4 PT2399 delay with current mirrors time control: matched transistors?

[Morocotopo]

I´m currently developing a four PT2399 delay, stol... ehh, inspired in Deadastronaut´s Abductor Delay, to get kind of a 4 head tape delay workalike. Yesterday I tested it´s sound for the first time, but to my surprise the delay chips have all slightly different delay times! Kind of defeats the purpose of the circuit, sounds like you can´t play in time! The time control is lifted directly from the Abductor, so it´s 5V fed through a pot to all the transistor´s Base, Collectors to pin 6 of the PT´s and Emitters to ground through a 560R resistor. That is a current mirror setup from what Deadastro said in the post  for his circuit. I read a bit about current mirrors but most are a bit different from the ones in the Abductor´s implementation, and besides I won´t pretend to fully understand what a current mirror is. But my guess is: since the idea is to have equal current going into each delay chip to have the same delay time, the current mirror circuit has to be exactly equal for each chip, and that means matched transistors (and I guess resistors too), right? So, should I match the transistors for Hfe with my DMM, as simple as that? Or is something else required?

Hope I´m clear with my question.

[deadastronaut]

i never matched my 3904's for the current mirroring...

pin 6 of each pt goes to collectors

join all bases together..

and have 560r on emitters...to ground

use one pt/Q to control delay time..

connect lugs 3/2 of a 1M pot..with a 1M resistor in series, to the Q1 base..lug 1 has a 470r going to 5v....

now they should be in sync...Looooooong delay.  ....you theif.

[Morocotopo]

I confess, I´m a thief!!!





Basically, rob, I´m adapting the Abductor to my needs, what I´ve changed is that all PT´s delay out sum with an inverting op amp, and the repeats are taken from the last delay chip, and each delay "tap" can be switched on or off to get different rhythms. In essence an uneccesarily complicated Abductor!

I have the time control set up just like you described, except no 1M R in series with the pot (that is a 1M one) anda 1K instead of a 470R from 5V to the pot. Will that make a difference? I´ll try it.
Thanks for the answers to my quests, Rob.