Simple, isn't it?
__________________
It's not whether you win or lose, it's how you lay the blame.
  Reply With Quote
Old 11th February 2006, 05:07 PM   #5
amperex is offline amperex  United States
diyAudio Member
 
Join Date: Feb 2005
Location: MI
Apparently, solid-state has huge variances...... Comparing simple transistors to vacuum tubes it does vary a lot.

But, I am not being silly here. OP-Amps & other solid-state IC devices can perform tasks tubes could never perform. I see ther future will have continued growth in op-amp designs.
  Reply With Quote
Old 14th February 2006, 01:17 AM   #6
Enzo is offline Enzo  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Lansing, Michigan
And the power transistotrs that vary their gain? It depends on how much current they are conducting, in the sense that your car will generate different amounts of torque at different engine speeds. You will usually see the gain of a transistor specified at a certain level of collector current. If you don't specify the current, then the gain is given as a range. It has absolutely nothing to do with any sloppy manufacturing tolerances.
  Reply With Quote
Old 14th February 2006, 03:16 AM   #7
amperex is offline amperex  United States
diyAudio Member
 
Join Date: Feb 2005
Location: MI
We used to built linear power supplies for the US Military. Believe me, transistors vary a lot at any given current. Power supplies providing 130 amperes at 13.8 VDC uses a $hit load of pass transistors.
  Reply With Quote
Old 14th February 2006, 08:46 AM   #8
diyAudio Member
 
Join Date: Jul 2005
Location: North Derbyshire
The basic answer is that different manufacturers IC's don't really sound (or perform) any differently. As already suggested, IC's and transistors have wide spreads of specifications - but you should design to make those irrelevent - this is what good design is all about.

In the (very!) distant past I've repaired equipment where you have to select resistor values when you replace a faulty transistor - this is incredibly poor design!, and isn't something you should ever see these days!.
__________________
Nigel Goodwin
  Reply With Quote
Old 14th February 2006, 02:15 PM   #9
amperex is offline amperex  United States
diyAudio Member
 
Join Date: Feb 2005
Location: MI
Default If you are refering to our design......

A group of pass transistors in a large lot in a high current linear type power supply is not a poor design. The extra heat must be spread across a large area, thus one or two pass transistors would not perform even with copper heat sinks or a heat sink with a copper spreader.

After all, specs having less than 3 mv ripple at 130 amperes @ 13.8 vdc as measured on the output & .2 volt overshoot at start-up is as good as it gets without a large battery on the output.

Cycling a contactor to a 'chatter type' condition five times a second from no load to full load with severe arcing has no effect on the linear power supply design either. Others tested lost regulation & tripped the crowbar circuit.

That is most likely the best high current power supply ever manufactured. 'Switcher' types do not come close either with regard to same performance under the same conditions.
  Reply With Quote
Old 14th February 2006, 11:35 PM   #10
Enzo is offline Enzo  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Lansing, Michigan
No, he didn't say using a large number of parts is a bad design. He said designs that are vulnerable to part variations are bad designs.
  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
newbie with input tran. question and wiring question imo Solid State 0 18th January 2006 10:10 PM
Capacitor Question /question on cap TunaFish Tubes / Valves 14 12th January 2004 02:23 AM
PS question - tformer question actually breguetphile Chip Amps 2 30th May 2003 01:29 PM
old speaker question, bullet midrange question & link to speaker project wallijonn Multi-Way 10 5th November 2002 06:03 AM


New To Site? Need Help?

All times are GMT. The time now is 09:22 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