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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 26th Aug 2017, 10:15 am   #1
alfabarry
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Default Sony TC-95A Quiet Line Out

Must stress I am a novice in these matters - I can change belts and apply switch cleaner and that's about it - and pose this to see if it's something capable of being rectified, rather than a design feature:

I have one of these '73/4 Sony "cassette corders" that appears to have had minimal use and functions brilliantly: i.e., plays at what sounds like the right speed, rewinds and ffwds at speed, gives clear and loud sound reproduction using the onboard speaker. Also records perfectly and has functioning tape counter and levels meter.

The only fly in the ointment (other than the inevitably absent bespoke power cord) is that when I use the "monitor" socket to output to my DIN-equipped radio, the volume is far too low. If I turn the TC95A to maximum volume, and the radio (any radio) likewise, I get an output that is just slightly too quiet for comfortable listening. I've used isopropyl on the volume and tone controls and cleaned the monitor socket using an interdental brush and isopropyl. To no avail - they were already crackle free anyway.

There is nothing wrong with the quality: sounds great. just too quiet. I think it should do better because I also have two TC-95s (one year older, a bit more basic and with assorted deficiencies) and these both output strong volume to my radios... in fact with both I have to keep the Sony volume at about half so that I get manageable volume control on the radio... they are that loud.

You may have gathered that I have an irrational emotional attachment to the TC-95 series!

Any thoughts?
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Old 26th Aug 2017, 10:57 am   #2
Ted Kendall
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Default Re: Sony TC-95A Quiet Line Out

Could be a simple mismatch, depending on the impedances involved. What is the radio?
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Old 26th Aug 2017, 3:39 pm   #3
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Default Re: Sony TC-95A Quiet Line Out

The radio I use most often is an ITT Schaub Lorenz Touring International 103. I have also tried all three TC95x with three ITT KB sets: a Weekend, a Golf Preset and a Touring International Marine.

All four radios give the same results: really loud with the two TC95s, but quiet with the TC95A.
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Old 26th Aug 2017, 6:55 pm   #4
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Default Re: Sony TC-95A Quiet Line Out

I couldn't come up with a circuit diagram or manual either.

What is the 'monitor' socket type. Is it a 5 pin din or something else ?
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Old 26th Aug 2017, 7:37 pm   #5
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Default Re: Sony TC-95A Quiet Line Out

If it's push pull transformer output then sometimes there's a resistor in series with the monitor output as shown in a typical schematic below, might be worth checking out:

http://sportsbil.com/sony/TC/TC-100.pdf

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Old 26th Aug 2017, 8:15 pm   #6
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Default Re: Sony TC-95A Quiet Line Out

Quote:
Originally Posted by Mooly View Post
What is the 'monitor' socket type. Is it a 5 pin din or something else ?
It takes a 3.5mm jack, so I use a 3.5 jack to 5pin din lead (since the radios take 5 pin din).

Thanks for your suggestion and for the TC100 schematic, Lawrence. Have attached that for the TC95a.
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Old 26th Aug 2017, 8:35 pm   #7
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Default Re: Sony TC-95A Quiet Line Out

This spec gives an input sensitivity of 60mV.
If the output is designed to match, it will indeed be somewhat low for many other devices, which typically expect 400mV or so.
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Old 26th Aug 2017, 8:44 pm   #8
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Default Re: Sony TC-95A Quiet Line Out

The output level will be a lot higher...

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Old 26th Aug 2017, 9:02 pm   #9
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Default Re: Sony TC-95A Quiet Line Out

It looks as though "monitor" is an earphone socket wired to cut off the speaker when the plug is inserted. There certainly should be plenty of "oomph" available. If it works properly with the same lead and amplifier fed from a different recorder, the most probable explanation is the 3.5mm. plug not making proper contact in the socket. Try wiggling the plug gently in the socket, and pulling it out and pushing it in a little.
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Old 27th Aug 2017, 6:37 am   #10
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Default Re: Sony TC-95A Quiet Line Out

I noticed that the sleeve of that monitor socket is not directly connected to ground, there's a resistor and capacitor there. This was a common trick to reduce the signal level to an earphone (by having that network in series with it) while still being able to use the break contact on the socket to disconnect the speaker. I suppose it's possible (although unlikely) that there's a problem there.

Does this recorder play correctly through its internal speaker? If not, the problem is likely to be 'further back', in the recorder's amplifier.

