Tascam 48 Op Amp replacement

Advertise with us
Shop deals on ebay
shop deals on amazon
GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
moamps said:
I didn't said that Tascams 42, 44, 48 and Revox PR99  are professional machines. Although, Studer said here http://wegavision.pytalhost.com/Revox/PR99IIp/revox03.jpg that PR99 is intended for professional use. I just did comparison according my experience of using and servicing between the models what can be seen on web very often (Tascam/Teac vs.  Studer/Revox).
When I say that Tascam is PRO, I have in my mind machines as ATR60, CD601, CD701, DA60, DA88 we used here in professional (OB) recording and broadcasting. Of course, YMMV.
@ ECS787s
You can replace C006, 007, 031, 032, 050 & 051 with higher values and higher max. voltage (25V instead of 16V). If new opamps will  draw more current, consider lowering the values of resistors R205, 206, 124,125, 83, 84.
Also replacing bipolar capacitors placed between stages is a good idea.
P.S.
There is a nice low noise discrete opamp (fet input) used as tape head preamp. 
 
Click to expand...
Sorry I didn't want to start a qualitative comparison of the brand. Professional has a specific meaning, but has been widely co-opted by marketing to up-sell products.

The TASCAM small format machines were widely used and good for what they were. It is difficult (impossible) for one brand to be both entry level and high end, while it looks like TASCAM tried.
========

None of this has much to do with the OPs pursuit, so back on topic. If replacing 5mA op amps with 50mA op amps, the important question is how many? You might get away with one or two op amps, but not 10 or 20...  That would require beefing up the PS.

There may be better choices for op amps that are better than stock, but not crazy current consumption. Good look in a large design like this there are multiple factors to consider.

JR 
 
Ecs787s said:
Ok, so I just checked the quiescent current of the "stock" op amps and they run between 3-6mA while the new lme49720s run around 10mA... So based on this, would it be a good idea to bump up the capacitance on those power supply rails?
Click to expand...

It would be a good idea to determine if the power supply is capable of supplying the extra current required.

-a
 
Ok guys, thanks for helping me out. So I've replaced U001, U003 and U004 with LME49720s. U002 was not replaced because I don't have the higher voltage version (49860) yet. So I've taken some voltages to see how I'm doing current-wise.

U001 pin 8 is now at 12.45v and drawing 6.5mA more current than stock. U001 pin 4 is now at -11.85v and drawing 7.5mA more current than stock.

U003 & U004 Pins 8 and Pins 4 are at both at 10.45v and -10.45 respectively and together are sucking 26.8mA more of juice.

So there you have it... roughly 41mA for 3 opamps per channel, without the final balancing U002 "PRO" +4 op amp. In my unbalanced world using RCA ins and outs, is 8 channels at 41mA each gonna kill this thing or what?
 
And by the way, I know that my piece of crap Tascam ain't "pro"... I'm just trying to have a little fun messin' with it. That's all its about... trying to get some extra mileage. Thanks for all your help.
 
Ecs787s said:
So there you have it... roughly 41mA for 3 opamps per channel, without the final balancing U002 "PRO" +4 op amp. In my unbalanced world using RCA ins and outs, is 8 channels at 41mA each gonna kill this thing or what?
Click to expand...

That's increase for 20mA/rail or 160mA/rail/8channels what,  as I said, shouldn't be problem, IMO.
 
moamps said:
Ecs787s said:
So there you have it... roughly 41mA for 3 opamps per channel, without the final balancing U002 "PRO" +4 op amp. In my unbalanced world using RCA ins and outs, is 8 channels at 41mA each gonna kill this thing or what?
Click to expand...

That's increase for 20mA/rail or 160mA/rail/8channels what,  as I said, shouldn't be problem, IMO.
Click to expand...
Ecs787s mentions 320mA, not 160. Does it matter? It's not a matter of opinion. Without seeing the PSU schemo and analysing the overall current consumption, I can't have an opinion. I would recommend a simple experiment: connect two 47R/15W resistors across the rails, and measure the regulated voltage, in particular, assess ripple and check the temperature of the regulators. Then one can emit a valid opinion; the rest is speculation.
 
abbey road d enfer said:
Ecs787s mentions 320mA, not 160.
Click to expand...

Hi summed currents from both (positive and negative) rails. Your experiment will be correct if resistors are 100ohms/5W min.
 
moamps said:
abbey road d enfer said:
Ecs787s mentions 320mA, not 160.
Click to expand...

Hi summed currents from both (positive and negative) rails. Your experiment will be correct if resistors are 100ohms/5W min.
Click to expand...
Holy crap! since when do pos and neg rails do add up? If ECS787s measurements are that wrong, I agree that the increase in current per rail is only 160mA. Whatever, it doesn't change the principles.
 
The +/-15V regs in Tascam 48 are designed using discrete transistors with maximum allowed current up to 2Amps .
The power transformer is overdesigned (there are impulse loads during tape rewinding, etc) so additional 4W of power cannot be
problem. 

http://www.torridheatstudios.com/ftp/Share/Pictures/Tascam%2048/2008%2009%2025/02.JPG
 

Similar threads

C
suggestion for replacing/upgrading 4136 quad discrete op amps?
Replies
3
Views
591
capacitor
C
gar381
Sold garSPA-62 Discreet Op-amps with card edge connectors new pricing. ALL GONE
Replies
8
Views
2K
ruairioflaherty
R
L
Allen & Heath System 8 Mk1/2 recap and mods
2 3
Replies
42
Views
8K
hwood123
hwood123
J
FETBloak/Bigbloak discrete op amp boards and parts
Replies
3
Views
1K
jaygunn
J
L
Another summing bus op amp comparison
Replies
13
Views
5K
abbey road d enfer
A

Latest posts

Back
Top