Studer A710 - need HELP in audio adjustment

[ivicajurcevic]

Hi,
This is my first post here and first of all I would like to say hallo to all from Croatia. I think that this forum is a right place for my hobby.

I recently got deck from service but I am not sure that calibration is made correct, so I would like to check, but I have a questions and asking for help.

From Service manual;

5. AUDIO ADJUSTMENTS
(A suitably adjusted tape transport is a prerequisite for all audio adjustments. All line outputs must be terminated with 600 Ohms).
What does this mean? I meant doing measurement on line output with converter XLR to RC. Should I connect resistor of 600 Ohm between HOT and GND wire on RC connector, in parallel with milivoltmeter for each channel?

5.2.2 Checking and adjusting the signal path without tape
General: The line level (at 250nWb/m) corresponds to peak level, i.e. the operating level according to US-standards is lower by 6dB.
What does this mean? Which peak level, which voltage? Isn't dolby tape 200 nWb/m for level adjustment?

The buttons INPUT CAL and OUTPUT CAL must be released.
Set switches DOLBY NR and MPX*FILTER to OFF position.
Set MONITOR switch to SOURCE position.
Feed in 315Hz with line level to the two inputs LINE INPUT.
Which voltage should be on line out?
Turn R14 on NA-Encoder 1.710.489 to center position.
connect millivoltmeter on P3 (P4) on Dolby Encoder 1.710.485 (High Com 1.710.483).
adjust to 730mV (High Com to 755mV) with R 104 ( R204) on Stereo Balancing Unit.
Connect millivoltmeter to LINE OUTPUT.
Adjust line level with R110 (R210) on stereo balancing unit.
Two potmeter/channel for level adjustment? Which voltage for level adjusting with R110 (R210)?

5.2.3 Checking and calibrating the PEAK READING METER
Feed in 315Hz with 2dB below line level at LINE INPUT.
Which voltage should I have on line out?

Vary the generator level with in the range 0 to -0.5 dB.
Both segments to the left of the Dolby marker (0 dB) must turn on or off simultaneously. Should this not be the case, the display requires recalibration.

5.3.1 Adjusting the reproduce level
Carefully demagnetize and clean all metal parts that come in contact with the tape.
Mount Hi- Fi reference cassette 4.75 (Fe). Set MONITOR switch to TAPE position and press TAPE SELECTOR IEC1
Set DOLBY NR switch to OFF position.
Start reference cassette, level tone section 250 nWb/m, 315 Hz, in PLAY mode. Adjust reproduce level with trimmer potentiometers REPRODUCE LEVEL L and R in such a manner that the desired line level is available at the LINE OUTPUT (Fig 54).
Which voltage on line OUT? What with peakmeter, 0 or 2 dB? Which potentiometers? Like in 5.2.2?
What If I use tape 200 nWb/m, 400 HZ, 0dB? (Teac test tape)?

Thats for now, I hope somebody will help me.

Thanks,
Ivica

[Pepika]

Hi Ivice,
zamoljen sam od strane Jürgena Heiliger da mu odn. tebi pomognem. Javio si se na pravu adressu, on je i meni pomogao dovesti u red Technics 1700 Auto Reverse!!!
Da bi ti se pomoglo potrebno je znati:
1. koje mjerne instrumente posjedujes
2. koju verziju Studera A-710 imas
3. dali je to Dolby ili HighCom verzija (zbog peak levela koji su im razliciti)
Tek kada dobije te podatke moze pokusati pomoci
Ja ovdje sluzim samo kad nesto zapne, oko sporazumijevanja.....
Pozdrav Ivice, odgovori mi ovaj upit a ja cu proslijediti dalje, a onda ce vjerujem Jürgen preuzeti komandu! Pepika (Pepi)

[ivicajurcevic]

Hi pepika i Bog,

Answers are:
1. Metrel MD9060 Ac+DC 100 kHz, TRMS DMM. For azimuth I use pc oscilloscope. I have TEAC and BASF test tapes with all tones. Also I have made tones for recording section.

2. It is written STUDER A710, on aluminium front. It has Dolby B and C, no HighCom. Serial number is: 001391

Pepika many thanks, puno ti hvala

lijepi pozdrav/Best Regards

Ivica

[Pepika]

Hi Ivica i Bog,
dobio sam odgovore na tvoja pitanja koje trebam prevesti. U prvome redu te Jürgen Heiliger upozorava da na uredjaju nista mehanicki ne podesavas!!! TONSKE GLAVE, MOTORE, VODILICE TRAKE NE DIRAJ!!! Sve sto zelis uciniti, prvo pitaj prije nego dobijes zeleno svjetlo! Drugacije nema pomoci!!!

A sada prijevod 1:1!

