Hi all,
I just built the grounded grid for monica dac using E180F/6688 instead of 5842 the results are simply astonishing. This in combination with charlize is so good that I might not be listening to my 2A3 loftin and white any longer. For lack of my review vocabulary, I will have to say that Ella and Louis are literally live in the room. My GF whose ears I often use for tweaking my equipment for the first time sat there for more than 3 songs (infact 13) without complaining. I highly recommend monica users to try this gain stage (and charlize ofcourse), it fixes the phase problem (i think) and really makes monica shine.
I would like to hear some comments from others who have tried the grounded grid. The only complain i have is that i miss the top end just a bit, but this might be attributed to the non-oversampling character of the DAC
Thanks,
Praveen
I just built the grounded grid for monica dac using E180F/6688 instead of 5842 the results are simply astonishing. This in combination with charlize is so good that I might not be listening to my 2A3 loftin and white any longer. For lack of my review vocabulary, I will have to say that Ella and Louis are literally live in the room. My GF whose ears I often use for tweaking my equipment for the first time sat there for more than 3 songs (infact 13) without complaining. I highly recommend monica users to try this gain stage (and charlize ofcourse), it fixes the phase problem (i think) and really makes monica shine.
I would like to hear some comments from others who have tried the grounded grid. The only complain i have is that i miss the top end just a bit, but this might be attributed to the non-oversampling character of the DAC
Thanks,
Praveen
Check the links here for the grounded grid or gg
http://diyparadise.com/mar06/gg.html
http://www.diyparadise.com/downloads.html
The original circuit is based on 5842, but i couldnt find any easily so decided to go with 6688. Yeo at diyparadise claims that he likes the 6688 even better. There was one tweak he recommended which worked very well for me. Place a diode pointing to g2 parallel to the 47R resistor there. This is supposed to improve the distortion characteristic even further.
I used schotkkys and pio bypassed with a solen cap for the first filter stage and this has been working really well for me so far. It does sound a little fatiguing while listening long, but the detail i get in return is much much more. I hope more ppl build this, cos if you already like monica this improves things quite a bit.
Praveen
http://diyparadise.com/mar06/gg.html
http://www.diyparadise.com/downloads.html
The original circuit is based on 5842, but i couldnt find any easily so decided to go with 6688. Yeo at diyparadise claims that he likes the 6688 even better. There was one tweak he recommended which worked very well for me. Place a diode pointing to g2 parallel to the 47R resistor there. This is supposed to improve the distortion characteristic even further.
I used schotkkys and pio bypassed with a solen cap for the first filter stage and this has been working really well for me so far. It does sound a little fatiguing while listening long, but the detail i get in return is much much more. I hope more ppl build this, cos if you already like monica this improves things quite a bit.
Praveen
Praveen;
I am using Ratheons without chokes or the diode fix. The comments from diyparadise site seemed to indicate that Mullards were the most prone to microphonics but again, the halos may help this out. The GE's were considered least sensitive to the problem so you may not have experienced it. Nice part about the halos is the money back garantee---but Herbie is not getting mine back!
Pete
I am using Ratheons without chokes or the diode fix. The comments from diyparadise site seemed to indicate that Mullards were the most prone to microphonics but again, the halos may help this out. The GE's were considered least sensitive to the problem so you may not have experienced it. Nice part about the halos is the money back garantee---but Herbie is not getting mine back!
Pete
praveen77 said:
Could you post some reading from the circuit you built? Did you use the plate chokes? Did you use a choke in the PSU? I was thinking about building it using IXYS current regulators as a plate load and regulating the B+ with a gas diode. Thoughts? Also does the Monica invert at the output or has Yeo inverted the outputs back into phase ala Scott Nixon's DAC?
G,
I am using plate chokes. I got them from electra print. The voltage at the plate is about 120v-125v when using a 160R cathode as shown at diyparadise.
I am not sure about the using a IXYS for plate load. You will want to post in the tubes forums about it. I think grounded grid works a little differently as the cathode voltage changes based on input. It might not be a good idea to regulate the current for this topology. But, I am not the expert so try in the tubes forums.
I have tried ccs and plate chokes before with a 12b4 preamp before. I marginally prefer the chokes, but its entirely a matter of personal preference i believe both work very well when implemented right.
I did have a phase problem not sure whether it was from monica or charlize ... but adding the gg fixed it.
Praveen
I am using plate chokes. I got them from electra print. The voltage at the plate is about 120v-125v when using a 160R cathode as shown at diyparadise.
I am not sure about the using a IXYS for plate load. You will want to post in the tubes forums about it. I think grounded grid works a little differently as the cathode voltage changes based on input. It might not be a good idea to regulate the current for this topology. But, I am not the expert so try in the tubes forums.
I have tried ccs and plate chokes before with a 12b4 preamp before. I marginally prefer the chokes, but its entirely a matter of personal preference i believe both work very well when implemented right.
I did have a phase problem not sure whether it was from monica or charlize ... but adding the gg fixed it.
