So I finally have a fully functional dcg3. Only myself to blame for silly errors but with the incredible help from Ian (IDM on this forum) it is all good.
Ian has been a saviour to this project for me and I am eternally grateful .
So the dcg3 playing this afternoon. Through an incorrect 10k pot labelled up wrong as I asked for a 20k....this to he remedied very soon. Playing as source an Rpi with hifiberry dac+pro.....still standard SMPS for the entire source.
Sounds very good indeed. I had the Rpi set up with the EQ to add some low level boost. I have 3" fullrange speakers that naturally dont go very low .
Well immediately with the dcg3 in place I had to turn the EQ off as the bass boost was now harming the SQ. Only listened to a couple hours but I am very pleased and happy in the knowledge I now have my probable life long pre amp . I just need to implement a proper chassis for it now .
One question I have.....I get some background hiss on some tracks.....FLAC radio on RPi included. Not coming through the music but at quiet movements in the song you get the hiss.
Is this an input impedance thing that can be helped with resistors ....bare in mind I still need to change to the 20k pot.
Tomorrow I shall test different sources to compare.
Ian has been a saviour to this project for me and I am eternally grateful .
So the dcg3 playing this afternoon. Through an incorrect 10k pot labelled up wrong as I asked for a 20k....this to he remedied very soon. Playing as source an Rpi with hifiberry dac+pro.....still standard SMPS for the entire source.
Sounds very good indeed. I had the Rpi set up with the EQ to add some low level boost. I have 3" fullrange speakers that naturally dont go very low .
Well immediately with the dcg3 in place I had to turn the EQ off as the bass boost was now harming the SQ. Only listened to a couple hours but I am very pleased and happy in the knowledge I now have my probable life long pre amp . I just need to implement a proper chassis for it now .
One question I have.....I get some background hiss on some tracks.....FLAC radio on RPi included. Not coming through the music but at quiet movements in the song you get the hiss.
Is this an input impedance thing that can be helped with resistors ....bare in mind I still need to change to the 20k pot.
Tomorrow I shall test different sources to compare.
Congratulations and kudos to IDM of course 
If the background hiss is noticeable on some tracks but not on all tracks then it's not primarily the system's background noise itself. With some given audio source gear at least. It's possible you could live with less voltage gain in the power amp if somehow adjustable. So your dynamic range and background blackness become better optimized. An indication of too much system gain is going too loud with too little volume pot turning. Higher impedance pot will not change the gain, only the tonal forwardness aspect.
P.S. We naturally expect the "triumphant return" video after the trouble description video we had once seen.
If the background hiss is noticeable on some tracks but not on all tracks then it's not primarily the system's background noise itself. With some given audio source gear at least. It's possible you could live with less voltage gain in the power amp if somehow adjustable. So your dynamic range and background blackness become better optimized. An indication of too much system gain is going too loud with too little volume pot turning. Higher impedance pot will not change the gain, only the tonal forwardness aspect.
P.S. We naturally expect the "triumphant return" video after the trouble description video we had once seen.
Maybe I missed the post with the answer jimk04 but what was the fix for the issue with the dc offset drifting?
I got my DCSTB powered up today and it worked first time, all output voltages within 10mV of each other, +- 17.15V. So glad I double checked all the parts before I powered it up.
Need to get a heatsink for the DCG3, looking for something that will allow me to fit it in a maximum 60mm high case. Anyone sourced one in the UK?
Any recommendations for hook up wire from the iSelect to phono sockets?
I got my DCSTB powered up today and it worked first time, all output voltages within 10mV of each other, +- 17.15V. So glad I double checked all the parts before I powered it up.
Need to get a heatsink for the DCG3, looking for something that will allow me to fit it in a maximum 60mm high case. Anyone sourced one in the UK?
Any recommendations for hook up wire from the iSelect to phono sockets?
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Hi killie.
Well it was all down to a mistake on my part getting 2 resistors values transposed. I had though I'd been showr careful....and I have good eyesight.....measure twice cut once and all that .
And I think Ian found a dry joint around the OP amp.
Had it playing for a good while today and it is doing a lovely job.
Regarding chassis....yes....find loads online and then the shipping is as much.
I bought a couple TEAC separates......tuner and cassette deck.....in their narrow form factor. Suits my rack nicely as I dont have much spare width.
Picked then up for maybe 30gvp shipped for the 2. Separate auctions. Nice sturdy shell and I will make a nice acrylic or wood face plate.
Good luck with the rest of your build
Well it was all down to a mistake on my part getting 2 resistors values transposed. I had though I'd been showr careful....and I have good eyesight.....measure twice cut once and all that .
And I think Ian found a dry joint around the OP amp.
Had it playing for a good while today and it is doing a lovely job.
Regarding chassis....yes....find loads online and then the shipping is as much.
I bought a couple TEAC separates......tuner and cassette deck.....in their narrow form factor. Suits my rack nicely as I dont have much spare width.
Picked then up for maybe 30gvp shipped for the 2. Separate auctions. Nice sturdy shell and I will make a nice acrylic or wood face plate.
Good luck with the rest of your build
Good man Ian.
Killie.....heatsink from RS components. Less than 10gbp iirc.
Edit
SK85-50-SA | Heatsink, 1.3K/W, 50 x 160 x 40mm | RS Components
Killie.....heatsink from RS components. Less than 10gbp iirc.