Dragi Ivice,
na pitanje za tongenerator nisam dobio odgovor, te polazim od toga da ga ni nemas. To nesto otezava cijelu stvar ali je moguce.
Kod koristenja skupih tonskih traka se mora upotrijebiti demagnetizer, koji se koristi samo kod potpuno izkljucenog uredjaja i dovoljne udaljenosti od tvojih traka!
Tvoj mjerni istrument nije bas jeftini Multimeter, koji je prije za klasicnog elektricara stvoren, a manje za  Elektronicara koji radi stime na audio uredjajima. Nadamo se da cemo svejedno uspjeti.
Ja ti preporucujem da Uporabni i servisni materijal za A710 dobro prostudiras prije nego sto pocnes sa radom, da mozes brze shvatiti i pronaci gdje se koji potenciometar nalazi jer ih ima more jedno, da ne pobrkas.....

Pitanje:
sto te je poljuljalo da sumnjas da uredjaj nije servisiran kako treba? Odgovori po tvom sudu koliko je vazno znati!!! Ili si otkrio neke smetnje?

Zato preporucujem, a ja sam osobno sa Konstrukterom A710 Marinom Ludvig u prijateljskim odnosima jos od 1983, i vlasnik sam od mene modificiranog B710/II da malo odstupimo od Studer preporuka i da obradimo cijelu stvar malo drugacije, a to je konkretno:
Studer kaze da se kod 710 izlazi i ulazi reguliraju kod 250nWb/m na 1,21 V ili 1,55 V. Ja kazem za 710 da se regulira kod 0dB (Dolby-Marka) na 1,21 V ili 1,55 V.
U centralnoj Europi je to jos od ranih Radio programa (1920) u profesionalnoj tehnici bilo 1,55 V normalno, u Americi i na Pacifiku (Japan) se uvrijezillo 1,21 V koji svejedno u Tehnici magnetnih traka korreliiraju.
Tvoj A710 pokazuje tvornicki vrijednost od +2dB (250 nWb/m) sigurno 1,55 V ili 1,21 V. To je prema zelji korisnika moguce namjestiti. Ja sam moj uredjaj B710/II prije 35 godina "profesionalizirao", zato sto jos A710 nije postojao. On radi jos uvijek i danas sa 1,55 V na 200nWb/m. To bi se moglo mjerenjem utvrditi (sinussignal between 300 and 1000 Hz)  ako ti uredjaj nije podpuno "razstiman"! Dakle, 1,21 V ili 1,55 V su ulazni - izlazni leveli u kalibracijskom modusu ("CAL")
My recommendation: Indicator readout 0 dB (200 nWb/m) -> inputs and outputs 1,21 V or 1,55 V.

Ti pises:
Turn R14 on NA-Encoder 1.710.489 to center position.
connect millivoltmeter on P3 (P4) on Dolby Encoder 1.710.485 (High Com 1.710.483).
adjust to 730mV (High Com to 755mV) with R 104 ( R204) on Stereo Balancing Unit.
Connect millivoltmeter to LINE OUTPUT.
Adjust line level with R110 (R210) on stereo balancing unit.
Two potmeter/channel for level adjustment?

Odgovor:
DA. Prvi pot (R104, R204) odredjuje ulazni level za Dolby, drugi pot (R110, R210) za izlazni napon kod  full scale (pogledaj i usporedi u shemi)

Which voltage for level adjusting with R110 (R210)?

Odgovor:
Predvidjeni CAL-Output-Line-Level: 1,55 ili 1,21 V (kod 200 nWb/m )

Ti pises:
5.2.3 Checking and calibrating the PEAK READING METER
Feed in 315Hz with 2dB below line level at LINE INPUT.
Which voltage should I have on line out?

Odgovor:
Ovdje preporucujem zbog jednostavnosti odstupanje od Studerovih preporuka, pratiti DIN i 250 nWb/m za 1,55 V ili 1,21 V staviti: na line-Level na oba kanala paralelno namjestiti (1,55 ili 1,21) i izjednaciti oba PPM- Kanala kod 0dB_ppm = 200 nWb/m na identicnu vrijednost VA ("Vary the generator level....")
Vary the generator level with in the range 0 to - 0,5 dB.
Both segments to the left of the Dolby marker (0dB) must turn on or off simultaneosly. Shouldthis not be the case, the display requires recalibration.

Ti pises:
5.3.1 Adjusting the reproduce level
Carefully demagnetize and clean all metal parts that come in contact with the tape.
Mount Hi- Fi reference cassette 4.75 (Fe). Set MONITOR switch to TAPE position and press TAPE SELECTOR IEC1
Set DOLBY NR switch to OFF position.
Start reference cassette, level tone section 250 nWb/m, 315 Hz, in PLAY mode. Adjust reproduce level with trimmer potentiometers REPRODUCE LEVEL L and R in such a manner that the desired line level is available at the LINE OUTPUT (Fig 54).

Odgovor:
Your "fig. 54" is wrong, Studer writes "fig. 5.4" Observe this figure - dali je greska u pisanju, bez tocke???
Ovdje vrijedi istokao i kod 5.2.2 i 5.2.3. sa poznatom Voltazom, 1,55 ili 1,21 ukoliko zelis slijediti moju preporuku. Izlazni Level lezi kod +1,94dB i 0dB/1,21 V kod 1,51 V i kod +1,94dB i 0dB/1,55 V kod 1,94 V. Dali je mjereni ton 315, 333, 400 ili 1000 Hz visok za tebe nema nikakvog znacenja!

