ControlRoom Circuit Problem

[mik]

Here's my control room complete schematic, as you can see it is just simple, the problem is that this topology can't handle 4, 3 RMS volt I need to drive active monitors, because wen I trim R66/39 1M to get right gain the follow stage get gross distrortion.

May I gai the follow stage changing R64/R55/R57/R60 to 47K instead 10 to get a ain of 5 ( 14db)

thank you .

 

[Kit]

Where´s the schematics?

 

[gyraf]

parsing problem? No image..

 

[mik]

image
sorry !
M.

 

[Boswell]

It sounds as though your problem is not lack of gain but inability of the output stage to drive your load to the required signal level.

What are the opamps in the output stage? I'm not too happy about supplying the power pins of the output stage op amps through 100R resistors, even bypassed with 220uF.

Is the 4.3Vrms that you need for your monitors the FS level or the average? If it's the average, the FS could well be 12-18dB more than this, and you won't achieve that using this circuit with only a +24V power rail.

 

[mik]

Well , at this moment the Op Amp are TL084, the PSU is 29 Vot instead 24, the goal is to go 14 db more to drive the monitors ( active) by the contron room volume pot,
I can I do ? add another stage ?
M.

 

[Svart]

add PNP and NPN for an output current amp. I've seen the schemos around here somewhere..

 

[Svart]

hmm thinking about that for a minute.. you could always parallel multiple opamps..

 

[mik]

[quote author="Svart"]add PNP and NPN for an output current amp. I've seen the schemos around here somewhere..[/quote]
Pleas Svart find it and post it ,the I've done Search , but didn't find yet.
M.

 

[mik]

something like this, but this circuits can only handle a max input of 0,7 V
How to impruve it to drive more volt ?
M.

 

[Svart]

i'll try to find it for you, I don't know where I saw it though. let me look.

 

[Kit]

Ok, stupid question....
What´s the problem here....do you need increased current drive or voltage gain?

 

[mik]

ok , I will wait for it.
thank you
M.

 

[mik]

[quote author="Kit"]Ok, stupid question....
What´s the problem here....do you need increased current drive or voltage gain?[/quote]

voltage gain,
M.

 

[mik]

ops, the problem is :
The Output of my Summing Amp is 1.5 Volt max, I've to drive it 14 db more, with no distortion for drive the poweramp for the monitors.
How to do,
Question : I've to add an Extra stage ?
if yes haw to build a stage that can Handle 2 or more volt and gain it with no distortion.

M.

 

[moamps]

Hi Mik:

I don't think you need extra buffers, etc.
First, you might check the maximum output voltage after you have lowered R44,47,58,65 to 47ohms and omitted R69 and 71. Also, check DC voltage at all OP outputs and confirm that they sit at around VCC/2.

Regards,
Milan

 

[mik]

hi Milan, I' will make a try
M.

 

[Svart]

do you need increased current drive or voltage gain?

Sounds more like his current capability isn't nearly enough to keep the voltage up. 48v differential should be plenty for small monitors.. My monitor amp uses +-24v for the rails and I can blow drivers with it.. only I use the LM3886 chip, like the gainclone.

 

[mik]

in my box I got the stereo out for recording units , and the out put for control room, but to patch the control room to an active motor pair the out put should be mutch hig then unity gain, I guest 10db more.. if not the volume is quit low.. that's the problem.

so I've to gain up the output of the summing amp 10 or more to have a good volume excursion.
M.

 

[Kit]

edited.