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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 24th Nov 2017, 11:52 am   #1
red16v
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Default Signal levels.

I’ve recently decided to power up the old Akai X201D and begin transferring my recordings from 40 years ago to my iMac. Powered it up - all ok, it’s like it was yesterday! Heads cleaned up nicely, the pinch wheel is still fine with no sign whatsoever of cracking etc. Demagnetised the heads etc. Put on a few test tapes to ensure all is basically well before starting the transfer process. By the way, a few of the tapes are suffering from sticky shedding syndrome and I discovered that wrapping some of that old plumbers very thin ptfe tape around the guides works wonders - for my tapes anyway!

I am using a Behringer analogue to usb converter and Audacity software on the iMac. But, in this configuration the Behringer does not have control of the “incoming” audio level. The software is telling me to use the iMac’s audio system controls to adjust the incoming levels. Further research informs me that this too does not work in conjunction with the Behringer (the pertinent controls are greyed out).

Now, my problem is that for most of the time the line level audio outputs from the Akai are overloading the ‘end to end’ playback chain and naturally this is leading to distortion on occasion. I can see quite easily on the Akai’s level meters that the signal is too great and I need to reduce it before it ‘hits’ the Behringer converter. How to do this? I used to have a cassette recorder which passed through ‘in to out’ signals via a level control - I used it to control the audio levels when I was recently transferring my old Betamax collection, but after completing that project I passed it on so it is no longer available to me (lesson learned!).

I was thinking of investing in a couple of in-line rca switchable attenuators in the first instance - give it a go and all that, what does the team think? Does anyone have any knowledge of a ‘cheap’ active device that might be suitable?
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Old 24th Nov 2017, 12:22 pm   #2
Peter.N.
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Default Re: Signal levels.

You can make up an attenuator with a couple of resistors or even pots, if you know the approx input impedance use one resistor of that value in series with the input and another across it on the output end.

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Old 24th Nov 2017, 12:25 pm   #3
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Default Re: Signal levels.

Hi,
I think it would be possible to use, in the first instance, a couple of resistors and volume pots to check how much the level needs to be reduced by. then you could make up a fixed attenuator ( or even use a good quality switch to be able to select the attenuation amount ) .
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Old 24th Nov 2017, 1:10 pm   #4
red16v
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Default Re: Signal levels.

Yes, I could make something up, but, after 30 years as a professional electronics engineer and now retired I have no interest in building stuff. Sorry about that, but after all that time building/repairing all sorts of electronic equipment my enthusiasm has gone. So, really looking for something off the shelf I can buy off the internet. Sorry about that.
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Old 24th Nov 2017, 1:35 pm   #5
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Default Re: Signal levels.

39 will buy you a pair of Rothwell 10dB attenuators which would do the job - cheaper to get the iron out.
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Old 24th Nov 2017, 9:25 pm   #6
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Default Re: Signal levels.

A much better option would be a basic 4 channel audio mixer.

With this, no matter what the levels sent from the tape machine, the mixer will be able to attenuate/amplify them to match the soundcard.


Kevin
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Old 25th Nov 2017, 7:36 am   #7
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Default Re: Signal levels.

Yes, like a Tapco Mix 60, these are good little mixers.

What a shame you no longer have the urge to get the iron out, I'd kill for your knowledge, maybe we can do a mind meld, that way I get some knowledge and you get some enthusiasm. Hold on, mind transfers are in the future, damn. : )

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Old 25th Nov 2017, 1:27 pm   #8
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Default Re: Signal levels.

Looks like that model is discontinued, any other thoughts? Behringer seem to do something similar, I don’t need anything fancy - just want to control two audio levels after all!

You’d kill for my knowledge? What would you gain knowledge of? You’d gain a knowledge of the complete TV studio production chain from the lamps suspended from the lighting rigs and everything that controls them, the cameras, the vision mixers, the sound desks, the distribution, the recording devices through to the final distribution amplifiers where the sound and vision leave the building. You’d gain knowledge of how that all worked in the analogue domain, and then repeat again 20 years later for it all in the digital domain. You’d learn how to problem solve from 5am in the morning until 11pm at night. You’d be doing it every other weekend including all the Bank holidays. In the end you'd be like me - knackered, mentally and physically. And you’d never want to pick up a soldering iron again.

