PSU Design
Hi Thorsten
Thanks again for taking the time to explain all of this in such detail. It's getting to the point where I'm starting to trust "my" interpretation of what the software is showing.
It does - and it's so obvious now! Why didn't I think of that?
Thought it would be much more complex.
So this is why some people use chokes.
OK - but I will still play it safe. If I see anything above 30V - I will use 50V components instead od 35V components.
Yes - I can see this effect.
I was going to ask the following question:-
"Shouldn't the resistor values be increased to maintain the same R*C values - or - has it changed now that we are using multiple filters? To replace the 10R/4,700uF, shouldn't we use 22R/2,200uF (and not 3R3/2,200uF)?
but then read your comment that there is no hard and fast rule. Also noticed in the software, that using the 22R values increases the time for the voltage to level out, to about 7 seconds. Is that a problem?
It sure does!
If you increase the first resistor to 50R, this increases the conduction time to almost 5ms and the output voltage is still 24.9V after 7 seconds. Is this a reasonable thing to do or am I going overboard?
The 6db rule:- Trying to achieve a -6db roll-off at a particular frequency - using sucessive filters?? I did say earlier that I would probably have more questions about this.
Well - I was thinkig about the parts and components that I already have. The 22V 25VA transformer provides higher voltage and more current than needed. I've already got some LM317/337, LM1085 and LM431. To go a bit further than RCRC-Reg and use RCRCRC-LM317/337-LM431, will only require two additional 2,200uF/50V caps (one for +15V and one for -15V). Might be worth it?
Hi Thorsten
Thanks again for taking the time to explain all of this in such detail. It's getting to the point where I'm starting to trust "my" interpretation of what the software is showing.
It does - and it's so obvious now! Why didn't I think of that?
Thought it would be much more complex.
So this is why some people use chokes.
OK - but I will still play it safe. If I see anything above 30V - I will use 50V components instead od 35V components.
Yes - I can see this effect.
I was going to ask the following question:-
"Shouldn't the resistor values be increased to maintain the same R*C values - or - has it changed now that we are using multiple filters? To replace the 10R/4,700uF, shouldn't we use 22R/2,200uF (and not 3R3/2,200uF)?
but then read your comment that there is no hard and fast rule. Also noticed in the software, that using the 22R values increases the time for the voltage to level out, to about 7 seconds. Is that a problem?
It sure does!
If you increase the first resistor to 50R, this increases the conduction time to almost 5ms and the output voltage is still 24.9V after 7 seconds. Is this a reasonable thing to do or am I going overboard?
The 6db rule:- Trying to achieve a -6db roll-off at a particular frequency - using sucessive filters?? I did say earlier that I would probably have more questions about this.
Well - I was thinkig about the parts and components that I already have. The 22V 25VA transformer provides higher voltage and more current than needed. I've already got some LM317/337, LM1085 and LM431. To go a bit further than RCRC-Reg and use RCRCRC-LM317/337-LM431, will only require two additional 2,200uF/50V caps (one for +15V and one for -15V). Might be worth it?
Supply for the servos.
I started to have a look at the supply for the servos in a little more detail. Assuming that they require +/-12V and about 1A, there are two transformers to choose from. One is 2*12V 30VA (12V@1.25A + 12V@1.25A) and the other is 2*15V 30VA (15V@1A + 15V@1A).
Each of these were used in modelling the supplies in PSUD - with interesting results. The higher voltage/lower current transformer can actually provide more current to the supplies than the transformer with the higher current rating.
The 12V/1.25A unit can supply 1A, but the voltage drops to 13.4V - too low to be regulated to 12V. To stay above the dropout voltage of most regulators, only 600mA can be provided at 15V.
The 15V/1A unit can supply 1A, and the voltage only drops to 16.2V. It can provide 1.2A at a voltage of 15.2V - enough to regulate to 12V.
So - in this situation, a 15V transformer can supply twice the current of the same sized (30VA) 12V transformer.
I started to have a look at the supply for the servos in a little more detail. Assuming that they require +/-12V and about 1A, there are two transformers to choose from. One is 2*12V 30VA (12V@1.25A + 12V@1.25A) and the other is 2*15V 30VA (15V@1A + 15V@1A).
Each of these were used in modelling the supplies in PSUD - with interesting results. The higher voltage/lower current transformer can actually provide more current to the supplies than the transformer with the higher current rating.
The 12V/1.25A unit can supply 1A, but the voltage drops to 13.4V - too low to be regulated to 12V. To stay above the dropout voltage of most regulators, only 600mA can be provided at 15V.
The 15V/1A unit can supply 1A, and the voltage only drops to 16.2V. It can provide 1.2A at a voltage of 15.2V - enough to regulate to 12V.
So - in this situation, a 15V transformer can supply twice the current of the same sized (30VA) 12V transformer.
Re: Supply for the servos.
Konnichiwa,
How do you arrive at +/-12V/1A? Have you checked the Motor Driver IC's used? What do they have as current limits (most are short circuit proof)?