The repro-level pots are mentioned in the Studer-servicehandbook and shown in figure 5.4. See my correction of your infos, mentioned above. The pots are located on the baseboard ("Interconnection-PC-Board") and require probably a special tool. The pots have the numbers R38, R39 (on 1.710.473) resp. R42, R43 (on 1.710.476). he positioning inside of the recorder is the same (fig.5.4).
U vezi one greske broja slike 54/5.4 , citaj uputsvo pazljivo i po nekoliko puta....

Pitanje:
Which voltage on line OUT? What with peakmeter, 0 or 2 dB? Which potentiometers? Like in 5.2.2?
What If I use tape 200 nWb/m, 400 HZ, 0dB? (Teac test tape)?

Odgovor:
Odgovor se nalazi gore; 200 nWb/m odgovara vrijednosti od 0 dB (Dolby-Marka; Output 1,21 V ili 1,55 V ovisno o tvom odabiru, 250 nWb/m odgovara vrijednosti od +2dB (output 1,51 V ili 1,94 V).

Common importance:
Magnetizirajuci level i elektricni level su u jednakom linearnom odnosu, dakle:

250/200=1,25

250=1,25x200

odnosno

1,21 V x 1,25 = 1,51 V
1,55 V x 1,25 = 1,93 V

S prijateljskim pozdravom,
Hans-Joachim Röhrs

Jürgen Heiliger takodjer,
i moja malenkost, Petar Glavas

[ivicajurcevic]

g. Petre puno vam hvala, također i gospodi Hans-Joachim Röhrs i Jürgen Heiliger.

Evo idem proći kroz vaša pitanja i da pokušam vidjeti da li sam sve shvatio;

U prvome redu te Jürgen Heiliger upozorava da na uredjaju nista mehanicki ne podesavas!!! TONSKE GLAVE, MOTORE, VODILICE TRAKE NE DIRAJ!!! Sve sto zelis uciniti, prvo pitaj prije nego dobijes zeleno svjetlo! Drugacije nema pomoci!!!
Tu nisam ništa mehanički podešavao.

Dragi Ivice,
na pitanje za tongenerator nisam dobio odgovor, te polazim od toga da ga ni nemas. To nesto otezava cijelu stvar ali je moguce.
Kod koristenja skupih tonskih traka se mora upotrijebiti demagnetizer, koji se koristi samo kod potpuno izkljucenog uredjaja i dovoljne udaljenosti od tvojih traka!

Tvoj mjerni istrument nije bas jeftini Multimeter, koji je prije za klasicnog elektricara stvoren, a manje za  Elektronicara koji radi stime na audio uredjajima. Nadamo se da cemo svejedno uspjeti.
Ja ti preporucujem da Uporabni i servisni materijal za A710 dobro prostudiras prije nego sto pocnes sa radom, da mozes brze shvatiti i pronaci gdje se koji potenciometar nalazi jer ih ima more jedno, da ne pobrkas.....
Tu mi je sve jasno. Nemam ton generator, ali sve tonove mogu napraviti u Audacity programu, mjerim izlazne napone točno na izlazu iz DAC-a. S njega idem na kazetofon.

Pitanje:
sto te je poljuljalo da sumnjas da uredjaj nije servisiran kako treba? Odgovori po tvom sudu koliko je vazno znati!!! Ili si otkrio neke smetnje?
Stavio sam test kazetu od Teaca MTT150 (Dolby level, 200nWb/m, 400 Hz, 0 dB) i peak metar je pokazivao više od 0 dB.

Zato preporucujem, a ja sam osobno sa Konstrukterom A710 Marinom Ludvig u prijateljskim odnosima jos od 1983, i vlasnik sam od mene modificiranog B710/II da malo odstupimo od Studer preporuka i da obradimo cijelu stvar malo drugacije, a to je konkretno:
Studer kaze da se kod 710 izlazi i ulazi reguliraju kod 250nWb/m na 1,21 V ili 1,55 V. Ja kazem za 710 da se regulira kod 0dB (Dolby-Marka) na 1,21 V ili 1,55 V.
U centralnoj Europi je to jos od ranih Radio programa (1920) u profesionalnoj tehnici bilo 1,55 V normalno, u Americi i na Pacifiku (Japan) se uvrijezillo 1,21 V koji svejedno u Tehnici magnetnih traka korreliiraju.
Tvoj A710 pokazuje tvornicki vrijednost od +2dB (250 nWb/m) sigurno 1,55 V ili 1,21 V. To je prema zelji korisnika moguce namjestiti. Ja sam moj uredjaj B710/II prije 35 godina "profesionalizirao", zato sto jos A710 nije postojao. On radi jos uvijek i danas sa 1,55 V na 200nWb/m. To bi se moglo mjerenjem utvrditi (sinussignal between 300 and 1000 Hz)  ako ti uredjaj nije podpuno "razstiman"! Dakle, 1,21 V ili 1,55 V su ulazni - izlazni leveli u kalibracijskom modusu ("CAL")
My recommendation: Indicator readout 0 dB (200 nWb/m) -> inputs and outputs 1,21 V or 1,55 V.
Super prihvaćam prijedlog za kalibraciju kod 0 dB (Dolby mark) na 1,21 V.

