I've built the guitar, built the amp, and next.......

[ecca]

Having got one head working next step will be to establish the head timing and see if I can replace the multi turn pot that controls it with a 1% resistor.
Next I will have to mix the outputs from the 4 heads and the original incoming signal with a TL072 , which I've seen a couple of circuits for or perhaps a 741 op amp.
I think the incoming signal will have to be pre-amped , again perhaps using the other half of a TL072 so as to drive all 4 'heads'.
Advice much appreciated on this.
Cheers
Ecca

[ErikMAMS]

....I will have to mix the outputs from the 4 heads and the original incoming signal with a TL072 , which I've seen a couple of circuits for or perhaps a 741 op amp.

I think the incoming signal will have to be pre-amped , again perhaps using the other half of a TL072 so as to drive all 4 'heads'.

Consider FET's (ie J201) for both - set up right they can give you a bit of "colour" instead of clinically clean. Alternatively with just one valve (ECC83) you can get the Meazzi preamp with the grid leak biasing and the mixer out.

Erik

[ecca]

Thanks Erik, what about an EF86 purely as the preamp ? I intend to build an EF86 free standing pre-amp. I dismantled my old Grundig tape recorder hoping to find a suitable transformer but it was incorporated into the motor,but never mind, I can use the echo unit as a food mixer instead if it doesn't work.

[neil2726]

Cor - I get lost after the on off switch!

[ecca]

Project on hold, going to Lanzarote for a couple weeks.........

[Detailed Infinity]

Keep on going Eric. I'm surprised you've not covered this before now. You have the expertise and the theory so go go for it.

Brian

[ecca]

Back home from the dreadful sunshine all day long.
Ordered the resistors and capacitors etc.
Get cracking soon again........

[Amanda]

I think I'm going to build an echo unit using Jean Claude's brilliant idea of using one PT2399 echo chip per playback head.
It won't be anything like as complicated as his wonderful model and I could do with some input from you.
The intention, obviously, is to replicate the echo patterns of a 4 head Meazzi.
I intend to make the controls simple like a Copicat.
Echo level and echo feedback controls.
Push button switches, one for each head.
But...... where, for example does that leave Apache ?
Which head would the feedback be taken from or is it invariably the 4th head ?
Wonderful Land ? 4th head feedback too ?
What does the team think ?

Ask the Oracle - Mr Charles Hall!!

[Amanda]

Thanks Erik, what about an EF86 purely as the preamp ? I intend to build an EF86 free standing pre-amp. I dismantled my old Grundig tape recorder hoping to find a suitable transformer but it was incorporated into the motor,but never mind, I can use the echo unit as a food mixer instead if it doesn't work.

ECC83 as pre and post amp using the Meazzi model J circuit!!

Passive mixing as per the model J - nasty transistor and op amp rubbish!!

Ah well back to the Factotum I have in bits!!

[ecca]

It's back on the bench.......
I'm designing a PCB for it straight off, I hate messing with veroboard and all that crap.
Were Apache and Wonderful Gland done on different machines ?