Yup. However in most cases high current demands from the drive will be transient in nature, so the lower voltage, higher current transformer with large value reservoir capacitors may still be the better choice.... ;-) Try calculating realistically the regulation of the transformer and make sure you use Schottky Diode (models for simulation).
Sayonara
Konnichiwa,
Fin said:
How do you arrive at +/-12V/1A? Have you checked the Motor Driver IC's used? What do they have as current limits (most are short circuit proof)?
Fin said:
Yup. However in most cases high current demands from the drive will be transient in nature, so the lower voltage, higher current transformer with large value reservoir capacitors may still be the better choice.... ;-) Try calculating realistically the regulation of the transformer and make sure you use Schottky Diode (models for simulation).
Sayonara
Supply for the servos.
Hi Thorsten
There is obviously more to it than I thought.........
It was just an approximation (or guess) to get an idea of what might be needed and to compare the transformers. Will look more closely at it now.
I've used the regulation figure supplied by the manufacturer but I need to alter things for Schottky Diodes. Results comimg soon.
BTW - do you have any comments on Post #221
Hi Thorsten
There is obviously more to it than I thought.........
It was just an approximation (or guess) to get an idea of what might be needed and to compare the transformers. Will look more closely at it now.
I've used the regulation figure supplied by the manufacturer but I need to alter things for Schottky Diodes. Results comimg soon.
BTW - do you have any comments on Post #221
Re: Supply for the servos.
Konnichiwa,
Always is.
First order approximations are fine for feasibility studies, for DESIGN you need real numbers.
You mean this paragraph?
I agree with it, except stick to LM317 Regs, as you need to / should keep the rails seperate untill you get to the common kelvin return (often inaccuratly called Star Ground) it matters nor what "sex" your regulator is. Usually the N-Channel/NPN types are better!
So go for RC\RC\RC\LM317\LM334(CCS)\LM/TL431 by all means. It pretty much matches "what I would do", if space, complexity and cost are not much of an issue.
Place the TL431 local next to the supplied pins and the CCS (LM334 for up to 10mA, otherwise FET's, IXYS adjustable Current Regs etc...) per 431 on the main add in supply board. Add some ferrite beads and RF chokes to the CCS and if possible cascode the CCS. Another RC circuit prior to the CCS may also be beneficial. Also, make sure to split each and every filter resistor into 2pcs, one in the positive line and one in the negative line.
As you can see the amount of effort and complexity in PSU's is nearly unlimited. If you go RC\RC\RC\REG\RC\CCS\SHUNT you can be pretty certain that your PSU noise and impedance is limited by the shunt only, all other noise should be minimal. Adding a further transistor to the shunt (high speed PNP type - see TI datasheet fig 21) can increase loop gain and drop the output impedance.
Also make sure to bypass the Adj/Cathode Resistor with a suitable Capacitor (single Os-Con is fine as this remains capacitive beyond the bandwidth of the TL431) to keep the shunt impedance low. Of course you might use a shunt regulator with a Op-Amp and suitable shunt transistor and so on....
Sayonara
Konnichiwa,
Fin said:
Always is.
Fin said:
First order approximations are fine for feasibility studies, for DESIGN you need real numbers.
Fin said:
You mean this paragraph?
Fin said:
I agree with it, except stick to LM317 Regs, as you need to / should keep the rails seperate untill you get to the common kelvin return (often inaccuratly called Star Ground) it matters nor what "sex" your regulator is. Usually the N-Channel/NPN types are better!
So go for RC\RC\RC\LM317\LM334(CCS)\LM/TL431 by all means. It pretty much matches "what I would do", if space, complexity and cost are not much of an issue.
Place the TL431 local next to the supplied pins and the CCS (LM334 for up to 10mA, otherwise FET's, IXYS adjustable Current Regs etc...) per 431 on the main add in supply board. Add some ferrite beads and RF chokes to the CCS and if possible cascode the CCS. Another RC circuit prior to the CCS may also be beneficial. Also, make sure to split each and every filter resistor into 2pcs, one in the positive line and one in the negative line.
As you can see the amount of effort and complexity in PSU's is nearly unlimited. If you go RC\RC\RC\REG\RC\CCS\SHUNT you can be pretty certain that your PSU noise and impedance is limited by the shunt only, all other noise should be minimal. Adding a further transistor to the shunt (high speed PNP type - see TI datasheet fig 21) can increase loop gain and drop the output impedance.
Also make sure to bypass the Adj/Cathode Resistor with a suitable Capacitor (single Os-Con is fine as this remains capacitive beyond the bandwidth of the TL431) to keep the shunt impedance low. Of course you might use a shunt regulator with a Op-Amp and suitable shunt transistor and so on....
Sayonara
Hi Thorsten
Finally figured out that the last two diodes in the dropdown list in PSUD are Schottky types. Using these in the simulation makes quite a significant and clearly visible difference to the shape of the waveform and the peak current values - thanks.
Working on it now. This has turned out to be a bit more than just copying someone else's handywork, but it is also a great learning exercise.
