Hi,
As you may have noticed Im also doing some mods and it appears each set of boards is slightly different. .One step at a time as is my usual method.
I am interested in your observations re uprate to 1000mfs/2200mfs ,sonically?
Also the 78L05s (78L15s) I hadnt listed this on mine.I wondered if those little regs are good enough for larger smoothing caps.?
Also I believe that all switching diodes including schottkys benefit from calculated bypass caps.Even if its only my sacd players noise senstive circuits that benefit.
Also Im a bit suprised at the comments re channel seperation.I though we had moved on from 60s thinking.
Ok there reaches a point when the specs become meaningless but it isnt 1db above a mean average unspecified rating.
As you may have noticed Im also doing some mods and it appears each set of boards is slightly different. .One step at a time as is my usual method.
I am interested in your observations re uprate to 1000mfs/2200mfs ,sonically?
Also the 78L05s (78L15s) I hadnt listed this on mine.I wondered if those little regs are good enough for larger smoothing caps.?
Also I believe that all switching diodes including schottkys benefit from calculated bypass caps.Even if its only my sacd players noise senstive circuits that benefit.
Also Im a bit suprised at the comments re channel seperation.I though we had moved on from 60s thinking.
Ok there reaches a point when the specs become meaningless but it isnt 1db above a mean average unspecified rating.
I did a lot of things at once so can not comment on the specific effect of uprating the smoothing caps from 470 mfd to 1000 mfd. These are on the raw supply before the regulators so would only make their job easier, not harder. Half wave regulation, 470 mfd smoothing to supply 6 op amp sections just does not add up...
If it was not such a silly halfwave rectified PSU I would have done DC with much more smoothing outside in a bigger PSU box.
It is possible but would need a few clever moves with regard to the PSu 0 volt line etc.
The regulators are implemented in a strange way, I only noticed this once I wanted to do some volatage measurements without any ICs in place. I got 20 volts out ofd the regulators....
Turns out, they have a 900 ohms I think it was resistor from input to output on the regulators. The moment current is drawn, the voltage corresponds with the regulators. I assume this is some way to allow more current to be supplied then the 78l15 will allow?
Anyways, sound is much more solid now, deeper gutsier bass and the difference using a bigger transformer much more apparent.
If it was not such a silly halfwave rectified PSU I would have done DC with much more smoothing outside in a bigger PSU box.
It is possible but would need a few clever moves with regard to the PSu 0 volt line etc.
The regulators are implemented in a strange way, I only noticed this once I wanted to do some volatage measurements without any ICs in place. I got 20 volts out ofd the regulators....
Turns out, they have a 900 ohms I think it was resistor from input to output on the regulators. The moment current is drawn, the voltage corresponds with the regulators. I assume this is some way to allow more current to be supplied then the 78l15 will allow?
Anyways, sound is much more solid now, deeper gutsier bass and the difference using a bigger transformer much more apparent.
Hi and thanks for reply.
It seems the se version I have is only similair to yours.
Space is a limiting factor in the small box/
The effect of 12 Vishay resistors/2 schottkys/silver wire in and on power supply PLUS Reducing the length of the lead from wallwart
to rather shabby quality socket has made a big difference in tonal quality,lowered the effect of the high noise and removal glaze/splashiness of metal films.Plus A smidgeon more umph which is what missing.
I will continue to run the newer Vishays in and move to the power supply next.Plus on board caps.
My impression was that It had two identical poss+ circuits after the half bridge and no pos/neg regulaters/will let you know when I open it up again in the new year.Certainly will up them if not go for super regs.
Incidently I have only replaced one pair of the 47k resistors with the quieter vishays.(for now)I am wondering if this is counteracting the electric noise circuit which I personally dont understand?/ie does it work by feedback of resistor noise.Me having used a quiter different type.
It seems the se version I have is only similair to yours.
Space is a limiting factor in the small box/
The effect of 12 Vishay resistors/2 schottkys/silver wire in and on power supply PLUS Reducing the length of the lead from wallwart
to rather shabby quality socket has made a big difference in tonal quality,lowered the effect of the high noise and removal glaze/splashiness of metal films.Plus A smidgeon more umph which is what missing.
I will continue to run the newer Vishays in and move to the power supply next.Plus on board caps.
My impression was that It had two identical poss+ circuits after the half bridge and no pos/neg regulaters/will let you know when I open it up again in the new year.Certainly will up them if not go for super regs.
Incidently I have only replaced one pair of the 47k resistors with the quieter vishays.(for now)I am wondering if this is counteracting the electric noise circuit which I personally dont understand?/ie does it work by feedback of resistor noise.Me having used a quiter different type.
upate
Well it took some time to get back after the holidays.I have still not got a circuit diagram so proceeded without. We definitely have different items.
The nifty splitting of rails remains,It is interesting.On the SE the resistor value is upped to 2.2k.
Having now replaced the 47k with a vishay the noise is down quite a bit.The 2.200 caps mayalso have helped but I am now getting a much nicer sound and I havent even touched those 5532s yet.Unless someone can I advise better im going for opa 2227s.
I guessed the 10mf was a dc blocking/couple cap and replaced them both with pre burnt in Silmecs.
Next time I open it up I will look / check the 47mfs that seem to be on the input signal.Someone earlier stated 4.7 but on this SE they seem to be 47. Circuit diagram would help?.
I will leave it to run in a bit longer but Im now convinced this could be a really really good disc unit.
