Calibration Tapes

Hello everyone. Just curious which calibration tapes you all are using. I bought a couple of sets from eBay from two different sellers, one was a former Nakamichi technician and the other seems to rule eBay when it comes to selling calibration tapes. Both claim that their tapes are recorded from reference calibrated decks. The two brands differ in accuracy, I have no idea which is accurate, if either. I noticed it recently when I serviced and calibrated my main cassette deck [Nakamichi CR-2a] with the latest calibration tape that I had bought. Recorded a vinyl onto cassette and it sounded fabulous. I played that cassette tape on a serviced Walkman and it sounded very good, but not superb. I hooked the scope up to the Walkman that I had calibrated from my original calibration tape but used the new calibration tape this time. It was then that I noticed that the azimuth was off. I checked other Walkmans in my collection that I restored from the past year or so, they too were off.

Seems there is no consistency with these home brew calibration tapes. Got frustrated and ordered a full set from Germany, from Hans Roth. I suppose if I just picked one brand and calibrated all my devices with it, it would be fine. But, I'd like to know that I was calibrating to a recognized and verified standard. What are you folks using for calibration tapes? Please don't tell me the 40 year old TEAC calibration tapes that sell for an arm and leg. Cheers! Norm

 

Thank you, MisterX, just read those posts. When I saw your TEAC calibration tape set, I started salivating. I do hope that you have recovered from the “C”. It’s something that I think about at my age. Norm

 

That is just crazy, $9.00 for the set. One tape goes for over $150-200 EACH on eBay...

 

The HPR ones from Germany are probably the best bang per buck in terms of calibration tapes. That's what I use myself.
There are more expensive options like this: https://www.test-tape.com/en/shop/c...81-mm-476-cm-s-400-hz-200-nwb-m-art-nr-76462/
But are these so much better to justify cost ? Unlikely, would prefer to replace them every once in a while especially level ones.

Hence why I would never go for the vintage TEAC ones, which apart from fact they cost a lot don't think they are actually better than HPR.
For level ones there's just no guarantee these are accurate anymore, especially the DIN ones which were problematic even when new back in the day.

 

As usual, Valentin, thank you for providing your feedback. Cheers!

 

Norm,

I share the same view as @Valentin and also rely on HPR tapes for a full set and specialty tests (like the AKAI PB 333 Hz 160 nWb/m equivalent). Keep in mind that test tapes have a limited operational lifespan—GennLab notes about 50 passes—so vintage options are largely a gamble anyway.

Alex

 

I did not know that, Alex, that the tapes are good for only about 50 passes. That seems incredibly short. I'm working on a Harman Kardon CD391 cassette deck currently, perhaps making it my reference deck. The W&F factory spec is 0.025% WRMS, Wideband frequency response. It's been a slow project. I am trying to identify which electrolytic caps need to be of the low leakage type so that I can place an order. I'm guessing they would be needed around any component where DC leakage would introduce timing and audio artifact issues within the circuit. Another issue is no one makes the lower valued ones anymore, seems all the manufacturers have moved to surface mount ceramics and film caps geared towards modern audio equipment. The problem with that is the size of the film caps which doesn't drop in nicely. I have the service manual for the deck but it does not include the schematic or wiring diagrams, which I need to trace the function associated with a given electrolytic cap. Looks like I'll need to hunt one down on eBay. Cheers! Norm

 

Agree too with @Valentin , for all the projects both walkmans and decks, I am using HPR test tapes. And also I notice the difference between fixyourudio and HPR tapes, on my WM-DDIII it was 0,025-0,03% difference which is a lot because originally after the service and all the adjustments, finally I got it around 0,1-0,2% wmrs, which is a bit higher than expected for that model. Without any touching of the device, just HPR tape, I measured 0,08% which tells me I am done with any adjustments needed. So just keep in mind that. I use fixyouraudio tape when I maintain plastic cheap walkmans where 0,02% wont make any difference

 

@worldwide137 Electrolytic caps in the range of 100nF - 1uF are still available although rare nowadays.
However they don't have to be electrolytics, MLCC with class I dielectrics (NP0/C0G) are suitable replacements for small values and have a few advantages:
1. lower leakeage current (2 orders of magntitude);
2. lower ESR;
3. much lower temp coefficient;
4. unlike class II/III dielectrics (X7R, Y5V) they have no C-V non-linearity.
The main reason electrolytics are used in such applications is because 1 and 4. But these can be achieved with other cap types.

Out of curiosity, what are the brand of capacitors in that deck ? Have you measured them ?

As for level tapes, they last more than 50 passes in practice (measured on already calibrated units), but on level ones some degradation will naturally occur
hence my previous remark that would prefer to have fresh ones every now and then than paying a lot on a vintage one that may be out of spec already.

 

Hi Valentin. Thank you for the pointers. At this point, I'm really uncertain with my choices of capacitor since I don't have the schematic diagrams to determine if the replacement caps should be general purpose, low ESR, low leakage current based on where the capacitor sits in the circuit. I'm trying to make educated guesses and Gemini has led me astray too many times to rely on it. I am planning to order a schematic from eBay shortly.

