Interesting results Fran.
These might help?
20x Electronic Tube Damper Silicone Valve Ring For EL84 12AX7 12AU7 12AT7es | eBay
Have you tried a regulated supply on the filaments, should get a similar result to batteries. I always use DC filament supplies.
These might help?
20x Electronic Tube Damper Silicone Valve Ring For EL84 12AX7 12AU7 12AT7es | eBay
Have you tried a regulated supply on the filaments, should get a similar result to batteries. I always use DC filament supplies.
If i want to diy a raspberry pi streamer dac wich kali reclock frequency do i choose from? 22/24mhz?
Boards are being made atm.😀
ALLO KALI Reclocker I2S FIFO Sparky SBC and Raspberry Pi 22/24MHz 192kHZ - Audiophonics
Boards are being made atm.😀
ALLO KALI Reclocker I2S FIFO Sparky SBC and Raspberry Pi 22/24MHz 192kHZ - Audiophonics
Yes, 22/24Mhz clocks will have better performance.
You wont be able to go over 192kHz on the Ad1862 with I2S anyway
I put some rubber o-rings on it last night, and I think it helped a little - these valves are almost cold, so I think rubber will be fine. I also sat the board on some bubble wrap as well and that helped too. I think you would have to rig something to mount it on o-rings if you were to use it in real life.
I think my DC supply was not quiet enough, so I need to work on that a bit more. I also might investigate trying to quieten the B+ more - its a very basic CLCRC setup at the moment, and at that, I think the inductor is quite low in value. More experiments over the coming days.....
OK, so I think I have this nearly sorted. I've stuck with 500r IV resistors, nothing fancy, just standard metal film ones. I have a nice pair of takman 300R so I might try them again now that the rest is sorted out.
The B+ is better filtered now (I only had one low value choke to use, but I upped the series resistor and that has helped I think). Probably a bigger change was in the transformer I was using. I had a large EI core transformer with a 130v secondary, and while that worked just fine, I found out the circuit was humming as I moved it around. Also it vibrated a bit which meant the microphonic tubes were feeling that. So my solution was to run 2 small 12v transformers back to back and this seems a better solution. I have about 15hrs of use on a set of D cells for the heaters now, and I think you could probably expect around 20 hrs or so. I have some LiFePO4 batteries here, but they are happier being kept between 3 and 3.6V, so I will just use a series diode to drop the voltage the half volt thats needed. Hopefully that won't cause issues. If it works well on test then I think I will add a switch system for it, and maybe a cheap voltmeter to show voltage. I'll probably put that on a momentary push switch because those little voltmeters can add noise.
Other than that, the circuit is dead quiet now, and sounds pretty good I have to say. I ordered a set of 3a5 RCA valves to try out - a good few users say its worth getting an excess number and then selecting for lowest noise and microphonics. I think mounting the board on flexible mounts should seal the deal.
So as I get to the end of experiments with this board, I think I can say it works very well and if you are willing to deal with the voltages, the microphonics, the DC leakage through the output caps at startup and the batteries then this works well as an output stage. I suppose it falls into the unconventional category, not being SRPP, and DHT. If you are someone who like messing about with line stages etc, this is not the worst option to build for one.
Its been a good learning experience, and one I would not have even tried if I hadn't had the module sitting here.
The B+ is better filtered now (I only had one low value choke to use, but I upped the series resistor and that has helped I think). Probably a bigger change was in the transformer I was using. I had a large EI core transformer with a 130v secondary, and while that worked just fine, I found out the circuit was humming as I moved it around. Also it vibrated a bit which meant the microphonic tubes were feeling that. So my solution was to run 2 small 12v transformers back to back and this seems a better solution. I have about 15hrs of use on a set of D cells for the heaters now, and I think you could probably expect around 20 hrs or so. I have some LiFePO4 batteries here, but they are happier being kept between 3 and 3.6V, so I will just use a series diode to drop the voltage the half volt thats needed. Hopefully that won't cause issues. If it works well on test then I think I will add a switch system for it, and maybe a cheap voltmeter to show voltage. I'll probably put that on a momentary push switch because those little voltmeters can add noise.
Other than that, the circuit is dead quiet now, and sounds pretty good I have to say. I ordered a set of 3a5 RCA valves to try out - a good few users say its worth getting an excess number and then selecting for lowest noise and microphonics. I think mounting the board on flexible mounts should seal the deal.
So as I get to the end of experiments with this board, I think I can say it works very well and if you are willing to deal with the voltages, the microphonics, the DC leakage through the output caps at startup and the batteries then this works well as an output stage. I suppose it falls into the unconventional category, not being SRPP, and DHT. If you are someone who like messing about with line stages etc, this is not the worst option to build for one.
Its been a good learning experience, and one I would not have even tried if I hadn't had the module sitting here.
DAC connected to PI2AES and RPI4
Completed DAC and connected to I2S output from PI2AES audio shield from PI2Design. Power supply are modified VRDN for 5 V and 12 V.
Woking well and I’m planning to put all of these together with a active volume control into a nice case.
Completed DAC and connected to I2S output from PI2AES audio shield from PI2Design. Power supply are modified VRDN for 5 V and 12 V.
Woking well and I’m planning to put all of these together with a active volume control into a nice case.
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Active volume control
I’m looking for a decent active volume control to add to DAC.
Looking at Doug Self Preamp from Linear Audio, and I want to omit tone control but just use active volume control part.
Can OPA627 buffer in DAC drive the active volume circuit directly or should I use another buffer in between.
Thanks
I’m looking for a decent active volume control to add to DAC.
Looking at Doug Self Preamp from Linear Audio, and I want to omit tone control but just use active volume control part.
Can OPA627 buffer in DAC drive the active volume circuit directly or should I use another buffer in between.
Thanks
Cool.
I wwondered with its 1 mA if a apaired D3A in triode mode would not be the ideal candidate...
Though this tube became expensive and dunno where the good sources are in Europe.
.Maybe the less good E180F ? Anyway in term of details hard to beat an opa 1611/1612...But of course details are not all.
I can't comment on that - but I am continuing to work on the 3a5 stage ( there's a thread over in the tubes forum on it). So, I bought a pair of RCA 3a5 from langrex in the UK, they are definitely less microphonic and are quieter as well, although you can't hear the others from the listening chair even at high enough volume. I've been using batteries on the filament and that cured the last of the noise. So I've gone on now to order a set of coleman filament kits and the gurus over in tubes recommend that plus a few other changes. So in a week or two I hope to have some changes made.
The other stage arrived and I tried that out as well. It gave excellent results too, but I think the 3a5 has a bit more magic. If you search for "YJ preamp kit srpp 6n2" you'll see it. Its far easier to implement than the 3a5 and is dead quiet in operation. Definitely an option. A friend prefers the 6n2 stage to the 3a5 so there might be just personal preference in it.
So lots of options out there for output stages..... one of the great bonuses of this DAC layout. Thank you Miro!!
Thanks for the tip fran. I never worked with tubes for some reasons... but it's going viral.