Well it took some time to get back after the holidays.I have still not got a circuit diagram so proceeded without. We definitely have different items.
The nifty splitting of rails remains,It is interesting.On the SE the resistor value is upped to 2.2k.
Having now replaced the 47k with a vishay the noise is down quite a bit.The 2.200 caps mayalso have helped but I am now getting a much nicer sound and I havent even touched those 5532s yet.Unless someone can I advise better im going for opa 2227s.
I guessed the 10mf was a dc blocking/couple cap and replaced them both with pre burnt in Silmecs.
Next time I open it up I will look / check the 47mfs that seem to be on the input signal.Someone earlier stated 4.7 but on this SE they seem to be 47. Circuit diagram would help?.
I will leave it to run in a bit longer but Im now convinced this could be a really really good disc unit.
I am very glad I found this thread...
Any replacement suggestions for the Op-Amps in the Phonobox II unit?
I have converted mine to battery power already...
See here: http://www.diyaudio.com/forums/showthread.php?s=&postid=1522425
Thanx
D
Any replacement suggestions for the Op-Amps in the Phonobox II unit?
I have converted mine to battery power already...
See here: http://www.diyaudio.com/forums/showthread.php?s=&postid=1522425
Thanx
D
If the originals are standard layout 8-pin DIP dual op-amps (ala 5534) then I strongly recommend you try the National LM4562.
LM4562 - Dual High Performance, High Fidelity Audio Operational Amplifier
I have used this chip to replace 5534 and others with no other cct changes as well as in a few from-scratch projects. It is awsome and waaaaaay cheaper
than the BB OPA chips.
Jess
LM4562 - Dual High Performance, High Fidelity Audio Operational Amplifier
I have used this chip to replace 5534 and others with no other cct changes as well as in a few from-scratch projects. It is awsome and waaaaaay cheaper
than the BB OPA chips.Jess
JesseG said:If the originals are standard layout 8-pin DIP dual op-amps (ala 5534) then I strongly recommend you try the National LM4562.
LM4562 - Dual High Performance, High Fidelity Audio Operational Amplifier
I have used this chip to replace 5534 and others with no other cct changes as well as in a few from-scratch projects. It is awsome and waaaaaay cheaper
Jess
Jess - you suppose I can just plonk in a set of National OA's?
D
Yep! if you compare the specs of the 5534 and the LM4562 you will find that the operating limits are wider for the National chip than any of it's predecessors.
Actually, you can have a lot ot fun OA rolling (just like the tube guys do
). carefully unsolder the original chip, clean up the pads on the board and solder in a good quality 8-pin chip socket. Then, you can try a variety of chips very easily and decide which one works best for you.Cheers
Jess
BTW guys...
I just noticed this up aways.
If you get noticeable improvement by shortening the length of the PS lead as stated, then you will get even more improvement by passing the wall-wart lead in one loop through a ferrite doughnut. Your could use a split ferrite choke as well, but would need a much larger size to get the wire to pass through twice.
See the bottom of this page:
Ferrite Chokes
Have fun!
Jess
I just noticed this up aways.
If you get noticeable improvement by shortening the length of the PS lead as stated, then you will get even more improvement by passing the wall-wart lead in one loop through a ferrite doughnut. Your could use a split ferrite choke as well, but would need a much larger size to get the wire to pass through twice.
See the bottom of this page:
Ferrite Chokes
Have fun!
Jess
Hi All
I have taken in a MKII unit that someone started to mod but gave up on. There are some tracks lifted but also some components removed. Being lazy, I wonder if anyone here with a MKII or SE could tell me the values of the following caps as marked on the PCB.
Failing this, I will have to trace the circuit as my MK1 has left my abode.
C3 and C4
C19 and C29
C22 and C12
C20 and C10
C21 and C11
I have taken in a MKII unit that someone started to mod but gave up on. There are some tracks lifted but also some components removed. Being lazy, I wonder if anyone here with a MKII or SE could tell me the values of the following caps as marked on the PCB.
Failing this, I will have to trace the circuit as my MK1 has left my abode.
C3 and C4
C19 and C29
C22 and C12
C20 and C10
C21 and C11
mzperx said:
I can't - i'm new here, so i'm under modertation and not allowed to PM anybody before i made some posts
My email - nebulu@gmail.com.
Hi Calvin,
what could I say still beyond my friend's satisfaction. He likes it as is. That's the most important thing.
In meantime I began to work on a fully diff and surface mounted version. In the input stage I would like to compare OPA211 and AD797. For 2nd stage OPA1632 seems to be the best choice. In the 3rd stage I would apply AD8620.
please look here:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=126579
bye
Zoltán
what could I say still beyond my friend's satisfaction. He likes it as is. That's the most important thing.
In meantime I began to work on a fully diff and surface mounted version. In the input stage I would like to compare OPA211 and AD797. For 2nd stage OPA1632 seems to be the best choice. In the 3rd stage I would apply AD8620.
please look here:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=126579
bye
Zoltán
IMHO the OPA211 is recently the best choice - it has the lowest distortion. The OPA1632 is O.K. The AD8620 is good, but it has low supply voltage. The best choice among FET OPAMPS is OPA827 (available from TI as sample only), but it is single.
Note if the balanced amp should be used as single ended optionally, then it is necessary to build separate single ended output stage as a difference amp.
Note if the balanced amp should be used as single ended optionally, then it is necessary to build separate single ended output stage as a difference amp.
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