Don’t get me wrong, I enjoyed every minute of it. When I retired and left the building for the last time I walked a few paces away, turned round, faced the building, crossed my arms and looked up at the complex and said to myself - I’ve been a very small cog in a very big machine, you’ve allowed me to be part of a group that have brought pleasure, joy and hopefully entertainment to millions upon millions of people and I thank you for the opportunity and privilege. So, I regret none of it, I had the time of my life, but enough is enough!
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Old 25th Nov 2017, 10:51 pm   #9
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Default Re: Signal levels.

Dear Red16V

You and I have had a very similar life. In 30 days, I leave the building for the last time, and I never want to see the inside of a piece of electronics again.

Tapco was the original company formed by Greg Mackie in the 60's, the name is still used from time to time by them.

The Behringer Xenix 502 would probably do you fine, but it is a little light on facilities. For about 15 more, the Xenix 802 will do everything you will ever need.

Behringer are a good company; no I have nothing to do with them. Run by a chap called Uli Behringer. I read an article about him once, at one point his engineering chief told him that with all the very high tech products his company now look after, his engineers needed some high level audio test equipment. His tech told him they needed Audio Precision test systems. Uli called in the sales manager for AP and without asking prices, he ordered a shed load of AP systems for his staff.

Sounds like a nice boss to have.


Regards

Kevin
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Old 26th Nov 2017, 7:48 am   #10
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Default Re: Signal levels.

There are two Tapco 50 mixers on ebay, 50 sheets each, which is a lot for what you need. and about the same for one Rothwell 10db pad. 50 is an insult for a shiney metal tube and two resistors. I'd be happy to do the soldering for you and knock up a stereo attenuator, but I have a suspicion that I have a very simple small mixer in the shed, though I think it's 4 into 1. Whatever, drop us a PM and I'll be happy to help.

Behringer stuff does have a bit of a reputation for being not too well made, but guess they'd do the job,

Put like that, I can see your point, I used to feel the same way about gardening, having weeded and mowed about 100 square miles of garden's over the years.

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Old 26th Nov 2017, 9:25 am   #11
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Default Re: Signal levels.

You don't say what Behringer you are using. Personally I use a UMC202HD. You can control the signal levels and they aren't expensive.
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Old 26th Nov 2017, 11:40 pm   #12
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Default Re: Signal levels.

I would guess that it is the UCA202 or UCA222. I have one here and I find that it is slightly too sensitive for cassettes recorded at a high level from a deck set up for normal hifi levels. I'm wondering whether I could find a phono connector with a large enough body to accommodate a couple of resistors to make something like a 6 or 10dB attenuator. The Neutrik NYS352 looks like it might work from the picture on the Cricklewood website but it would help if I could see the internal construction.
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Old 27th Nov 2017, 4:31 pm   #13
red16v
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Default Re: Signal levels.

Quote:
Originally Posted by bluepilot View Post
You don't say what Behringer you are using. Personally I use a UMC202HD. You can control the signal levels and they aren't expensive.
Apologies for the delay in responding. If I look at the top of the Behringer it says it is a UCA222, if I look at the rear of the unit it says it is a UCA202 (?). If I connect the unit up to my Windows laptop (W7) and run up the Audacity software it says the audio levels cannot be controlled by the software and that I must use the W7 audio level controls. This is correct and works - I can control the input audio levels.

However, if I connect it up to my iMac running macOS High Sierra then again the Audacity software says it cannot control the audio levels and that I must use the Mac system mixer to control the incoming audio levels. But, when I go to the system mixer the controls are 'greyed out' and no control over the incoming audio levels is possible. Is this correct operation? I have asked this question on a Behringer user forum and the response was that this behaviour is correct (as daft as it appears).


For logistical reasons I want to use the iMac and not the Windows laptop.

So, given that when I have everything up and running on the iMac and I can see the levels on the Audacity software meters are 'hard over' and the monitored audio is sometimes distorted I came to the conclusion that I need to (sometimes) reduce the audio level going into the Behringer.

