Salas, got the chips, header pins, and spark fun boards coming for both preamps from mouser. Thanks Mark, will let you know what I think
Its a slow integrator as you described. Driving anti offset voltage moves through a resistor to the input feedback node of the DCG3's discrete audio circuit. With the weak spec TL072 as DC servo I had seen the noise floor rising by 6dB and some additional THD vs using better chips. Although it worked fine for offset control. So I concluded that the servo chip can inject some part of its shortcomings also. At least in this circuit.
BTW here are the pins I tried. Headers I got from Thai shop etc in the past. Upper row does not fit the U1 socket. If over-pressed the most it may do is jam in and stay high. Fits my prototyping breadboards though. Maybe fitting older style double wipe DIP-8 sockets too. Surely not for modern ones with the gold plated round inserts. The bottom row fits into them nicely.
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attenuator pin logic
My DCG3 pre has an I-select board (technically I think it is In-select). I bought a TKD CP-2511 attenuator for the volume control. It is not clear to me if the CP-2511 has the same pin logic as the ALPS RK-27 the I-select circuit was designed for. Got to get the basics right. Any help would be appreciated.
Thanks,
Don
My DCG3 pre has an I-select board (technically I think it is In-select). I bought a TKD CP-2511 attenuator for the volume control. It is not clear to me if the CP-2511 has the same pin logic as the ALPS RK-27 the I-select circuit was designed for. Got to get the basics right. Any help would be appreciated.
Thanks,
Don
Salas, I am thinking of building a balanced DCG3 with boards as I need balanced out to my amp. I'd like to be able to feed it single ended sources as well. Is there any issue with using a 1:1 transformer to convert SE to balanced and then switch between the balanced outs of the transformers and the native balanced out?
And say the single ended signal would be 1vrms and the balanced 2vrms. Would a 3x gain offer enough volume range for either signal?
If the single ended was 500mv rms and gain was set to 4x would that be too much for a 2vmrs gain as well?
If the single ended was 500mv rms and gain was set to 4x would that be too much for a 2vmrs gain as well?
Start with 3X. It seems to work nicely at a friend's balanced DCG3 for various types of RCA and XLR source gear he uses. You will see if you have any need for more in your own system. SE to BAL 1:1 input transformer is going to bring SE at same level to BAL anyway.
Well... better late than never (2016!)? Perhaps this answer is in the thread someplace—So far, I haven't found it via search.
Can't wait to build this pre—just waiting on one of Tea's fine kits—amasing parts and making a chassis plan. Using Muses (been done here I see) I'm going to power it from it's own mini-supply, and In-select.
Working on SissySIT so I Quasimodo'd a few transformers. Since the setup for this pre is centertap if doing dual-mono—I had to review Mark's documentation to see about that setup. I'll make little plugin rigs that are effectively doubles of the ones shown in the pic—which were for the RAW supply on FSP/UFSP.
Point is—Really nice snubbed waveform on the Antek AS-0518 with 56R.
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Large studio monitor style with anti tank mine scale mid dome magnet as established by ATC. You can't go wrong with such a form factor speaker. Well finished also. Congrats!
Adding secondary RCA output
Hi guys. Sorry to go over old ground. I asked a similar quantity last year but I have changed direction a little.
I had a REL subwoofer that I was advised at the time to bridge R15 and add 220R from the hot line out to the new RCAs for the SW. This was assuming I was going to go from stereo outputs >y cable> REL mono rca input. Also this was on the basis of the REL having an input impedance of 2.5k if I remember correctly.
Now however, having given the REL to my son and i now use a Polk DSW400 for which I do not know the inout impedance. I shall be taking the additional RCAs from the DCG3 into a small summing/low pass active filter...schematic below. It has 10k summing into NE5532.
It would be very awkward for me to bridge R15 as removing it all from the chassis is tricky. So my question is if I leave them in situ can I add the additional R to the new outputs? Shall I start with adding 51R or maybe 100R?
Thanks for your help
Hi guys. Sorry to go over old ground. I asked a similar quantity last year but I have changed direction a little.
I had a REL subwoofer that I was advised at the time to bridge R15 and add 220R from the hot line out to the new RCAs for the SW. This was assuming I was going to go from stereo outputs >y cable> REL mono rca input. Also this was on the basis of the REL having an input impedance of 2.5k if I remember correctly.
Now however, having given the REL to my son and i now use a Polk DSW400 for which I do not know the inout impedance. I shall be taking the additional RCAs from the DCG3 into a small summing/low pass active filter...schematic below. It has 10k summing into NE5532.
It would be very awkward for me to bridge R15 as removing it all from the chassis is tricky. So my question is if I leave them in situ can I add the additional R to the new outputs? Shall I start with adding 51R or maybe 100R?
Thanks for your help
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Hi Everybody,
finally i´m in the DCG-3 (actual GB) and while awaiting the Boards/Kits am
planing all the rest to squeeze out all the lovely tone-juice from this Preamp ;-)
Reading through the long thread i found the recommendation for the toroidy
transformers with magnetical and electrical shield.
Still i´m not shure which Volumecontrol i want to use. There are plenty of
variations: normal ALPS, conductive plastic TKD ones, Muses, the DACT-Style stepped attenuators or relais based stepped volume controls and all those things.
And are there any special components you´d recommend?
Greetings
Ulf
finally i´m in the DCG-3 (actual GB) and while awaiting the Boards/Kits am
planing all the rest to squeeze out all the lovely tone-juice from this Preamp ;-)
Reading through the long thread i found the recommendation for the toroidy
transformers with magnetical and electrical shield.
Still i´m not shure which Volumecontrol i want to use. There are plenty of
variations: normal ALPS, conductive plastic TKD ones, Muses, the DACT-Style stepped attenuators or relais based stepped volume controls and all those things.
And are there any special components you´d recommend?
Greetings
Ulf
Having two 10k summing resistors at the sub's filter already just tap from the line out RCAs to another parallel output RCAs set.