5.2.2 Checking and adjusting the signal path without tape
General: The line level (at 250nWb/m) corresponds to peak level, i.e. the operating level according to US-standards is lower by 6dB.
Iz service manuala:
The buttons INPUT CAL and OUTPUT CAL must be released.
Set switches DOLBY NR and MPX*FILTER to OFF position.
Set MONITOR switch to SOURCE position.
Feed in 315Hz with line level to the two inputs LINE INPUT.
Which voltage should be on line out?
Turn R14 on NA-Encoder 1.710.489 to center position.
connect millivoltmeter on P3 (P4) on Dolby Encoder 1.710.485 (High Com 1.710.483).
adjust to 730mV (High Com to 755mV) with R 104 ( R204) on Stereo Balancing Unit.
Connect millivoltmeter to LINE OUTPUT.
Adjust line level with R110 (R210) on stereo balancing unit.
Znači guram u deck na line in testni ton 315 Hz, 1,21 V. Na P3(P4) namještam napon 580 mV, s potmetrima R104(R204)?
Line level moram namjestiti na 1,21 V mjereno na LINE OUT (deck u source modu), s potmetrima R110 (R210)? Ako je sve OK s peakmetrom, on bi trebao pokazivati 0dB?

Ti pises:
5.2.3 Checking and calibrating the PEAK READING METER
Feed in 315Hz with 2dB below line level at LINE INPUT.
Which voltage should I have on line out?

Odgovor:
Ovdje preporucujem zbog jednostavnosti odstupanje od Studerovih preporuka, pratiti DIN i 250 nWb/m za 1,55 V ili 1,21 V staviti: na line-Level na oba kanala paralelno namjestiti (1,55 ili 1,21) i izjednaciti oba PPM- Kanala kod 0dB_ppm = 200 nWb/m na identicnu vrijednost VA ("Vary the generator level....")
Vary the generator level with in the range 0 to - 0,5 dB.
Both segments to the left of the Dolby marker (0dB) must turn on or off simultaneosly. Shouldthis not be the case, the display requires recalibration.
Ako sam dobro shvatio, guram 315 Hz, line level napon 1,21 V. Peakmetar mora pokazivati 0dB?

Ti pises:
5.3.1 Adjusting the reproduce level
Carefully demagnetize and clean all metal parts that come in contact with the tape.
Mount Hi- Fi reference cassette 4.75 (Fe). Set MONITOR switch to TAPE position and press TAPE SELECTOR IEC1
Set DOLBY NR switch to OFF position.
Start reference cassette, level tone section 250 nWb/m, 315 Hz, in PLAY mode. Adjust reproduce level with trimmer potentiometers REPRODUCE LEVEL L and R in such a manner that the desired line level is available at the LINE OUTPUT (Fig 54).

Odgovor:
Your "fig. 54" is wrong, Studer writes "fig. 5.4" Observe this figure - dali je greska u pisanju, bez tocke???
Ovdje vrijedi istokao i kod 5.2.2 i 5.2.3. sa poznatom Voltazom, 1,55 ili 1,21 ukoliko zelis slijediti moju preporuku. Izlazni Level lezi kod +1,94dB i 0dB/1,21 V kod 1,51 V i kod +1,94dB i 0dB/1,55 V kod 1,94 V. Dali je mjereni ton 315, 333, 400 ili 1000 Hz visok za tebe nema nikakvog znacenja!

The repro-level pots are mentioned in the Studer-servicehandbook and shown in figure 5.4. See my correction of your infos, mentioned above. The pots are located on the baseboard ("Interconnection-PC-Board") and require probably a special tool. The pots have the numbers R38, R39 (on 1.710.473) resp. R42, R43 (on 1.710.476). he positioning inside of the recorder is the same (fig.5.4).
U vezi one greske broja slike 54/5.4 , citaj uputsvo pazljivo i po nekoliko puta....

Da fig. 5.4, ne 54 tj bila je greška u pisanju.
E sad da li bi ja ovdje trebao išta raditi s potmetrima R38 (R39), budući je level namješten prije? U biti bi ovo trebala biti samo kontrola. S test kazetom 200nWb/m, 400 Hz, 0 dB idem u play i kontroliram: na peakmetru moram imati pokazivanje od 0 dB (Dolby level)  i na LINE OUT moram jeriti 1,21 V?

Još dodatno pitanje; Otkud napon od 1,21 V za 200 nWb/m?

Još jednom puno hvala/Best Regards

Ivica

[Pepika]

Bog Ivice, ovo je sada za tebe samo informacija da ovo prevodim i saljem Hans-Joachimu i Jürgenu Heiliger!