Edit
SK85-50-SA | Heatsink, 1.3K/W, 50 x 160 x 40mm | RS Components
Is it REALLY bad idea to have dcstb in a separate chassis to dcg3. Connected by umbilical for the DC. Probably a max length of 6 inches wire between both boards?
Trying to squeeze it all in a small chassis I think is going to give me problems with trafos close by to dcg3 and RCAs etc.. so considering separating trafo and dcg3 in a box on top/underneath.
Trying to squeeze it all in a small chassis I think is going to give me problems with trafos close by to dcg3 and RCAs etc.. so considering separating trafo and dcg3 in a box on top/underneath.
Hi guys,
My uncle & I assembled a DCG3 preamp with DCSTB DC Power stabilizers. Used two 18 0 18 toroidal transformers for power. I'm using Salas I-Select Mesmerize Type input selector and volume control.
This is then fed into Anaview AMS - 1000-2600 power amp - Imported from Germany.
Power amp, pre-amp, selector, transformers are encased in one chassis.
Output - Jeff Bagby kairos continuum - assembled by us (model - mpbarneyspeakers).
DAC - Grace audio - M9XX
The problem: When I switch on the amplifier - I get an initial buzz. This happens even when the volume is cut off. The buzz lasts for 2 seconds and its gone. Everything is fine after that. The sound is not from the amp - I connected an alternate pre-amp and there is no buzz. I get the buzz when connected through DCG3 preamp.
Can anyone help me out with this please?
Thanks,
Billy
My uncle & I assembled a DCG3 preamp with DCSTB DC Power stabilizers. Used two 18 0 18 toroidal transformers for power. I'm using Salas I-Select Mesmerize Type input selector and volume control.
This is then fed into Anaview AMS - 1000-2600 power amp - Imported from Germany.
Power amp, pre-amp, selector, transformers are encased in one chassis.
Output - Jeff Bagby kairos continuum - assembled by us (model - mpbarneyspeakers).
DAC - Grace audio - M9XX
The problem: When I switch on the amplifier - I get an initial buzz. This happens even when the volume is cut off. The buzz lasts for 2 seconds and its gone. Everything is fine after that. The sound is not from the amp - I connected an alternate pre-amp and there is no buzz. I get the buzz when connected through DCG3 preamp.
Can anyone help me out with this please?
Thanks,
Billy
The main DCG3 board has local decoupling capacitors so it won't oscillate with longer PSU cables. I had tested with lab leads power lines during the project's development and it could oscillate if without C6 C7. If the SQ will go down a bit I don't know, I only know it should work stably, subjectively its for you to evaluate.
Do a couple of experiments. First put 150k resistors at the preamp's line outputs (one per channel hot to ground). If that won't help, modify to can switch the amp later than the preamp.
If one of those tests will work, its about a short period that bothers the amp before the preamp's relay establishes output connection. Else there would be buzz all the time and not only for 2 secs. If it proves so, establish separate power on switches. Unless the resistors are enough.
Useful to can warm up this Class A preamp before listening sessions also. Always switch the preamp first, wait to hear the relay click, switch on the power amp. When powering down do the reverse procedure.
Interesting system that one you described BTW. Does it sound coherent as a whole? Any pictures of the build?
If one of those tests will work, its about a short period that bothers the amp before the preamp's relay establishes output connection. Else there would be buzz all the time and not only for 2 secs. If it proves so, establish separate power on switches. Unless the resistors are enough.
Useful to can warm up this Class A preamp before listening sessions also. Always switch the preamp first, wait to hear the relay click, switch on the power amp. When powering down do the reverse procedure.
Interesting system that one you described BTW. Does it sound coherent as a whole? Any pictures of the build?
I've now got my DCG3 powered up. Voltages on the DCSTB are:
+17.15, -17.07
+17.12, -17.13
After 15 minutes the voltage drops across R10 (7.5ohm fitted) are 0.98V and 0.96V, so 131mA and 128mA.
Before I set the DC offset I'm going to connect the iSelect board and just wanted to check I've got the wiring correct. I take an AC feed from one half of a transformers (approx 17V AC) and connect it to the AC in on the iSelect. I connect from 'OUT' on the iSelect board to 'IN' on the DCG3. Is it best to use 2 Gnd wires from the iSelect 'OUT' with a Gnd going to each of the 2 'IN' connectors on the DCG3 or just use 1 Gnd wire going to one of the 'IN' connectors on the DCG3? Photo is of my lash up, it won't look like this when it goes in a box and those big heatsinks as just temporary to make sure everything works.
+17.15, -17.07
+17.12, -17.13
After 15 minutes the voltage drops across R10 (7.5ohm fitted) are 0.98V and 0.96V, so 131mA and 128mA.
Before I set the DC offset I'm going to connect the iSelect board and just wanted to check I've got the wiring correct. I take an AC feed from one half of a transformers (approx 17V AC) and connect it to the AC in on the iSelect. I connect from 'OUT' on the iSelect board to 'IN' on the DCG3. Is it best to use 2 Gnd wires from the iSelect 'OUT' with a Gnd going to each of the 2 'IN' connectors on the DCG3 or just use 1 Gnd wire going to one of the 'IN' connectors on the DCG3? Photo is of my lash up, it won't look like this when it goes in a box and those big heatsinks as just temporary to make sure everything works.