Re: Re: Re: Re: Re: more gain
Konnichiwa
I hope all arrived well, keep the unit playing for a week or two straight, just to make sure there is no early failure.
Then change the following resistors (according to my PDF copy of the schematic) from 4K53 to 18K:
R73
R75
R76
R99
This reduces the full scale input level in inputs A/B by 12db, or from nearly 10V to 2.5V.
In the output stages you can either the resistors as is and use external attenuators, or you can change the following resistors (according to my PDF copy of the schematic) from 499R to 2k:
R10
R14
R18
R22
R26
R30
R34
R38
R42
R46
R50
R54
That should produce the same change in sensitivity for the outputs.
While you are at it, you MAY wish to upgrade several electrolytic capacitors to wires, as they are strictly speaking are superfluos "belts & braces", namely (again according to my PDF copy of the schematic):
C26
C27
C41
C42
(the above are input coupling capacitors to the input stage which by itself is then AC coupled to the Input buffers for the DAC, the two coupling capacitors are needed and should be upgraded to Elna Silmic etc, they are C6 & C28 47uF/25V )
Also check if C43 to C48 block any material DC voltages in operation, if there are only a few mV they may also be safely upgraded to a wire, otherwise consider the designated treble channels (5/6?) coupling capacitors to be changed to 470nF...1uF film capacitors (this gives an acoustic 100Hz highpass first order if the 499R resistors are changed to 2k, which should be well far enough from any treble crossover frequency to not matter). It may be even be fine for the midrange section.
Of course you might also want to upgrade the Op-Amp's while you are in there and messing with SMD components. I would concentrate on the MF & HF channels.
The results should be a more "domestic hifi" compatible and notably cleaner sounding digital X-Over.
Sayonara
Konnichiwa
KevinTams said:
I hope all arrived well, keep the unit playing for a week or two straight, just to make sure there is no early failure.
Then change the following resistors (according to my PDF copy of the schematic) from 4K53 to 18K:
R73
R75
R76
R99
This reduces the full scale input level in inputs A/B by 12db, or from nearly 10V to 2.5V.
In the output stages you can either the resistors as is and use external attenuators, or you can change the following resistors (according to my PDF copy of the schematic) from 499R to 2k:
R10
R14
R18
R22
R26
R30
R34
R38
R42
R46
R50
R54
That should produce the same change in sensitivity for the outputs.
While you are at it, you MAY wish to upgrade several electrolytic capacitors to wires, as they are strictly speaking are superfluos "belts & braces", namely (again according to my PDF copy of the schematic):
C26
C27
C41
C42
(the above are input coupling capacitors to the input stage which by itself is then AC coupled to the Input buffers for the DAC, the two coupling capacitors are needed and should be upgraded to Elna Silmic etc, they are C6 & C28 47uF/25V )
Also check if C43 to C48 block any material DC voltages in operation, if there are only a few mV they may also be safely upgraded to a wire, otherwise consider the designated treble channels (5/6?) coupling capacitors to be changed to 470nF...1uF film capacitors (this gives an acoustic 100Hz highpass first order if the 499R resistors are changed to 2k, which should be well far enough from any treble crossover frequency to not matter). It may be even be fine for the midrange section.
Of course you might also want to upgrade the Op-Amp's while you are in there and messing with SMD components. I would concentrate on the MF & HF channels.
The results should be a more "domestic hifi" compatible and notably cleaner sounding digital X-Over.
Sayonara
Thanks T
excellent info as ever.
I'm currently using it with attenuators on the o/p and running near full volume on my TVC.
I'll have to buy SMD components as I have little experience with them and no stock but I would sooner replace a few resistors than put an unecessary active stage in the signal path.
I'll post a short report on the DCX thread linking to this, incase anyone else is looking for this info.
regards
Kevin
excellent info as ever.
I'm currently using it with attenuators on the o/p and running near full volume on my TVC.
I'll have to buy SMD components as I have little experience with them and no stock but I would sooner replace a few resistors than put an unecessary active stage in the signal path.
I'll post a short report on the DCX thread linking to this, incase anyone else is looking for this info.
regards
Kevin
Konnichiwa,
Feel free to repost the info from above.
However please note (and include):
1) The resistor designations and values are based on the PDF schematics I have. There is no specific reson to doubt their accuracy, however the information is in essence UNVERIFIED and may contain errors.