I do ask myself - if the audio input levels were controllable from Audacity whether the Behringer was connected to the W7 laptop or iMac, how is this being achieved? Is the Audacity software talking to the Behringer via the usb cable and controlling some sort of amplifier/attenuator on the input of the ADC inside the Behringer? I think this very unlikely, and given that even the supposedly correct W7 operation says to use the W7 system audio controls I think it very likely it is just simply controlling the level of the incoming digitised audio coming up the usb cable where overload distortion will have already occurred in the Behringer.

Sorry if this all seems a bit jumbled! I just want to transfer these tapes once, in as best quality as I can with minimum 'faffing'. I think the Xenix 502 looks as though it will do the job, I cannot find any sort on manual for it on-line prior to purchase and I do wonder how the 2 RCA phono inputs (track inputs) pass through the input level controls?

Thanks to all for your replies and I look forward to reading any further feedback or suggestions.
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Old 27th Nov 2017, 4:51 pm   #14
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Default Re: Signal levels.

On Audacity, the input level is controlled by the slider with a microphone symbol. Left hand side below Pause Play and Stop. What happens if you drop the level of this?


Kevin
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Old 27th Nov 2017, 5:52 pm   #15
red16v
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Default Re: Signal levels.

On my software the (microphone) slider is on the top line to the immediate right of the two horizontal level meter displays.

Does not work. If you hover over the control you get a help bubble that says 'Recording level, Unavailable; use system mixer). The gain control mimic on the slider moves to the extreme right hand end of the scale and stays there - which seems logical.

If you change the recording source to be the iMac's built in microphone then the level control functions as you would expect and can be moved up and down.

I am running Audacity v2.2.0.
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Old 27th Nov 2017, 9:04 pm   #16
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Default Re: Signal levels.

There is no input level control on these Behringer interfaces - neither software controlled nor hardware controlled. The only solution is to use an external attenuator of some kind.
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Old 28th Nov 2017, 9:32 am   #17
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Default Re: Signal levels.

The output from the Behringer is a digital signal. If clipping occurs it will have already happened at the A/D stage. Even if you could adjust the volume in Audacity you wouldn't get rid of the clipping. As said above, you need an attenuator at the input to the Behringer. If you don't want to do any soldering then you'll have to buy something or take Andy up on his offer.
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Old 28th Nov 2017, 11:10 am   #18
red16v
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Default Re: Signal levels.

jamesperrett - many thanks for the confirmation.
bluepilot - thanks also for confirming my suspicions.
Andy - thank you for your offer, yes the internals of the Behringer could be better but it only has to do the job for an intense week or two (I hope!).

I will proceed down the route of buying a separate mixer as they don't seem that expensive and I can always pass it on to someone else after I've finished with it.

I have played a few more of the tapes now - interesting to hear myself as I was 40+ years ago!

There are a few recordings I found interesting - mainly some 'Sounds of the Seventies' from the early 1970's with presenters such as Michael Wale, Alan Black, whispering Bob. The recordings, at various linear speeds, seem to be of reasonable quality although alarmingly one or two of the tapes have shed their oxide to the extent that there are large sections of no oxide at all - just clear plastic backing. In this case I simply rewound the tape when the shedding got bad enough in the hope that once I have sorted out my audio level control issue I will play the tapes once and once only since I think they would not stand up to multiple replays or even rewinding. The less play the better I think?

I guess I will have to look up baking and other related matters? Some squealing from the tapes that my plumbers ptfe trick is not able to deal with. Ongoing.

Thanks all for your very helpful comments so far.
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Old 29th Nov 2017, 8:45 pm   #19
kevinaston1
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Default Re: Signal levels.

You can download an Xenix 802 manual here;

http://www.music-group.com/Categorie...0575/downloads

With a little mixer like this, you can take any input level from -60 to +22dBu, and match it to your recording device with no problems.

Kevin
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Old 4th Dec 2017, 5:39 pm   #20
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Default Re: Signal levels.

That's a co-incidence - I was just wrapping up a repair on an 862 when I saw your post! These cheap mixers - and their bigger Behringer friends - get a very bad press from many users. True, they certainly don't stand up to abuse but if used carefully in a home studio they will last well. Thrown in a flightcase after a lively gig - no.
They are good designs made with cheap components so that well-specced gear can be available to less well off users. Come to think of it, that was NAD's philosophy too.
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