While we are still on the supplies for the servo's, and if any one is looking for the larger value capacitors, I noticed that Percyaudio.com has Nichicon KG Gold Tune in 10,000uF/35V snap in type for US$4.95. I hope these are suitable as the price is acceptable (for me anyway). Nichicon KG
Understood - I think! This means they will both be 15V supplies until they connect to the "ground" on the main PCB - where one supply will be connected in reverse?
Space:- Should be OK, especially if I can place a small board with the regulators directly above the circuit to be supplied.
Complexity:- Still figuring that out. Fortunately, the "horrible" DAC, with it's six supply pins, is very close to the edge of the PCB. There is an easy point where one supply can be connected which could feed all six 5V pins. Alternatively, each pin could be given its own regulator, connected to the supply side of the resistor feeding each pin. This would obviously be more complex - but I suppose it could be possible with a small board positioned directly above the DAC.
Is it worthwhile giving each pin its own 431?
If so, should the local decoulping stay in place?
Cost:- Might have solved this one. The main problem here is the cost (and availability) of quality capacitors. However, I just discovered Handmade Electronics in the US have Nichicon Muse KZ, FG, FX and ES at reasonable prices. Much cheaper that I can get Panasonic FC for - but I hope they are suitable. If anyone is interested, the datasheets are here:- KZ, FG, FX, ES.
I need to do some research on the ferrite beads and RF chokes etc. Might need to come back to this later.
Split each resistor:- For example - instead of 10R - 2200uF, you suggest - 5R - 2200uF with another 5R in the line to the other lead of the capacitor?
I would like to try this. The power supply seems to be the area where most corners are cut - and now I can see why.
This last step would get me really confused at this stage. I'll have a serious look at the 431 setup and see if I can get it all to fit neatly.
Hopefully everyone else who reads this discussion appreciates your efforts here as much as I do.
Finally figured out that the last two diodes in the dropdown list in PSUD are Schottky types. Using these in the simulation makes quite a significant and clearly visible difference to the shape of the waveform and the peak current values - thanks.
Working on it now. This has turned out to be a bit more than just copying someone else's handywork, but it is also a great learning exercise.
While we are still on the supplies for the servo's, and if any one is looking for the larger value capacitors, I noticed that Percyaudio.com has Nichicon KG Gold Tune in 10,000uF/35V snap in type for US$4.95. I hope these are suitable as the price is acceptable (for me anyway). Nichicon KG
Understood - I think! This means they will both be 15V supplies until they connect to the "ground" on the main PCB - where one supply will be connected in reverse?
Space:- Should be OK, especially if I can place a small board with the regulators directly above the circuit to be supplied.
Complexity:- Still figuring that out. Fortunately, the "horrible" DAC, with it's six supply pins, is very close to the edge of the PCB. There is an easy point where one supply can be connected which could feed all six 5V pins. Alternatively, each pin could be given its own regulator, connected to the supply side of the resistor feeding each pin. This would obviously be more complex - but I suppose it could be possible with a small board positioned directly above the DAC.
Is it worthwhile giving each pin its own 431?
If so, should the local decoulping stay in place?
Cost:- Might have solved this one. The main problem here is the cost (and availability) of quality capacitors. However, I just discovered Handmade Electronics in the US have Nichicon Muse KZ, FG, FX and ES at reasonable prices. Much cheaper that I can get Panasonic FC for - but I hope they are suitable. If anyone is interested, the datasheets are here:- KZ, FG, FX, ES.
I need to do some research on the ferrite beads and RF chokes etc. Might need to come back to this later.
Split each resistor:- For example - instead of 10R - 2200uF, you suggest - 5R - 2200uF with another 5R in the line to the other lead of the capacitor?
I would like to try this. The power supply seems to be the area where most corners are cut - and now I can see why.
This last step would get me really confused at this stage. I'll have a serious look at the 431 setup and see if I can get it all to fit neatly.
Hopefully everyone else who reads this discussion appreciates your efforts here as much as I do.
Konnichiwa,
Copying only works where you try to get EXACTLY where whaever is copied is. That would mean for a starter identical starting points.
I would expect them to work well, after all,as I said, consider the Servos "Audio Power Amplifiers".... ;-)
Yup.
You know what I think of that DAC... ;-)
Decoupling capacitors - yes.
Yes. This of course works only if the supplies remain seperate untill they are joined at the main kelvin return(s). The advantage is that you introduce a significant impedance also into the ground line, which would normally carry all sorts of leaked noise from the mains. Once you draw out all current loops (intentional and parasitic) in a complete interconnected system it should become clearer. Try this article masquerading as interconnect review:
http://www.sstage.com/articles/pete01.htm
Sayonara
Fin said:
Copying only works where you try to get EXACTLY where whaever is copied is. That would mean for a starter identical starting points.
Fin said:
I would expect them to work well, after all,as I said, consider the Servos "Audio Power Amplifiers".... ;-)
Fin said:
Yup.
Fin said:
You know what I think of that DAC... ;-)
Fin said:
Decoupling capacitors - yes.