This is, of course, a mono jack socket (2 contacts, tip and sleeve). Using a modern stereo plug there may cause problems.
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Old 27th Aug 2017, 7:55 am   #11
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Default Re: Sony TC-95A Quiet Line Out

Quote:
Originally Posted by alfabarry View Post
Quote:
Originally Posted by Mooly View Post
I couldn't come up with a circuit diagram or manual either.

What is the 'monitor' socket type. Is it a 5 pin din or something else ?
It takes a 3.5mm jack, so I use a 3.5 jack to 5pin din lead (since the radios take 5 pin din).

Thanks for your suggestion and for the TC100 schematic, Lawrence. Have attached that for the TC95a.
Interesting, thanks. I asked because having seen the circuit, 'monitor' is simply another speaker feed.

As Tony says, there appears to be a 150 ohm in series with the monitor feed but that in itself should have little effect if you are connecting a hign impedance DIN input across this.

You say the TC95 and the TC95A that you have all play correctly on their built in speakers.

It might be worth checking that the TC95 uses the same 8 ohm speaker such as shown here and not a 16 ohm. Although that wouldn't help with the issue, it would be a plausible reason for the lack of voltage from this version.

You should also check that the connection to the din lead is good i.e. measure resistively that the din plug pins really do go to the appropriate points on the TC95 and that there is no hidden high resistivity getting in the way somewhere.

If in doubt then try connecting the DIN lead direct across the speaker without going through the socket and assumed 150 ohm.
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Old 27th Aug 2017, 8:08 am   #12
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Default Re: Sony TC-95A Quiet Line Out

Thanks Julie, Tony, Mooly.

I had a play with my 3.5mm to din leads: I had already noted that one of the these was clearly too short (visibly so) and produced quiet output from all three Sonys. However the other two work perfectly with the TC-95s, but not with the 95A. I've tried jiggling them about but there was no effect - I'd expected some extra noise at least but playback remained solid (and low) unless I retract.

Tony's point about a deliberate reduction in signal level to an earphone chimes with a thought I had that this was a design feature rather than a fault, i.e., to protect earphone wearers - and a feature possibly not found on the earlier 95 ?

In the light of Julie's remarks I've been ferreting around for other 3.5mm jack leads and I have found one that gives noticeably louder output than all the others: but it's still way below that of the 95s and still requires max volume on player and near max on the radio to get an acceptable level. Still this suggests that the plug itself might indeed be part of the issue and that what I really need is a vintage 70s jack to din. But why only with the 95A and not the (older) 95s?

I have throughout struggled to understand why this 95A is so different from the visually near identical TC95s upon which it was based... which all deliver loads of volume with all but one of my modern 3.5mm plugs.

Mooly, I attach the 95's schematic for comparison alongside that of the 95A posted earlier.
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Old 27th Aug 2017, 8:38 am   #13
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Default Re: Sony TC-95A Quiet Line Out

The TC95 seems to show an 8 ohm speaker as well. Not that then.

If you have found a lead that gives different levels to all the others then that suggests that something really is different.

You need to measure these leads on a multimeter and make sure that there is no internal resistance. Some leads might have deliberate attenuation added internally at the plug.

If you get an old DIN lead, chop off one end and connect the relevant wires directly across the speaker then you should get your full output. That has to be the starting point if you haven't got other test equipment such as an oscilloscope which would allow you to observe signal amplitudes.
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Old 27th Aug 2017, 8:46 am   #14
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Default Re: Sony TC-95A Quiet Line Out

You could also do the high tech test of just sticking a pair of wires into the radios din socket (correct pins of course) and connecting that pair of wires to the speaker. Perhaps just add a low value resistor (anything from 10 ohm to 1k) in series to protect the TC95 from an inadvertent short.
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Old 27th Aug 2017, 9:38 am   #15
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Default Re: Sony TC-95A Quiet Line Out

There may be a resistor in the dIN plug of "quiet"lead
The monitor socket is for an earphone not line out.
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Old 27th Aug 2017, 9:39 pm   #16
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Default Re: Sony TC-95A Quiet Line Out

Thanks to everyone for their contributions.

In the light of Mooly's idea that the DIN leads might have deliberate attenuation added internally at the plug, I've been experimenting with 3.5mm to 3.5mm output from the TC-95A's "monitor" socket.