2) I have not applied these changes to any DCX, the values and suggestions for removal of Cap's etc are strictly based on "what I would do if I had this unit!".
Sayonara
KevinTams said:
Feel free to repost the info from above.
However please note (and include):
1) The resistor designations and values are based on the PDF schematics I have. There is no specific reson to doubt their accuracy, however the information is in essence UNVERIFIED and may contain errors.
2) I have not applied these changes to any DCX, the values and suggestions for removal of Cap's etc are strictly based on "what I would do if I had this unit!".
Sayonara
Since it was a very interesting thread and I may try to build this phono preamp one day, I collected and tried to arrange correctly all the informations that was discussed in the last 14 pages. Here the text file.
I think it is a great tool to build this project. Thanks again to all the others users that contributed to this thread.
Have fun
I think it is a great tool to build this project. Thanks again to all the others users that contributed to this thread.
Have fun
Algar_emi said:Since it was a very interesting thread and I may try to build this phono preamp one day, I collected and tried to arrange correctly all the informations that was discussed in the last 14 pages. Here the text file.
I think it is a great tool to build this project. Thanks again to all the others users that contributed to this thread.
Have fun
Hi,
If you can take a look at Kofi Annan's "B+..." thread on this subject there are lots of useful construction tips and techniques discussed there on building this phono stage and tube gear in general.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=54534
Best,
fred
Hi, I'm Kofi Annan.
You know, I used to listen to a solid state phono preamplifier. That is, until I made Thorsten's Phono Pre (TM). Thorsten's Phono Pre (TM) has eleven essential vitamins and minerals, never needs winding and really sounds fantastic. It keeps beverages cool in the summer and hot in the winter, starts bold, finishes clean and never leaves an aftertaste.
It outperforms phono pres from other galaxies and my friend Jaques Chirac says its the best phono pre he's ever heard bar none.
So, if you want to lose weight, increase your bustline, have smoother, healthier hair and finally gain the confidence you need to meet Mr. Right, then you need Thorsten's Phono Pre.
This was an unpaid endorsement for Thorsten's Phono Pre (TM).
Seriously, this thing sounds great. Please learn from my many, many mistakes in the thread Kofi Annan in: "B+... PLUS!" thread. Follow the grounding scheme. If you do it right, you'll love it like me, Kofi Annan.
Kofi
You know, I used to listen to a solid state phono preamplifier. That is, until I made Thorsten's Phono Pre (TM). Thorsten's Phono Pre (TM) has eleven essential vitamins and minerals, never needs winding and really sounds fantastic. It keeps beverages cool in the summer and hot in the winter, starts bold, finishes clean and never leaves an aftertaste.
It outperforms phono pres from other galaxies and my friend Jaques Chirac says its the best phono pre he's ever heard bar none.
So, if you want to lose weight, increase your bustline, have smoother, healthier hair and finally gain the confidence you need to meet Mr. Right, then you need Thorsten's Phono Pre.
This was an unpaid endorsement for Thorsten's Phono Pre (TM).
Seriously, this thing sounds great. Please learn from my many, many mistakes in the thread Kofi Annan in: "B+... PLUS!" thread. Follow the grounding scheme. If you do it right, you'll love it like me, Kofi Annan.
Kofi
Hi there,
I have built this phono preamp and I must say it seems a definate step up from the VSPS which I built previously.
I do have one issue though - it seems quite light in the bass department. The bass is there, but doesn't go down terribly deep. With the VSPS, if you knocked the turntable - you heard it through the speakers. With this one absolutely nothing.
My first though is have i got enough output coupling capacitance. I am driving a preamp with a 33.3K fixed stepped attenuator as load. I have 10uf of output coupling cap. I understand that this amp is designed with at least 100K of load. Do I need to increase my capacitor further- or should i be looking elsewhere.
Shoog
I have built this phono preamp and I must say it seems a definate step up from the VSPS which I built previously.
I do have one issue though - it seems quite light in the bass department. The bass is there, but doesn't go down terribly deep. With the VSPS, if you knocked the turntable - you heard it through the speakers. With this one absolutely nothing.