Fin said:
Yes. This of course works only if the supplies remain seperate untill they are joined at the main kelvin return(s). The advantage is that you introduce a significant impedance also into the ground line, which would normally carry all sorts of leaked noise from the mains. Once you draw out all current loops (intentional and parasitic) in a complete interconnected system it should become clearer. Try this article masquerading as interconnect review:
http://www.sstage.com/articles/pete01.htm
Sayonara
Running out of questions......
Hi Thorsten
Only two questions today.
Yes - Sounds best with no supplies going to it at all!
And the resistors, inductors...?
Do you know of any software like PSUD, that models decoupling or of any easy way to determine the appropriate size of the decoupling capacitors?
Hi Thorsten
Only two questions today.
Yes - Sounds best with no supplies going to it at all!
And the resistors, inductors...?
Do you know of any software like PSUD, that models decoupling or of any easy way to determine the appropriate size of the decoupling capacitors?
Re: Running out of questions......
Konnichiwa,
If every pin has it's own shunt regulator, fed via a CCS and suitable inductors and ferrite beads - remove them.
Not really, it ain't quite working that way. The TL431 needs a bypass cap of a given minimum size to prevent it oscillating and to avoid a rise of the supply line impedance at high frequencies. You can work that out from the datasheet. The additional bypasing requires complex parasics to be accounted for and to be modelled, this can become complex. Best stick to the system of decoupling often called "tripplets" or whatever new stuff people came up with recently.
Sayonara
Konnichiwa,
Fin said:
If every pin has it's own shunt regulator, fed via a CCS and suitable inductors and ferrite beads - remove them.
Fin said:
Not really, it ain't quite working that way. The TL431 needs a bypass cap of a given minimum size to prevent it oscillating and to avoid a rise of the supply line impedance at high frequencies. You can work that out from the datasheet. The additional bypasing requires complex parasics to be accounted for and to be modelled, this can become complex. Best stick to the system of decoupling often called "tripplets" or whatever new stuff people came up with recently.
Sayonara
Re: Re: Running out of questions......
Any suggestions for the suitable inductors and ferrite beads?
Should they be used on digital and analogue suppy pins (I suppose that again depends on whether the analogue pins are truely analogue - like your comment about the Os-Cons for decoupling the analogue pins)? The existing arrangement only uses inductors on the digital supply pins - not on the "analogue" supply pins.
Thanks
Any suggestions for the suitable inductors and ferrite beads?
Should they be used on digital and analogue suppy pins (I suppose that again depends on whether the analogue pins are truely analogue - like your comment about the Os-Cons for decoupling the analogue pins)? The existing arrangement only uses inductors on the digital supply pins - not on the "analogue" supply pins.
Thanks
Re: Re: Re: Running out of questions......
Konnichiwa,
High resonance frequency for the inductor and a lot of stated impedance for the ferrite bead at low frequencies.
Digital - I'd condier them mandatory. Ananlogue you can usually manage without, except they are components of the "penny" type, so why skimp? At audio frequencies their effect is swamped by the CCS , but higher up they will block noise, no matter what the source.
Sayonara
Konnichiwa,
Fin said:
High resonance frequency for the inductor and a lot of stated impedance for the ferrite bead at low frequencies.
Fin said:
Digital - I'd condier them mandatory. Ananlogue you can usually manage without, except they are components of the "penny" type, so why skimp? At audio frequencies their effect is swamped by the CCS , but higher up they will block noise, no matter what the source.
Sayonara
Don't know if this has been answered since, I haven't read the whole thread yet.
Bricolo got confused on where to connected the ground leg(s) of a shunt regulator: near to the bridge, or near to the load.
The crux of shunt regulation is that is makes the (variable) load current run in a loop. This loop is formed by the load circuit, the shunt element, and any traces connecting these at the top (supply line) and bottom (signal ground potential).
The physical area of this loop must be as small as possible.
Hence.
If the shunt element is 'perfect' then the lines that connect its top to the supply voltage and its bottom to the supply null only carry DC current.
(As an aside: the ground node of the lower output voltage setting resistor of an LM317-type of regulator also must be connected with its own private trace to the load's local signal ground, as the bottom of said resistor constitutes the reference for the reg. See ALW's various postings on this.)
Bricolo got confused on where to connected the ground leg(s) of a shunt regulator: near to the bridge, or near to the load.
Bricolo said:
do you mean, the shunt+cap's ground should be placed at the chip's ground? so no direct connection to the bridge?
I don't understand the last one
The crux of shunt regulation is that is makes the (variable) load current run in a loop. This loop is formed by the load circuit, the shunt element, and any traces connecting these at the top (supply line) and bottom (signal ground potential).
The physical area of this loop must be as small as possible.
Hence.
If the shunt element is 'perfect' then the lines that connect its top to the supply voltage and its bottom to the supply null only carry DC current.
(As an aside: the ground node of the lower output voltage setting resistor of an LM317-type of regulator also must be connected with its own private trace to the load's local signal ground, as the bottom of said resistor constitutes the reference for the reg. See ALW's various postings on this.)
