DIY Tape Delay Problems

[Harry]

Well after assembling this wretched thing using discarded cassette player parts I'm having some problems. I'm hoping someone out there has made one before and knows about tape delays.

1) After running this thing. It makes a distorted boomy noise that sorta resembles a guitar, is it really supposed to sound like this? I've made sure that the signal to the record head is low but that doesn't seem to help. I've also made sure the input booster isn't clipping the guitar signal. Do the heads have to be VERY precisely placed? Right now they are what I would think as "Good enough" at least for testing.

2) Right now it does delay the signal, not well, but enough to know it's operating. I'm having trouble sending the original "non-delayed" signal to the output jack for a slapback. I've tried going directly from the input jack to output jack (where the dotted line is on the picture below) and then it won't even delay. I've also tried connecting the output jack to the output of the first booster and that made it squeal and put up a big fight.

Here's my layout:


Thanks for reading. All help welcome. I can probably post a sound file if you think that it would help.

[A.S.P.]

the record/play heads need to be perfectly parallell (vertically),
and at the exactly same height.
simplified:
In the first case (azimuth), you loose treble,
in the second, volume (well, and treble, too)
if not aligned well.

Combining dry & delayed, requires buffering the dry,
and combining the 2 with resistors (or an adder/mixer),
otherwise you`ll shorten the dry signal with the low
output impedance of the delayed-amp.
(maybe you can pick a buffered dry signal from somewhere in
the first recorder`s signal chain).

last, but not least: 1st recorder in REC- 2nd in PLAY-mode, not to forget...

[Harry]

the record/play heads need to be perfectly parallell (vertically),
and at the exactly same height.
simplified:
In the first case (azimuth), you loose treble,
in the second, volume (well, and treble, too)
if not aligned well.

I'd like to say hopefully that is the problem, but I'm getting sick of trying position those heads. I did notice the volume change when the Rec. head was moved towards and away from the tape.

Combining dry & delayed, requires buffering the dry,
and combining the 2 with resistors (or an adder/mixer),
otherwise you`ll shorten the dry signal with the low
output impedance of the delayed-amp.
(maybe you can pick a buffered dry signal from somewhere in
the first recorder`s signal chain).

So you mean wiring it like my diagram with the dotted line but also adding resistance to each outgoing signal? The more I spend tinkering with electronics the more I don't understand it seems.

Thanks for the help I'll have to mess around with it some more over the next couple days to see if it works.

[Ge_Whiz]

Er... have you ever wondered why some enterprising company has never put a cassette-based tape echo on the market? I think you're getting close to the answer. Incidentally, how are you getting three heads up to the tape? You need to include an erase head, right?

[Harry]

Actually about the erase head, it dissappeared I think maybe one of the cats stole it, one of the many examples of how unlucky I am. So right now I have rewind the tape, erase it using a seperate tape player, rewind it again and pop it back in. The other heads are set on some double sided adhesive foam to bring it to height. It's understandable why companys haven't used cassettes, mostly because there is no real advantage of using a cassette over a better quality tape loop (for tape delay).

[Peter Snow]

Actually about the erase head, it dissappeared I think maybe one of the cats stole it, one of the many examples of how unlucky I am. So right now I have rewind the tape, erase it using a seperate tape player, rewind it again and pop it back in. The other heads are set on some double sided adhesive foam to bring it to height. It's understandable why companys haven't used cassettes, mostly because there is no real advantage of using a cassette over a better quality tape loop (for tape delay).

Hi Harry,
A couple of observations:

1) Many years ago I had a circuit for a tube based tape delay unit and it used a permanent magnet to erase the tape instead of an erase head.  Now, I don't know if there will be other side effects from this, but if some residual noise is generated it will probably be masked by the next sound recorded onto the tape by the record head.  Anyway, you can certainly use an erase magnet for testing purposes.  Oh... and keep it away from the cats

2) I don't think that pieces of double sided tape stuck under the record and playback heads will be precise enough (unless you are really lucky).  Most tape head assemblies I have seen are mounted on a plate that has adjustment screws to precisely adjust the height and azimuth. You will probably get some sound out of it, but it will be a bitch to adjust to the point where you get any reasonably useable results. The chances of getting them correctly aligned when mounted by tape is pretty slim, I would think. 

HTH,

Peter

[Harry]

Many years ago I had a circuit for a tube based tape delay unit and it used a permanent magnet to erase the tape instead of an erase head.

The erase head I pulled from the player was actually just a little magnet. So I was thinking of maybe using some other permanent magnet. I've also heard of some players using a record head and recording a very high frequency to "erase" the tape.

I don't think that pieces of double sided tape stuck under the record and playback heads will be precise enough (unless you are really lucky).  Most tape head assemblies I have seen are mounted on a plate that has adjustment screws to precisely adjust the height and azimuth. You will probably get some sound out of it, but it will be a bitch to adjust to the point where you get any reasonably useable results. The chances of getting them correctly aligned when mounted by tape is pretty slim, I would think.

Yeah, your probably right. I'll have to come up with something.

[Ge_Whiz]

The main problem with cassette tape is that it is designed to have only one place where a record/replay head can go - right in the middle, where it presses the tape up against the little felt pressure pad on the bronze spring. Without such close contact between tape and head - as well as precise head alignment - I think you'll find it difficult to get acceptable results. In my experience, most casette record/replay heads are bigger than the erase heads, so it's not possible to locate one where the erase head was.