Daisy chaining time base correctors (TBCs)?
 

Is there anything against daisy chaining two TBC's? Let's assume my VCR has a TBC built in, I can then certainly add in a Datavideo 1000 TBC right (this seems to be commonplace):

[VCR with TBC (maybe a simple TBC)] -> [Datavideo 1000 TBC] -> [recording device]

But what about two TBC's in a chain?

[VCR with TBC (maybe a simple TBC)] -> [Datavideo 1000 TBC] -> [Datavideo 1000 TBC] -> [recording device]

or:

[VCR with TBC (maybe a simple TBC)] -> [AV Toolbox TBC] -> [Datavideo 1000 TBC] -> [recording device]

The thought is that perhaps the 2nd TBC would continue to further improve the video synchronization signal or further clean up the signal?

If a VCR already has a TBC, then why feed it to even another TBC? Pro's or Con's with daisy chaining TBC's?

i dont know about running 2 external TBC's

but you definitely want 1 built into the VCR and 1 external TBC.
the VCR's built in TBC and the external TBC do 2 different things.

not sure what deck you are referring to with a "simple TBC"
but you are going to want either a Panny AG-1980 or a JVC deck

A lot of the confusion on this topic is due to the loose usage of the term "TBC" in electronics marketing. Strictly speaking, the DataVideo and the AVT-8710 devices are true, full-frame TBCs, where the "TBC" in a VCR is not exactly the same thing -- 99% of them are what are called line TBCs, not a full-frame TBCs. Most of the visual improvements you get from a VCR TBC come by way of the DNR circuitry anyway. So in terms of answering your question, you have to differentiate between the different types of these so-called TBCs and understand that they fall into a few different categories and are for the most part complimentary.

What type of equipment you can chain together and yield further improvements depends on the function of the device. As far as chaining DataVideo TBCs together -- no -- there are no further improvements to be gained there and only issues of audio synch.

On the other hand, many devices that are sold as "TBCs" or including TBCs are not/do not, but sometimes they have other useful functions.

For example, if you have a copy protected tape that won't play well with the VCRs TBC engaged, but has flagging issues when the VCRs TBC is off, you can run it through a Panasonic ES-10 on passthrough and then through a DataVideo TBC to bypass the copy protection. Some DV camcorders provide similar fixes for the flagging issue that can't always be addressed by a VCR's line TBC or a full-frame TBC like the DataVideo model.

What are you specifically trying to do?

Stick with one TBC. There is no quality improvement by adding another one.