My Niece's First Vinyl System

[Ray P]

I posted in the ads section here a few weeks back looking for a turntable to be the basis of a first vinyl system for my niece - nice uncle Ray!

Anyway, as a result Nigel (Vinylspinner) donated a Dual 505-2 and sold me an Arcam Alpha 2 amp and matching tuner for a great price.

I also acquired a pair of Morduant Short MS902 bookshelf speakers that were very cheap, fully functional and in excellent cosmetic condition, similar to these:

[Ray P]

I completely stripped down, cleaned and refurbished the Dual 505-2 and bought a replacement stylus and it's now working very well.

[Ray P]

With the turntable up and running I plugged the system together and 'hey presto' decent music, with the only issue being a low level crackle-like noise, the same in both channels, that cleaning pots and switches with Deoxit hasn't eradicated.

I reasoned that as the amplifier is close to 40yrs old the first thing to do was to replace all the electrolytic capacitors - I've done that using Elna and Nichicon types. I increased the voltage rating from 35V to at least 50V on some of them (the supply rails are at 33.9V) and I replaced the 6800uFfilter caps with 8200uF versions that I had to hand. I also replaced the rectifier diodes with ultrafast types that I found in the spares stash. The result of the recapping was an immediately obvious improvement in the sound quality, a much more open fluid and open sound - the system is starting to sound really very good considering the outlay so far is only around £150 (including the replacement stylus) - however, I still have the low level crackle!

[Ray P]

So, just this crackle noise to fix and my niece will be good to go!

I'm at a bit of a loss on how to resolve the noise as it is quite low level, doesn't change with the volume level and is the same in both channels. I've put a link to a recording of the noise below - it seems to have a timebase to it with a 'peak' around every second, so I'll appreciate any suggestions of where I should start looking. I''ve included schematics below too.

https://www.dropbox.com/scl/fi/1pco9q5u ... c3f7j&dl=0

Arcam Alpha 2 schematic - PSU and Power amp.jpg (119.02 KiB) Viewed 3893 times

Arcam Alpha 2 schematic - Phono and Preamp.jpg (100.51 KiB) Viewed 3893 times

[Morgan Jones]

OK, so it doesn't change with volume level, putting it after the volume control. And is the same in both channels, making it something common to both channels, which makes it power supply. But you've replaced the electrolytics, which would be the first suspects. I would suspect stuff around the mains going into the mains transformer. Specifically, dirty contacts within the mains switch, or dodgy 100n capacitor across the mains. Maybe even dirty contacts from fuseholder to mains fuse. If it's the mains switch and you can take it apart, a baby bud and Brasso will do nicely to clean the contacts. Forget switch cleaner - it will be corrosion, not dirt. Your niece doesn't know how lucky she is!

[Ray P]

Spot on about the mains, Morgan. I felt as though I was chasing ghosts and as I was about to pack up I thought, let's cheer myself up see how the system sounds in my listening room and, abracadabra, the amp is silent. It looks as though I have a bit of diagnosis on the mains to do. Oh, and, given the expenditure, it sounded delightful in the listening room and I think she's going to be a happy young lady, and very cool amongst her peers with the retro system.

[Mike H]

Excellent.

My observation is the noise sounds very regular.

[Ray P]

I gave it a good session today, mostly digital as I only have one LP (it's a good one though, Tori Amos, Little Earthquakes) and I'm really please with the sound quality that it delivers. I'll call this a successful project.

[Tony Moore]

Well done Ray! That looks like a very nice "starter vinyl" system.

[Mike H]

Excellent, congratulations. Still curious what the noise wa all about.

[Ray P]

Still curious what the noise wa all about.

I've not had time to investigate it yet, Mike, sometime over the coming weekend.

[Ray P]

Seems that unplugging a wifi extender get's rid of the mains noise - not a problem as I only use it to get a signal in the garage when I'm Zwifting on the static bike set-up.

In other news, yesterday I got her a first system upgrade - I bought a Thorens TD-150 on Ebay for just £75. The Thorens is in working order and looks to be in pretty good condition, but I'll strip it down and give it a complete service and I think it'll scrub up nicely and be a good improvement on the Dual 505-2 I'm starting her off with. Apart from the sound quality aspect, I think she'll love the retro look of it.

[Nick]

Might be worth checking the 100nf cap across the mains input in the amp (if replacing use an X2 or X1), and/or adding a more effective mains filter. Would suggest its going to be susceptible to mains interference.

[Ray P]

Might be worth checking the 100nf cap across the mains input in the amp (if replacing use an X2 or X1), and/or adding a more effective mains filter. Would suggest its going to be susceptible to mains interference.

Thanks Nick. I actually ordered a replacement cap over the weekend, though I am thinking there is something wrong with the wifi extender as the amp is silent on the upstairs ring and I don't get the same problem with a different wifi extender plugged in, so I'm inclined to buy a replacement for the noisy extender too.

[Greg]

In other news, yesterday I got her a first system upgrade - I bought a Thorens TD-150 on Ebay for just £75. The Thorens is in working order and looks to be in pretty good condition, but I'll strip it down and give it a complete service and I think it'll scrub up nicely and be a good improvement on the Dual 505-2 I'm starting her off with. Apart from the sound quality aspect, I think she'll love the retro look of it.

The user handbook and the service manual are on vinyl engine.

For now that may be all you need, but if you or your niece are interested in improving the sound quality over standard, there are several things you can do. I had a TD150 Mk2 for many years and applied these changes to it with very positive sound quality results.

I removed all the mechanical switch and arm lift mechanism, relying on hand cueing the arm and introducing an on/off switch for the power. At the time I had no requirement for 45 rpm and the belt sits naturally without the guide on the 33 rpm motor spindle position. These changes messed up the top plate appearance so I replaced it with better damped iron on veneer. I applied self adhesive bitumen sheet to the underside of the chassis and sub-chassis. To cope with the additional weight, I replaced the springs with stronger Linn LP12 ones (drop in replacement), in my day available foc from Linn dealers or of course now from eBay. I removed the foam from inside the springs. Finally, although the handbook states the bearing has self lubricated bushings with a nylon thrust plate which should not require attention, I found adding some lubrication beneficial. Thereafter more can be done but it involves constructing a new plinth and armboard which is probably, for now, a step too far. Hope the service goes well!