Praveen
Pete,
It is a catalogue item (AC8037) from Jack. Specs are 75+H @ 20ma rating about $80/pr. But think about the AC9037 too, its a 100+H @ 10ma. I think we are only running around that much current. I was very tempted to try the 270+H chokes from lundahl but then they were twice the price. I dont seem to miss any bass so am just going to stay with Jacks chokes for now.
When I played with the B+ the sound changes significantly between 125V +/-5v. I was really surprised by the extent of change. I am sure this is going to change with tube life, so put in a pot in the psu so that I can adjust it every couple of months if needed. It still sounds absurd that I could hear the difference at such low variation in plate voltage. But I confirmed my hallucination to be accurate with another pair of ears too.
Just ordered the halo dampers ... Will post my opinions when i get it. Learning new things here everyday
Praveen
It is a catalogue item (AC8037) from Jack. Specs are 75+H @ 20ma rating about $80/pr. But think about the AC9037 too, its a 100+H @ 10ma. I think we are only running around that much current. I was very tempted to try the 270+H chokes from lundahl but then they were twice the price. I dont seem to miss any bass so am just going to stay with Jacks chokes for now.
When I played with the B+ the sound changes significantly between 125V +/-5v. I was really surprised by the extent of change. I am sure this is going to change with tube life, so put in a pot in the psu so that I can adjust it every couple of months if needed. It still sounds absurd that I could hear the difference at such low variation in plate voltage. But I confirmed my hallucination to be accurate with another pair of ears too.
Just ordered the halo dampers ... Will post my opinions when i get it. Learning new things here everyday
Praveen
Hi Pengboon,
I cant compare it to vinyl cos i dont have such equipment (some day).
But, I am running this with Klipsch RB25s (61/2 in driver) w/o subs and i dont miss the bass most of the time.
I had monica directly wired to charlize first for a few weeks. I do believe there is better bass extension now. But not that much (i think). The reason is, for me this effect was dwarfed compared to the improvement across the whole audible spectrum (bass control, resolution, *live* factor etc). If you like monica so far ... definitely try this. From what i understand Monica is a current dac and doesnt drive voltage driven amps very well unless merged with something like this gg stage (my 12B4 doesnt work as well in this setup).
On a side note I just finished putting this is in a chassis. Fun factor for me was i have the whole thing including 3 power supplies in one chassis with a remote stepped attenuator. No hum, no interconnects etc ... just one wire to the usb port (yes i added a usb to spdif convertor too) and o/p for speakers. Absolutely love this setup.
Praveen
I cant compare it to vinyl cos i dont have such equipment (some day).
But, I am running this with Klipsch RB25s (61/2 in driver) w/o subs and i dont miss the bass most of the time.
I had monica directly wired to charlize first for a few weeks. I do believe there is better bass extension now. But not that much (i think). The reason is, for me this effect was dwarfed compared to the improvement across the whole audible spectrum (bass control, resolution, *live* factor etc). If you like monica so far ... definitely try this. From what i understand Monica is a current dac and doesnt drive voltage driven amps very well unless merged with something like this gg stage (my 12B4 doesnt work as well in this setup).
On a side note I just finished putting this is in a chassis. Fun factor for me was i have the whole thing including 3 power supplies in one chassis with a remote stepped attenuator. No hum, no interconnects etc ... just one wire to the usb port (yes i added a usb to spdif convertor too) and o/p for speakers. Absolutely love this setup
.Praveen
No bass extension...
Hi,
The issue of NO BASS EXTENSION in your system is because of the two reasons:
1. Your speakers (crossover problems)/I suggest high efficient speakers like horns or vintage speakers with anilco magnet)
2. Your preamp and/or amps (most amps nowadays have NO output transformers since output caps produce very weak bass)
I am using Monica 2 in my system and have no problem with no bass extension(not full bass but at least midbass).
I also have read someone has tried to replace the PS caps 2200uF with 6800uF or 3x2200uF would increase the bass extension. But you have to use 2200uF caps and I do not know why? Good luck.
Hi,
The issue of NO BASS EXTENSION in your system is because of the two reasons:
1. Your speakers (crossover problems)/I suggest high efficient speakers like horns or vintage speakers with anilco magnet)
2. Your preamp and/or amps (most amps nowadays have NO output transformers since output caps produce very weak bass)
I am using Monica 2 in my system and have no problem with no bass extension(not full bass but at least midbass).
I also have read someone has tried to replace the PS caps 2200uF with 6800uF or 3x2200uF would increase the bass extension. But you have to use 2200uF caps and I do not know why? Good luck.
Hi Praveen,
OK, glad to hear that. I am planning a GG too, just waiting for the plate chokes being wound now.
Hi Singleended40,
My vinyl playback is in exactly the same system. preamp (12B4), power amp (EL84 PP), and speakers (Coral Beta 8 BR). So the difference is definetely between the sources.
thanks for all your advice...
OK, glad to hear that. I am planning a GG too, just waiting for the plate chokes being wound now.
Hi Singleended40,
My vinyl playback is in exactly the same system. preamp (12B4), power amp (EL84 PP), and speakers (Coral Beta 8 BR). So the difference is definetely between the sources.
thanks for all your advice...
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