Studer A820 in for repair!

dminches · Oct 21, 2018

microstrip said:
IMHO you are comparing apples with oranges ... But I will avoid the digital/analog wars ...

Anyway, IMHO there are good technical reasons for avoiding the external tape repro amplifiers for some one wanting an optimal system. The tape head is a complex system and the input stage must match it accurately. Unless the amplifier designer knows what is the head and cables being used he can't do a perfect job, and then each customer is a special case. It seems to me such burden is beyond what ATAE considers reasonable.

Why do you think that external tape repros can’t do this?

c1ferrari · Oct 21, 2018

Ron Resnick said:
It is indeed interesting (and puzzling) that professional audio studio people unanimously vote against external tape repro amplifiers.

I can't confirm it; however, I would imagine a number of "name" mastering houses commission MUCH outboard gear -- including tape preamps, etc. -- that are designed and executed by the studios' in-house technical staff.

c1ferrari · Oct 21, 2018

Bruce B said:
I have one 10x worse than Fred..... Tim de Paravicini... I had asked him a couple of times if he would mod on Studer A80's. When he found out I was using outboard tape pre's, he outright called me an a-hole. He then went off into a diatribe degrading me, cursing and made me feel like I was the scum of the earth. Enough said!

Wow! Sorry to hear that, Bruce.

microstrip · Oct 21, 2018

dminches said:
Why do you think that external tape repros can’t do this?

The number of components and the variation needed in the input stage is too large to allow an usable switching system. And the designers would have to supply configuration tables for all possible heads and cable length / capacity.

dminches · Oct 21, 2018

I can’t speak for Nick Doshi but I am sure he has considered all this in the design of his preamp.

Tapetech · Oct 21, 2018

The so-called dilemma of using an external tape preamp is easily solved. You buy a tape deck/external tape preamp package where the external tape preamp has already been carefully tuned to the specific play head and head cables that are being used. That tuning should be performed by an experienced RTR technician. The results are well worth the effort in my opinion and justifies the use of an external tape preamp. I have yet to find a stock tape deck that doesn't sound better when using my external tape preamp (after I adjusted for optimum performance). For instance, how many people that buy and use an external tape preamp check, adjust or even know about head resonance? The frequency of this resonance effects the overall SQ. When I am matching my external tape preamp to a new tape deck, I do a sweep test for resonance and adjust the preamp to optimize it. There are, of course, many more preamp adjustments to make as well. Here is an example of some of my tests for proper head resonance.

Ron Resnick · Oct 21, 2018

Fred Thal said:
That's just not true, Ron.

Bruce Brown's reply to you listed some examples that contradict your assertion.

I could add many more.

One in particular, one that many people strangely never mention, is the same company that arguably launched this whole idea of outboard tape audio electronics in the first place.

It most certainly wasn't Doc Bottlehead, arriving very late to the tape scene.

It was a company called Inovonics, originally in Campbell, California.

Inovonics was Jim Wood. An absolutely brilliant electronics designer. And a delightful person. I have tremendous respect and admiration for Jim.

Need a second opinion? Ask any of the guys still living who were at Ampex, designing tape electronics back in the day about Jim Wood.

One of the five available "tape stages" (I'm still not sure I like using that term) that ATAE offers a buyer of our one hundred thousand dollar Model Two tape playback system, is a repro amplifier circuit designed by Jim.

I know, you think ATAE should make our line of different "tape stages" available for sale, separately.

Your good friend Mike Lavigne has always told me this, too.

I respect your well intended opinions, and thank you for them, but there are several important technical considerations that would make this highly problematic for me.

I prefer eliminating technical problems. Not creating them.

