Will do Mooly and - as always - many thanks for all your time/help. Very much appreciated indeed
Quick question about the 47uF caps, C205/255 which you mentioned were well and truly in the signal a while back. Would it be OK to use a 68uF film cap for these two positions? I just happen to have a pair here, and after the success of replacing all those 'back-to-back electro/film bypass' combinations in the signal path with just a single film cap I'd like to get rid of those two electrolytics too
Lastly, I'm thinking I'll need to do something to attenuate my CD source with this amp. The Aux1/Aux2/Tape1/2 inputs are 150mV sensitivity & 50K impedence. I don't really want to muck about with changing all the inputs, so I guess I could build a potential divider behind the Aux1 phono sockets? How would I work out suitable resistor values to achieve a better match between source and pre-amp? Ta!
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Just found this thread:
http://www.diyaudio.com/forums/parts/73634-inline-attenuator-help.html
Think the -15.6db attenuation (post #2) should do fine for the Aux1 input on my amp.
http://www.diyaudio.com/forums/parts/73634-inline-attenuator-help.html
Think the -15.6db attenuation (post #2) should do fine for the Aux1 input on my amp.
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If a 68uf will physically fit it will be fine.
Attenuators... very much trial and error believe it or not, at least in order to get the setting just right. It's what feels right as you listen and turn the volume control. 2 volts rms from CD vs "150 mv" that was common back in 70's is a difference of 22db. However CD is fixed to the 2v rms maximum, it can never exceed that level.
CD is a 16 bit technology. 16 bits gives 65536 separate possible combinations. Players are designed (the "unnofficial" standard) that the 65536th level, which is maximum, equates to around 2 volts RMS (2.8v peak). That value can never be exceeded in playback. In practice the program material is well below that level to allow for the loudest peaks that come along... assuming a good recording that isn't compressed
With old sources such as cassette/reel to reel etc that absolute limit doesn't apply and it was acceptable to allow peaks to go well over the nominal "max" 0db level. If you didn't then the quieter parts would be buried in the noise.
So what all this means is that although the numbers can appear to be calculated out exactly (and they can), in practice it often won't give the desired "feel" to the volume control range.
The answer is to rig up a 10k or 22k pot (or presets) and find the setting that works best for you. Then just measure the resitances and substitute fixed resistors.
Attenuators... very much trial and error believe it or not, at least in order to get the setting just right. It's what feels right as you listen and turn the volume control. 2 volts rms from CD vs "150 mv" that was common back in 70's is a difference of 22db. However CD is fixed to the 2v rms maximum, it can never exceed that level.
CD is a 16 bit technology. 16 bits gives 65536 separate possible combinations. Players are designed (the "unnofficial" standard) that the 65536th level, which is maximum, equates to around 2 volts RMS (2.8v peak). That value can never be exceeded in playback. In practice the program material is well below that level to allow for the loudest peaks that come along... assuming a good recording that isn't compressed
With old sources such as cassette/reel to reel etc that absolute limit doesn't apply and it was acceptable to allow peaks to go well over the nominal "max" 0db level. If you didn't then the quieter parts would be buried in the noise.
So what all this means is that although the numbers can appear to be calculated out exactly (and they can), in practice it often won't give the desired "feel" to the volume control range.
The answer is to rig up a 10k or 22k pot (or presets) and find the setting that works best for you. Then just measure the resitances and substitute fixed resistors.
Thanks Mooly - managed to find a couple of 47uF MMX film caps (which the Naim guys rave about when used in the feedback positions) in the parts box so used those. I don't know if it's placebo or not but they seem to have had a very positive effect on the sound. Lovely well balanced sound now which seems to handle all facets of the frequency range equally. Lovely and grain free on vocals too - like a very good valve amp in fact. I think getting rid of all the obvious electrolytics in the signal path in the control & EQ sections has really paid off handsomely, even though it was a bit of a pain to do. I'll get some pictures up later should anyone else fancy doing the same to their amp.
Thanks for the explanation regarding CDs playback levels - all makes a bit more sense now I'll see if I have some spare pots. Apologies for yet another 'newbie' type question, but how would I wire this up to the phono socket(s) to test? Would I still need a second resistor to create the 'L' pad?
The amp is sounding so good now - can scarcely believe the design is pushing 32+ years old!
