DIYHiFi.org

This thread is split from 'Damp the capacitors and full speed ahead"

Something I've been playin' with the last few days.
The caps are floating.
Except those Rubycon ZL caps, I've put them there.

I think its probably because the hole spacing is incorrect. What other reason could it be, cooling? Stop over heating when soldering?

With the recent "snubber" discussions I was under the impression that cap leads are a major source of inductance.

Hi Carlos

Is that a Pioneer 575? I've got one of those I brought for a spare dvd player.
Is it worth modding?

Yes.



It sounds much better right now, but it has more to improve and more things to change...
I'd say it's very promising, and it seems a good transport.



Maby it doesn't deserve to be a spare.

Interesting Carlos
Sorry its off topic
So it may be worth modding and using as a transport
It certainly sounds a bit shite in standard form but it should be fun doing a few mods to it if its worth it.
Do you still use the standard op-amps Carlos? I've also noticed you've changed the 5v reg to a LM340, I've got a LT323 spare I could use?

Yes.



Nah...
It sounds like crap.



I'm a stereo man , so I focus only on the two front channels.
Yes, I changed the nasty 4560 for an OPA2132, some PSU caps and some (radical) changes on the 2nd order lowpass filter.
Removed muting and the series (2x) 220R resistors on the output for a 50R, direct from the output coupling cap to the RCA plug.
Next thing may be a new analog stage, as the player's op-amps are feeded by a single 12V PSU, no use to bother much more with these.



Yes, I changed the original JRC 7805 with an LM340-T5, and put a heatsink on it.



Maby, but I never used that reg, try it.
It's not a good idea to try several regs here, it's not so easy to desolder the original reg, double layer PCB... If you cut the legs, you'll remove one by one - much easier.

Oh, I did some changes on the switching PSU...

Cheers Carlos,

I've just been listening to the Pioneer with my GC amp, hmm. it certainly does sound bad
Well I always trust your taste and ears Carlos so it must be worth doing some work on it
I do happen to have a spare smd OPA2132 so I'll stick it in along with the 5v reg, remove those nasty muting transistors and lower the impedance of the output resistors .
Regarding the filter having radical changes I've not seen op-amps implemented like whats used in the pioneer before
I've also noticed there is 100uf coupling caps before the op-amps.
I wonder why the op-amps are run by single supplies, is it to keep costs down?

Scrutinizer:
Can you please be so kind and create us a new thread for the Pioneer DV-575, and move our posts?
We are way off-topic here...
Leo, we will continue later, gotta go now.

Speaking of dampening vibrations (is this the original topic?), common pratice is to cover the crystal and its two caps with a blob of Blu-tak. This is audible and "harmless". You may knew about this tweak, Carlos, but since it?s not in the pic, I posted BTW .

Blu-tak two minuscule SMD caps?

Yes. They?re still caps don?t they? They?re attached to the PCB which is prone to vibrations, unless you already soldered some leads and the caps are now floating The main thing to dampen is the crystal. Do it, p?. It?s a good tweak.

Cheers

Hi,



Following that reasoning, would it then not make more sense to isolate the entire PCB?

Cheers,


P.S. My next speaker will be a CAP.

Still believe the mags?
Bathroom reading...



Waaaait!!!
You don't need to remove the muting transistors.
After the output coupling cap you have: 22k to ground, and then 220R+muting transistor+220R, and then the RCA plug.
If you remove the two 220R series resistors the muting transistor doesn't connect to the signal anymore.
Then, put a 50R resistor under the circuit directly from the cap to the RCA.



Nothing so different, it's an inverting op-amp with the voltage reference for NI input coming from the dac.
I don't have the service manual but I followed the circuit and after the dac you have:

- 100uf coupling cap (!!!!)
- 5.6k
- ceramic cap to ground
- 1.5k
- 10k feedback resistor
- ceramic cap from input to output

What I've done on the filter was:
- remove the SMD 5.6k and change it for a normal 4.7k film resistor (yes, there are holes to mount normal resistors on this position). This way I gave the output stage a little more gain (TI recommends 2x, even higher...).
- removed both filter caps and installed a 27pf from input to output (feedback).
I didn't have anything else than ceramics at such a low value.
I tried 200pf styroflex but the sound was not so good, a much lower value was needed.



Don't make me cry.
I changed those for 6.8uf bipolar electros (those pinky caps you see on the pic), bypassed with 100nf polyprop.



Yes.

BTW, how to bypass a single supply SMD op-amp, my way:
- Bent the legs to size, cut them short, put the cap on top of the op-amp and solder directly at the V+ and V- pins.
I used a 33uf/40v Philips cap.

Thanks Carlos

Well I've finished most of your above mods, I had to use 10uf NP coupling cap before op-amps, 47pf ceramics for the fb and 47uf for the OPA2132 decoupling(its the nearest values I had)
The 1000uf decoupling cap for the dac changed to 2200uf Nichicon FG, the other 10uf cap for the dac changed to 10uf FG.
Its been running for about an hour and already the sound is way better
I'll have a scrounge around for some better rectifier diodes,

I knew this wouldn?t go without an answer


My point was that I think it?s the crystal the component most subject to outside vibrations, not counting the transport, and when you can do a simple reversible tweak by putting a blob of Blu-Tak around the crystal, so why not around the decoup caps next to it as well...? Nothing too complicated for a start.

Nevertheless:

If isolating an entire PCB is advisable even when it?s resting inside an already isolated, solid enclosure (my "#$%& Rega Planet 2000 is on its sorbothane feet), so blu-tacking a crystal even when it?s resting on an isolated PCB is still mandatory, don?t you think? On the other way round it?s like when someone puts a well-made Wadia on an air-bearing platform, or whatever. It still gains on sonics.

Frank, for isolating a PCB I will sandwich it between two cork washers per screw. Is this a good idea?



I heard that given the necessary gain a 4700uF/250V WonderCap beats a Neumann too.
KIDDINNNNNNNNNNG