[budx3385]

I bought the single channel models to install in my Rotel 965BX (several DIY net-audio mods - see another thread). They sounded lousy at first (weak deep bass, too fast => harsh), then I moved the ground leads from the PCB lug to the RCA ground, which improved the SQ considerably. But they still need help, IMHO.

The Burson website has a "hot tips" page

http://www.bursonaudio.com/Burson_Di..._Opamp_101.htm

that recommends adding a bypass capacitor across the V+ and V- pins. Has anybody done this?

I would really appreciate recommendations. THANKS.

 

[budx3385]

I sure would like some advice from experienced DIYers.

 

[multibit16]

The Bursons sound best with a good quality PSU, I used these in a cdp and found they was far from harsh.
Did you fit the Net-audio clock? I found these in two different cdp's made them sound thin and bright.
I don't know the Rotel 965BX, where was the Bursons fitted? I/V or output filter/buffer section?

 

[budx3385]

yes, I installed the net-audio Rockclock and its PSU first, which sound great. I don't find the Bursons thin, rather dimensional, but harsh. They are fitted in an output buffer location, where NE5554s were originally.
Did you find another clock more suitable? How about different amp replacements? I wonder about the Zapfilter, in particular.
thanks

 

[multibit16]

I fitted the Rock clock and its psu in a friends cdp, on its own the sound seemed better than stock at first, it seemed more impressive sounding but after a while my friend found it tiring to listen too, I tried that clock in one of my own modded cdp's inplace of the tent labs clock, it also made mine sound tiring.
Other clocks I've tried are Elso's clock7, Trichord clock4, LCaudio , Burson clock and a PFM Flea powered Tent XO.

My two favourites are the PFM flea and the Burson.

I've been through dozens of op-amps in I/V and buffer/filter stages including a few diy discrete's.
So far for I/V my favourite is Pedja's common base stage and for buffers/filter my favourite was the Burson although the Burson sounds a lot better with decent regulation.
Also a lot depends on the cdp and its dac, I prefer multibit over any bitstream types, I want to try the Pass D1 I/V stage next, I've never tried the zapfilter

 

[budx3385]

Wow, you're definitely experienced! Thanks for all your comments. Do you have the original URL for Pedja? I see a lot of postings in pinkfishmedia and diyaudio. The regulation in the 965 may be suspect, but I don't know how to fix that myself. And of course it is a bitstream DAC, but it is the only one favored in many postings. I find its sound with the Rockclock very enjoyable, but the amp stage clearly needs help, because swapping makes huge differences. I have ordered small bypass caps for the Bursons, as directed by their staff - we'll see if that helps.

All suggestions welcomed !!!!!!!

 

[Nordic]

If its hte same guy, google Pedja Rogic, I built his fet buffer, and its the best I have heard my little system sound, so I can realy recommend his work...

 

[budx3385]

thanks

google easily found pedjarogic.com

a bit over my head, really - how could I obtain something a it easier ? If these circuits work as well as his hit rate would suggest, then there must be some ready-made mods available somewhere that I could use in my Rotel, no?

 

[multibit16]

I'm afraid Pedja's comon base stage only works with multibit dacs mainly TDA1541 based.
I've built his dac (below) I'm very happy with it

also recently built the Ezdac.
I had a look for the 965BX service manual but cannot find it, you can give the bypass caps a try with the Burson although I doubt it'll totally cure things.
have you changed the output coupling caps etc? if we can find the details for your regulation it should give us some idea's what you can do to improve it

 

[multibit16]

Other thing you could try, if this cdp uses a bitsream dac with voltage output is if the op-amps are say singles and it uses just one for each channel you can try taking the op-amps out and bypass pin 3 and 6 (single op-amps not duals) with a wire link.
You'll loose quite a bit of output volume but it should give you an idea how good the dac sounds, you also get an idea how much influence the output stage is having

 

[budx3385]

I can try that. If I'm wrong and these single opamps are I/V, will that jumper damage the circuitry? and if it makes it obvious that the DAC output is much better, what other options are there for the solution for the output stage?

The caps near these opamps are 220 uF BGs, and there are tiny bypass caps on them and also on the voltage pins of the opamps, so I am also dubious that adding caps to the Bursons will help much.

I added 2 new BGs to the PS that came with the net-audio 965 upgrade kit.

Thank you

 

[budx3385]

impressive work in your photo, sir !

 

[multibit16]

All your doing is removing an active stage, the output will still go through the coupling caps anyway to get rid of any DC offset.
If its a bitsream dac the op-amps are more than likely just buffer/filter stage.
Just make sure you bypass the right pins on the op-amp basically the input and output making sure the op-amp has been removed. you'll need to know if the output of the dac goes to pin2 of the op-amp (inverted input) or pin3 of the op-amp (none inverted input) if it goes to pin2 then you link this one to pin6, if it goes to pin2 you link that to pin6

Before trying the bypassing of the op-amp does this unit have 5534 op-amps? if so see if theres a compensation cap across pin 5 and 8. if so try removing it and seeing if the Burson sounds any better, also if you don't mind the occasional pop and click whilst skipping tracks remove the muting transistors on the output (I presume it uses them) there could be around two on each channel, some cdp's use relays which are better.
make sure the coupling cap on pin 6 of the op-amp is good quality, a film would be best but these are bigger, if theres a polar cap then try a good non polar, for a film cap you can try a much lower value

Try a few simple things first before splashing out on another output stage

 

[multibit16]

Quote:

Originally Posted by budx3385 /img/forum/go_quote.gif impressive work in your photo, sir !

Thank you

 

[budx3385]

thanks for the great tips

I will pursue these and get back to you