I‘m pleased to see the price increase, though (payed 50-100€ per module once)
Guessing from my own 5 pieces: they all worked with a nice tone (as mentioned in the offer), but not a single one was without extended noise. Which was easily resolved by exchanging caps.
For regular DI use you shorten each 2nd input to reduce the noisefloor induced by the open channel.
Most important: these boxes absolutely need a load of about 50-300 Ohm, they don‘t work on regular line inputs without distortion. Sound does change with load, so you may try different resistors for best results.
The true magic appears with headphones connected, afaik my AKG K501 are 120 Ohm impedance, a perfect match.
(that‘s why I want to mod one for line input as a monitoring device)
On the pictures you see the 2 amplifier-balance modules in the middle, bottom (with the 4 big caps) is power condidtioning, top is the impedance conversion module. If you unplug the latter you have access to the line input poles.
Notice the different mounting orientation of the output transformers to reduce crosstalk.
Keep switching PSUs away from these units.
There‘s often an ultra low current 40-80V high frequency AC noise passing the PSU filter which may damage the semiconductors. I had a couple of such failures that fortunately self-healed within some hours or days.
It‘s quite tricky due to the omnipresence of such PSUs and the ability of the HF to creep across lines.
(that‘s my guess from experience with a small 24V switching PSU and the damage on my 2 V676a mic preamps)
Long story short: the offer is an invitation to a full DIY job - you could just get the modules yourself.
They are difficult to google because there‘s a small battery cell with the same V357 code.
ps: the N324 broadcast PSU (mentioned in the offer) is a 7pound monster, capable of 100W power delivery.
Probably the most sophisticated non-switching design ever created.
