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Old 8th November 2010, 01:08 AM   #11
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Hello

Maby it's a too low bias, because of the background noise and distorted a bit in loud parts, maby it needed more bias ?

Btw, the music was record using my Adcom cd player as a source and it was from a Naim music cd.

I have a scope and I can do a thd spectrum analysis with my sound card.

I presume that if it's the bias, I need to record a 1khz signal and monitor the output with a scope to get the highest signal, or doing a FFT of the signal to adjust the bias for the lowest THD ?

Thank you

Bye

Gaetan
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Old 8th November 2010, 03:40 AM   #12
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by gaetan8888 View Post
Hello

Maby it's a too low bias, because of the background noise and distorted a bit in loud parts, maby it needed more bias ?

Btw, the music was record using my Adcom cd player as a source and it was from a Naim music cd.

I have a scope and I can do a thd spectrum analysis with my sound card.

I presume that if it's the bias, I need to record a 1khz signal and monitor the output with a scope to get the highest signal, or doing a FFT of the signal to adjust the bias for the lowest THD ?

Thank you

Bye

Gaetan
Usually you try to assure that the response at 1kHz and 10kHz in terms of amplitude match well - this should be done at typically -10dB or the specific amplitude Sony recommends. (Cassette is typically done at -20dB) Under-bias and you usually end up with a rising response at 10kHz and more thd%, under-bias and the opposite will be true. (IIRC there is also a trade off with modulation noise as the bias is increased.) The best thoughts on this subject are most likely found at tapeheads.net - I've abandoned largely abandoned tape, and now only have a mildly massaged ReVox G-36 MKIII with half track heads. It's sounds very good, but I find tape too expensive a medium to indulge fully.
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Last edited by kevinkr; 8th November 2010 at 03:48 AM.
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Old 8th November 2010, 03:44 AM   #13
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by gaetan8888 View Post
Hello

I've done the MP3 at 320k.

Better to download it today since the direct link was for today.

Thank you

Bye

Gaetan
Got it, will give it a listen tomorrow..
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Old 4th July 2011, 10:00 PM   #14
NH4012 is offline NH4012  United States
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Quote:
Originally Posted by gaetan8888 View Post
Hello

Anybody know about the Sony TC-770 portable open reel tape recorder ?

Like specs, bias and level adjustements, price wen it was new, etc... ?

Is there any modifications to made it sounding better ?

It's a rare machine.

I have this machine, and today, after cleaning all belts, etc, and lubricating it, it's doing very good recording at 7 1/2 IPS, it's very musical with an excellent soundstage.

It's a four track recording head, but it have two playback head, one four track, and one two track.

I'm not sure, but I think it sound as good as my Revox A-77 wen I was using it at 7 1/2 IPS, but it's being long time since I've ad my Revox A-77 at home.

I was thinking to sell it, but since it sound very good I'm not sure if I will keep it or sell it.

Thank

Bye

Gaetan
The TC770 was made in two versions, one that recorded and played 1/2 track stereo with the option of also playing 1/4 track tapes, and one that recorded and played 1/4 track with the option of also playing 1/2 track tapes.
Both versions featured balanced XLR mic inputs, 3 head design, very fine electronics, DC servo motor and operation on internal battery pack or AC making them serious field recorders for recording music in locations where AC power was unavailable. I've owned one since new and made many fine live music recordings in the 1970's and 1980's but since have used other machines for that purpose. The battery pack has been unavailable for many years and now few folks even know what the TC-770 was. I'm just cleaning and putting mine back into service to service because it's the only 1/2 track machine I currently own on which to play tapes I made 30-40 years ago on my 770 and on a Revox A-77 1/2 track which I no longer own. I don't recommend modifications because it's hard to work on, manual seems to be unavailable and frankly, it's already soooooo good. If you have any specific questions, I'll try to answer them.
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