My first though is have i got enough output coupling capacitance. I am driving a preamp with a 33.3K fixed stepped attenuator as load. I have 10uf of output coupling cap. I understand that this amp is designed with at least 100K of load. Do I need to increase my capacitor further- or should i be looking elsewhere.
Shoog
Konnichiwa,
You should not have any issues with LF response, unless something is fundamentally wrong.
You might want to try measure the LF response, compared to the RIAA standard. Are you sure the interstage coupling section is 10nF & > 3M3 (3.3 Megaohm)?
No, it is designed to drive loads of at least 10KOhm or higher with a 2.2uF output coupling capacitor (-3db @ 8Hz with 10K Load overall, -3db @ 4Hz with 100k Load).
Sayonara
Shoog said:
You should not have any issues with LF response, unless something is fundamentally wrong.
You might want to try measure the LF response, compared to the RIAA standard. Are you sure the interstage coupling section is 10nF & > 3M3 (3.3 Megaohm)?
Shoog said:
No, it is designed to drive loads of at least 10KOhm or higher with a 2.2uF output coupling capacitor (-3db @ 8Hz with 10K Load overall, -3db @ 4Hz with 100k Load).
Sayonara
Hi,
Thanks for the reply.
I opened up the case and altered the cartridge loading from 51K as specified to the recommended cartridge load of 47K. I also added an additional 100pf of load to come up to the cartridge spec. Before I was relying on the cable capacitance.This has helped a bit. Sound seems a little more balanced overall.
Still the bass doesn't go really low to my hearing. I checked the coupling cap and its definately 10nf. When you say 3M3 load - is this the parallel 10M resistor and the ECC88 Grid load ?
Shoog
Thanks for the reply.
I opened up the case and altered the cartridge loading from 51K as specified to the recommended cartridge load of 47K. I also added an additional 100pf of load to come up to the cartridge spec. Before I was relying on the cable capacitance.This has helped a bit. Sound seems a little more balanced overall.
Still the bass doesn't go really low to my hearing. I checked the coupling cap and its definately 10nf. When you say 3M3 load - is this the parallel 10M resistor and the ECC88 Grid load ?
Shoog
Konnichiwa,
I doubt this makes any difference appreciable...
That might help some balancing the HF side.
In some cases the 10M resistor does not allow current flow in the ECC88 (overbias), in these cases it can be lowered down to 3M3 without worry.
Are you sure all key values are as specified? Maybe your other Phonostage(s) did not have an accurate EQ and instead an LF boost? You can try increasing the series resitor in the RIAA Network if you want to boost the LF from "flat".
But it may be best to make some measurements first.
Sayonara
Shoog said:
I doubt this makes any difference appreciable...
Shoog said:
That might help some balancing the HF side.
Shoog said:
In some cases the 10M resistor does not allow current flow in the ECC88 (overbias), in these cases it can be lowered down to 3M3 without worry.
Are you sure all key values are as specified? Maybe your other Phonostage(s) did not have an accurate EQ and instead an LF boost? You can try increasing the series resitor in the RIAA Network if you want to boost the LF from "flat".
But it may be best to make some measurements first.
Sayonara
I may try altering the 10M resistor.
I would say that overall the balance is probably fairly neutral and my previous phono amp probably had a little more boost. The bass control is probably a little tighter. I will listen a bit more before doing much else.
Thanks for the input, and the design.
Shoog
I would say that overall the balance is probably fairly neutral and my previous phono amp probably had a little more boost. The bass control is probably a little tighter. I will listen a bit more before doing much else.
Thanks for the input, and the design.
Shoog
fred76,
Hi, i'm also based in Manila. Wondering if I might be able to get in touch with you regarding some specialized help on a couple of projects? Feel free to email me from this forum.
Also, would be inteerested to buy sell or swap gear and curious if there are any audio enthusiat groups in town?
Been in Manila for almost 4 years now, but have recently gotten into the music hobby and enjoying it alot.
Regards,
Mark
Hi, i'm also based in Manila. Wondering if I might be able to get in touch with you regarding some specialized help on a couple of projects? Feel free to email me from this forum.
Also, would be inteerested to buy sell or swap gear and curious if there are any audio enthusiat groups in town?
Been in Manila for almost 4 years now, but have recently gotten into the music hobby and enjoying it alot.
Regards,
Mark
fred76 said: