Studer A820 MKI vs MKII

Mike Lavigne

Member Sponsor & WBF Founding Member
Apr 25, 2010
8,657
2,317
450
#2
PM member "Ki Choi".

i have three A-820's; 2 MkII's and 1 Mk1 that Ki tells me is 'almost' a MkII. over time he has upgraded it and installed the newer firmware. but personally i don't know enough to answer your question.

it could be mostly the firmware.
 

yjwu

Well-Known Member
Jun 28, 2011
63
1
83
Taipei, Taiwan, Republic of China
#4
If you ever completed the adjustment of pinch roller gap to 0.1mm you will know that your A820 was a Mk-I.

You should also find a pair of 811/813 which enable HX-pro capability in recording in a A820 Mk-II. You will not find "REC-AMP 820.812 820.712" marking on a A820 Mk-II, instead it will read as "REC-AMP 820.811 820.712".

What happened to rec-amp 1.820.812.XX was still a mystery.

Side_Control_Arm_Right.JPG

Pinch_Roller_Gap_Adjustment_0.1mm.JPG

Pinch_Roller_Gap_Adjustment.JPG
 
Apr 8, 2019
20
8
3
67
Portland, Oregon
#5
I just looked at the audio archive page, it is not reliable, I found several mistakes on it in a casual read.

MKII firmware can be applied to MKI machines (done it several times)
it has a few minor differences that apply to the old deck and are useful (timing and damping differences in control loops for motor control) that also require changes to some of the control cards (all denoted on SI's from Studer and available)

But mostly it adds variable bias adjustments that are used in HXPro and skimming.

HXPro is only really useful at slow speeds (its intended purpose) and was mostly there for slower (read 3 3/4 and 7 1/2 ips) Master Recorders. Not that useful to the audiophile, are you really worried about recording at either of those speeds? I think not.

Skimming is a technique that is intended for archiving purposes. It has never been widely accepted, reason for which you will see why shortly. The technique is to use a sufficiently small bias signal during playback of tapes that have been in storage for a long time to strip off any print thru that may have occurred. It has been shown in the lab to work and provide a reduction in print thru artifacts. Now I walk up with THE master of (insert name here) and you want to run some bias thru the record head while playing this tape? Not gonna happen.

The changes are in the audio cards, particularly the record cards to implement these changes. I have never seen a MKII in the wild, I have seen upgraded Mk I's with the newer record cards.

In other words, no real changes that anyone here would care about that can't be added to a MK I machine.

all these changes are documented in the manuals and SI's from studer which are available on line free. https://www.reeltoreel.nl/studer/

Cheers
Alan
 
Likes: srs148

yjwu

Well-Known Member
Jun 28, 2011
63
1
83
Taipei, Taiwan, Republic of China
#6
Thank you Alan for your comment on HXPro and skimming.

According to SI some early Mk-I's had non-rolling ceramic pad on both tension arms.
Several range of serial numbers of Mk-I had early type of capstan motor, which need matching driver board.

There was also a HW/SW compatibly table on that service information.
 
Apr 8, 2019
20
8
3
67
Portland, Oregon
#8
Yes, there were, most of the non rolling tension sensors were retrofitted in the field. I have seen some still existing as well. An interesting note, Studer went back to the non rotating sensor in the D820 version where the scrape flutter is less invasive to the signal.

While they are referred to as ceramic, they appear more as glass, highly polished surfaces. There is also some disagreement about use of rotating vs fixed guides with "highly slippery surfaces" (read PTFE, teflon) Jeff Gilman of Precision Motorworks advocates a non rotating scrape filter for Ampex ATR machines. All rotating elements in the transport path will show up at some level as spectral contamination of the flutter signal. Its a question of which is worse/better in terms of fm of the audio signal.

There were many variants of ALL Studer machines over the years and it needs to be paid attention to when examining machines for purchase.
 
Last edited:

c1ferrari

Member Sponsor & WBF Founding Member
May 15, 2010
2,111
32
225
#9
waltzingbear's comment regarding HXPro for slower speeds resonates with my recollection of an e-mail authored by Martin Berner.
 
Apr 8, 2019
20
8
3
67
Portland, Oregon
#12
I have that part in stock, I'm not sure its any different really than the ceramic one. Just less expensive to produce. To really know I would have to mount it up and test it, and since I don't have an A820.... that becomes difficult as well as uninteresting.
 

srs148

Active Member
Jan 4, 2016
36
0
38
#13
I just looked at the audio archive page, it is not reliable, I found several mistakes on it in a casual read.

MKII firmware can be applied to MKI machines (done it several times)
it has a few minor differences that apply to the old deck and are useful (timing and damping differences in control loops for motor control) that also require changes to some of the control cards (all denoted on SI's from Studer and available)
.....
HXPro is only really useful at slow speeds .... Not that useful to the audiophile, are you really worried about recording at either of those speeds? I think not.
.....
Skimming ...Now I walk up with THE master of (insert name here) and you want to run some bias thru the record head while playing this tape? Not gonna happen.
.....
The changes are in the audio cards....

In other words, no real changes that anyone here would care about that can't be added to a MK I machine.

Cheers
Alan
Really insightful, Alan. Thanks for sharing.

Are the audio card changes worthy of making to older cards?
 

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