Yes, I did measure a few of the caps. I pulled the three largest value caps from PCB-2, the Logic Control board, though the power supply taps into it directly as well. I tested all three - One is out of spec [2200µF], the other is close to out of spec and bulging [10000µF], third [4700µF] was in spec but towards the lower/mid range of -20%. Two of the capacitors are unmarked by name, only show a symbol presumably Matsushita/Panasonic and the third TK [Toshin Kogyo]. Cheers!

 

Norm,

Good luck with your HK project deck! Those 3 caps pictured are toast

As Valentin suggested, low-value electrolytics can be replaced with film caps with good results—especially around Dolby chips, where it's actually recommended.

I checked HiFi Engine, and they seem to have the schematics for your model. Check it out; working on a deck without schematics is mission impossible (at least for me!).

I've only done a full recap on one of my decks (Akai GX-F71), as it had catastrophic failures across almost every functional level, from the power supply and playback to recording and autocal. But it's a special deck to me, so it was worth the effort and expense. I don't think a full recap is always warranted for vintage decks, and opinions are divided on the topic. Sometimes new problems appear during a recap, and older PCBs can be stressed too much (lifted pads, etc.). So you know the old saying, "If it ain't broke..." I always save the old caps I replace, and in 95% of cases, they're actually still within spec.

As for the reference recorder, I prefer a 3-head deck with full manual calibration capability: levels on both channels and bias. This way you can really get the most out of each cassette tape, as they vary significantly in MOL and SOL.
Alex

 

Thanks Alex. While both the HK301 and HK391 are two-head decks, both have a built in tone generator for levels and bias adjustments and fully accessible via the front panel. The only inconvenience, adjustments are not real-time, I have to rewind and playback. Yes, I agree with you, both MOL and SOL can vary widely among tape formulations. What puzzles me is that some tapes will have one channel that is a little lower. For example, I will calibrate to a particular tape. Run the calibration on another tape and the level on one channel will be a little lower. I can understand if both channels were lower, but here it's only one channel. Seems odd to me. Norm

 

@euroflash Unfortunately, I do not have an account at HIFI Engine and they are not accepting new registrations. Norm

"Sorry, but due to ongoing issues with brute force attacks, bot registrations and organized scraping of our content by diyaudio site members and moderators (which they refuse to take down as it's not against their rules), registrations are closed. I'm looking at alternatives to both account verification and the password based login system."

 

Norm,

Unfortunately, this "channel imbalance" you observed is all too common. I often re-record some of my old tapes and run into this exact issue. I usually use my Akai deck's auto-tuning feature first, and when it rejects the tape, I know right away that either the level or frequency response is off in one channel. Then I switch over to my Technics deck with full manual calibration, and I can see precisely what's going on.

It's surprising how many tapes in that condition I've pulled out of rotation—even from great brand names like Maxell, TDK, and Sony. Some are premium types too...

Alex

 

Some tapes have degradation, even if NOS. Can be related to storage condition or can be related to some batches being worse than others.
Seen situations where side B of a tape has poor frequency response or dropouts compared to side A, on sealed cassettes. Can happen.

As for those caps, I would replace them although what's underneath is glue not leakeage. Many of these big ones are glued to the PCB to withstand vibrations especially during shipping.

Smaller value ones measure a couple and see how they measure. Don't need to know exactly what function it performs to continue.
These can be replaced with C0G dieletric MLCCs which are better than the original electrolytics in all regards.

Film ones are different (MLCCs are a type of ceramic), having 2 extra advantages both of which in my opinion are not really needed: no microphonics and perfectly flat impedance in the Mhz range.
In the microphonics department the MLCCs are already better than the original electrolytics and having flat impedance in the Mhz is not something relevant for this application.
As you already stated film ones tend to be large and won't be a perfect fit on the PCB original footprints, hence why I think the C0G MLCCs are a very good replacement in case it's needed to replace them.

 

Very useful info, Valentin. I completely agree, once one pulls out the old caps, you might as well replace it. Of those big three, one was beyond the -20%, one other close, and the third was bulging. I am working on the transport at the moment while I wait for the caps to come in from Mouser.

I know this is going to show some ignorance, this is the first time I've decided to work on the reel table in a cassette deck. There is a washer that secures the reel spindle assembly. I was expecting to see a split washer but the washer appears to be all metal with no split. I don't want to just take a flat tip screwdriver to it and mar up the plastic spindle. How do you remove it safely, it seems pretty stubborn? Norm

 

The washer I think is nylon not metal, just a very thick one.
Seen these type of non-split washers before (especially on Panasonic walkmans, but decks also), they are removed by force.
The outer lip will twist upwards, bending the washer, while the inner part can slide in this position. They can be reused just fine.

 

You are so right, Valentin, the washer is indeed of a thicker plastic variety. I did get it off by gently prying it off. Now, I can properly clean that filthy spindle assembly. One of them has a reflective optical disk for movement detection, will have to be careful not to get it wet.