Replica Pre QUAD 22 - Questions on mids

[Scabiko]

Hi,

I just replicated a simplified circuit of preamp 22 of Quad, added a PSU and used on the audio signal path caps of 4.4uf (instead of only 2.2 uf) and of 0.47 uf. The pre seems to lack of mids. Modifiying the value of 0.47 uf to a lesser value would increase mid presentation? the 2.2uf cap, has any effect on mids? are there any other mods or changes to improve mid´s definition?
Thank you for your time and consideration. Sebastian

 

[nafunga]

Hi,
Are you sure you'r talking about the Quad 22? Coupling caps are around 0.1uf or less on this model, not 2.2uf or 4.7uf.. Is this a transistor amp? I've done quite a bit of work on 22's over the years so am reasonably familiar with the circuitry.

Kind regards,

David..

 

[Scabiko]

Thanks for your reply. I am trying to transmit to you what the tecnitian who made it for me told me. Unfortunately, he does not speak English. I will reconfirm with him and get back. I can tell you that on signal path I have 0.47 evox rifa caps (metallized polypropilene) and the cap of 4.4uf was put instead to the electrolityc cap of 25 uf included in the original plan. I really don´t know the importance of the 25 uf cap on the signal.

Please note that we did not put tone controls and from the 0.47 uf signal cap goes straight to the output (passing through certain resistors). We omitted a cap of 0.5 uf that goes before the tone controls on the original plan.

Best ragdrs, Sebastian

 

[ejp]

The only electrolytic capacitors in a Quad 22 are the EF86 bypass caps and the coupling caps to the balance control. The correct value is 25uF, and there is no conceivable reason to lower it to 4.7uF. There are no 2.2uF capacitors anywhere. Your tech has made a major mistake, or several, which will reduce bass response considerably.

Better late than never;-)