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Old 22nd September 2010, 02:05 PM   #31
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Simon Hi

I've done the +5 rail on the SAA7220 with it's own reg and a couple of caps and there is a significant difference to the sound in keeping with your findings.

Ok, I'm a long way off your level but with all the diodes now replaced to uf's, all the mono board caps replaced and some Oscons where it matters it's coming along nicely.
Your transformer for the DAC supply in my machine ( pun coming )..... transformed the sound quite surprisingly - thanks again for this sale.

The case was already heavily damped with bitumen pads and stiffened on the base with 18 mm of well painted mdf but damping the transport as you and Paul already did also seems to have helped somewhat.

Could you talk me through adding +5 v regs in other critical areas or in which bring about the real noticeable improvemenst, like the 7220?

Many thanks

Andrew
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Old 23rd September 2010, 09:03 AM   #32
SimontY is offline SimontY  United Kingdom
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Hi Andrew,

Everything should run off its own voltage regulator but some changes will give more noticeable gains than others. You've done the number one thing, and the DAC already has its own almost-dedicated voltage rails in this player. The -5 and +5 are dedicated at least, the -15 is shared with the output op-amps. It's not the end of the world.

I would suggest treating the decoder chip to a dedicated reg next, and if you're feeding all of these off the same 6800uF smoothing cap then you should make that cap a nice big one. It will pay dividends.

I'd probably stick a 7805 on the RAM chip next. Because this is a low-power chip and the decoder on this model is the small surface-mount SAA7310 (rather than huge power-guzzling SAA7210) heatsinks won't likely be needed. Lift 3601 and feed the new reg there for the decoder. 3609 feeds the RAM.

The audible gains will start to taper off now but you should still do these mods. Soon you must add a low-jitter clock to really hear what this machine wants to do!

Simon
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Old 12th October 2010, 11:04 AM   #33
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Hi Simon

I notice the digi out cable is removed from the 7220 on your machine
and you seem to have used the old RCA socket hole to feed cable in from the offboard PS.
I've looked at this before and wondered it it worth whipping off.
I won't use an offboard DAC now or in the future so is it safe to just
unsolder and remove ?

Andrew
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Old 12th October 2010, 11:08 AM   #34
SimontY is offline SimontY  United Kingdom
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Hi Andrew,

I removed it mainly for the working room it created, but it's probably worth whipping off just to be sure it's not doing any harm. You can just remove it completely.

Simon
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Old 1st November 2010, 10:25 PM   #35
MiL is offline MiL  Sweden
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Hi All,

I use my 19 year old alfa as a transport and I wonder what are the must do modifications to enhance the performance?
I run a Moon 300D which produces some nice tunes but I guess it would be nice to give it as good signal as possible.

Any suggestions appreciated for an amateur modder.

/Mike
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Old 2nd November 2010, 12:04 AM   #36
SimontY is offline SimontY  United Kingdom
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If you're using an off-board DAC I'd suggest selling the Arcam on and using a quiet pc as your source, which will sound better and not skip so much.

Otherwise, I'm sure you can't go wrong with replacing all the old electrolytic caps and possibly even regulating the servo chips as I did. You could also make sure the laser output power is set correctly.

Simon
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Old 7th November 2010, 02:04 PM   #37
wlowes is online now wlowes  Canada
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Default I got pretty radical with my alpha

Hi Simon, - great thread. I am amazed how many times I find myself following your path.
I got interested in the Alpha due to interest in the Lampizator site. It peaked my interest in the tda1541a. One came up on ebay from a seller right here in Toronto, Canada where I live. Rest is history. I grabbed the alpha and built a 6np2 based output stage. As I was working, at some point I screwed up the mono board. Rather than fix it,I made the Apha into a super USB DAC by scrapping the CD and mono and adding a very nice Peter Daniel USB DAC as the digital front end. Basically grab the I2S signal from the PD DAC, straight into the ARCAM audio board for a NOS USB DAC.
I have not replaced the audio transformer, so thanks for this tip.
On the audio board, I replaced the big electrolytics with BG STD and BG NK. Then, every small electrolytic with Sanyo OsCon SEPC 100uf 16v. Very nice.
I pick up the signal right off the dac chip straight to the triodes. Sound will likely be much like your PASS output. Bypassing the crappy opamps is hudge. One big improvement I am sure you have done is to kill everything downstream of the DAC. basically cut off every resistor, cap and transistor past the dac. Start with R1, R101 right on thorugh to kill power and distortion coming from op amps, transistors etc. Big jump in clarity. Don't miss the Mute section over by the main power supply. All that is left is the power supply and dac chip. everything else is disconnected from the circuit.

Last thing I did for vibration control was to mount the USB and DAC boards on wood, then filled some old cotton socks with sand, and lay them in around in any open spaces around the boards. Now with 5 transformers and sand, this thing is seriously heavy. I just set it on bubble wrap to isolate it from the world. Another significant jump.
The other thing that helps is clean power supply and a good cord. I have an isolation transformer, and filters in my main amp, and the arcam gets power from there.
I will cahnge the transformer and consider the diodes if you think that will help.

Overall sound is liquid smooth with incredible 3D sound stage wider than speakers and 20 feet deep. Symbols shimmer and bells ring. Silence is deep. Incredible space and air. I can't stop listening to this thing.
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Old 7th November 2010, 04:23 PM   #38
SimontY is offline SimontY  United Kingdom
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Hi, it sounds like you've made a real beast of a DAC box there. I've probably left a bit of the original output stage in place. I tried running both at the same time so I could easily A-B them but it doesn't work, the op-amps interfere with the Pass stage and it doesn't work properly. I will have a look at removing more stuff from the output board when I next go in. The only real reason I have for doing so is to upgrade the cheap caps I put on the DAC's PSU.

I've not tried an isolation transformer on this player because I'm listening in a small room and would hear the hummm, but I was pleased by the improvements gained in doing this with my previous cd player.

I think I have a tiny bit of grain to the sound that can be squeezed out so I'll have to get tweaking my Alpha again some day. Some better psu caps for the DAC and better clocking should just about complete it.

Oh and I realised the other day I'm using a standard power cord on the main box (upgraded one on the external supplies) so there's room for a tiny improvement there I think.

Simon
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Old 11th November 2010, 12:28 PM   #39
MiL is offline MiL  Sweden
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Thanks Simon,

I changed some caps, dampened the transport as suggested elsewhere in this forum and put a BNC connector on the dig out. It really made some difference so much that it bettered the streaming over USB.
Kindly could you tell me what regulators to change and what brand? Also how do I check the and regulate the laser output power?
I know how to solder but I have limited knowledge in electronics.

Any suggestion is highly appreciated.

/Mikael
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Old 12th November 2010, 09:15 AM   #40
SimontY is offline SimontY  United Kingdom
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Hi Mikael,

Good to hear your mods have reaped some rewards. Regarding regulators, I wouldn't bother changing any as such, but you'll want to consider adding a dedicated regulator for each of the decoder (SAA7310) and digital filter (SAA7220). LM317 would be better than generic 7805 and super regulators would be much better still. An example would be: Fidelity Audio SPOWER low noise Voltage Regulators which are a very, very good example of a super regulator. The output FET will need to be heatsinked on the regulator supplying the SAA7220 as this chip draws a lot of current.

You should also consider reclocking the SAA7210 and SAA7220. Your digital output would now be getting pretty awesome I think.

I haven't yet set my laser power but I do need to try (I get skipping a lot). There are, however, clear instructions for doing this using a test disc and volt-meter - given on page 11 of the service manual

Simon
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