I would like to share the transformation process of this Bella Extreme "Bella L/P" preamp.
This original Bella Extreme "Bella L/P" (BellaMax) preamp was originally built a couple years back for a customer as a straight forward, no frills design. It was recently sold and now has a new owner who is having it custom built (maxed out) to beyond what any BellaMax has ever seen.
I will continue to add to this thread as the process continues.
Questions and comments are welcome.
Here are the details of what is going into this unit.
-A new maxed out dual mono power supply is being built in a separate chassis.
-New high current toroidal transformers
-Choke filtered 100% polypropylene filter capacitor banks
-Dedicated, separate high current transformers for the tube filament supplies
-Separate, dedicated power supply for the Khozmo 48 step remote volume control
-Transformer coupled balanced input with transformer coupling on RCA inputs
-3 transformer coupled single ended inputs
-1 XLR balanced input
-High quality relay operated input selector
-Transformer coupled balanced outputs with transformer coupling on RCA outputs
-2 transformer coupled single ended outputs, 2 XLR balanced outputs
-Khozmo 48 step remote attenuator
V-Cap OIMP and V-Cap TFTF bypass on output coupling capacitors prior to transformers
-Passive HT bypass circuit
-Matching dual aluminum chassis'
Here is what it looked like in its original state.
(http://responseaudiony.com/bella%20lp%20original.jpg)
The beginning of the dual mono, choke filtered polypropylene power supply chassis.
(http://responseaudiony.com/Bella%20lp%20PS1.jpg)
Looks Great! :thumb:
Can I ask about the trafo coupled ins and outs? I am guessing the trafo replaces coupling caps on the outputs, so the main advantage is not using a coupling cap? But why are you using a trafo coupled input? I would never use a source that has a DC offset in it's output, so do not have an input coupling cap in my preamp...
Also, do you bypass the caps in the power supply? I was so happy with the Clarity TC power supply caps I have not tried bypassing them, but a poster on audiocircle just said bypass caps made an improvement over using the TC series caps by themselves so I am considering trying it...
Hello Dave
When using transformers at the output, you still need capacitance before the transformer. Without it, you have some problems in the lower frequencies.
Ther are no capacitors at the input. The signal first goes into a balanced selector then into the balanced transformers. We have built countless preamps with and without transformer inputs and if done right, both can provide exceptional results. There are some "tricks of the trade" when it comes to having the right resistance for this configuration. I have had other preamps using transformer coupled outputs come through here that the customers said did not sound right and after testing, found that the manufacturer did not implement the output circuit properly. After some tweaks, we had it performing wonderfully and measuring the way it should.
As far as bypassing power supply caps, I rarely find the need to bypass polypropylene capacitors in the power supply but i do do it on some capacitors and it is done on the LeAnna as i found a difference with the Clarity TC caps as well as on the final filter caps as they are an electrolytic. One recommendation I do have is regarding tube power supplies. For piece of mind, I always install diodes at the tube sockets of power supply tubes. This is installed in all our tube power supies for the new Musica Bella "LeAnna" preamps.
Thanks for the info Bill, I look forward to following your build! :thumb:
:drool: Wow what a pretty power supply. This preamp is going to be pretty serious.
Now where does this transformation of the Bella Extreme Bella L/P preamp rank amongst the other Purity Audio preamps? What would the newly transformed Bella L/P preamp compare to in the Purity Audio line?
Hi there Sleepy
I don't know where to put this Bella L/P in with the Purity line.
Most people know is was the Bella circuit itself that transformed into the Purity line but this L/P is completely custom.
I think I would now place it more towards a maxed out Musica Bella full size version LeAnna preamp.
http://responseaudiony.com/leanna.htm (http://responseaudiony.com/leanna.htm)
We have a customer we have been talking to that is looking at building a maxed out LeAnna with the dual mono, external preamp, custom made Autoformer volume controls (dual mono, non remote), balanced ins and outs and a whole lot more.
I am even starting to get inquiries for LeAnna Econo versions with upgraded polypropylene external power supplies and upgraded analog circuits with the Khozmo attenuators.
I will post build threads of these should they go through.
Cool stuff as always from you Bill. Wonderful idea posting the photos and concept. going to Capitol Audiofest this year ?
charles
Thanks Charles. I enjoy sharing these custom builds as much as I enjoy building them. With custom work such as this, we come across all levels. From standard, bare bones to all out assaults.
CAF depends on the weather. We will have a Silver Statement Series II with Ultra power supply there with ModWright and Daedalus.
If the weather is decent, the wife and I will hop on the bike and cruise down for a day or two. Unfortunately, the weather has been so severe and unpredicted this year, especially for the east coast, we won't know till a couple days prior what's going on.
Here are a couple more pictures. The preamp is now complete and in the hands (system) of its new owner. More information and pictures can be seen at:
http://www.responseaudiony.com/gallery.htm (http://www.responseaudiony.com/gallery.htm)
The finished power supply
(http://www.responseaudiony.com/PS.jpg)
The two chassis'
(http://www.responseaudiony.com/insides.jpg)
Up and running in test system
(http://www.responseaudiony.com/fullsystem.jpg)
Here is a picture I wanted to share. The customer had a new face plate done up for the upper main chassis. It is now known as the Musica Reference
(http://www.responseaudiony.com/AndrewSell.jpg)
Now that is a power supply to write home about. Wow !. :drool:
charles
Thanks. Charles. It seems quite a few cunsumers are looking at dual mono, full polypropylene power supply designs for their preamps now.
When time allows, I will be running a full dual mono LeAnna in my system.