Revox A77 head mounting - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Ted Kendall · 30th Dec 2017, 10:29 am

Good show! That fault with the backplane sounds an absolute

As you have found, properly set up, the difference in quality betwen half and quarter track is small. The signal-to-noise ratio is 3dB worse because of the halved track width, and dropouts due to coating faults or tape damage will be more frequent. And, occasional problems with LF crosstalk aside, that's about it.

monaro0162 · 31st Dec 2017, 4:03 pm

Thanks Ted,

When I do an audacity trace on the MK3, the comparison will be between new 4-track heads, and the used 2-track heads, which have about 3mm of wear. I also have a trace of the other 2-track A77 that I have (a MK4) which has visibly less head wear, may be 1.5 to 2.0mm. Audacity is a great tool I'll be looking at the HF roll-off curves in detail.

As a less critical test, for a bit of fun, I am going to set up both the 2 track and the 4 track units to make recordings of the new years eve celebrations broadcast on BBC Radio 2 and BBC 6music. For Radio 2, the source will be an A76 tuner that I've had for a while, but not used much, due to lack of a decent aeiral. I installed a new loft aeiral yesterday and the reception and sound from the A76 is excellent.

The third machine I have (another 2-track) will be used to record the same broadcast, but the source will be 320kb/s AAC via a Roberts Stream 93i internet radio. (yes, digital, I know..)

It will be interesting to see if I can tell any difference between the recordings during a blind test when my wife will be switching the sources.

Its been a very busy year for me, both with work and this hobby. Its my birthday today - happy new year to you all

30th Dec 2017, 10:29 am	#21
Ted Kendall Dekatron Join Date: Jul 2008 Location: Kington, Herefordshire, UK. Posts: 3,671	Re: Revox A77 head mounting Good show! That fault with the backplane sounds an absolute As you have found, properly set up, the difference in quality betwen half and quarter track is small. The signal-to-noise ratio is 3dB worse because of the halved track width, and dropouts due to coating faults or tape damage will be more frequent. And, occasional problems with LF crosstalk aside, that's about it.

31st Dec 2017, 4:03 pm	#22
monaro0162 Pentode Join Date: Sep 2016 Location: Stansted, Essex, UK. Posts: 185	Re: Revox A77 head mounting Thanks Ted, When I do an audacity trace on the MK3, the comparison will be between new 4-track heads, and the used 2-track heads, which have about 3mm of wear. I also have a trace of the other 2-track A77 that I have (a MK4) which has visibly less head wear, may be 1.5 to 2.0mm. Audacity is a great tool I'll be looking at the HF roll-off curves in detail. As a less critical test, for a bit of fun, I am going to set up both the 2 track and the 4 track units to make recordings of the new years eve celebrations broadcast on BBC Radio 2 and BBC 6music. For Radio 2, the source will be an A76 tuner that I've had for a while, but not used much, due to lack of a decent aeiral. I installed a new loft aeiral yesterday and the reception and sound from the A76 is excellent. The third machine I have (another 2-track) will be used to record the same broadcast, but the source will be 320kb/s AAC via a Roberts Stream 93i internet radio. (yes, digital, I know..) It will be interesting to see if I can tell any difference between the recordings during a blind test when my wife will be switching the sources. Its been a very busy year for me, both with work and this hobby. Its my birthday today - happy new year to you all