Fair enough, Fred. Yes, I overlooked your outboard tape repro amplifiers as well as Jim's.

microstrip · Oct 21, 2018

Tapetech said:
The so-called dilemma of using an external tape preamp is easily solved. You buy a tape deck/external tape preamp package where the external tape preamp has already been carefully tuned to the specific play head and head cables that are being used. That tuning should be performed by an experienced RTR technician. The results are well worth the effort in my opinion and justifies the use of an external tape preamp. I have yet to find a stock tape deck that doesn't sound better when using my external tape preamp (after I adjusted for optimum performance). For instance, how many people that buy and use an external tape preamp check, adjust or even know about head resonance? The frequency of this resonance effects the overall SQ. When I am matching my external tape preamp to a new tape deck, I do a sweep test for resonance and adjust the preamp to optimize it. There are, of course, many more preamp adjustments to make as well. Here is an example of some of my tests for proper head resonance.

Great to have input from someone with experience on this subject. Now the question is how many audiophiles have had this work carried for their tape amplifiers?

Just look at ATAE THP-2 tape head pre-preamplifier - the components on the left side aren't there for embellishing the board, and I think that they must be tuned for the head/cable system.

Fred Thal · Oct 21, 2018

Ron Resnick said:
Fred, as I have suggested to you two or three dozen times privately over the last four years I think you could have a business reconditioning machines the way you reconditioned that A820 in 2014, charging whatever are the parts costs with a reasonable profit margin for you.

Hi Ron,

Well, maybe we could indeed sell a service like you describe to one or two unsuspecting audiophiles.

But it wouldn't be ethical.

Anyone who actually understands the A820 will tell you that A820s are ticking time bombs today.

Just look at that ancient, embedded Motorola 6803 microprocessor architecture, staying busy looking every few milliseconds to read code from obsolete and failing EPROM and RAM chips.

How could anyone possibly warranty that technology today?

If you absolutely must have an 820 transport based system, then please just keep using the nice 820 you already own, while you wait patiently for our forthcoming revision to our original (circa 2006) Model One. (Sorry that it's taking so long.)

As for now, I'm greatly more enthusiastic about our Model Two and I think you need to get acquainted with one. As re-manufactured by us, the venerable A80 transport is nothing short of an elegant, enduring classic!

Ron Resnick · Oct 21, 2018

Tapetech said:
. . . You buy a tape deck/external tape preamp package where the external tape preamp has already been carefully tuned to the specific play head and head cables that are being used. That tuning should be performed by an experienced RTR technician.

. . .

This makes perfect sense to me and, in fact, is exactly what Fred advises.

Do audiophiles think this way and plan this way before they buy the Doshi external tape repro amplifier? I do not think so.

So why does the Doshi make so many people happy? Is it simply that the Doshi is flexible enough to match whatever tape machine and repro head Nick finds himself having to deal with?

microstrip · Oct 21, 2018

dminches said:
Ron, I respectfully disagree based on the number of posts I have read that Fred has posted which have disparaged audiophiles time and time again. He has posted a number of time on his studer achives list and even referenced WBF in order to show what fools we are. I don't know what you and Fred talk about. All I know is what he has posted.

Fred irate posts in the Studer list concerning WBF referred to Studer experts, a subject where he has strong opinions. Although I would prefer a more moderate and civilized speech, I can understand his opinions and find them very natural, considering what I have learned from the Studer list along more than 18 years.

Fred Thal came to WBF on a personnel invitation of Ron - IMHO we should be very happy to have him with us. Different approaches and views are some of the keys to WBF success.

dminches · Oct 21, 2018

Ron Resnick said:
This makes perfect sense to me and, in fact, is exactly what Fred advises.

Do audiophiles think this way and plan this way before they buy the Doshi external tape repro amplifier? I do not think so.

So why does the Doshi make so many people happy? Is it simply that the Doshi is flexible enough to match whatever tape machine and repro head Nick finds himself having to deal with?