Attachments
Some progess....
but it still lacks the "analogueness" of the Arcam!
Here are my notes:
-------------------------------------
CD723 Upgrade
Modification Sequence (intended to address the biggest problems first, so that later mods can be properly judged. Listening to be conducted at each stage to assess the sonic impact):
1. Upgrade PSUs
a) +/- 15V for I/V stage
b) +5.4V for DAC (gives 4.9V on DAC after 100R/220uF filter)
c) +12V for Servos
d) +5V for VAM1201 signal processing
e) +5V for clock
2. Modify circuits
a) Fit Tent Clock
b) Adjust for 2mA FSC
c) Change o/p filter from CF to KYW circuit
d) Try AD812
e) Output null circuit to remove o/p caps (or maybe use BG caps and leave the offset (single ended class A?)
f) Removal of muting transistors (and maybe replace by relay)
3. Upgrade components
a) BG NX Hi-Q for Vref
b) Silmic decoupling caps for I/V
4. Mechanical Mods
Implementation
1a and b) 20VA 0-15, 0-15 Avel Toroid with electrostatic screen. 11DQ090 rectifiers generating 2 identical rails with 3R3 – 470uF (FC) – 10R – 2,200uF (YXF) – connector to local reg board which contains 3 X LM317. Each LM 317 set for 46mA quiescent with 220uF FC to decouple each ref pin. Still using decoupling on audio board, 220uF 25V FC for I/V, 470uF 25V FC for DAC, 39uF 35V FC for DAC Vref.
Listening
1a) More detail and noticeably cleaner sounding (compared to 7815/7915 Audionics PSU). Still somewhat thin and sibilant but good separation between instruments.
1b) Much of the thinness has gone, the sound has much more body and greatly improved tonality and texture of voices and instruments. Increased detail and tunefulness on bass, treble seems less distinct however percussion sounds tighter and more realistic. Slightly mechanical quality to the music and maybe a bit dull.
Note: Concerned about sharing of OV line for +5 and +15 V lines which means that the DAC supply current (5mA) returns through approx 3cms of shared CAT5 wire. This will impact regulation of the +15V supply.
1c) Seemed to give more scale and control to the music. Not a massive difference but certainly not worse.
1d) Restored some of the top end and some liveliness. Quite a significant and fundamental improvement in sound. Might be worth investigating an even better PSU. Still concerned over 1b and whether or not it’s a real step forward.
Tried reversing 1b, which surprisingly made no or minimal change to the SQ (surprising because when it was first implemented it made a very noticeable difference). Noticed at this point that the tracking ability on some CDRs was poor. To improve the tracking ability I reinstalled the two 3R3 resistors in series with the supply lines to each servo IC. This made no difference to the tracking ability or the sound.
Changed to 2c using 120R and 13nF as output filter. This gave much clearer SQ, in retrospect the CF version is grainy and coloured.
2d. Left feedback resistor at 3K3 since with the existing bias resistor values this seems to give 2mA FSD.
1e + 2a Fitted Tentclock with the recommended PSU. Needed to reduce the bias resistors in the regulator by 10X to obtain the correct o/p voltage and decent load reg. SQ improved further, better timing and rhythms and generally cleaned up and more coherent sound.
2d. Fitting the AD812 seemed OK until connected into the system. Faint whisling can be heard during play. Instability seems to be occurring. Need to investigate further. Tried NE5532 again – nowhere near as good as the RC4227. NE5532 is closed in and thin sounding.
-------------------------------------------
but it still lacks the "analogueness" of the Arcam!
Here are my notes:
-------------------------------------
CD723 Upgrade
Modification Sequence (intended to address the biggest problems first, so that later mods can be properly judged. Listening to be conducted at each stage to assess the sonic impact):
1. Upgrade PSUs
a) +/- 15V for I/V stage
b) +5.4V for DAC (gives 4.9V on DAC after 100R/220uF filter)
c) +12V for Servos
d) +5V for VAM1201 signal processing
e) +5V for clock
2. Modify circuits
a) Fit Tent Clock
b) Adjust for 2mA FSC
c) Change o/p filter from CF to KYW circuit
d) Try AD812
e) Output null circuit to remove o/p caps (or maybe use BG caps and leave the offset (single ended class A?)
f) Removal of muting transistors (and maybe replace by relay)
3. Upgrade components
a) BG NX Hi-Q for Vref
b) Silmic decoupling caps for I/V
4. Mechanical Mods
Implementation
1a and b) 20VA 0-15, 0-15 Avel Toroid with electrostatic screen. 11DQ090 rectifiers generating 2 identical rails with 3R3 – 470uF (FC) – 10R – 2,200uF (YXF) – connector to local reg board which contains 3 X LM317. Each LM 317 set for 46mA quiescent with 220uF FC to decouple each ref pin. Still using decoupling on audio board, 220uF 25V FC for I/V, 470uF 25V FC for DAC, 39uF 35V FC for DAC Vref.
Listening
1a) More detail and noticeably cleaner sounding (compared to 7815/7915 Audionics PSU). Still somewhat thin and sibilant but good separation between instruments.
