Increasing Quad 33 output

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13-May-2017 02:08 PM

hummph

hummph

Posts: 19

Hi,

Is it possible to increase the output level of the Quad 33 from the standard 500mV?. I have a dada revised 33 and prefer the sound to my revised 44. I would like to use it with some Quad 11's which have a sensitivity of 1.4v for full output.

Thanks

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14-May-2017 08:53 AM

Joost Plugge

Joost Plugge

Posts: 905

It can be done, by lowering the feedback instead of increasing the feedback as we propose in the kit. I never did this, because of the single supply in a 33, the distortion will increase considerably when you increase the output. Maybe EJP has a answer.

Joost Plugge

DaDa Engineering

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14-May-2017 12:14 PM

EJP

EJP

Posts: 1342

The overall gain of a Quad 33 is about 5, given by (R411+R412)/R412, presently (1800+470)/470. You can tweak these values, keeping the sum roughly constant, to get the desired gain of nearly 15 that you want, e.g. R411=2k2 and R412=150R for gain of 13.222 and nominal output level of 1.32V. There will indeed be an increase in distortion as Joost states but whether it is audible or indeed significant is another question.
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15-May-2017 05:40 PM

hummph

hummph

Posts: 19

Thanks that's very useful info. To start with I will try R411 2k and R412 270R which is the same overall resistance but should give a gain of about 8 times.(If I've got my maths right!)

Regards

Ken

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21-May-2017 12:08 PM

hummph

hummph

Posts: 19

Well, I successfully changed R412/ R411 and the increase in gain is a great improvement.There is slightly more sound "creeping" through from the radio input when the tape input is used,but not enough to be a problem-just switch of the tuner!. Not sure if any increase in distortion is audible but I prefer the sound to the rather 'laid back' presentation of the(upgraded) mk2 44. I may try some MAX4066's switching ic's in that and see if there's any improvement- but that's another story!

Ken

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22-May-2017 02:36 AM

EJP

EJP

Posts: 1342

That's odd about the radio. Unused inputs are shorted to ground. May be time to spray inside the switches. Just remove the knob, spray as little isopropyl alcohol in as possible but as far in as possible, and work the switch 20 times. No WD40.

EJP
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08-Jun-2017 08:29 AM

Joost Plugge

Joost Plugge

Posts: 905

I hope I got it right (EJP?), but that only is true when you release the radio button, otherwise the radio input is still working. The tape input also functions as a monitor function. So some cross input rubish is normal, and amplified in this case. 

Joost Plugge

DaDa Engineering

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