Monica 2 and the grounded grid

[praveen77]

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

[singleended40]

Hi,

I got the Monica 2 for awhile but never done anything like you mentioned. Would you please tell me how to buid the ground grid 6688 (is this tube or what else?)? Thanks for help.

[praveen77]

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

[Peter Menting]

Praveen; Got pretty much the same result with my 6688 GG but noticed some "blurring" in the high end. Suspected the 6688 to be microphonic and bought a pair of Halo dampers for them, cleard the problem right up and the sound is truly great.

Pete

[praveen77]

Pete,

Glad to see my observations are shared by others. I will get the dampers and see what happens. What tubes are you using. I did get a chance to compare a pair of mullards vs ge. Both are pretty good, but the mullard sounded a bit more cleaner i believe.

Praveen

[Peter Menting]

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

[praveen77]

Pete,

I believe i read somewhere in these forums that mullards were better for microphonics ... cant find it again though. So I believe i might have misread something. Thanks for your comments, I will try the halo and the raytheons.

Praveen

[singleended40]

Friend of mine built a single-ended parallel 2A3 amp using WE 417A/5842 tubes as driver tubes. The amp sounds stunning and very musical without microphonics. Why are you using 6688 instead of 5842?

[Peter Menting]

Singlended40;
Just a co-incidence really; Yeo published the schematic change from 5842's to 6688, I had two of them and the price for the 5842's was very high. No particular reason not to use the 5842 if you wish.

Pete

[G]

Originally posted by praveen77
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

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?