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Postby Orphan Audio » Thu Jan 25, 2007 12:43 am

The limitation in output level direct from Electrodyne modules is not because of the supply voltage to the opamps. (ok, technically it is)
These modules require an output transformer with gain to get full +24dbm output, much like typical Neve modules which also run off 24v. (even though Neve opamps are Class-A instead of the Electrodyne Class-AB)
This is true of most modules removed from modular custom consoles of the 60,s and 70,s. They were never designed to exist outside of the console frame without transformers and sometimes additional gain stages as well.
Removing and racking most of these classic modules is no simple "yank and rewire" operation. It requires knowlege of the original console signal path, gain structure and an open mind to careful circuit changes that will preserve the original sound, output levels and headroom before distortion.
Ken Hirsch
Orphan Audio LLC
http://www.orphanaudio.com
Quad Eight Electronics LLC (tm)
http://www.quadeightelectronics.com
Electrodyne Corp.(tm) (a division of Orphan Audio)

"Education is the cure for everything"
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Postby brianroth » Sun Jan 28, 2007 12:05 pm

Ken...amen!! An excellent posting.

To be honest, I haven't tested those modules in order to determine whether or not they can actually drive a 150 Ohm (or lower) load impedance, in order to use the simple solution of a step-up transformer to derive a higher output level prior to clipping, and thus overcome the limitations of a single-ended 24 VDC power supply rail.

I suspect they will "rebel" when loaded into 150 Ohms or lower.

Hence, my gut instinct for the need of an output buffer stage for a rack-up of the individual modules......

Bri
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Postby Orphan Audio » Thu Feb 01, 2007 4:28 am

The A-1000 opamps used in the Electrodyne modules should have no problem driving a 150 or 600 ohm load.
The long hidden secret of the A-1000 (carefully potted inside that cylindrical plastic case) is that it is actually a Fairchild u709 IC opamp driving a pair of high current output transistors, similar in drive capability to opamp output pairs used on many other manufacturers all discrete opamp designs.
If you are still uncertain, locate some LA-62 line amps to drive the outside world. However we have found the LA-62,s are much more valuable converted to high quality mic preamps with the right internal connections pulled out to a gain selector switch.
The A-2000 and A-3000 opamps used in many of the later Electrodyne modules (711, 712 etc..) are all discrete topology.

A quick shameless plug for Orphan Audio and Quad Eight LLC:
We have a huge inventory of NOS Quad Eight/Electrodyne/Langevin parts. Knobs, Levers, opamps, card amps, switch/pot assemblies, engraved front panels, etc.... and are in the process of moving the entire Electrodyne/Langevin document archive to our hedquarters. We also provide repair, engineering and repackaging services for many classic consoles and modules.
Email us for parts / schematic requests, or visit our website and forums.
And now back to our regularly scheduled program, already in progress.......


If you look at the spec sheet and note the slew rate of the 709 compared to modern opamps you would not expect it to sound so good, but obviously it does.
Surprised it,s not all discrete? No one who used them ever suspected it by the amazing sound they got. Consider how highly valued these modules are now, and will be in the future.
Knowing whether there is an IC in the circuit or not, will not change the sound.
A more modern surprise about IC opamps is that the famous and highly coveted "Air Neve" consoles are actually populated mostly by 5534 opamps. From the preamp stage all the way thru to the bus outs. Rupert is no dummy, he used his ears to get what he wanted in that console. He chose those opamps for a very good reason.

Uneducated naysayers who dismiss certain opamps just because of rumour or a bad experience with a poorly designed circuit be damned!

The truth is:
"There are no bad opamps, just a lot of bad ways to use them."
Ken Hirsch
Orphan Audio LLC
http://www.orphanaudio.com
Quad Eight Electronics LLC (tm)
http://www.quadeightelectronics.com
Electrodyne Corp.(tm) (a division of Orphan Audio)

"Education is the cure for everything"
Orphan Audio
Analog Enthusiast
 
Posts: 7
Joined: Fri Jan 19, 2007 3:33 am
Location: Simi Valley, Ca.

Re:

Postby Orphan Audio » Sat Feb 14, 2009 9:19 pm

Orphan Audio wrote:The A-1000 opamps used in the Electrodyne modules should have no problem driving a 150 or 600 ohm load to about +16dbm.
The long hidden secret of the A-1000 (carefully potted inside that cylindrical plastic case) is that it is actually a Fairchild u709 IC opamp driving a pair of high current output transistors, similar in drive capability to opamp output pairs used on many other manufacturers all discrete opamp designs.
If you are still uncertain, locate some LA-602 line amps to drive the outside world. However we have found the LA-602,s are much more valuable converted to high quality mic preamps with the right internal connections pulled out to a gain selector switch.
The A-2000 and A-3000 opamps used in many of the later Electrodyne modules (711, 712 etc..) are all discrete topology.

A quick shameless plug for Orphan Audio and Quad Eight LLC:
We have a huge inventory of NOS Quad Eight/Electrodyne/Langevin parts. Knobs, Levers, opamps, card amps, switch/pot assemblies, engraved front panels, etc.... and are in the process of moving the entire Electrodyne/Langevin document archive to our hedquarters. We also provide repair, engineering and repackaging services for many classic consoles and modules.
Email us for parts / schematic requests, or visit our website and forums.
And now back to our regularly scheduled program, already in progress.......


If you look at the spec sheet and note the slew rate of the 709 compared to modern opamps you would not expect it to sound so good, but obviously it does.
Surprised it,s not all discrete? No one who used them ever suspected it by the amazing sound they got. Consider how highly valued these modules are now, and will be in the future.
Knowing whether there is an IC in the circuit or not, will not change the sound.
A more modern surprise about IC opamps is that the famous and highly coveted "Air Neve" consoles are actually populated mostly by 5534 opamps. From the preamp stage all the way thru to the bus outs. Rupert is no dummy, he used his ears to get what he wanted in that console. He chose those opamps for a very good reason.

Uneducated naysayers who dismiss certain opamps just because of rumour or a bad experience with a poorly designed circuit be damned!

The truth is:
"There are no bad opamps, just a lot of bad ways to use them."
Ken Hirsch
Orphan Audio LLC
http://www.orphanaudio.com
Quad Eight Electronics LLC (tm)
http://www.quadeightelectronics.com
Electrodyne Corp.(tm) (a division of Orphan Audio)

"Education is the cure for everything"
Orphan Audio
Analog Enthusiast
 
Posts: 7
Joined: Fri Jan 19, 2007 3:33 am
Location: Simi Valley, Ca.

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