[blazin]

Hello all,

I am trying to figure out a way to seperate the preamp section amd amplifier sections of the Jolida 302b...My ultimate goal is to be able to use the Jolida's preamp section with it's volume control to feed a variable  signal to my solid state amp.I would like the option of  going back and forth between solid state amp and the Jolida's tube amp section.I was thinking something along the lines of having a set of RCA pre-outs and pre-ins on the Jolida that could just be jumpered together like some of your 70's receivers camefrom the factory...Is this possible? ANY help would be greatly appreciated.Thanks

[JoshK]

I don't think these have a true preamp section, am I wrong?  I thought they were just a pot in front of the first gain stage in the amp.  Either way, you can tap a second set of outputs from the output of the pot.  However, this has a cost.

If you parrallel a second set of outputs, it changes the load see by the source.  You can work out the load resistor on the output of the second RCA outs so that the load is still reasonable (calculate from parrallel with the pot, the tube's grid leak, the SS amp input's load).  The trouble could be with the driving current of the source.  What kind of source do you have?  Is it a SS output stage?

I just saw the last part of your post, which I looked over reading too quickly.  Yes you could add a preamp output and preamp input in a similar fashion as I mention above.  If you are going to use only one amp section at a time, it reduces the load the source has to drive.  I would stick to the input impedance of your amp (the pot's impedance) for the preamp input load resistor (input hot to ground). 

[blazin]

Wow...So you think I could add a preamp in and preamp out like I want?I would only be driving either the Jolida's tube amp section or SS amp at one time.I just want the option of using either SS power or tube power but not BOTH at one time.Any one care to walk me through the mod...?Here is a link to the schematic...
http://www.ellisaudio.com/302b.pdf

[Bill Baker]

Hi Blazin,
 Josh is correct in that the Jolida does not have an active preamp. It is a source selector and volume control in front of an amplifier. You can very easily use a set of preamp outputs to drive your amplifier but the success would depend on the output of your source. You are essentially using a passive preamp here. Be sure to keep your cables short as well.

 The new 302 and 502 amps come with a variable output for a subwood which is basically what you are doing. You are driving a SS amp just as you would with a powered subwoofer. When using the controls to drive the SS amp, you would not need to turn the Jolida on as you would only be 'borrowing' the front controls.

 You can also install a pre in and main out without trouble.

[blazin]

So, I can use the volume control on the Jolida to control my SS amp output? Could anyone point me in the right direction as to where on the schematic to come off with the pre-out and pre-in sections?Thanks so far for the info guys...

When you say "source output" are you refering to say my CD player's output voltage?It is a Rotel 971 player if that helps...

[Haoleb]

IIRC from when I had the amp open you would basically just sort of split off of the volume pots output. There is quite a bit of room in the chassis so at least it will be rather straightforward. You should have told me you wanted to do this and I could have performed the mod before I shipped it out