1b) Much of the thinness has gone, the sound has much more body and greatly improved tonality and texture of voices and instruments. Increased detail and tunefulness on bass, treble seems less distinct however percussion sounds tighter and more realistic. Slightly mechanical quality to the music and maybe a bit dull.
Note: Concerned about sharing of OV line for +5 and +15 V lines which means that the DAC supply current (5mA) returns through approx 3cms of shared CAT5 wire. This will impact regulation of the +15V supply.
1c) Seemed to give more scale and control to the music. Not a massive difference but certainly not worse.
1d) Restored some of the top end and some liveliness. Quite a significant and fundamental improvement in sound. Might be worth investigating an even better PSU. Still concerned over 1b and whether or not it’s a real step forward.
Tried reversing 1b, which surprisingly made no or minimal change to the SQ (surprising because when it was first implemented it made a very noticeable difference). Noticed at this point that the tracking ability on some CDRs was poor. To improve the tracking ability I reinstalled the two 3R3 resistors in series with the supply lines to each servo IC. This made no difference to the tracking ability or the sound.
Changed to 2c using 120R and 13nF as output filter. This gave much clearer SQ, in retrospect the CF version is grainy and coloured.
2d. Left feedback resistor at 3K3 since with the existing bias resistor values this seems to give 2mA FSD.
1e + 2a Fitted Tentclock with the recommended PSU. Needed to reduce the bias resistors in the regulator by 10X to obtain the correct o/p voltage and decent load reg. SQ improved further, better timing and rhythms and generally cleaned up and more coherent sound.
2d. Fitting the AD812 seemed OK until connected into the system. Faint whisling can be heard during play. Instability seems to be occurring. Need to investigate further. Tried NE5532 again – nowhere near as good as the RC4227. NE5532 is closed in and thin sounding.
-------------------------------------------
Re: Some progess....
Konnichiwa,
I note you have one of the old TDA1541 based mashines. In a different thread I pointed out that the TDA1541 has a "singular sound", I mean it. NOTHING ELSE sounds like it. I don't care if you have a cheap all plastic Philips CDP with TDA1541 or the latest Marantz CD-7 or a Marantz DA-12. They all share exactly this "analogueness" (they do differe very much on the rest though).
So, don't expect (ever) to match the old Arcam in this department.
Excellent work (except the 812.... Make sure the PSU Bypass is soldered directly to the chip and is low inductance.
So, one question.
Is your current 723 still mediocre, or is pretty decent but not a match for the Arcam?
The RC4227. Rarely saw it discussed, a quite nice diual Op-Amp. For me oversahdowed by real high speed stuff, but it deserves more mention/note for those people who seem to be "unlucky". To wit, I practically NEVER humming amplifiers, oscillating amplifiers, oscillating Op-Amp's, you name it. I just seem to get all such things most people call "dicey" to work first time, reliably, go figger.
Sayonara
PS, RC4227 is a Dual OP-27 IIRC....
Konnichiwa,
Dave S said:
I note you have one of the old TDA1541 based mashines. In a different thread I pointed out that the TDA1541 has a "singular sound", I mean it. NOTHING ELSE sounds like it. I don't care if you have a cheap all plastic Philips CDP with TDA1541 or the latest Marantz CD-7 or a Marantz DA-12. They all share exactly this "analogueness" (they do differe very much on the rest though).
So, don't expect (ever) to match the old Arcam in this department.
Dave S said:
Excellent work (except the 812.... Make sure the PSU Bypass is soldered directly to the chip and is low inductance.
So, one question.
Is your current 723 still mediocre, or is pretty decent but not a match for the Arcam?
Dave S said:
The RC4227. Rarely saw it discussed, a quite nice diual Op-Amp. For me oversahdowed by real high speed stuff, but it deserves more mention/note for those people who seem to be "unlucky". To wit, I practically NEVER humming amplifiers, oscillating amplifiers, oscillating Op-Amp's, you name it. I just seem to get all such things most people call "dicey" to work first time, reliably, go figger.
Sayonara
PS, RC4227 is a Dual OP-27 IIRC....
Firstly, I would like to thank KYW for the serious amount of time he's spent
helping Fin and me. I have seen a lot of threads where KYW comes under
attack for voicing his opinion, well as far as I'm concerned all the things
I have tried on his suggestion have been beneficial (and believe me I tried
many suggestions here and elsewhere on the lovely WWW and gone many steps
backwards!).
You will notice at this point that I have not tried passive trimming of the
output offset to remove the output caps. I'm not sure at this point that I
agree with KYW on this particular point - the dc offset (about 1.5V) as it
stands drifts around by up to 30mV, I don't want drift this on my volume
pot. Also, in the Arcam I tried trimming the offset (from a Ben Duncan
acticle) using LT1021 and although the sound improved slightly from the
emitter follower Arcam used, just removing the whole lot and running a
higher i.e. 3.5V dc offset sounded much better (does this put the opamp in
single ended mode?). Any bias currents added into the inputs of an opamp
must be super clean, as far as I can see.
