Got rid of the hum in the left B&G Neo 8 by swapping the Arcam Alpha 8 power amp for a DIY TA2022 amp in stereo mode.
PS for this amp is 2*22vac 400VA toroidal transformer from toroidy, followed by a capacitor bank of 4*10000uF/63V plus the 2*4700uF on the TA2022 board.
Powering the woofers is the 2xTDA7293/channel amp with a 300VA 2*24Vac toroidal transformer followed by 6x4700uF PS capacitors.
Both amps have softstart circuits, but only the woofer amp has spkr-protection, I have a spkr-protection board on the way for the TA2022 amp as well.
Source is a Rpi 3 via XMOS USB to I²S, then to an ES9023 DAC (for now, my DAC/headamp is currently acting as preamp) and on to my AD797+BUF634 headamp with C-L-C filter on the AD797 supply. From there I’ve split the signal with Y-cables giving me sort of two outputs from the headamp/DAC combo.
One pair of cables goes to the FreeDSP classic that handles LF crossover and dipole compensation, the other goes to the TA2022 amp directly.
Alot of new parts that need to settle, but I am pleasantly surprised by the sound thus far. I know there’s alot more to squeeze out, going digital in on the FreeDSP and hook up nice DAC’s via I²S from the gpio header (bypassing the adau1701’s internal A/D’s and D/A’s).
More to come, I am going to listen to the fruits of my labour 🙂
…well I have sound from all drivers.
I have some hum in the left HF, the one previously silent.
The sound was a bit anemic, but given new filter capacitors and cold amps that’s to be expected.
I need to raise the gain in the LF, so that means taking the FreeDSP classic to the windows PC to fix that in SigmaStudio.
Hopefully I’ll also get rid of the hum in the left HF, shouldn’t be a busted driver as I get music from it. It measures 8ohm (B&G Neo 8 ).
Now I need to rest lol.
My beloved dipole speakers are getting some TLC in the form of new caps in the crossover (mids/highs).
The highs are handled by the not unknown B&G Neo 8 magnetostats.
Mids are handled by Dayton Reference series aluminium drivers. RS180S-8
The new caps are JB JFX Premium series from hifi-collective
I etched the boards with the toner transfer method (it’s been years since I etched my own PCB’s, so excuse the quality).
I know, I need to dust off the crossover “box” and tidy up the wiring.
Inductors are 1.2mH Jantzen Cu foil and Intertechnik 2.4mH.
Wiring is 4*0.6mm 99.9999% silver in PTFE tubing.
After having dusted off the crossover “box” and fixed the wiring, I’ll glue the stand-offs to the lead-rubber (black in pics) with a very nice silicone adhesive I’ve found.
More to follow.
The first crossover board is etched and drilled and I have populated the MKP’s.
JB JFX Premium series from hifi-collective
The PCB is 10*15cm 70u Cu.
Caps are: 68uF, 20uF and 10uF.
I’ve been in too much pain to do any real DIY. I did collect the acousticly transparent fabric that I will stretch over a wooden “box” frame, think upside down box with cloth walls. I’ll fasten the fabric with a very strong spray glue. I do this to make the dipole speakers somewhat more child-proof, my daughter will start to crawl around any day. And then walking… And she’s very curious.
Not really a cheap solution though, with shipping the fabric and the glue came to about 900sek. Fortunately the wood for the frame will be alot cheaper to buy.
Not much else done over the last days. I did etch my first PCB in years, and using the toner transfer method.
It’s a PS for the enhanced chipamp.
I populated the softstart for the 2*tda7293/channel amp the other day.
I’ll clean up the internal wiring of that amp while I install the softstart. I’ll use sleeves for all wiring etc, not that it shows, but it feels better knowing it’s nice and tidy in there.
I started populating the second audio-widget PCB. Still waiting for the USB B PCB connectors though….
Sorry about the bad image quality, I didn’t use my DSLR but the Camera in my phone.
It’s time to move on from the modified Analog Metric DAC. Well it’s been for a while.
I have three populated Red Baron boards, one Pedja Rogic DDNF I/V board, a few jfet tube hybride output boards with passive I/V, some SM5814 boards, WM8805 boards, WM8804 boards, the audio-widget boards (though I am not sure they work with OS with NPC SM5814), and some other stuff I don’t remember atm. I’m currently on the way to get a follow up after my neck surgery, so I don’t have anything in front of me, but have to rely on my not so great memory lol.
This unfortunately means I don’t have any pics available to put in this post now either.
I’ll use one of the Red Baron boards for the headamp system, if I can get it to work with XMOS USB (or audio-widget) followed by an SM5814. The XMOS is capable of putting out SPDIF IIRC. So I could go XMOS – WM8805 – SM5814 – TDA1541A.
The other two Red Baron boards, I’ll either use two in parallel, summing the I-out before I/V. Or, if at all possibly, get them to work with some sort of DSP (preferably the FreeDSP classic as I have two of them) via I²S out. I don’t know if I can run them in slave mode, sort of a must to get them working with the FreeDSP.
As you can tell, this post is more or less me “thinking out loud” so to speak. Though any and all advice is appreciated 🙂
I tried “re-wiring” the outputs on the FreeDSP classic board, the board that worked well but for the total silence in the left channel mids/highs (passively x-overed).
The output I thought might be bad works now, but I still don’t get sound from the B&G Neo 8 that I use for HF.
I think Maybelline the old PIO’s in the x-over has passed their prime. I have some MKP’s on a way to replace them.
On top of that the amp driving the woofers had blown its main fuse. Mains are 230VAC here and the fuse was 1.6A slow blow. Granted, I don’t have any softstart in that amp, yet. I’m not sure if I should use a higher value fuse? 300VA toroid, each channel of the amp has two tda7293’s.
Going for a walk with the fiance and my daughter now, more to come.