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Re: A Modern Loftech TS-1 Audio Test Set

Posted: Fri Apr 06, 2018 6:52 pm
by Carl_Huff
Any progress to report on this John??

Re: A Modern Loftech TS-1 Audio Test Set

Posted: Sat Apr 07, 2018 9:37 am
by JR.
I have been distracted by life,,, always things to fix and/or improve.

I have wanted to do a next, better version of this for almost 30 years, and the modern technology would make this easy-peasy. That said I don't need yet another time/money black hole. I determined decades ago this would not be a hugely profitable venture.

I like the idea of a drop in board swap to bring an old tired TS-1 back to life, stronger and better, but it is hard to avoid feature creep as this thread reveals. A digital/software based audio engine could support lots of new tricks, but display/control interface needs to accommodate the new tricks.

The simplest is just a board swap that covers the original functions (only better).

I would still love to do something like this, but maybe not this lifetime... 8-)

JR

Re: A Modern Loftech TS-1 Audio Test Set

Posted: Sat Apr 14, 2018 7:00 am
by mediatechnology
I like the idea of a drop in board swap to bring an old tired TS-1 back to life, stronger and better, but it is hard to avoid feature creep as this thread reveals. A digital/software based audio engine could support lots of new tricks, but display/control interface needs to accommodate the new tricks.

The simplest is just a board swap that covers the original functions (only better).
Fluke 8050A Meter Displays: https://madnessinthedarkness.transsys.c ... r_displays

Image

Re: A Modern Loftech TS-1 Audio Test Set

Posted: Tue Feb 19, 2019 7:43 am
by mediatechnology
WRT output squarewaves:

The DAC output will require a buffer to drive balanced audio loads.
Make the output buffer switch from linear operation to squaring with a simple switch or transmission gate controlled by a port pin.
Switch an internal circuit node in the buffer to increase an internal stage gain or mode change from op amp to comparator.

There. Done. DAC ringing avoided.

Re: A Modern Loftech TS-1 Audio Test Set

Posted: Tue Feb 19, 2019 9:52 am
by JR.
mediatechnology wrote:
Tue Feb 19, 2019 7:43 am
WRT output squarewaves:

The DAC output will require a buffer to drive balanced audio loads.
Make the output buffer switch from linear operation to squaring with a simple switch or transmission gate controlled by a port pin.
Switch an internal circuit node in the buffer to increase an internal stage gain or mode change from op amp to comparator.

There. Done. DAC ringing avoided.
It seems we've discussed this before but are you worried about "Gibbs" Phenomenon? This strikes me as more of a cosmetic issue, and the waveform should be square enough for typical (tilt) testing. The amount of deviation from a perfect square wave is reduced as the HF bandwidth of the DAC output is increased.

Of course the features for an imaginary version will only be limited by imagination. I imagine a linear stage saturated to output a square wave could have perturbations as it comes out of saturation and reverses direction twice per cycle, could even worse than Gibb's squiggles.

JR

Re: A Modern Loftech TS-1 Audio Test Set

Posted: Wed Feb 20, 2019 8:46 am
by mediatechnology
in large scale production I have seen small specialty circuits come and go
You mean like the 74C926?
I have an idea: Why don't you code a PIC to emulate the 74C926 so that TS-1 owners who need one aren't orphaned.
TS-1 Schematics: viewtopic.php?f=16&t=404&p=4531

Provide us the source code and pinout translation and someone else, if you don't want to, can DIY the adapter.
Most of the 74C926 available on ebay are from China and may not be real.
Domestic ones run $20-45 each and apparently a lot were used in process control displays.

(For that matter you could use a PIC to replace the entire upper-right-hand portion of the schematic and re-issue an updated TS-1. LM13700s are still being made by TI and IIRC Uli.)

All hat, no cattle.
I want to see some cattle.
A PIC 74C926 replacement is a start.

And I can assure you that if you come up with something I won't piss all over it.

BTW I have no clue about the Gibbs thing. I would also buy one of these Fluke things in a heartbeat: viewtopic.php?f=6&t=918&p=12730#p11246