Revox C270 Channel 1 dual output mod'n. Any info

[TIMTAPE]

I'm not very familiar with this last Revox series. This Revox C270 has a modification notice on the front panel as per the photo. The Service Manual doesnt appear to have details on the mods involved. I'm not sure if this was a factory mod or performed by a third party. Does anyone anyone, perhaps Ted or Barry, know anything more about these mods pls?

Thanks, Tim

[Ted Kendall]

That's a new one on me - perhaps ch1 output is routed to both ch1 and ch2, which I suppose is easy enough to check, and could have been done with a simple Y-connection. I don't know if the unit is ex-BBC, but perhaps it was used for transferring Uher tapes, which were half track mono.

[TIMTAPE]

Thanks Ted, will check at the output XLR's.

[DMcMahon]

I did a search for this on Microsoft 365 Copilot.

It did not find anything specific but did say it had found a reference to Bulletin 7-89 for the Revox B77 and said it could contruct a PDF of likely contents, I think based upon general upgrade/modification information it had found, as per the attached PDF.

This PDF has nothing to do with the C270 modification and possibly little to do with the actual B77 bulletin contents, but is interesting to see that Copilot can generate this type of document which may not be relevant or accurate to the search in question.

David

[Ted Kendall]

Like most AI - a waffle-fest.

[Michael Maurice]

If the contents of that bulletin are anything to go by, I'd say thanks but no thanks. It's very inaccurate and misleading.

[Trigon.]

I'm not a fan of AI, but for interest here's Google Gemini's not unreasonable guesses in response to the question What is the Revox C270 Channel 1 dual output mod? (which may well have no definitive answer...):-

The Revox C270 Channel 1 dual output mod is an aftermarket modification for the Revox C270 reel-to-reel tape recorder, likely intended to provide a second, independent, or buffered output for Channel 1.

While details on this specific modification aren't commonly listed in the general overhaul kits or service manuals, here is a breakdown of what it most likely entails, based on common vintage audio modifications:

- Purpose of a Dual Output Mod
The primary goal of a "dual output mod" on a single channel of a professional tape machine like the C270 is usually one of the following:

Buffered Split Output: To provide an additional, electrically isolated, or "buffered" output signal for Channel 1.

Benefit: This allows the signal to be sent to two different destinations (e.g., a mixing console and a monitoring system) without the load of one device affecting the signal level or quality delivered to the other.

Separate Monitoring/Metering Feed: To dedicate one output to the machine's primary function (like feeding a console) and the second to a dedicated metering device, analysis equipment, or a separate monitor chain.

Alternative Level/Impedance: To create a second output that is either Unbalanced alongside the original Balanced output, or one output with a fixed Calibration (CAL) level and another with the Uncalibrated (UNCAL) variable level.

Since the Revox C270 already has LINE OUTPUT CH 1 and LINE OUTPUT CH 2 (which can be switchable between calibrated and uncalibrated levels), the "dual output mod" for Channel 1 would specifically be about getting two distinct outputs from Channel 1.

- Common Revox C270 Modifications
The C270 is a professional-grade machine often subjected to upgrades. Common and similar modifications often revolve around the audio path:

Recapping/Overhaul: Replacing all electrolytic and tantalum capacitors.

EQ Board Swaps: Changing the plug-in Equalization boards (like switching from NAB to IEC curves).

Tube Electronics: Some enthusiasts replace the original solid-state audio electronics with custom tube (valve) circuits for a different sound profile.

Output Stage Upgrades: Replacing or bypassing sections of the original output amplifier with higher-performance components.

The "Channel 1 dual output mod" would likely be a simple circuit addition to the Reproduce Amp or Output Amp board for Channel 1 to split and buffer the signal before it reaches the existing output connector.

Would you like me to look for discussions or diagrams related to specific third-party Revox C270 audio circuit modifications?

Cheers

[stacman]

Is 7 89 when the mod was carried out? July 1989?
Regards

[TIMTAPE]

Thanks all. Ch 1 goes to Ch1 and Ch2 output XLR's. No Ch 2 is audible in any switch position. At headphone socket and meters, channel switching is as normal except never Ch2. I assume the mod was done July 89 as per the label. Someone from TH forum has given me a name to chase up so I've emailed them, awaiting a reply. Thanks again, Tim