Ron, when I got my Doshi tape preamp Nick had my head block. He wired out the head and calibrated the tape preamp. I would consider this to be a complete setup and not just connecting any old tape pre to a wire out head.

microstrip · Oct 21, 2018

dminches said:
Ron, when I got my Doshi tape preamp Nick had my head block. He wired out the head and calibrated the tape preamp. I would consider this to be a complete setup and not just connecting any old tape pre to a wire out head.

Good to know about it - it is the first time I read it! We do not get this idea from the dealer advertisements or the reviews, that cover mostly the "fancy" components!

Ron Resnick · Oct 21, 2018

dminches said:
Ron, when I got my Doshi tape preamp Nick had my head block. He wired out the head and calibrated the tape preamp. I would consider this to be a complete setup and not just connecting any old tape pre to a wire out head.

I agree!

Tapetech · Oct 21, 2018

microstrip said:
Great to have input from someone with experience on this subject.
...the components on the left side aren't there for embellishing the board, and I think that they must be tuned for the head/cable system. View attachment 44765

You are correct. The left-most capacitors and resistors on that board do effect head resonance.

astrotoy · Oct 23, 2018

Great picture of Fred and his Ampex ATR-102.

Fred Thal · Oct 25, 2018

If someone is reporting that two tape machines of the same make and model sound different, what would you first suspect as the most probable cause?

Hint: It probably isn't about who changed out all the electrolytic capacitors. (More to say on that, a little later today, time permitting.)

To know the answer, you first need to understand some of the science of analog magnetic recording and reproducing.

Only a beginner could mistakenly believe that one just acquires a professional analog recorder-reproducer from someone and starts in using it to make top quality recordings.

Only a beginner might not understand that the recorder must always be carefully aligned for recording on the same tape stock (production batch) that they're using.

No one else can do this critical record alignment for you ahead of time, unless they have some of the exact tape stock (from the same production batch) in their possession.

And only a beginner might not understand that the even more critical, very first step in aligning any recorder, is to first transfer in the reproducing section's alignments for equalization and fluxivity from your own calibration tapes.

It's dishonest to suggest that analog magnetic recording and reproducing is simple.

Newcomers to the technology definitely require training.

Absent that training, you'll hear beginners reaching faulty conclusions, asserting all kinds of silly things that are simply untrue.

Returning to the opening question and answering it: if two tape machines of the exact same make and model sound different, the most probable cause is that their alignments differ.

Ninety-nine percent probability on that.

Fred Thal · Oct 25, 2018

What if someone were reporting that a Studer A820 that had some of its electrolytic capacitors changed by one shop, sounded noticeably different (or worse) than another A820 that had those same capacitors changed by another shop?

For simplicity, let's assume that we're talking about a noticeable sound quality difference in playback. (See my previous post for some comments on the importance of aligning a machine for recording.)

Some might be tempted to posit that it's the capacitors themselves that might be the cause.

But if we trace the A820s audio signal path thru repro amp 710 (also found in the A810 and A812) we discover that the only electrolytic in the path is C36, which is employed there for inter-stage coupling. (We're ignoring C6 and the sync path.)

There were five versions of the 710 produced over time, each with essentially only minor engineering changes made periodically over its many years of production.

However, the 710's following line amplifiers (on separate cards) were also supplied in differing versions, with those differences being much more significant.

So all of this detail probably needs to be carefully specified, before making observations about perceived sound quality differences between any two, seemingly similar A820 machines.

With all that said, it's still far more probably a matter of exactly matching the two machine's alignments.

microstrip · Oct 25, 2018

I would never buy any equipment with replaced capacitors unless this work was carried by someone I know and trust. The best horror story I know concerns a guy who trimmed the capacitor leads too long, causing a short in a Krell amplifier... Unfortunately many people feel they are able to do it, even without proper tooling. See this exemplary horror picture taken from a youtube video on the art of replacing electrolytic capacitors ... If Frankenstein had solder joints this would be the soldering iron to use in the movie!

bonzo75 · Oct 25, 2018

Did the short in the Krell cause any external damage?

Studer A820 in for repair!

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