Hi @amirm. I recently took the time to rewatch your excellent video on Understanding FFT in Audio Measurements. Wishing to put some learning in to practice and just out of curiosity I'm using my somewhat cheaper QA401 to test an old Cambridge Audio DacMagic to see how it compares to this...
It was the first cassette deck I’d tested and was surprised at the relationship and interaction between recording level, frequency response and distortion.
When I recently repaired and serviced a three head Sony TC-K611S cassette deck I kept a few measurements.
L/R Phase is set by adjusting head azimuth. This is what the manual says is in spec (btw the Rigol MSO5000 scope does fuzzy XY). If the azimuth is out then L and R will not be in phase. I...
No, the ZTX653/753 are clipped on separate strips of heatsink - can be seen in the pic above and below the main reservoir caps. There are 9 transistors mounted so I presume in addition to the drivers, one is the bias spreader and the other the VAS. From what I can see there doesn't appear to...
You're right @restorer-john piddly arsed heatsink. However on closer inspection it looks the aluminium flag heatsinks are actually screwed in with some sort of self-tapper / captive nut arrangement - I'll have a better look once I've got the pcb out.
On a positive note, they have segregated...
Next project... service this Linn Intek amp that I've owned from new since ~1990. Nicely made kit. All Rubycon caps. It has a slight power on thump on the left channel and higher measured DC offset on that channel (15.4mV vs. 1.9mV).
@LTig Thats a good call as it would be easy to design replacement phono boards as the current pair are vertically mounted daughter boards. I'll have a listen to see how it sounds before deciding if it's worth the effort as I don't intend to keep it.
On the bench.... just about finished the repair and refurbishment of a 1980 NAD 3030 "New Acoustic Dimension Stereophonic Amplifier" (!)
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Main problem was the 2N3055/MJ2955 output transistors as distortion in the right channel prematurely increased with power output, albeit within OEM spec...
On the bench right now is a 1979 Rotel RX-300 receiver.
Classic problem: blown rectifier diode due to faulty electrolytic(s). Got it working and halfway through a recap this afternoon. Sounds ok. I'll give it an alignment next, even though the FM receiver seems sensitive enough as is.
I've...