Recalibrating Cassette Format Portastudios to use Type I Normal Bias Tapes

I'm not sure what the railroading looks like - presumably tracks along the tape length? Do they have the same width as the record head gaps - in other words, do they show the magnetised track? I'll have a look at some of my older tapes to check. The only TDK type II I have had problems with are SAX C60s from '82/'83 - I've had a number of them that suddenly started playing back one or two tracks on the 244 at seriously reduced volume a few weeks after recording.
 
Yeah, they're lines that appear across the width of the tape, evenly spread out across the entire thing. I love TDK's, one of my favorite tapes are the TDK Pro SM's but from what the dudes over at T-heads say, the railroading issue causes uneven response or something like that, and gets worse with use. Only the 80's tapes and maybe early 90's though, and even then, not all of em so it's tough to know whether you'll get a bad batch when you buy NOS. When I see all the issues that the older brands of tape have as they age, the more I realize that Maxell is the best brand of all time IMO. All their old 1/4" stock still records like new and is basically guaranteed not to have SSS, and their cassettes are all still good. There may be some issues with certain types, and everybody has their own biases (see what I did there?) but you know what yr getting with a Maxell tape.
 
Something has come into this old brain! Many years ago an contributor designed a "basic" cassette recorder as a DIY project (Wireless World I think and JL Hood)
My point is, his tests showed that even type 1 tapes gave better results using the 70mu sec EQ than the original 120mu sec.

Might be worth biasing a couple of T1 ferrics at type ll setings and see wha'appen?

Dave.
 
Thanks for this. I suppose I've come close to doing that - I recorded on the TDK AD type 1 using the 244's type II EQ setting. I must say it sounded magnificent.
 
Yeah, those tapes are nice. If I could ever find a Maxell XL-I S, I'd try it in my 246, or Audio Technica RMX64 to see what it sounded like. I've never really heard a quality type I before that I was aware of. I've heard that those TDK's you mentioned sounded better than type II for some things.
 
Just to update this thread, I've just this minute set the bias on my spare 244 for Maxell UR C90. It took about 30 mins and required about a turn and a quarter anticlockwise of the 4 bias trimmers. It sounds pretty magnificent to me. A little bass light maybe, but I prefer this. The top end holds up very well at 16 kHz - as good as at 10k and 1k.
 
Whoa. I would've thought the bass would be fuller now as type I typically has better low frequency response (down to 50Hz in some cases). I think that was only the really upper quality type I "super ferrics" though, which the last remaining tape being made, the Maxell UR is not. I dubbed off 8 copies of some songs to give some people last week and used those UR's and I was surprised at how decent they were.

Anyways, I want to hear something recorded on this 244. Can you put up a track recorded like this on Soundcloud or something. It's so cool that you did this. Could you go into more detail about the bias trimmers and how you got these results?
 
I cannot think of a "mechanism" that would cause the bass response of tape to be influenced by formulation?

The changes due to bias will affect MOL and HF reff midband (reff= 333Hz NOT 1kHz for tape IIRC?) but LF response will surely be solely due to the EQ ?

I also cannot see how meaningful decisions can be made about sound quality unless THD is measured for each tape type and bias point?

Dave.
 
Hi Level Anything – glad you liked this, If you send me a message with your e-mail I will send a link to some recordings when I get a chance to post them – may take a week or so as I’m away from home.

To set the bias I used a frequency generator on my tablet, using 25Hz, 100 Hz, 400 Hz, 1k, 6.3k, 10k, 12.5k and 16k. Plugged this in to the aux input and recorded on the UR cassette at 0dB, dbx in (can’t bypass dbx easily on the 244). Played back and adjusted the bias trimmers - the cross headed screws in a line of 4 beside the playback amp pcb) channel by channel so as to give best response after another recording – and so on until I got a reasonably flat response with good top end. Turning the trimmers anticlockwise reduces the bias current. I turned them about ¼ turn at time and about 1/1/4 turns in total. Response at 25Hz is now -3dB, which isn’t bad, 16k (+2dB) is as good as SA was. It is -7dB at 20k for both due to the dbx filters. Purists will howl but I find this works for me.

Dave – point taken about the distortion. I can’t hear any more than normal so I guess it just works for me!
 
Just had to add that I've been using the 244 with UR tape all week and I'm still very pleased. No dropouts and brilliant levels and response. I did a comparison using my original deck with SA and can't hear any difference. If anything the (minimal) dbx artefacts are reduced. I digitised the files and Wavelab shows plenty of information up to 19k and beyond.
 
That's awesome. I got the songs today and will listen to em tomorrow. Do you live in the US? If so, you can buy 10 packs of type I tape through National Audio Company for really great prices. It's awesome tape too. Regardless, ebay always has cheap type I bricks for sale too.
 
Glad you got the songs OK. Just mucking about so apologies for bad playing. Am in the UK but can get bricks of 10 UR for a really good price here too.
 
Yeah, I was just saying in another thread that Maxell is stopping the sale of UR here in the states. I always had a terrible view of it until recently when I recorded to 6 blanks that I needed quick and I thought they were okay. Better than I had remembered. I still prefer late 80's Maxell UR and that TDK AD but these days it's down to the wire.
 
Thanks Level Anything. I'm amazed at what these machines are capable of. I've been using the 244 again this week with UR quite a bit and not had a single dropout - I often got these even with early - mid 80s SA. Put some news strings on the acoustic yesterday and it captured the ringing harmonics beautifully. I'd strongly recommend this recalibration to anyone that can't get hold of decent new type II cassettes.
 
I've just tried the experiment of using my 244 re-calibrated for type 1 (Maxell ) UR with the pitch control set to max speed. This extends the frequency response a fair bit - it is now ruler flat from 50 Hz to 16 kHz and just 3dB down at 25 Hz and 18 kHz - all recording at 0dB. I think this is an incredible result - way beyond the spec for type II - just wondering what the implications are for running at top speed in terms of head and motor wear. Any thoughts?
 
I would conjecture the head and motor wear at 12% beyond fixed speed would be negligible. The relative wear rate due to the tape to head pressure in a cassette machine like the 244 as well as the factor of the low tape speed is minimal compared to an open reel machine running at 15ips.

The only downside to running the transport in vari mode (i.e. using the pitch control) is higher wow and flutter. The wow and flutter spec is measured in fixed mode. Whether or not you can hear the difference is another question...on that point I would conjecture you can't.
 
Thanks for this. What is the reason for the higher wow and flutter in vari mode? I'm so used to w&f getting lower as speed increases I didn't think of this! I didn't notice any difference but I'll check the recordings again.....
 
Yeah you probably won't hear any difference...that was just the only con I could think of with your scenario.

There is additional circuitry including a carbon element rotary potentiometer involved when using the pitch control. Think of what a dirty pot does to your audio...same potential with the pitch control. It's not fixed and stable like when it's in the fixed mode. Hope that makes some sense.
 
I've just played back the recording - acoustic guitar - and I can't hear any w&f - maybe it helped that I cleaned up the pitch control pot when I last took it apart? In fact the recording is the cleanest and clearest I have ever made - no trace of dbx breathing, zero noise and crisp detail. I can't quite believe a 34 year old recorder can deliver this from cassette - but it does!
 
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