Using as receiving machines a JVC micro hifi and one of the TC-95s, I find absolutely no sign of any volume deficit. Cassette to Cassette copying using the 95A monitor socket to the aux socket on one of the 95s is flawless. Listening to the 95A via the JVC is also fine - volume levels are broadly similar to playing a cd on the same system.

So this would seem to be a DIN plug issue. What I don't understand though is why, if a DIN plug has added attenuation, would it not impact output from all the players? Although they deliver differing levels when passing output from the TC-95A, there is little or no difference between the leads when outputting from the TC-95s.

I dug out yet another 3.5 jack to DIN... a cheap and cheerful Kenable I think... and hey presto, the 95A has now moved to about 50% of the volume offered by the 95s. This is quite liveable with... I get decent volume with the 95A set at about 75% of max and the radio at 50%.

So I've now tried 4 different DIN plugs passing TC-95a output to the ITT radios. And i get three different performances: two are just far too quiet, period. One is significantly better but still a bit too quiet, and one is OK-ish (but still needing higher volume settings than with the TC-95).

However, connected to a TC-95, there are negligible differences in output between any of these four DINs... all four are capable of delivering sound to the radios with masses of volume in hand. Looks like with the right DIN, or using a radio with a 3.5mm jack input rather than DIN, the "monitor" socket works OK as a line out. But this still strikes me as bizarre given the TC-95's cheerful outputting of loads of sound via all these DIN plugs.
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Old 27th Aug 2017, 11:24 pm   #17
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Default Re: Sony TC-95A Quiet Line Out

There are two different ways for a 5-pin DIN socket to be wired, depending whether it is being used as an input or an output and whether it is on an amplifier or a source device. Earth is always pin 2, but the signal might be on either pin 1 or pin 3. (Note, the numbers go 3, 5, 2, 4, 1!)

Have you got a multimeter? If so, you could test your cables to see how they were wired .....
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Old 28th Aug 2017, 7:29 am   #18
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Default Re: Sony TC-95A Quiet Line Out

Quote:
Originally Posted by julie_m View Post
Have you got a multimeter? If so, you could test your cables to see how they were wired .....
Thanks Julie for the pin info. I've been trying to find a multimeter that I recall buying (but using only once to test a grounding sheet) a few years back so as to check - as both you and Mooly have suggested. It would be good to know - so if I don't find the thing I'll get hold of one. It will be a good learning experience (remember you're dealing with a novice here) - but how would it take me forward in answering the question as to why the same DIN cable provides decent sound on one Sony (TC-95) but not on another (TC-95A)?

I might know why one cable was better than another with the 95A, but not why all cables.. seemingly irrespective of differences in the plug's internal wiring, deliver similar performance on the 95. There must surely be a difference between the 95 and the 95A for there to be this difference between the way the Sonys deal with the signal coming from the same DIN plug?
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Old 28th Aug 2017, 7:47 am   #19
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Default Re: Sony TC-95A Quiet Line Out

I had a thought on this......

Our hearing is such that it is actually quite difficult to tell the difference between say a 1 watt or a 3 watt amplifier, or a 20 watt and a 50 watt.

What that means is that although subjectively both players might sound 'clear and loud', there could actually be quite a difference in the final voltage seen across the speaker... player depending.

I'm guessing you haven't got a scope and so on but what you could try is making a test tape (or you may have one) with a 400Hz or thereabouts test tone on it. If you played that back and connected your meter (set to a low AC voltage range) across the speaker then you could compare actual levels. Or simply measure the voltage coming from the socket.
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Old 28th Aug 2017, 8:48 pm   #20
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Default Re: Sony TC-95A Quiet Line Out

Quote:
Originally Posted by Mooly View Post
I'm guessing you haven't got a scope and so on but what you could try is making a test tape (or you may have one) with a 400Hz or thereabouts test tone on it. If you played that back and connected your meter (set to a low AC voltage range) across the speaker then you could compare actual levels. Or simply measure the voltage coming from the socket.
Thanks Mooly. Interesting and do-able. I can create a test tape using Audacity so when I get hold of the multimeter I'll be able to give this a go with one of the ITTs. As for the TC95A, at least thanks to this thread I've established that this is a DIN-specific issue and that it's monitor output works perfectly with 3.5 jack fed equipment. Shame I really want to listen to it using DIN-fed ITT radios.....!
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