DIY: AD-20 gain mod... possible?

[lordbelial]

Hi!

I have been talking recently about the lack of the AD.20. the minimun 17db of gain.

Anybody has ever think on modify the Ad-20 to turn the minimun gain into 0db (or even 10db would be enough!!!)

I'll really like to mod my AD-20 in order to modify the gain, and I think it will be helpful for all the AD-20 users, because I don't think that anyone of the Ad-20 could have ever used the maximun gain (70 db I guess...), so, if it could be possible to set the gain range to 0-53 or 10-63 db will be enough.

I don't know if this GAIN MOD could be possible to perform, so I'm looking forward to the attention of the ones who could be interested in this thread and this GAIN MOD.

Any suggestion?

[udovdh]

Any suggestion?

AD-20 is the inbox? Or am I mixing things up?
In general: if it uses opamps and uses resistors to set the gain you can vary that gain by changing resistors.

[lordbelial]

Any suggestion?

AD-20 is the inbox? Or am I mixing things up?
In general: if it uses opamps and uses resistors to set the gain you can vary that gain by changing resistors.

AD-20 Zefiro Inbox.

I should have to reopen the AD.20 and check if the resistors ara "normal" resistors or SMD...

[Chuck]

Any suggestion?

AD-20 is the inbox? Or am I mixing things up?
In general: if it uses opamps and uses resistors to set the gain you can vary that gain by changing resistors.

AD-20 Zefiro Inbox.

I should have to reopen the AD.20 and check if the resistors ara "normal" resistors or SMD...

Definately not surface mount. That box has been around for quite a while.
Maybe while you are in there swap out the crappy op-amp with something a little better sounding and call it the lordbelial mod!

[poorlyconditioned]

Any suggestion?

AD-20 is the inbox? Or am I mixing things up?
In general: if it uses opamps and uses resistors to set the gain you can vary that gain by changing resistors.

AD-20 Zefiro Inbox.

I should have to reopen the AD.20 and check if the resistors ara "normal" resistors or SMD...

Definately not surface mount. That box has been around for quite a while.
Maybe while you are in there swap out the crappy op-amp with something a little better sounding and call it the lordbelial mod!

Actually the opamp in there is fine.  It is cheap, but fine, since it is after the discrete transistor stage, where the gain is being achieved.

What needs work is the transistor front end.  And that is a lot of work, unfortunately.  And I don't know how to design with discrete stuff.

Hmm.  If I was really going to modify that thing I would replace the  transistor front end *plus* the opamp, with something good like an AD8620.  But that is a lot of work too.

As far as reducing gain, it *might* be possible to just reduce gain at the opamp.  But I have not tried this.

Have fun!

  Richard

[Chuck]

Any suggestion?

AD-20 is the inbox? Or am I mixing things up?
In general: if it uses opamps and uses resistors to set the gain you can vary that gain by changing resistors.

AD-20 Zefiro Inbox.

I should have to reopen the AD.20 and check if the resistors ara "normal" resistors or SMD...

Definately not surface mount. That box has been around for quite a while.
Maybe while you are in there swap out the crappy op-amp with something a little better sounding and call it the lordbelial mod!

Actually the opamp in there is fine.  It is cheap, but fine, since it is after the discrete transistor stage, where the gain is being achieved.

What needs work is the transistor front end.  And that is a lot of work, unfortunately.  And I don't know how to design with discrete stuff.

Hmm.  If I was really going to modify that thing I would replace the  transistor front end *plus* the opamp, with something good like an AD8620.  But that is a lot of work too.

As far as reducing gain, it *might* be possible to just reduce gain at the opamp.  But I have not tried this.

Have fun!

  Richard

Is there 1 pot or 2 in the AD-20? It may be easier to swap out the volume controls with smaller values to reduce the gain then.