Just a thought...
You might want to include schema, and parts list and pictures on your site. The reference to the diyaudio thread clearly works but requires the customer to parse through the iterations and modifications of your project ~ 1000 posts.
Just my opinion...
I might be a "buyer"!
You might want to include schema, and parts list and pictures on your site. The reference to the diyaudio thread clearly works but requires the customer to parse through the iterations and modifications of your project ~ 1000 posts.
Just my opinion...
I might be a "buyer"!
My audiophile approach to (My "audiophile" LM3886 approach)
I have just completed by fourth Ref C and this one is a killer.
Well there have been speculation as to some of these mods that i am going to list here.
1- dual transformers with dual secondaries (220VA). each transformer supplies only one polarity rail one for negative one for possitive ( you need dual rectifiers to do this mod
2- i have a seperate power supply per op-amp. at 18V 7818/7918 with seperate transformers
gone is the noisy zeners. and the hot resistors.
sound
the tops are much cleaner and much more balanced.
mids (never liked the mids on this amp to much - compared to my digital amp) very clean and very detailed yet smooth - on a par with my digital amp (tripath eval board RB-tk2350 - also modified)
Bass cleaned up as well. more definition also beter balanced less of a muddyness (not that it to muddy to start of with)
Regards
Rudi
I have just completed by fourth Ref C and this one is a killer.
Well there have been speculation as to some of these mods that i am going to list here.
1- dual transformers with dual secondaries (220VA). each transformer supplies only one polarity rail one for negative one for possitive ( you need dual rectifiers to do this mod
2- i have a seperate power supply per op-amp. at 18V 7818/7918 with seperate transformers
gone is the noisy zeners. and the hot resistors.
sound
the tops are much cleaner and much more balanced.
mids (never liked the mids on this amp to much - compared to my digital amp) very clean and very detailed yet smooth - on a par with my digital amp (tripath eval board RB-tk2350 - also modified)
Bass cleaned up as well. more definition also beter balanced less of a muddyness (not that it to muddy to start of with)
Regards
Rudi
Attachments
Another question Rudi, as you have build several of these now.
Have you tried swapping out the 12V zeners with a hogher voltage version, such as 15 or 18V? I wonder how that would compare to the 78xx/79xx. Just that it might be an easier mod for others to make.
If you haven't tried it, maybe I'll give it a go and see what I hear
.
Have you tried swapping out the 12V zeners with a hogher voltage version, such as 15 or 18V? I wonder how that would compare to the 78xx/79xx. Just that it might be an easier mod for others to make.
If you haven't tried it, maybe I'll give it a go and see what I hear
.Hi Brian
the PS for the opamps are individual units (one per opamp). so i basic removed the resistors and zeners and wired the PS to the 100uf caps onboard. so you have 3300uf - 100nf - 78xx/79xx 100nf - wire to board -100uf - 100nf
regarding giving the opamp a higher voltage from the zener, i have not tried it. did not like the idea to start with. rather regulate it properly and without any option of x talk on the supplies
cheers
Rudi
the PS for the opamps are individual units (one per opamp). so i basic removed the resistors and zeners and wired the PS to the 100uf caps onboard. so you have 3300uf - 100nf - 78xx/79xx 100nf - wire to board -100uf - 100nf
regarding giving the opamp a higher voltage from the zener, i have not tried it. did not like the idea to start with. rather regulate it properly and without any option of x talk on the supplies
cheers
Rudi
rudi said:
Hi Rudy, I too also made an amp almost exactly as you describe, but it is such a drastic change I did not feel comfortable calling it a "Mauro MyRef" anymore. It is now a Russ "MyREF".
But I would tend to agree that all of the changes are good.One thing to note though, I have noticed on the scope, that the 78xx/79xx are not really much better noise wise than the zeners. I wonder if the problem we both solved is more noise from your power resistors than the zener. The biggest problem with the zener seems to be the brute force inefficiency.
I ended up using noise compensated 317/337 pair for my design as noise was significantly less on the rails than with the 78xx/79xx. In the end though I think my design was overkill.
Intersting your comment on the mids, I have never heard any lack there even with my original REV A, so I am very surprised. That could all be about component selection, or some other factor.
Good work.
If there is enough interest I would be glad to show the "RussRef" but I think that is for another thread.
Cheers!
Russ
Hi-
The reason we started the web site is basically that group buys can be a real pain to manage, and people always get left out. We hope to keep these boards and kits available on a continuing basis (unless we run out of money
). It's really just a lot easier to deal with this way: no Wiki to maintain, no flood of emails to keep organized, etc. So, take your time.Hi Russ
I would like to see what you have done.
