Another AU-919

OK MULTIMODE,....Let us know when you get your amp back. We want to know what you think. I want to know how the MC section works out.
 
Hi ghamilton, Multimode collected his amp this afternoon, but not before a 2 hour session playing his favourite music, and some of mine too, we had a great time!

We couldn't check the MC input as I don't own an MC cartridge, I am sure Multimode - David, will tell us all about it when he gets it set up again.

Also, I forgot to thank you for leading me to those WIMA capacitors you liked in your MC Head Amp, my apologies.
 
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I certainly enjoyed the afternoon, and I'm glad John did too. Some 'domestic' tasks needed my attention when I arrived home, so setting up the system had to wait awhile. :(

I connected the AU-919 to the turntable and speakers 15 or 20 minutes ago. As I write I'm listening to Peter Skellern's LP 'Astaire' via the modified Moving Coil input...and it's wonderful! :D

The signal-to-noise ratio is spot-on with the new resistor values, and the volume control set between the 9 o'clock and 1 o'clock positions gives the range of volume I want from the speakers. Perfect!

The MC mod, the glue removal, the 'new improved' components, and the correction of original build errors (notably Sansui's omission of a resistor in the MM stage) have come together to make the amp surely better than new. John is absolutely a master craftsman! :thumbsup:

I'll report further when I've found the time to do some back-to-back comparisons between the MC and MM+SUT inputs. That may need to be next week.
 
I certainly enjoyed the afternoon, and I'm glad John did too. Some 'domestic' tasks needed my attention when I arrived home, so setting up the system had to wait awhile. :(

I connected the AU-919 to the turntable and speakers 15 or 20 minutes ago. As I write I'm listening to Peter Skellern's LP 'Astaire' via the modified Moving Coil input...and it's wonderful! :D

The signal-to-noise ratio is spot-on with the new resistor values, and the volume control set between the 9 o'clock and 1 o'clock positions gives the range of volume I want from the speakers. Perfect!

The MC mod, the glue removal, the 'new improved' components, and the correction of original build errors (notably Sansui's omission of a resistor in the MM stage) have come together to make the amp surely better than new. John is absolutely a master craftsman! :thumbsup:

I'll report further when I've found the time to do some back-to-back comparisons between the MC and MM+SUT inputs. That may need to be next week.
That's great. Can't wait to hear more about this.
 
As another thumbs up for those Wima caps, just finished another 717 this morning using them for the phono eq board for the low uf values. Really wakes up the phono stage. Here she is with one of my Denon tables giving a spin with the Eagles. Sansui gear is da bomb to work on :)
Sansui AU717.jpg
 
I have yet to conduct meaningful back-to-back tests between Moving Coil and Moving Magnet + Step-Up Transformer input into my amplifier. First I want to make sure everything along the way is on top form, especially the cartridge & arm settings and the fluid level and viscosity in the damper (SME 3009 Series 111 arm).

For now, I'll just repeat what I told John in a Conversation after listening through the refurbished AU-919:
"The amplifier is exceeding my greatest expectations. I'm hearing a much better quality of sound than I can ever recall, possibly even from when it was new. I'm not just satisfied with the renovation, I'm absolutely delighted with it! :D"
 
I'm now ready to write my report... and it's going to be a long one, so draw up a chair and have a beer or two to hand. ;)

I left a new phial of SME FD2013 fluid to dribble into the cleaned damper overnight, and then spent this morning going through every setting of the Series III arm for the first time since I installed it in June 1979! All settings were found to be precisely to SME specs other than the bias compensation which was lower than their Instructions advised. Co-incidentally, Hyperion told me yesterday that it had been recommended by a "reliable" AK member to set the compensation on the Series III arm to around half the figure specified by SME as they'd got it too high. I can now confirm that finding.

My next step was to put on Hi-Fi Sound test record HFS75 and test everything that it covers other than Wow & Flutter (they are measured by metering rather than listening). I tried reducing the cartridge tracking from its existing 1.75 gram to 1.5 grams (the range for the Signet MKIII is 1 - 2 gram) but decided that 1.75 gave just very slightly better results on a particularly difficult track of the test record (almost certainly no difference at all in most real-life listening).

Using the 'Determination of Tracking Pressure and Bias Correction' tracks on the test record, the changes I made to tracking pressure were each accompanied by experiments with bias correction, and I concluded that the ideal for the 1.75 gram tracking that I'm staying with was SME's 1.0 setting (this being the bias correction position on the arm intended to accompany a 1 gram tracking pressure). I'd had the bias correction set at the 1.2 position for almost 38 years and forgotten about it until now, however I recall arriving at it in conjunction with that very same HFS75 test record. The differences between the 1.0 and 1.2 positions were infinitely small, but 1.0 seemed a tiny bit better for the difficult inner track (see below), so that's where it is now set.