Thanks for the explanation regarding CDs playback levels - all makes a bit more sense now
I'll see if I have some spare pots. Apologies for yet another 'newbie' type question, but how would I wire this up to the phono socket(s) to test? Would I still need a second resistor to create the 'L' pad?The amp is sounding so good now - can scarcely believe the design is pushing 32+ years old!
Easiest way to experiment is perhaps to use an old phono lead. Just cut it in half and wire the preset pot across the half that goes to the CD player. The other half goes to the amp with the centre lead conected to the wiper of the preset and the grounds of the two halves connected together... like this
Once you have it set right just measure the resistances and pick the nearest values
Once you have it set right just measure the resistances and pick the nearest values
Attachments
Hi John, to alter the input sensitivity you either have to use an attenuator as outlined or alter the actual gain of the preamp section of the Sony. If you did the latter then the "sensitivity" of the phono stage would be altered too, because that feeds into the main preamp... you would be reducing the gain that much the phono stage wouldn't drive the amp to anything like normal levels. It would also have to be done with a scope and generator to ensure the opamp was correctly compensated with running at a lower gain... it alters the whole character of the amp really.
I feel a simple resistive divider really is the best solution, the "cutting a phono lead" enable you to get the values exactly how you want, then just fit them to the input socket you use for CD etc. The noise contribution of the attenuator is half of a quarter of nothing when you compare it to the noise of the Sony.
I feel a simple resistive divider really is the best solution, the "cutting a phono lead" enable you to get the values exactly how you want, then just fit them to the input socket you use for CD etc. The noise contribution of the attenuator is half of a quarter of nothing
when you compare it to the noise of the Sony.
Hey Mooly - sorry I haven't given any updates on this after your helpful suggestions. To be honest I am having a very hard time dragging myself away form listening to it - sounds so good now! It was good before but after recapping it it's just on another level altogether.
The only problem thus far is a VERY slight balance to the right-hand speaker. This may well have been there before the re-cap but it's just more obvious now. I only noticed this when using headphones. Even then I wasn't sure and had to use the mono button on the amp to make sure and everything then snapped into the middle perfectly. Using the reverse L+R the sound the stereo was then slightly favoring the left channel. Must try another source to see if it's unique to that one input or not.
- John
The only problem thus far is a VERY slight balance to the right-hand speaker. This may well have been there before the re-cap but it's just more obvious now. I only noticed this when using headphones. Even then I wasn't sure and had to use the mono button on the amp to make sure and everything then snapped into the middle perfectly. Using the reverse L+R the sound the stereo was then slightly favoring the left channel. Must try another source to see if it's unique to that one input or not.
- John
Another job for a scope and generator
There can be many reasons for that effect. Seems like its not room (or ears lol) related if its the same yet correctable with headphones by switching to mono.
You can do a simple test. You need a test CD with test tones on it that are within the measurable frequency range of your meter. Most meters will be OK with up to 400hz or so.
Just play the tone starting at low volume (you don't need speakers connected as you say the effect is present on H/phones... suggesting loading isn't an issue) and measure the AC voltage at the speaker output as you turn the volume up. Output should be the same for both channels of course with fairly close limits. See what that shows.
Even if the meter were inaccurate at higher frequencies, say up to 10khz or more, as long as it showed a useful reading it would still be possible to compare left and right as the meter inaccuracy would be consistent and you are just comparing one output with the other.
Slightly more obscure could be that the inter channel separation or crosstalk (strange to say this is a topic I was considering starting anyway) might not be consistent left to right and right to left over the frequency range and so giving this imbalance effect.
There can be many reasons for that effect. Seems like its not room (or ears lol) related if its the same yet correctable with headphones by switching to mono.
You can do a simple test. You need a test CD with test tones on it that are within the measurable frequency range of your meter. Most meters will be OK with up to 400hz or so.
Just play the tone starting at low volume (you don't need speakers connected as you say the effect is present on H/phones... suggesting loading isn't an issue) and measure the AC voltage at the speaker output as you turn the volume up. Output should be the same for both channels of course with fairly close limits. See what that shows.
Even if the meter were inaccurate at higher frequencies, say up to 10khz or more, as long as it showed a useful reading it would still be possible to compare left and right as the meter inaccuracy would be consistent and you are just comparing one output with the other.
Slightly more obscure could be that the inter channel separation or crosstalk (strange to say this is a topic I was considering starting anyway) might not be consistent left to right and right to left over the frequency range and so giving this imbalance effect.
