Studer A810 with Tube Repro

[audioblazer]

After putting my system out of commission for a few months while waiting for renovation of my new audio room to be completed , I was excited to put the reel to reel through its pace but unfortunately it was not be .
Discovered that the system sounded much louder on the left speaker compared to the right speaker . Did the following trouble shooting

1. Change to different XLR cable ( 6m) . Left side louder . Ruled out cables problem.
2. Used different input on the preamp side to rule out problem of the preamp. Left side louder
3. Swapped cables on the output of the Tube Repro . Now it's louder on the right side
4. Swapped cable (0.6m XLR ) on the output of the studer to the input of Tube Repro . Right side louder
5. Plugged XLR cables to the output of the Studer directly . Same problem . Left side louder. Swapped cables , now right side louder .

Help. What do you think is the problem ?

 

[jdza]

Clean the heads thoroughly and demag before you start looking in other places. Do you take the head output directly from the heads or after the headblock amp? If directly from the head ,it and the selector switch (please don't use a switch) are the only common denominators .If not dirty/magnetised heads ,check the switch.

 

[Edward Pong]

did you calibrate the output levels of the Studer with the MRL calibration tape? Need to use the CCIR or NAB depending on the tape you are playing back.....Likely the 1K levels are off between channels....

 

[audioblazer]

I thk it should be from head directly . Was modified by Dan Schmalle of Tape Project . Sent Studer A810 directly to him when I made the purchase from some guy in audiogon . There is a switch to switch it between using stock electronic or Tube Repro.
MRL calibration ? I would have suppose it should have been done when I send it for modification .
I had the same problem 1-2 times at my old place . However after unplugged & re plugged it was fine . This time it didn't work . The big problem is that I don't know of a tech in Malaysia which can trouble shoot for me . I doubt I have played more than 150 hours after owing it for a about 4 years

 

[audioblazer]

Do not know how to upload video . Took a snapshot .

 

[Edward Pong]

try pushing the uncal button, adjust pots so level is the same - then try the tape. The output levels should be calibrated for different tapes so the meters will read correctly... 250 nW/m, 396 nW/m etc.
the fact it sounds the same with stock & tube repro likely means your tubed repro is still using the calibration circuits in the Studer...
good luck!

 

[audioblazer]

Correction . I don't mean it sound the same with stock electronic & Tube Repro , which is much more superior. I meant with both tube Repro & stock electronic , it sounded louder on the left side

 

[Edward Pong]

I understand, did you try to push uncal button & adjust levels? This should balance the output of your 2 channels

 

[stellavox]

Now hold on here - you mentioned that there is a switch to select between stock electronics or the tape repro? As jdza mentioned, maybe the switch wired directly to the output of the playback head. if so, then the difference in levels could be in the head itself.

Suggest you direct the question to Bottlehead, who did the mods. We don't have enough information.

Charles

 

[Edward Pong]

But if he can go to pure stock, then the uncal is a reasonable place to start... the uncal should be able to adjust the playback levels...
he should really do a playback calibration with the MRL tape. Most people do not understand that...playback levels can go off & I do a calibration of the playback levels, 1K, 10K everytime I make a tape copy otherwise you do not know what levels you're at...

 

[Tapetech]

But if he can go to pure stock, then the uncal is a reasonable place to start... the uncal should be able to adjust the playback levels...
he should really do a playback calibration with the MRL tape. Most people do not understand that...playback levels can go off & I do a calibration of the playback levels, 1K, 10K everytime I make a tape copy otherwise you do not know what levels you're at...

The OP is describing a major level difference between L and R channels (with both head-direct out and stock deck out). That would not be a calibration problem. A .5 dB difference between channels would be an example of a calibration problem. It's rare for decks to drift out of cal more than that.

The OP's symptoms point to a dirty head.

 

[c1ferrari]

Salient advice...

Suggest you direct the question to Bottlehead, who did the mods.
Charles

audioblazer -- would you know if your A810 has had a deck alignment

 

[audioblazer]

 

[c1ferrari]

Clean the tape path with IPA, isopropanol, then degauss.
Call me in the morning...hehe.

 

[audioblazer]

Yes will clean it once I find it . Messy after shifting

 

[audioblazer]

Suggest you direct the question to Bottlehead, who did the mods. We don't have enough information.

We are working on an interesting Studer A810 mod right now. A client has sent us an A810 to mod for direct head output, and has ordered a Tube Repro to use with it. The nature of the head connection via very short cables to a small preamp on the head block makes this a bit different setup than the usual setup we find on other decks where the head cables are quite long and easy to reroute to jacks on the back of the deck. Splicing long cables onto the short head cables is doable but seemed rather ungainly. So I decided to rethink this mod and see if we could squeeze in a 4PDT pushbutton switch that would allow us to offer switching between the internal playback electronics and a set of direct head outputs that will be mounted on a currently blank panel on the back of the deck next to the existing XLR jacks. After a few hours of fabricating some aluminum angles we think we have managed to squeeze the switch in where that scary red tape cutter button is normally mounted on the headblock (I guess some machines have this red cutter button and others have a black U shaped cover over that hole) . The mod requires no machining of the Studer and is completely reversible.
This what I got from tape project where my Studer was modded by bottle head . 1st class co & very responsive

 

[christensenleif@msn.com]

try pushing the uncal button, adjust pots so level is the same - then try the tape. The output levels should be calibrated for different tapes so the meters will read correctly... 250 nW/m, 396 nW/m etc.
the fact it sounds the same with stock & tube repro likely means your tubed repro is still using the calibration circuits in the Studer...
good luck!

hi Ed
unless the head pre amp is a common factor......
it might well be and it would feed both downstream electronics, whether inboard or outboard
better ask Dan
best
Leif

 

[Edward Pong]

Leif,

certainly only Dan knows for sure how this is hooked up....but just a suggestion, especially if it can be switched back to totally stock, then try the uncal & adjust playback levels...
Hopefully, it's something simple like that... not the heads etc.
Best
Ed

 

[Ki Choi]

Your photo of the A810 with its VU meters being off tells me that your 4PDT head switch is in internal electronics position and the issue is with Studer repro electronics. If the switch was in direct head position, your VU meters will be inoperable considering no CH1&2 signals being fed.

I would suggest you check to make sure the direct wiring scheme is good and working first by:

1) reposition the switch to direct head position (you can play the tape and make sure both VU meters are not working and no signals are coming out from the CH1 & 2 output XLRs

2) have a voltmeter ready and connect it to Bottlehead Tube Repro's outputs (it would be good if you can get an old pair of RCA cables that might have come with your home electronics and cut it and have shield and signal wires tied to the voltmeter leads with meter setting at AC auto range).

3) thread DocB's IEC cal tape he sends out with TP orders. DocB's tapes have longer test tones than MRL tapes, and you will have ample time to measure the voltage output levels from RCA cables.

4) play the cal tape. Most of our non-consumer machines and majority of external tape preamps will output about AC 1.25V at 1Khz test tone. As you can guess the actual level isn't as important as checking to see if both channels are around 1.25Vs and same.

If you are challenged to do the above test, any local electronics repair shop can help you if you tell them you want the outputs of the premamp verified.

Tell us what you find. Once you can confirm your switch and wiring are good and the Tube Repor is working properly, we can move on to the Studer internal electronics next.

Ki

PS. Long live DocB - who started all these tape madness...the good kind.

 

[audioblazer]

Yup , don't think I can do what u suggested . When I switched to internal electronic , the imbalanced in the right & left channel is obviously .
Now I play by adjusting the trim pot provided in Tube Repro with much more gain in the right channel , easily 4-5db I thk . Thanks