Tube channel strip prototype. It’s alive!

The tube channel strip prototype is alive. Not running any marathons just yet. Still have some tweaking to do, but I just had to post a vid of the “just fired it up” moment.

Thanks for all the help from guys on here, especially Ian!

https://youtu.be/u65V9wnhzuE

That sounds good Dan ,post  us up a tune man.

Nice video Dan. It is always a great feeling when your hard work pays off with a working unit.

Which tube sockets are you using.? Are they PCB mountable or is the build all point to point underneath?

Cheers

Ian

Hot dang, that sounds REALLY good! Great work!

Everything, including the tube sockets, are entirely point-to-point / turret board construction. I must admit that it is not nearly as easy to keep things tidy with this many components as a PCB build would be. The three 10-conductor wires connecting the eq section to the Grayhill switches are very stiff, and it makes it difficult to work with.

It would be much easier to use PCB mounted rotary switches and keep all the eq section attached right to the front panel. But then, it loses the point-to-point “cool” factor.

I’m having a devil of a time with that meter. Tried everything and it doesn’t want to work. Maybe it’s broken.

BluegrassDan said:

I’m having a devil of a time with that meter. Tried everything and it doesn’t want to work. Maybe it’s broken.

Click to expand...

I think the design expects it to have a built in bridge rectifier like a 'proper' VU. Many of today's VU meters do not include this. You can try testing it with a 1.5V battery and a 3K series resistor which should flip the needle if you get the polarity correct. If it flips no matter which way the battery is connected then it must have a built in bridge. If it flips only one way and tries to wrap itself round the zero stop with the battery the other way round then it does no have the bridge.

Cheers

Ian

Very nice dan.  Who wouldn't want one of those.  I like the Ribbon mic input switch.  Also sourcing from Jensen rather than trying to find all the RCA transformers these days make a lot of sense.  Nicely done.

Ian,

This meter has a built in rectifier. The 1Meg pot was defect, so I replaced it with a split pair of 500k resistors and tweaked until it put the GR at 0. The gain reduction does not move the needle for some reason. Tracking down the gremlins now.

Turns out there were a few problems:

1. The T4B, while compressing, was not sending signal down pin 5 to the meter. Swapping out the T4B fixed this.

2. The meter has a bridge rectifier, BUT it also had a parallel resistor for some reason which was messing up R25's value. Removed the resistor, jumpered the pads, and everything worked correctly.

And here is day two's demonstration video with singing through a Peluso P87 (courtesy of John Peluso).

Any input is always welcome.

https://youtu.be/Ej5N9FdGaqo

Sounds good! Is this still your preamp circuit based on the modified Hamptone preamp?

Yep. Same preamp circuit.

I’ll tell ya, I’m about to consider an external PSU. It is so difficult to quiet these things down, even with a potted and shielded torroid.

wow!! sounds like a hit machine!

together with the neumann mic it sounds like christmas eve!

nice singing too!!

That is one beee-u-t-ful piece of hardware!

Bummer about the meter.  Do you have another one you can try?

The meter is working fine now.

QUESTION:

I included a switch to bypass the mic preamp section for LINE IN. Using a Jensen JT-11P-1 line input transformer that goes directly to the LA2A circuit. Can anyone think of why the LINE IN would change sonically? It seems like an impedance issue, as it sounds very muddy with a loss of high frequencies. I did the Jensen schematic with 11k across the transformer secondaries.

Thoughts?