Hi,

I've recently acquired an early 80s Quad 405 which had been converted
to a Quad 405-2 by Quad in 1996 (the front label has been change to
'Quad 405-2'). This upgrade appears to have involved replacing the
complete output boards as those in the amp are marked 405-2.

These '96 boards are fitted with TLO71 opamps and I have read
elsewhere on the net that these ought to be replaced by OPA604 opamps.
Is this really worth the effort? The TLO71s are soldered in, not in a
socket. Are the OPA604s a direct replacement or should other components
be changed as well?

Regards,

John Smith.

wrote in message
ups.com...
Hi,

I've recently acquired an early 80s Quad 405 which had been converted
to a Quad 405-2 by Quad in 1996 (the front label has been change to
'Quad 405-2'). This upgrade appears to have involved replacing the
complete output boards as those in the amp are marked 405-2.

These '96 boards are fitted with TLO71 opamps and I have read
elsewhere on the net that these ought to be replaced by OPA604 opamps.
Is this really worth the effort? The TLO71s are soldered in, not in a
socket. Are the OPA604s a direct replacement or should other components
be changed as well?

**Swapping OP amps in Quad 405s is the least productive way to improve
performance. Moreover, some suitable OP amps (5534, for instance) require
more supply current to operate correctly. There's an excellent treatise on
hot-rodding a 405 on the 'net. I'll try to find the link.

This is the best, most comprehensive set of instructions I have found. It is
backed by logic and science. To perform all the mods is quite a job, but
worthwhile, IMO.

http://www.geocities.com/ResearchTri...uad405doc.html


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

wrote:

Hi,

I've recently acquired an early 80s Quad 405 which had been converted
to a Quad 405-2 by Quad in 1996 (the front label has been change to
'Quad 405-2'). This upgrade appears to have involved replacing the
complete output boards as those in the amp are marked 405-2.

These '96 boards are fitted with TLO71 opamps and I have read
elsewhere on the net that these ought to be replaced by OPA604 opamps.
Is this really worth the effort? The TLO71s are soldered in, not in a
socket. Are the OPA604s a direct replacement or should other components
be changed as well?

What are you trying to achieve ? OPA604s draw 6mA supply current instead of the
2.5mA of the TL071. That might require a component change for example.

Graham

wrote in message
ups.com...


** Groper Alert !


I've recently acquired an early 80s Quad 405 which had been converted
to a Quad 405-2 by Quad in 1996 (the front label has been change to
'Quad 405-2'). This upgrade appears to have involved replacing the
complete output boards as those in the amp are marked 405-2.

These '96 boards are fitted with TLO71 opamps and I have read
elsewhere on the net that these ought to be replaced by OPA604 opamps.


** Don't be shy - why not post links to the snake oil scam artist's sites
??


Is this really worth the effort?


** Absolutely not !!!!!!


The TLO71s are soldered in, not in a socket.


** More reliable that way.

Plus discourages tinkering by fools.



Are the OPA604s a direct replacement or should other components
be changed as well?


** The OPA604 is not readily available in 8 pin DIP - only the tiny SMD
version is around now. Makes substitution a real PITA.

There are NO advantages in changing to an OPA 604 and several disadvantages
compared to the TL071:


1. The OPA604 actually has several times more harmonic distortion than the
TL071, see #

2. It draws greater DC supply current requiring other changes to the 405.

3. It will create a disturbing switch off * PLOP * that is not there
with an 071.



# http://www.dself.dsl.pipex.com/ampins/webbop/072.htm

# http://www.dself.dsl.pipex.com/ampins/webbop/opa604.htm




........ Phil

In article ,
Trevor Wilson wrote:
**Swapping OP amps in Quad 405s is the least productive way to improve
performance. Moreover, some suitable OP amps (5534, for instance)
require more supply current to operate correctly. There's an excellent
treatise on hot-rodding a 405 on the 'net. I'll try to find the link.

Is there anything wrong with the TL071 series? The TL072 and NE5532 are
still two of my favourites despite their age.

--
*Ham and Eggs: Just a day's work for a chicken, but a lifetime commitment

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article ,
Trevor Wilson wrote:
**Swapping OP amps in Quad 405s is the least productive way to improve
performance. Moreover, some suitable OP amps (5534, for instance)
require more supply current to operate correctly. There's an excellent
treatise on hot-rodding a 405 on the 'net. I'll try to find the link.

Is there anything wrong with the TL071 series?

**In the 405? Not especially. For other purposes, there are better OP amps,
IMO. The AD825 is superb.

The TL072 and NE5532 are
still two of my favourites despite their age.

**Indeed. The 5532 is still an excellent OP amp.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

In article , Trevor Wilson
writes

"Dave Plowman (News)" wrote in message
...
In article ,
Trevor Wilson wrote:
**Swapping OP amps in Quad 405s is the least productive way to improve
performance. Moreover, some suitable OP amps (5534, for instance)
require more supply current to operate correctly. There's an excellent
treatise on hot-rodding a 405 on the 'net. I'll try to find the link.

Is there anything wrong with the TL071 series?

**In the 405? Not especially. For other purposes, there are better OP amps,
IMO. The AD825 is superb.

The TL072 and NE5532 are
still two of my favourites despite their age.



**Indeed. The 5532 is still an excellent OP amp.

Still used in a lot of Pro recording and mixing gear)...

--
Tony Sayer

Phil Allison wrote:


** The OPA604 is not readily available in 8 pin DIP - only the tiny SMD
version is around now. Makes substitution a real PITA.


RS claim to have them in stock:

http://www.rs-components.co.uk/1/268...0MHz-DIP8.html

Regards,

John.