0.) Herr Peter vielen dank, ebenso Herren H-J Röhrs und Jürgen Heiliger.
1.) Ich werde mich durch die Fragen und Antworten schlängeln das wir sehen ob ich alles verstanden habe;
2.) Mechanisch habe ich nicht verstellt.
3.) Hier ist mir alles klar! Habe kein Tongenerator, aber kann alle Töne mit Audacity Programm erzeugen, messe ausgang spanung              genau am ausgang aus DAC. Von da gehe ich auf Kassetenrecorder.
4.) Habe die Test Kassete von TEAC MTT150 (Dolby Level, 200nWb/m, 400Hz, 0 dB) und Peakmeter hat gezeigt mehr als 0 dB!
5.) Super, den vorschlag akzeptiere ich für kalibrierung bei 0 dB (Dolby Mark) auf 1,21 V!
6.) Das heisst, ich schiebe auf Line In Testton 315 Hz, 1,21 V. auf P3(P4) justiere süpanung 580 mV, und mit potmetern R104 (R204)??
     Line Level muss ich auf 1,21 V setzen und gemessen auf Line Out (Deck ist in Source Mode), mit denn Potmetern R110 (R210)??
     Wenn alles Ok mit Peakmeter, muss er 0 dB zeigen???
7.) Wenn ich gut verstanden habe, ich schiebe 315 Hz, Line Level Spanung 1,21 V. Peakmeter muss 0 dB zeigen???
8.) Ja, fig. 54 war schreibfehler, soll 5.4 heißen!
      Soll ich jetzt hier was machen mit den Potmetern R38 (R39), da die Levels schon früher eingestellt waren? Das sollte nur kontrolle sein. Mit Testkassete 200nWb/m, 400 Hz, 0 dB gehe in Play Modus und kontroliere: auf Peakmeter muss ich 0 dB (Dolby Level) haben, und auf Line Out muss gemessen werden 1,21 V???
     
     Noch eine zusätzliche Frage; woher Spanung von 1,21 V für 200 nWb/m???
     
     Noch mal viellen dank/ Best Regards

     Ivica

Herren H-J Röhrs und Jürgen Heiliger, so weit mit der übersetzung, bitte um entschuldigung falls schrebfehler vorligen, als ich nach Deutschland kamm 1973 gabs keine Integration und Sprachschulen wie Heute.............................
Gruß, Pepika   

[PhonoMax]

Dear Petar, dear Ivica,

at the beginning a big "thank you!" to Petar for his translations, which unquestionably simplified the situation for all participants. I prefer now to answer in English directly in order to release Petar from his burden.
I hope, my answers as 'interlinear glosses' between the questions do not cause more confusion than net-common thread-quotings would do.

2.) Mechanisch habe ich nichts verstellt.
I hope so, dear Ivica. The adjustment of the head azimuths of a 710 (SONY-heads) is possible for the recording and reproducing heads as well. In later times Revox cassette recorders were equipped with a Canon-head-compound, which allowed no longer a separate adjustment of recording and reproducing heads. Not a brilliant compromise in a Studer-unit....

3.) Hier ist mir alles klar! Habe kein Tongenerator, aber kann alle Töne mit Audacity Programm erzeugen, messe ausgang spanung              genau am ausgang aus DAC. Von da gehe ich auf Kassettenrecorder.
Ok, that sounds fine.
I am, nevertheless, not really happy with your multimeter for audio measurements, but I hope, it will work fine (enough) for our purposes.

4.) Habe die Test Kassette von TEAC MTT150 (Dolby Level, 200nWb/m, 400Hz, 0 dB) und Peakmeter hat gezeigt mehr als 0 dB!
This indicates a faulty adjustment of the 701-peakmeter. I assume, that a preowner or a service clerk  understood the peak program meter of the 710 as a VU-Meter and adjusted the meter with a lead of some decibels. Studer-Revox defined the lead of VU-Meters (250 to 300 ms)  implemented in recording equipment since the time of the A77 traditionally to 6 dB, while the G36 still had a Gossen-VU-Meter with 7 dB lead. But the 710 was equipped always with a peakmeter according to DIN (more or less) with 10 ms integration time. So far: NO LEAD in level indicators of 710-recorders.
Demagnetize the heads (710 OFF!!!) properly prior to every use of your TEAC MTT150.

5.) Super, den vorschlag akzeptiere ich für kalibrierung bei 0 dB (Dolby Mark) auf 1,21 V!
Ok, I also registered your intention. All my following answers will take this into account.

6.) Das heisst, ich schiebe auf Line In Testton 315 Hz, 1,21 V. auf P3(P4) justiere Spannung 580 mV, und mit potmetern R104 (R204)??
     Line Level muss ich auf 1,21 V setzen und gemessen auf Line Out (Deck ist in Source Mode), mit den Potmetern R110 (R210)??
This is completely correct. Applying 1,21 V ("+4 dB") 300,400 or 1000 Hz to the line inputs (XLR-2=hot, connected XLR-3 and XLR-1 as cold) you have to measure 580 mV at contacts P3 and P4 (against machine's ground). If you observe a different level, adjust R104 and/or R204. Subsequently test the output levels for correct 1,21 V between XLR-2 and XLR-1 connected to XLR-3). Deviant levels should be corrected by adjusting R110 and R210. Compare STUDER-Fig. 5.2.