KYW - To answer your questions:
1) The CD723 is definitely not mediocre now!
2) Is it better than the Arcam? During "conscious" listening i.e. in an
A-B comparison it's probably better. However the real test is "subconscious"
listening (like I'm doing now, whilst typing) and at the current mod status
the CD723 has just got to the stage where I don't have to swop back to the
Arcam after half an hour of so. I occasionally do "unconscious" listening as
well - not useful for judging hifi. As an aside, with injudicious mods I can
easily make the Arcam sound more overtly detailed (more like the CD723) but
it also loses the analogueness and I generally return to almost original
spec (albeit with improved clock and OPA627s throughout).
3) The RC4227 used to be sold by Maplin (in the days when they had some
interesting parts and some of them were even in stock). I think they were
made by Raytheon in their Scottish fab, which is long since gone. They were
probably made on about 300 micron technology with a haggis substrate. Jokes
aside, they are the best sounding duals I have in the bitbox.
4) I will have another go with the AD812, it's the first time I have had
a hooting op-amp and it only does it when connected to the system. I'm just
too lazy to drag my ancient Textronix into the living room to investigate.
5) Early on in this thread you mentioned something about bad sound
relating to Pana FC with Wima polyprop in parallel as output caps. I can
confirm that the player sounds better without the Wimas. I need some caps to
replace the FCs that will fit on the pcb, Sonicaps etc are too big, can you
suggest the best small option - one of the BGs?
Another aside: My friend's Cambridge Audio CD2 is markedly superior to the
Arcam. In another thread someone stated that most >£200 modern CD players
are better that the CD2. If so, please, please, please someone tell me which
one to buy 'cos when I took said CD2 to the local hifi shop it demolished a
Naim CD5i, comfortably bettered a £1600 Unison Research machine. Only an
Accuphase player at £3000 was more detailed but it was also rather
unengaging. This seems to support KYW's view that the TDA1541 does something
special.
Cheers,
Dave
helping Fin and me. I have seen a lot of threads where KYW comes under
attack for voicing his opinion, well as far as I'm concerned all the things
I have tried on his suggestion have been beneficial (and believe me I tried
many suggestions here and elsewhere on the lovely WWW and gone many steps
backwards!).
You will notice at this point that I have not tried passive trimming of the
output offset to remove the output caps. I'm not sure at this point that I
agree with KYW on this particular point - the dc offset (about 1.5V) as it
stands drifts around by up to 30mV, I don't want drift this on my volume
pot. Also, in the Arcam I tried trimming the offset (from a Ben Duncan
acticle) using LT1021 and although the sound improved slightly from the
emitter follower Arcam used, just removing the whole lot and running a
higher i.e. 3.5V dc offset sounded much better (does this put the opamp in
single ended mode?). Any bias currents added into the inputs of an opamp
must be super clean, as far as I can see.
KYW - To answer your questions:
1) The CD723 is definitely not mediocre now!
2) Is it better than the Arcam? During "conscious" listening i.e. in an
A-B comparison it's probably better. However the real test is "subconscious"
listening (like I'm doing now, whilst typing) and at the current mod status
the CD723 has just got to the stage where I don't have to swop back to the
Arcam after half an hour of so. I occasionally do "unconscious" listening as
well - not useful for judging hifi. As an aside, with injudicious mods I can
easily make the Arcam sound more overtly detailed (more like the CD723) but
it also loses the analogueness and I generally return to almost original
spec (albeit with improved clock and OPA627s throughout).
3) The RC4227 used to be sold by Maplin (in the days when they had some
interesting parts and some of them were even in stock). I think they were
made by Raytheon in their Scottish fab, which is long since gone. They were
probably made on about 300 micron technology with a haggis substrate. Jokes
aside, they are the best sounding duals I have in the bitbox.
4) I will have another go with the AD812, it's the first time I have had
a hooting op-amp and it only does it when connected to the system. I'm just
too lazy to drag my ancient Textronix into the living room to investigate.
5) Early on in this thread you mentioned something about bad sound
relating to Pana FC with Wima polyprop in parallel as output caps. I can
confirm that the player sounds better without the Wimas. I need some caps to
replace the FCs that will fit on the pcb, Sonicaps etc are too big, can you
suggest the best small option - one of the BGs?
Another aside: My friend's Cambridge Audio CD2 is markedly superior to the
Arcam. In another thread someone stated that most >£200 modern CD players
are better that the CD2. If so, please, please, please someone tell me which
one to buy 'cos when I took said CD2 to the local hifi shop it demolished a
Naim CD5i, comfortably bettered a £1600 Unison Research machine. Only an
Accuphase player at £3000 was more detailed but it was also rather
unengaging. This seems to support KYW's view that the TDA1541 does something
special.
Cheers,
Dave
Dave, reading your comments in the last post, struck a chord with me as I have just been trying out different opamps in my new Gainclone buffers.
It seems that more detail almost equals less musicality in my experience and somebody else confirmed this on the Gainclone forum.
