Thought this might be of interest to those contemplating modding their 7510’s. This is the path I took, rightly or wrongly, that gave my 7510 a good improvement in sound quality. Apologies up front for the length of the post.
I first tackled the external SMPS and replaced it with an ALW super reg set for 12v. At the same time I bypassed the 7510 internal diode that’s inline with the incoming supply. The result was a smoothing of the sound which at first sounded a little laid back but I soon realized it became easier to listen to and I noted more detail coming through.
Next I tackled the o/p caps and replaced them with Blackgates, I also replaced the opamp coupling caps with some Nichicon Fine Gold caps. The nasty ceramic bypass caps CC1/CC2 where removed as well. This again improved the sound with more depth in the midrange and a seemingly deeper bass. I did this well before learning of ‘MOD21’ and only later discovered the opamp coupling caps had a reverse DC offset across them and needed repositioning correctly.
Next I replaced the 4558 opamp with an OPA2134, I can’t say this really improved the sound it merely changed the signature and sounded much more like my old Naim CD5…not surprising as it also uses the same opamp. Later the OPA gave way to an LM4562 and this was a major improvement in sound quality, literally everything was better…it’s a very positive upgrade for the 7510 IMHO.
The next mods focused on the supply, I wanted to feed the ALW 12v directly into the opamp and add a second ALW to feed 5v to the DAC cct.
The incoming 12v is fed to a 10v regulator and then to a 5v regulator via a ribbon cable on the second PCB. The 10V and 5v is then fed back to the first PCB via the same ribbon cable.
The opamp draws its volts via an SMD 11R resistor (R1) so I removed this and injected the ALW 12v there. This was not good, the sound became harsh and muddled for some reason. I discovered R1 has a very noticeable affect on the sound, so I reconnected the 12v via this resistor and the sound improved dramatically…lesson learnt! I suspect R1 adds some supply decoupling and LC damping of the supply rail.
After I had sorted this out I experimented with removing the two input supply caps ECC15, these had a strong affect on the sound, without them I found the sound became very up-front hard in presentation that also got confused during complex music, replacing these caps with a single 4700uF Blackgate restored the previous sound and also added what seemed to be a bit more detail and bass depth.
The last supply change I made was to add the 5v ALW super reg. I cut the +5v return wire from the ribbon cable and fed the +5 volts from a super reg mounted inside the case, see pic. I used remote sensing of the DAC cct. This was a very good move, it’s very difficult to put into words but the sound became more analogue like… listening was now compelling; you didn’t want to end it…hard to describe…it just sounded ‘right’.
To see what else was possible I also tried part of the MOD21 upgrade and bridged R11/R14 with a solder blob, this opens up the top end allowing more detail through but I found it also added an edge to vocals and a sting to the treble, so I removed it. I also replaced C6 and 5 with some spare polystyrene caps I had in the spare box as per MOD21 Pt2.
That's as far as I've got and as far as I think its possible to go. I'm now experimenting with a TDA1541A NOS dac and the results so far are very encouraging with greater potential for improvement IMHO.
Anyhow here are some pictures for you to laugh at:
http://i94.photobucket.com/albums/l8...C/DSCF4011.jpg
http://i94.photobucket.com/albums/l8...C/DSCF4012.jpg
http://i94.photobucket.com/albums/l8...C/DSCF4013.jpg