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Thanks for that Mooly - I'll try and get hold of some test tones from the internet somewhere and burn those onto a CD.
Bizarrely, the channel balance sounds OK through the speakers (though the layout of my room isn't symmetrical so the channels could still be unbalanced in absolute terms). I would therefore point the finger of blame at the headphone output, but if that were the case surely one channel would still be louder with phones when switching to mono, and this isn't the case.
I think I'm getting to the point now where I may have to get someone to look at it for me - even though it's a minor niggle. I'm getting tired of taking the lid of this thing
Bizarrely, the channel balance sounds OK through the speakers (though the layout of my room isn't symmetrical so the channels could still be unbalanced in absolute terms). I would therefore point the finger of blame at the headphone output, but if that were the case surely one channel would still be louder with phones when switching to mono, and this isn't the case.
I think I'm getting to the point now where I may have to get someone to look at it for me - even though it's a minor niggle. I'm getting tired of taking the lid of this thing
Hi again Mooly!
Had other things going on, but I need to get back to sorting out those resistors for better matching the output transistors to the circuit. Rather than having to repeatedly solder on various values of resistor to the underside of the PCB (and thereby run the risk of lifting a track) would it be an idea to solder in a socket which would allow me to just quickly fit resistors in place for testing? Reckon this would be so much simpler than having to keep flipping the whole power-amp section over onto its side to fit different value resistors.
I know you can get turned sockets for op-amps and the like, but can one purchase individual pins? Something like that would be ideal for quick changing of resistors in the output stage.
Thanks,
- John
Had other things going on, but I need to get back to sorting out those resistors for better matching the output transistors to the circuit. Rather than having to repeatedly solder on various values of resistor to the underside of the PCB (and thereby run the risk of lifting a track) would it be an idea to solder in a socket which would allow me to just quickly fit resistors in place for testing? Reckon this would be so much simpler than having to keep flipping the whole power-amp section over onto its side to fit different value resistors.
I know you can get turned sockets for op-amps and the like, but can one purchase individual pins? Something like that would be ideal for quick changing of resistors in the output stage.
Thanks,
- John
Yeah you can get turned pin single in-line sockets which you can cut as needed. See for example Rapid Electronics - Cables & Connectors
Hi John... I still watching
Pleased it's all working OK
Thanks Mooly
Hopefully I'll get around to try out different resistor values in the outputs within the next few weeks.
- John
Hi John, Mooly, Jaycee and everyone else who contributed to this subject, I've just sat and read all 54 pages tonight! Fantastic team work from some seriously skilled, knowledgeable techs.
I'm just starting out recapping amps (Quad 405s, 303s etc) and fault finding after tinkering with hifi for years and years.
I was bought a 2nd had Sony TA-F60 Sony TA-F60 on thevintageknob.org when I was 12 (I'm 40 now!) as a Christmas present, the power supply failed and was repaired and failed (twice) by a local tech, I was ever so fond of it so bought another when it came up for sale locally, it failed 1 week after buying it! The private seller admitted it had just been repaired and actually sent it back to be repaired again, it lasted a few months this time! My dream is to gain enough knowledge to tackle these amps, hopefully get one going reliably, fingers crossed!
I use a Luxman LX33 integrated valve amp as as my main hifi amp but have a system for music production and it would be wonderful to see the vu leds of the TA-F60 working again while I play!!
Anyway I'm rambling, I definitely learnt a lot reading these posts and you've spurred me on to get the Sonys out the loft and at least try to assess them.
Thanks ever so much
Paul
I'm just starting out recapping amps (Quad 405s, 303s etc) and fault finding after tinkering with hifi for years and years.
I was bought a 2nd had Sony TA-F60 Sony TA-F60 on thevintageknob.org when I was 12 (I'm 40 now!) as a Christmas present, the power supply failed and was repaired and failed (twice) by a local tech, I was ever so fond of it so bought another when it came up for sale locally, it failed 1 week after buying it! The private seller admitted it had just been repaired and actually sent it back to be repaired again, it lasted a few months this time! My dream is to gain enough knowledge to tackle these amps, hopefully get one going reliably, fingers crossed!
I use a Luxman LX33 integrated valve amp as as my main hifi amp but have a system for music production and it would be wonderful to see the vu leds of the TA-F60 working again while I play!!
Anyway I'm rambling, I definitely learnt a lot reading these posts and you've spurred me on to get the Sonys out the loft and at least try to assess them.
Thanks ever so much
Paul