There are three tracking pressure/bias correction test positions on the record - for outer, centre and inner groove positions. The outer position carries three bands which are progressively more difficult to track. Bands A and B were handled easily, whilst the 'super high level' Band C was also handled but with some protest (the test record sleeve carries a warning that "Band C should be attempted only with the very finest cartridges and arms... and can cause amplifier input overload". The centre test position on the record has a single track, which was handled with ease. The inner position also has a single track, and this was handled adequately but not with the absolute smoothness of the centre band and the outer bands A & B.

At last I could get to the MC versus MM+SUT back-to-back tests.

First I played the opening to Mike Oldfield's 'Tubular Bells' - over and over again, swapping inputs and MC/MM selector, levelling the volume as quickly as I could, and then listening. No conclusion reached. I moved onto other genres, including Direct Cut jazz, classical with and without singing, and easy listening. Finally, and appropriately, I played several tracks from the treasured 'This is the Sansui Sound' LP that came with the amplifier.

There wasn't much at all to choose between the two input modes. Some tracks seemed better in one mode at low volume but in the other at high volume, and the genre of the music (smooth or not so smooth) also seemed to affect the results. Both modes were surprisingly close to each other, even the output volumes were almost identical at the same position of the control. Decisions, decisions!

I eventually decided that feeding the MM input via the step-up transformer was the winner, but only by a nose. The main reason for this choice is that the attack was more realistic when playing high volume, high impact, jazz and orchestral pieces (like the cannons in Tchaikovsky's '1812 Overture'). Putting it another way, the MM+SUT combination gave a better representation of what the AU-919 is about. But only just!

Huge thanks are due to John (Hyperion) for making the comparison possible, and I hope he's not disappointed that I won't be using the modification that he put thought and effort into.
 
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Not disappointed at all, I just made it possible for you to make a proper comparison, without which we never would have known. :thumbsup:
 
Oh well,...Close,...But no cigar. That old signet just don't like the MC in the 919. My low output Grado matches very well.
 
Thanks, John. :)

The Signet does like the MC input, Mr Hamilton, but just not quite as much as it likes its half-sister the transformer! :p ;)

After my above 'report', I played a couple more records through both inputs. It really is the closest call, but I believe I've gone the right way. I've now been thinking about the reasoning behind the difference:

The Signet MKIII cartridge and the Signet MK10T transformer were normally sold together, they even share the same user manual, and when they were current they were reviewed together. Since they were developed as a unit in effect, they are probably best left to work together.

I suspect that other Moving Coil cartridges might work better with the modified MC input than through a transformer or head amp into the MM input. For example, the Audio Technica AT-OC9/II and /III moving coil cartridges don't come with a transformer, and they need to see an impedance of at least 100 ohms. I'd be looking at the excellent AT-OC9/II if needing a new cartridge (the OC9/II is preferable to the newer OC9/III as that seems to have suffered a little from cost reduction).
 
I've continued to experiment with, and enjoy, music played through the restored (improved!) AU-919.

Amongst the several LPs that I played last night was Pink Floyd's 'Dark Side of the Moon' album. The 'sound effects' from this were so realistic that closing my eyes had me sitting in the front row at a live performance. Earlier, I'd played some Dire Straits with enjoyment. I'd drifted away from 'prog rock' many years ago, but I'm now drawing towards it again (albeit in small doses).

The sound stage since the 919 was restored is better presented than I can recall from any time in the past. I listened to a record of a Hammond organ accompanied by guitar to my left and drums to my right (Jimmy Smith's 'Organ Grinder's Swing') and though the record is very familiar to me I'd never before noticed the complete separation and precise placing of the instruments, even down to the individual items in the drum kit.

I'm also more than content with my old Spendor BC1 speakers after flirting with the idea of upgrading. It's too easy to always want 'something better' but I can't now distinguish any aspect of the Spendors that needs improving for me. Comments are sometimes read about weaknesses in the bass, but it is fine when the speakers are driven under the very positive control of the AU-919 - much better than I experienced with some other top-line amplifiers in trials 'back when'.

I said in my Introduction to AK that I'd rediscovered hi-fi after losing interest several years ago. I can now confirm that I've returned with a vengeance, thanks to AK and Hyperion! :biggrin:
 
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