Need help designing an audio circuit - Tape delay unit

cowboybob said:

Can't recall (nor can I find any evidence of) my mentioning square waves. So I'm at a loss as to why you continually (and wrongly) persist in accusing me of "wrong and misleading information". All I mentioned was an oscillator. I'm sure most members know how to generate a sine wave from the output of a 555. Somewhat surprised that you don't seem to know that. I'd be glad to provide a schematic (in LTSpice) for you if you would like.

Click to expand...

So you're suggesting using considerably more parts then the original schematics, a much more complicated system to give poorer results - and you consider that 'good advice'?.

the reason the bias current needs to be a sine wave is that it needs to scramble the magnetic domains. this requires a constantly changing field. a square wave gives two steady states of +/- values (more like the DC erase in effect).

unclejed613 said:

darn, i used to have a parts drawer full of bias oscillator boards, about cubic inch, with transistors and transformer all in a metal can. they had two power pins, and 3 output pins, one of which was ground , and a tap for the record head bias, and a pin that was the whole secondary for the erase head.... the oscillators were made by Toko (i think). they put out 90Vrms@50khz. i used one in a prototype miniature oscillator/voltage multiplier that put out 250V@0.5mA

Click to expand...

The datasheet for National semi's LM1818 tape recorder/player IC shows a Toko bias oscillator module. Erase is done with DC.
I didn't copy the datasheet because the module and IC are not made anymore because NOBODY makes a tape recorder/player anymore.

audioguru said:

The datasheet for National semi's LM1818 tape recorder/player IC shows a Toko bias oscillator module.

Click to expand...

TDK made them as well, you see a lot of TDK ones in VCR's.

Would it just be possible for me to make one of these transformers myself?

DHughes said:

Would it just be possible for me to make one of these transformers myself?

Click to expand...

Yes, if you have the correct core, wire, and the knowledge and skill to do so.

However, all VCR's have them in - and there are millions thrown away.

DHughes said:

Would it just be possible for me to make one of these transformers myself?

Click to expand...

hi,
I would consider stripping one out of an old tape recorder, go to to your local recycle centre and pick up a scrap unit.

E.

Why not just use an old tape recorder complete? All you then need is an extra playback head and pre-amp/mixer (been there, done that...many moons ago).

Nigel Goodwin said:

So you're suggesting using considerably more parts then the original schematics, a much more complicated system to give poorer results - and you consider that 'good advice'?.

Click to expand...

Had no idea you could divine the OP's concern about the component count. That is truly an amazing gift.

The original schematic I referenced (the tube type, strictly as an example of a basic analog tape recorder) was by far the simplest of those thus far considered in this thread. Obviously a straight swap of transistor for tube (your first divining of my intentions) was ridiculous, but I let that slide.

The pertinent element was the concepts that the schematic demonstrated. And without a great deal of effort on the part of the OP he can (should he chose) incorporate those concepts into his efforts at designing (as in this thread's title) the tape delayed echo device.

Sorry, but I'm still quite comfortable with the advice I have thus far offered. And will continue to do so.

This is all starting to become very amusing...

if you need heads, you can get those pot of old VCRs as well..... the big ones on stands, not the heads in the drum... sometimes you get one with record and play heads side by side in one headshell.

unclejed613 said:

if you need heads, you can get those pot of old VCRs as well..... the big ones on stands, not the heads in the drum... sometimes you get one with record and play heads side by side in one headshell.

Click to expand...

VCR's use a single head for linear audio record and playback - the other head is the audio erase head (used for audio dubbing, when you obviously can't use the full erase head).

The OP already has the heads from a compact cassette tape recorder/player. VCR heads are different.