By the way: You can find a better-readable reproduction of the potentiometer-position-layout from Fig. 5.3 and 5.4 on PDF-page 66 in section 7/3 of the service-manual. The audio block diagram on the same page may of additional interest for you. Try to understand it.

     Wenn alles Ok mit Peakmeter, muss er 0 dB zeigen???

This is true, too. In the case of deviant level indications you have to readjust the meter indication to 0dB by using the pots R36 and R49 as shown in Fig. 5.3 or on page 66 ("Peak-Meter-Cal").

7.) Wenn ich gut verstanden habe, ich schiebe 315 Hz, Line Level Spanung 1,21 V. Peakmeter muss 0 dB zeigen???
That's right!


8.) Ja, fig. 54 war Schreibfehler, soll 5.4 heißen!
     Soll ich jetzt hier was machen mit den Potmetern R38 (R39), da die Levels schon früher eingestellt waren? Das sollte nur kontrolle sein. Mit Testkassette 200nWb/m, 400 Hz, 0 dB gehe in Play Modus und kontroliere: auf Peakmeter muss ich 0 dB (Dolby Level) haben, und auf Line Out muss gemessen werden 1,21 V???
This is correct. Compare for the pot positions Studer-Fig. 5.4 (right half).
As I wrote already in the text of yesterday, Studer installed two versions of the interconnection board/reproduction head preamplifiers. The level pots of the second version are designated as R42 and R43. The position of the reproduction level-pots, on the other hand, is the same for both board types.

Finally another hint: Studer also installed  two types of balancing ouput-amplifiers in the A710. I don't know, which type appears in your A701. If the two big output transformers of the balancing board are located in the center of the 1.915.904-board, you have the line-output-amplifier of the Studer 169 in your A710. This is an early example of Paul Zwickys experiments with a transformer coupling of outputs, to keep the advantages of a transformer coupling and to avoid the classical imperfections of transformers of a limited volume. This here was a first step, but requires special treatment to adjust the feedback from transformer to the amplifier. If I recall that correctly, Paul describes the adjustment in his handbook for the 169. If your 710-output makes no problems, please keep distance from an adjustment of R116/R216 of 1.915.904.00.

Later Paul extended his  research regarding the (finally quite special) combination of a transformer with a microphone amplifier, which led him to the construction of the legendary microphone input of the 961/962 (and another international patent...). This construction combines the advantages of an electronically balanced input with the advantages of a transformer-coupled, balanced microphone-amplifier  in a transformer-/amplifier-array.
Nevertheless: Tempi passati.

Another hint:
Up to now we did not mention the process of the bias- and recording-level- resp. equalizing-adjustment at all. That's another story.

Noch eine zusätzliche Frage; woher Spannung von 1,21 V für 200 nWb/m???

The inital impact for the professional audio technology originated in the early telephone techologies and their technical definitions. American telephone companies used a level of +10 dBm (0,775V x 3,16=2,45V) and used since the late 1930s early VU-meters (300 ms!, begin of their history) for measuring purposes. For these VU-meters leads of 6dB came into general use, meaning, that the static indication level of these VU-meters was adjusted to 0 VU at a level of 4 dB above 0,775V = 1,21V (more correct 1,225 V) or a level of 2,45V-6 dB=1,225V).

The Central-European 1,55V came up on a comparable way.: Established also on 0 dBm = 0,775V under the conditions of a power of 1 mW at 600 Ohms the removing of the load (in early radio times) caused a level rise of 6 dB:

0,775V + 6dB=1,55V

The level of 1,55V was born...

That's it.

Hans-Joachim

[Pepika]

By the way......
To Hans-Joachim, Jürgen and Ivica,

It has been an honor to help you, but I think the decision to continue in English is a better idea. For any further help, I am at your disposal every Time!

Best Regards, Petar

[ivicajurcevic]

Gentlemen,

many thanks to all of you, source of information here is huge, and your help to me is priceless.

Now, I am ready for playback part of calibration of my Studer A710, same I will do with my Revox B215. After that recording part is coming.

Best Regards
Ivica

[ivicajurcevic]

Hi again to all,
thanks to you I finished with reproduction part of adjustment and I am 100% OK now. Now I made recording part and I am not satisfied with results, so I need one more help . From service manual:

5.4.2 Adjusting the azimuth of the record head (not used for units from no. 2521 )
Caution:
When making this adjustment, use only high quality cassettes that have been spooled forward and backward once. The tape must not show
any mechanical damage or deformations along the edges.
— Clean all parts that come in contact with the tape with a moist felt stick (included in the REVOX cleaning kit) and subsequently demagnetize these parts.
— Load cassette and press the TAPE SELECTOR button that corresponds to the type of cassette. For cassettes coded according to the IEC scheme, the AUTO position can be used.
— Feed in line level —20dB, 10kHz, at LINE INPUT; line level —20dBu should be available at the LINE OUTPUT ( MONITOR switch in SOURCE position).
77,5 mV?