I think that i pick up the difference in the mids is the fact that my mid driver is actually a ribbon and not a cone. cones are very slow and "hides" these changes.
but for the rest. I just wanted to build a all out amp to compare with my digital. (this one is on a par)
the one thing about my mod that does not work with your boards are the fact that i have dual rectifiers. and for that reason i can run a transformer per polarity rail. one transformer for possitive and one transformer for negative. this made big difference aswell compared to the one bridge per amp.
cheers
Rudi
I would like to see what you have done.
I think that i pick up the difference in the mids is the fact that my mid driver is actually a ribbon and not a cone. cones are very slow and "hides" these changes.
but for the rest. I just wanted to build a all out amp to compare with my digital. (this one is on a par)
the one thing about my mod that does not work with your boards are the fact that i have dual rectifiers. and for that reason i can run a transformer per polarity rail. one transformer for possitive and one transformer for negative. this made big difference aswell compared to the one bridge per amp.
cheers
Rudi
Mods on Rudis Rev C
I have had an opportunity to listen to the Rev C Rudi made at various stages. In my mind and to my ears, the most recent changes have made a dramatic impact across the frequency spectrum.
The changes were:
1. 318 fed from 78xx/79xx rather than the noisy zeners. These were chosen above 318/337 since the latter tend to be wider band, allowing greater potential for noise contamination.
2. 318 operating voltage increased to 18V-Op-amps prefer to run at higher voltages in general.
3. Seperate transformers for the 318's to reduce power supply noise further.
4. Seperate 200VA transformers for the 3886, one feeding +, the other -
Vs the old, single transformer configuration, bass is now MUCH better controlled, especially the very low frequency stuff. Highs and mids have become much more transparent.
One of the charming characteristics of teh amp is it's mid presence, which has improved with these mods.I must also say that highs are not sharp/bright/metallic at all, although this has tended to be a characteristic of this amp from the start.
Vs Rudi's existing 2350 digital class T amp, I prefer the REVC, and that is a bold statement, since up until these mods, I was pretty convinced that the Class T was the way to go.
Do yourselves a favour and implement these changes, they are VERY worthwhile.
I have had an opportunity to listen to the Rev C Rudi made at various stages. In my mind and to my ears, the most recent changes have made a dramatic impact across the frequency spectrum.
The changes were:
1. 318 fed from 78xx/79xx rather than the noisy zeners. These were chosen above 318/337 since the latter tend to be wider band, allowing greater potential for noise contamination.
2. 318 operating voltage increased to 18V-Op-amps prefer to run at higher voltages in general.
3. Seperate transformers for the 318's to reduce power supply noise further.
4. Seperate 200VA transformers for the 3886, one feeding +, the other -
Vs the old, single transformer configuration, bass is now MUCH better controlled, especially the very low frequency stuff. Highs and mids have become much more transparent.
One of the charming characteristics of teh amp is it's mid presence, which has improved with these mods.I must also say that highs are not sharp/bright/metallic at all, although this has tended to be a characteristic of this amp from the start.
Vs Rudi's existing 2350 digital class T amp, I prefer the REVC, and that is a bold statement, since up until these mods, I was pretty convinced that the Class T was the way to go.
Do yourselves a favour and implement these changes, they are VERY worthwhile.
rudi said:Hi Russ
I would like to see what you have done.
the one thing about my mod that does not work with your boards are the fact that i have dual rectifiers. and for that reason i can run a transformer per polarity rail. one transformer for possitive and one transformer for negative. this made big difference aswell compared to the one bridge per amp.
cheers
Rudi
You are correct of course.
One thing to remember about Mauro's design (not so much a factor in mine) is that has certain practical design goals which manifest themselves in low component count.
On my design I actually left the PS as a seperate PCB simply because I was tweaking and changing it all the time.
Cheers!
Russ
Re: schematic...
Hi Paulo
unfortuneately i do not have software that can do a nice schematic for you. but I did a quick hand drawing of how the main trofos get hooked up.
for the op amp, i used two standard power supplies and just removed the zener and resistor
the power supplies are then wired to the 100uf caps
cheers
Rudi
UnixMan said:
Hi Paulo
unfortuneately i do not have software that can do a nice schematic for you. but I did a quick hand drawing of how the main trofos get hooked up.
for the op amp, i used two standard power supplies and just removed the zener and resistor
the power supplies are then wired to the 100uf caps
cheers
Rudi
