Replace magnet with a mono play head?

[Mike Watterson]

Is it possible on a cassette deck with magnet erase but that has AC Bias, to fit a regular mono play/record head and an amp to drive it? I've maybe four decks like that. Two are stereo "boombox" style of thing, one transportable mono and one a Sangean/Roberts World Radio. I'd not bother with the couple of "walkman" style machines as they are really only for casual recording/dictation, though not too bad for portable playback, one has AM/FM radio.

Should it use the bias oscillator as drive via an amp, or should it use a higher frequency due to using a regular head rather than a proper erase head?

What sort of drive level might be needed?

Does a magnet for erase halve the dynamic range, or just increase noise or what?

As a side issue I presume to add support for playing non-type 1 tapes only switchable equalisation is needed but that changes for recording are more problematical (more bias, harder to erase?). Simple solution is only playback support.
Is this correct?
Type 1: Any ferric or compatible mix. They might not all be exact same formulation?
Type 2: "Chrome"
Type 3: Ferric and Chrome in layers (to improve LF over Type 2? Is it rare?)
Type 4: "Metal"


My Sony TC186SD has low, med & high bias. It has Fe, FeCr and Chrome Equalisation.
https://www.hifiengine.com/manual_librar...86sd.shtml
It's working fine. I'm the second owner. Never did anything except clean head & roller.

I have also an Awia M700. The belts had all turned to goo when I was given it (one previous dead owner).
I ordered new ones, but they seem very difficult to fit, so it's been in bits over a year in a box. It does all four kinds of tape, though the switches suggest only two levels of bias (250% and 110%, unless the lowest is a misprint and is 100%) and two levels of equalisation, 70 and 120uS.
   
https://www.hifiengine.com/manual_librar...m700.shtml

Should I make the effort to replace the belts? What is best to clean the flywheels/pulleys etc of the old bits of belt?

I've also three other alleged HiFi units with cassette, two are dual decks, not sure if AC or magnet or DC erase.

[ppppenguin]

My view is that if you want a high quality cassette recorder, then don't use one with permanent magnet erase in the first place. if the designers intended it to be hgh quality they would have fitted a proper erase head. AFAIK, the main penalty for PM erase is excess hiss. Example of older discussion: https://www.tapeheads.net/showthread.php?t=17934 I suspect a PM will struggle to erase high coercivity tapes such as metal. Not a direct comparison but I've failed to erase high coercivity video tape of 1970s vintage using a older bulk eraser** that wasn't designed for the job.

I keep a couple of high quality cassette decks (Tandberg TCD310) around for transcribing cassettes. Probbaly got some old walkman style players lurking in a cupboard. Otherwise I don't use the medium.

If you're interested in cassette as a medium and want to use it for recording at better than dictaphone quality then use a decent deck. This could include the Sony Walkmans with record capability though I think these now sell at excessive prices. If you want to make high quality recordings then it's a lot easier to use a digital recorder. Anything from a smartphone to a Zoom H4.

**Reminds me that I have an oldish bulk eraser here that was intended for Umatic and similar video cassettes. It's coming to the B&B stall at Harpenden next month.

[Mike Watterson]

My view is that if you want a high quality cassette recorder, then don't use one with permanent magnet erase in the first place. if the designers intended it to be hgh quality they would have fitted a proper erase head.

If you're interested in cassette as a medium and want to use it for recording at better than dictaphone quality then use a decent deck.

Agreed. Silk purses and Sows Ears come to mind. I'm not interested in cassette for its own sake, though some folks are. I've hardly played a cassette or recorded in 20 years. I got an Archos 160 GB HDD based PMP/Video/browser 14 years ago, better than portable CD. Battery died a couple of years ago, but replaced by phone before that.

I have a Zoom H4N for portable recording (uncompressed Wav) and an external Creative USB box with line I/O, optical I/O, mic & ear (uncompressed Wav).

I'd use the Sony TC186SD if I wanted something on tape, though I might fix the Awia M700 if I thought I could (I have the new belts) and it made much difference.

It was the Roberts RC818 (Sangean AT818CS) that made me wonder. It's not bad but let down by the magnet erasing. Not likely to matter if recording from SW and if I REALLY wanted something off VHF-FM radio, I have a PC beside a standalone HiFi tuner and also laptop beside an almost HiFi mini-JVC system.

Probably even 256 kbps MP3 on my phone is better than any cassette? More recent MP3 from CD is 320 k. Though I'm more likely to play from Laptop into the HiFi as I don't go out much and when I do, too short a journey for music.

[Crackle]

Hi Mike
Swarfega works well for dissolving and removing the black goo from more sensitive plastic parts and material. But acetone is better on metal flywheels and pulleys.
I believe cellulose thinners will also dissolve the black goo. But be careful of using any of these aggressive solvents around plastic parts.
I wonder about the value of replacing a PM erase head with an electronic erase head when there are so many cheap cassette recorders around. (I have about 10 for sale), unless it is purely for the technical design challenge.

Mike

[Mike Watterson]

Thanks
1) It's particularly the Roberts World Band set built in cassette deck, so a separate cassette recorder doesn't apply. I'd not bother with any of my other recorders as I have maybe 3 decent decks. Possibly a 4th really good one if I repair the Aiwa, though it might not really be better, just more tape types and fancier.
2) I have never seen a cheap recorder with AC erase, only table top HiFi models. Even some Micro and Mini alleged "HiFi" all-in-one models don't have AC erase, though have AC bias.
3) I'd not generally bother as such cassette decks are usually poor in other areas.

Researching it, it seems that there was only a brief period when portables used AC erase, then they cost reduced to a magnet. Heads with DC erase seem rare. The "new" USB enabled cassette players appear to be atrocious compared to any built in sound card and a late 1980s pocket model, never mind a HiFi deck connected to a decent sound card or external box.

I have at least one old cassette head. I suppose if the gap is too small I can use a higher frequency. Between 55 kHz and 100 KHz, seems to be used. All the schematics seem to just use the bias oscillator. I can put a scope on an erase head and see what level it is.

I have acetone. It's only on the metal parts that's stubborn. The plastic pulley wheels are sort of non-stick anyway.

[Crackle]

2) I have never seen a cheap recorder with AC erase, only table top HiFi models. Even some Micro and Mini alleged "HiFi" all-in-one models don't have AC erase, though have AC bias.

Thats odd because I don't think I have seen ANY cassette recorders with a magnet erase head. Maybe I have misinterpreted what type of erase head they all have.

Mike

[Refugee]

Some have magnets and others have a head with DC applied to it. Most of these used DC bias and made awful recordings.
AC bias without AC erase was less common and a bit pointless.

[Mike Watterson]

Thats odd because I don't think I have seen ANY cassette recorders with a magnet erase head. Maybe I have misinterpreted what type of erase head they all have.
Mike

They often are head shaped. Clue is the lack of a pair of wires.
Other clues is that they only engage the tape when record is selected. If only the play/record head moves forward on play, it's a magnet, even if it looks like a head.

DC erase seems to be rare. Easily spotted with the aid of the cheapest scopes.

Quite a lot of portable reel to reel and cassette from 1959 did have AC bias but magnetic erase, either via a magnet in a holder the full tape width (guides needed) or a head styled holder that either rotated or moved forward.

I'd love to have the vintage German portable reel to reel with battery valves and spring driven transport, also the early Sony transistor portable reel to reel that also used a wind up spring drive for the tape transport. I've no idea how bias and erase worked on them.

I don't remember any DC bias cassette players, but I did have at least one portable reel to reel that probably had DC bias. My first machine was a 2nd hand Grundig Cub for Christmas from my grandparents. Maybe 1965.