What I found, (flack jacket on) was that the NE5534 was actually preferable to the OPA627 when it came down to musicality. And I know another person who has finished with the 5534's in his modified CD723 after trying many candidates for that job!
And I wonder what opamps that CD2 uses?
It seems that more detail almost equals less musicality in my experience and somebody else confirmed this on the Gainclone forum.
What I found, (flack jacket on) was that the NE5534 was actually preferable to the OPA627 when it came down to musicality. And I know another person who has finished with the 5534's in his modified CD723 after trying many candidates for that job!
And I wonder what opamps that CD2 uses?
Konnichiwa,
No sweat. I appreciate the way in which you do try to work out things for yourself and try to actually learn something. In such cases I am always to contribute whatever little knowledge and experience I posess....
There are people who simply cannot deal with a well founded and voiced opinion that runs counter to theirs.
Appreciated. When I made my mod's I figured the +/-10mV drift was "harmless". Never had any audible problems linked to DC on the volume control.
No, it does not put it into SE Mode, but it would seem to move you away from the "zero crossing" point. With some class B Op-Amp output stages this will improve the sound, on modern high speed Op-Amp's the output stage needs a lot of quiescent current to get the bandwidth, so it is not much of an issue.
Absolutely.
My original point was that there is a VERY NICE CD Player trapped in that CD-723 case only waiting to get out. It is not the last word in anything, but given the low cost and fairly easy mods I think it's worthwhile.....
Yes, I got them there too. Maplin is absolutely the pit's nowadays, shame, ain't it?
And probably made by old scottisch ex-virgins... Well, it does explain a few things....
Yeah, it was seriously good at the time.....
It will sound even better once the FC's are gone too (DC servo or Ofset Trim).
You only need to use 2.2uF (if your load is 10k or higher) as coupling Cap, in that you can get ICW (aka "clarity cap") or Ansar Polypropylenes from Cricklewood electronics. I am (as you well know) not a fan of using BG's. If you are actually blocking sufficient DC even WIMA MKS4 tend to sound better (after breakin) to my ears. But you may feel different, so try them. For "open window" type sound try a pair of the Audyn Tinfoil Capacitors (Audiocom has them in the UK).
Me too. Enquiring minds want to know.....
However, remember the concepts of moral affordability and of pecuniary affordability, and allow for some (a lot?) of wishfull thinking.
I call them as I hear them. Can't do any more. But tell you what, maybe we should start badmouthing the TDA1541 so we can buy up some more cheaply for our own use? How about a 16 or 32 pcs TDA1541 parallel DAC?
But I'm afraid this particular Schroedingers kitten has well and truely escaped it's Box (as you would of course if you where locked into abox with some nerve gas), maybe we should get Dirk Gently to investigate?
Sayonara
Dave S said:
No sweat. I appreciate the way in which you do try to work out things for yourself and try to actually learn something. In such cases I am always to contribute whatever little knowledge and experience I posess....
Dave S said:
There are people who simply cannot deal with a well founded and voiced opinion that runs counter to theirs.
Dave S said:
Appreciated. When I made my mod's I figured the +/-10mV drift was "harmless". Never had any audible problems linked to DC on the volume control.
Dave S said:
No, it does not put it into SE Mode, but it would seem to move you away from the "zero crossing" point. With some class B Op-Amp output stages this will improve the sound, on modern high speed Op-Amp's the output stage needs a lot of quiescent current to get the bandwidth, so it is not much of an issue.
Dave S said:
Absolutely.
Dave S said:
My original point was that there is a VERY NICE CD Player trapped in that CD-723 case only waiting to get out. It is not the last word in anything, but given the low cost and fairly easy mods I think it's worthwhile.....
Dave S said:
Yes, I got them there too. Maplin is absolutely the pit's nowadays, shame, ain't it?
Dave S said:
And probably made by old scottisch ex-virgins... Well, it does explain a few things....
Dave S said:
Yeah, it was seriously good at the time.....
Dave S said:
It will sound even better once the FC's are gone too (DC servo or Ofset Trim).
Dave S said:
You only need to use 2.2uF (if your load is 10k or higher) as coupling Cap, in that you can get ICW (aka "clarity cap") or Ansar Polypropylenes from Cricklewood electronics. I am (as you well know) not a fan of using BG's. If you are actually blocking sufficient DC even WIMA MKS4 tend to sound better (after breakin) to my ears. But you may feel different, so try them. For "open window" type sound try a pair of the Audyn Tinfoil Capacitors (Audiocom has them in the UK).
Dave S said:
Me too. Enquiring minds want to know.....
However, remember the concepts of moral affordability and of pecuniary affordability, and allow for some (a lot?) of wishfull thinking.
Dave S said:
I call them as I hear them. Can't do any more. But tell you what, maybe we should start badmouthing the TDA1541 so we can buy up some more cheaply for our own use? How about a 16 or 32 pcs TDA1541 parallel DAC?
But I'm afraid this particular Schroedingers kitten has well and truely escaped it's Box (as you would of course if you where locked into abox with some nerve gas), maybe we should get Dirk Gently to investigate?
Sayonara
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