Bellari RP220 MODS

  • Thread starter Thread starter Wingpen
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Sure...new opamps and new tubes make it sound much better...If you are not afraid to go a little deeper would I replace the input trannies...I used Lundahl transformers, OPA2604 opamps (had to bypass a resistor to stop it from oscilatting) and I have a couple of old 12ax7 tubes that I swap in and out for different sounds...neat project but money is probably better spent on a whole different pre (The Lundahls are 50$ a piece!)..However, it is usable now :)

Ray
 
I used a lundahl 1530 for the tranny...I am not sure about those opamps as the link for the search had expired..I used Opa 2604's...which oscillated a little....I don't have a schematic so I can't offer any suggestion other than the 2604..I did replace a bunch of junky capacitors as well with Orange Drops...

Ray
 
Just did a google search for Bellari mods and found this thread.
rsolinski, I've installed Cinemag input trannys in my RP220. Did you remove any resistors after you Lundahls? With the gain knob cranked, my unit doesn't clip with this tranny in.
I removed a 10K resistor following the secondary from an MP110 when I installed Cinemags in it.
 
The best things you can do to mod the Bellari is to replace the piece of shit transformer with something better. Which is something that some of you guys have already done, I see, so good job fellas.

The next best thing you can do is to attenuate / pad the signal, in some way, right before it reaches the output opamps. You see, once you push the tubes and get some decent harmonics out of them, you're already clipping the solid state outpute phase. You can get a lot more use out of the initial tube gain stage by inserting some sort of pad between it and the solid stage gain stage at the output.
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That pad sounds interesting because the bad part of this amp is those chips on the output..be cool to bypass these and use an output tranny..but for all that time and expense I could just build a better tube pre from scratch...I didn't fool with any resistors after changing tto the lundahls,...I should have looked for a zobel network and jumpered it as the Lundahls do not need any termination...

Ray
 
rsolinski said:
That pad sounds interesting because the bad part of this amp is those chips on the output..be cool to bypass these and use an output tranny..but for all that time and expense I could just build a better tube pre from scratch...
Click to expand...

Would it be a pain in the ass to split the signal, and route it so that, out of one of the 1/4" outputs in the back, you could have a signal that bypasses the output opamps? I'm assuming you could then just run out of that 1/4" in to a decent transformer-based DI box?
 
I should have looked for a zobel network and jumpered it as the Lundahls do not need any termination...
Click to expand...
Has anyone noticed a zobel on the stock transfomer?

Also, would a pad be as necessary if you upgraded that opamp like an OPA2604? That's what I've done with mine.
 
I put 2604's in it but I am not a fan of any monolithic chips (opamps etc...)..I did the black lion mod too (I am the reviewer on the reviews page on his web site)..Since then I have built a few API 312's and racked some yamaha pm1000's and they just plain crush the rp220 in terms of headroom and tone..next up is a tube pre from scratch and probably one of sca's c84 double balanced pre's (similar topography to those DAV units people are raving about)..I might even sell the 220 if I don't use it in the next year or so...

Cheers,
Ray
 
Ray,
When you changed your transformers, did it decrease the gain of the input stage?

Craig
 
yes..I put lundahls in with a 1:7 turns ratio..it still has boatloads of gain tho...with an ldc you can barely turn it up at all!

Ray
 
Hi,

I'm new here. I'm having trouble installing a 1530 onto my RP220. Does anyone here know which terminals the red/yellow/black/white cables go to on the 1530? Also where do I connect the 1530's ground (I know stupid question, but I'm asking it from a logistical perspective - in other words, which junction on the PCB would be best???)
 
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