— Start record in play mode ( press REC and PLAY ).
Set MONITOR switch to TAPE position.
With screwdriver size 00 for cross recessed head screws adjust screw Y (Fig. 5.5) in such a manner that maximum level is obtained for both channels (minimum phase difference) .
When I done azimuth I had difference in voltage value between L and R channel (85 mV and 135 mV), but they were in phase (and in XY plane it was 45 degree). I just made a little turn to right side and I got 120 mV on both channel, but chanel were not in phase (in XY plane it was not much less than 90 degree). Is this correct? I used TDK D90 tape.

The following adjustments apply for one type of tape only.
For other tape types, proceed in the same manner. The position of the corresponding trimmer potentiometers can be determined from Fig 5.4
All of settings first I do for normal tape (bias, level, equalization) and after for chrom and metal, or I change tapes in each setting (bias, level, equalization)?

5.4.3 Adjusting the tape bias
Same preparations as described in 5.4.2. (mean I must record tone 10 kHz, -20 dB?) and...
Adjust the corresponding trimmer potentiometers on the oscillator PCB (refer to Fig. 5.4) in such a manner, that maximum output level is obtained for both
channels. Write down the actual values (in dB) and deduct from this valuetheamount shown in Fig. 5.8.
My deck has serial number 1391 and I think that I have Sony heads, because I can adjust records head azimuth. Which column for delta U is mine; left or right? I think left (for example delta U for TDK MA is 4 (dB?).
Should I have same max value for both channel, or just max value which can be different for each channel? I made with max but different voltage between channels (probably wrong!)
Set this calculated value with the corresponding trimmer potentiometers.
For max value and for value according to table in fig 5.8 I use same potmeters? (R37-R42)
Caution:
The channels influence each other. When adjusting for maximum level, the optimum compromise must be found.


5.4.4 Adjusting the record level and equalization
Feed in line level —20dB, 315Hz, at LINE INPUT.
77,5 mV?
The INPUT CAL button must be released. Set DOLBY NR switch to OFF position.
Start tape transport in record mode. Adjust trimmer potentiometer LEVEL
(potmeters R39-R44?)
(record equalization 1.710.486) in such a manner that no level jump occurs
when changing the MONITOR switch setting from SOURCE to TAPE.
That was OK.

Preadjust the trimmer potentiometer EQUALIZATION
(R45-R50?)
(record equalizer 1.710.486) with the following frequencies relative to 315 Hz:
IEC 1 10 kHz 0 to +1 dB
IEC 2+4 14 kHz 0 to +1 dB
Here I had a problem. I could not made enough voltage for 10 kHz and 14 kHz. 315 Hz was 77,5 mV but with equalization I had up to 50-60 mV, more or less.
Check the frequency responses for all three tape types and adjust for best possible linearity with the aid of trimmer potentiometer EQUALIZATION.
Again R45-R50?
Load IEC2 cassette and start tape transport in record mode.
Feed in Dolby level OdB, 250Hz. When
changing the MONITOR switch setting
from SOURCE to TAPE, the indication
at the PEAK METER should not vary. In
case of a difference adjust trimmer LEVEL (1.710.471).
After these adjustments check the azimuth of the sound heads.

i dont know where is a problem with equalization. I turned potmeters all the way but without results (small changes). Maybe in bias adjustment because I had different voltage on channels. Maybe my line in voltage (77,5 mV) was to high?

Hope that this has simple answer and solution

Best regards
Ivica

[PhonoMax]

Dear Ivica,

I hope, that your subseqeuntlich quoted statement is completely correct. This is necessary because the quality of the reproduction channels' adjustment affects directly the fundamental quality of the adjustments of the record-sections. Depending on your subsequently quoted questions regarding the Lissajous-based alignments (your X/Y-plane)I have some doubts.

Hi again to all,
thanks to you I finished with reproduction part of adjustment and I am 100% OK now.

5.4.2 Adjusting the azimuth of the record head (not used for units from no. 2521 )

— Feed in line level —20dB, 10kHz, at LINE INPUT; line level —20dBu should be available at the LINE OUTPUT ( MONITOR switch in SOURCE position).

The wording of Studer in the sm is a bit misleading. The absolute level is here of lower importance. Studer just tries to avoid any adjustment in the saturation regions of the tape and in the low-level-regions as well. Look at the level meter and use the level corresponding to -20 dB.

When I done azimuth I had difference in voltage value between L and R channel (85 mV and 135 mV), but they were in phase (and in XY plane it was 45 degree). I just made a little turn to right side and I got 120 mV on both channel, but chanel were not in phase (in XY plane it was not much less than 90 degree). Is this correct? I used TDK D90 tape.

Following your observations the level discrepancies are not correct. I hope that your A710 uses definitely Sony-heads, which are the only ones with separately adjustable record- and reproduce heads. If the heads do NOT agree with fig. 5.5 (section 5/4 of the service manual) your heads could be those of Canon. In 1986 I discussed the head-problems of the 710 with Walter Derrer. But the infos I got did not fit completely to my experiences in the last 15 years. Additionalyy I can't exclude, that a narrow sparepart-situation caused a modification of 710s to Canon-heads. I suppose that your 710 owns Sony-heads.

