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Old 5th March 2012, 11:04 AM   #431
gvelim is offline gvelim  United Kingdom
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Quote:
Originally Posted by Rajapruk View Post
I have made the basic mods with super regs for 5+ and 15-volt, and bypassed the output caps, now I want more!
I highly recommend your next target is to fix the master clock before any other improvements as otherwise you won't have a good foundation to assess a mod's effect - my personal experience.

Replace XO and HEX Inverter, power them from a Flea PSU with the appropriate cap selection for bypassing. Highly recommending Crystek XO (CCHD-957) and PotatoSemi Hex Inverter (PO74G14A).

Quote:
Originally Posted by stormsonic
Great, you isolated chip and crystal with ferrite beads. Maybe bigger capacitor after ferrite beads (SP-Cap parallel to C32 and C121).
@ Stormsonic, complemented the XO PSU bypassing with a 0603/NPO 470pf and 1206/ECPU 0.15uf in addition to the 0805/ECHU 100pf and which fit very nicely in the +Vss pad and the 2 surrounding little GND holes. The compo of 0603/0805/1206 is highly recommended due to the ESL differences of the packaging.

I confirm this has positive impact to bass and stage clarity.

Changed the Diodes to Schottky however I haven't noticed any improvement with this mod.
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Last edited by gvelim; 5th March 2012 at 11:06 AM.
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Old 7th March 2012, 12:38 AM   #432
matcc is offline matcc  Hong Kong
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Hi all,
I've got the UWB module for the replacement of the 7805, 7815 and 7915.
The 5V one working fine. But the 7815 and 7915 one working hot like burnning.
I replace the NE5532 to the LM49720. Is it the reason to draw much current from the modules?

I've got the input voltage of the modules is around +-23V.....
The power transformer modified with the R-core AC12V in 30VA.
Thanks!
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Old 7th March 2012, 07:53 AM   #433
gvelim is offline gvelim  United Kingdom
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From experience it gets hot to the point you cannot touch the heat sink for more than 5". Your option is to replace the 56R resistors with 100R to decrease power dissipation ... ensure the voltage drop doesn't affect the min Vin tha UWB requires.

If you don't use RCA you can remove the opams too so you can reduce current draw.
Also you can feed the 7505 UWB from the UREG to further relief the 7515 UWB

Finally you could go for 9V transformer as long as your UWB can handle the voltage drop. Bear in mind this approach streches the DC/DC buck converter in the digital psu.

For me the 100R/4W worked well, but made sound a bit brighter.
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Old 7th March 2012, 03:33 PM   #434
matcc is offline matcc  Hong Kong
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The heatsink can't touch even a sec. I am quite sure it higher than 70c.

I need to use the RCA so there is no way to decrease the current drop.
Now I need to remove the 15v modules until I found the solution of it.

Thanks! Will update my mod later...
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Old 7th March 2012, 03:52 PM   #435
matcc is offline matcc  Hong Kong
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I would like to know is the MC34063 just for step down to 5V in higher current?
Can I just pass it with the 7805 something?
I am not sure why really need to use it after I read the data sheet.
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Old 7th March 2012, 06:37 PM   #436
gvelim is offline gvelim  United Kingdom
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Quote:
Originally Posted by matcc View Post
Now I need to remove the 15v modules until I found the solution of it.
Have you excluded one or more OpAmps oscillating ? How much is the voltage drop against R400 ?

Quote:
Originally Posted by matcc
I would like to know is the MC34063 just for step down to 5V in higher current? Can I just pass it with the 7805 something
If you do this, you will have 7805 to deal with 16.8V at its input which will be a lot of power to dissipate. The MC34063 does this very efficiently especially more comfortably the higher the input voltage is. Hence MC34063 was purposefully put there.
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Old 7th March 2012, 07:35 PM   #437
gvelim is offline gvelim  United Kingdom
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Quote:
Originally Posted by aptsys View Post
Hi,
Is the AD797 in place of all the op amps at U55, U56, U59 and U60, or are the ones for differential to single ended also replaced?

Do all of the AD797's run hot or is it only certain ones?
Hi aptsys, here is the setup with the AD797

Opening the new DacMagic????

All 4 of them feel equally hot on the browndogs.

Assuming in this setup, 15mA go to the SRegs + 2 x OPA2120 and with
1) R400 at 100ohm I measured 5.86 voltage drop which gives 11mA per opamp
2) R400 at 56 ohm I measure 3.84 volatge drop which gives 13mA per opamp

hope that clarifies the situation

Last edited by gvelim; 7th March 2012 at 07:41 PM.
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Old 8th March 2012, 02:00 PM   #438
matcc is offline matcc  Hong Kong
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Quote:
Originally Posted by gvelim View Post
Have you excluded one or more OpAmps oscillating ? How much is the voltage drop against R400 ?
It is 5.22V there......
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Old 9th March 2012, 05:14 PM   #439
gvelim is offline gvelim  United Kingdom
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5.22V across R400 translates into 93mA spared across Dexa UWB and the 6 x LM49720 which you can assume for each consuming 10-14mA. That is 0.45W @ 30V Rail-to-Rail per opamp and with thermal resistance @145C/W you should be looking at around 80C at room temperature.

LM49720 datasheet gives idle current of 10mA which drives 0.3W @ 30V RtR, which again is > 60C temperature.

Unless you have a high bandwidth oscilloscope to check the outputs for oscillations then you cannot tell whether the high temp is normal or due to a flaw in your mod.

I had cases of oscillations because of opamp bad soldering that got fixed after re-soldering the IC.
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Old 10th March 2012, 01:06 AM   #440
matcc is offline matcc  Hong Kong
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Thanks for the help!

Now I just put the 78/7915 back there. Becoz I found the sound after the modules mod not as well as the original one. Ok, the transparency is better and the soundstage bigger. Great performance but not musical.

I've ordered the OP1642 for the last stage for the RCA output already. I tried to bypass and get the output from Phase + of the Balance. Also great performance but not musical to my system. That's why I keep it.

I am thinking to separate the digital and analog power. The plan is 78/7915 get the power from the other 12-15VAC transformer. I think this would be the easier way to reduce the heat problem and make the sound better, right?
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