Additionally I hope, that your alignment of the reproduce channels, especially of the repro-head-azimuth was correct. Otherwise it is selfunderstandingly impossible to adjust the record-azimuths in an appropriate way. If these requirements are fulfilled according to the state of the art, I have to assume, that you 1) did not find the main maximum in the alignment-process with the Lissajous-X-Y-procedure on your oscilloscope or 2) the level-adjustment of the record-channels is out of order. Both channels must be as precisely as possible in phase AND offer the same level within a field of ± 3dB.
The Lissajous-indication of the scope (identical sensitivity for x- and y-channel!) especially in cases of cassetterecorders and amateur-tape-recorders cannot be stable. You have to adjust as perfect as possible. That's all you can do.

Final hint to find the main maximum: BOTH channels MUST be in phase, must offer the same levels and MUST reduce levels in identical ways, when you turn your alignment-tool clockwise AND counterclockwise.

The following adjustments apply for one type of tape only.
For other tape types, proceed in the same manner. The position of the corresponding trimmer potentiometers can be determined from Fig 5.4

Your following question is not completely understandable for me:
All of settings first I do for normal tape (bias, level, equalization) and after for chrom and metal, or I change tapes in each setting (bias, level, equalization)?

My comment:
Studer in the recording channels just offers the separate adjustments of bias, level and equalization for the magnetically severely differring tapes according to IECI (Ferro), IECII (Chrome) and IECIV (Metal).

The bias alignments take place in every case with 10 kHz and a level of -20 dBs to avoid tape saturations. Comparing the A710-service-manual with that of the B710 I assume, thal you have a headset of the type 1.116.710.01. So far your column must be the left one. For the tape-appropriate bias-alignments a in both channels identical ΔU is important. The adjustments of level and equalizing follow the bias.
On the other hand: The fig. 5.8 in section 5/6 of the sm should be self-explaining. The curve-graph follows your clockwise adjustment-turn increasing bias ("over-bias") from maximum to the correct bias-level (fig. 5/8). The bias is controlled just with the six pots R37-R42 (3 tape types for left and right). The mutual inductive bias influcencing of both channels must be taken into account. Over the bias-adjustments left and right you have to find acceptable compromises.


5.4.4 Adjusting the record level and equalization
Feed in line level —20dB, 315Hz, at LINE INPUT.
Follow the 710-levelmeter indication -20 dB.  Condition: You adjusted the meter correctly. Also in this case (315 Hz) Studer tries to avoid any tape saturation.
The level adjustment takes place through pots R39-R44 (3 tape types, left and right).

Preadjust the trimmer potentiometer EQUALIZATION
(R45-R50?)
(record equalizer 1.710.486) with the following frequencies relative to 315 Hz:
IEC 1 10 kHz 0 to +1 dB
IEC 2+4 14 kHz 0 to +1 dB
Here I had a problem. I could not made enough voltage for 10 kHz and 14 kHz. 315 Hz was 77,5 mV but with equalization I had up to 50-60 mV, more or less.

My comment:
The reason might be a wrong bias-adjustment, a not appropriate millivoltmeter (you are using a multimeter), a concave tape or a worn-out head. Maybe there are other reasons, but the named came into my head, when I read your sentences.

R45-R50 are definitively the equalizing pots in the 710s. Don't forget, that he Dolby-encoding processor of the right channel in the 710s uses a level-determinant pot (R16) to allow a precise 'paralleling' of both encoding processors. If someone modified the adjustment of the R16 (500 Ω) inappropriately you have to expect a different level between Dolby-encoding left and right.

The dimensioning of the rec-eq-adjustment of the 710 is not satisfying. Your remark

"I turned potmeters all the way but without results (small changes)."

is well known to me. I had and still would have the same problems, when I would adjust my modified B710. Due to my research the reason  must be a wrong or inappropriate dimensioning of the eq-device. So I planned around 1985 to redesign the original eq-adjustment-device. But I never did it and tried to come along with a modification of the bias-adjustment.

Regarding that wrong dimensioning I years ago talked to the constructor Marino M. Apparently we did not come to a satisfying end of our discussion or had a more interesting prologation of our discussion about other topics: I, at least can't remember what Marino said to me.... When I shall meet him the next time, I ask him about 'the whys'.

If one knows backgrounds or wants to know them, answers are regularly no longer simple, and putative solutions turn into difficulties, as we can discover sometimes in the Studer-history.

Hans-Joachim

[ivicajurcevic]

Dear  Hans-Joachim,

many thanks for helping me. Yes, like you said, I found that level adjustment and both azimuth adjustment are interact. But with a few iteration now I am completely satisfied.
I made one recording, Pink Floyd: Wish you were here album, on TDK SA, and I am happy with result, it is hard to see what is source and what is a tape.

Best Regards
Ivica