[BUILD] TB550A

[rob61]

Let me start by saying I use the pair I built on almost every session. I really like the sound of these EQs. Thanks for making these kits available. As you may recall, I found a signal loss when switching them in. Would a THAT input eliminate that? I built a pair of Jeff Steiger's EQs as well, and I've noticed I don't get signal loss when switching them in (all settings at zero). Not sure what the difference is, but if a THAT input would eliminate the signal loss, I'd like that option.

Next, would there be a way to add a "divider" switch or internal jumper to change the decibel gain/reduction steps to +/- one db instead of two db? That would be a dream come true. Switch off, normal two db operation. Switch on, one db per step operation.

 

[horvitz]

Rob,

Glad you are enjoying them and they're seeing so much use!  That's very cool to hear.  Based upon what we discussed back when you built them, the unbalanced input is most likely the culprit with your loss when switching them in.  Since you've built both, you can obviously see that Jeff's EQ is as different from this as any other two EQs would be from each other but one thing that his has is a balanced input so it is probably playing much nicer with the gear just before.  That being said, I would expect that the IC input option would get you sorted out.

As for the divider switch, sort of like on the 5500, that's something that I haven't thought about in a while.  It's not such a simple matter but perhaps I'll give it a some more thought.  It would certainly be a very nice option.

  Brian

 

[qmp audio]

24v 51x option for round 2?

 

[horvitz]

24v 51x option for round 2?

Well, it's on my list of things I'd like to do but to be honest, I don't think I'm going to be able to find the space for the additional components.  We'll call it a maybe for now.

I do have the thing about 50% laid out right now and it's coming along nicely.  The IC input option is worked out.  There will be a toggle switch on the PCB to let you switch between IC and regular input.  There will also be a header and shunt to select hard or soft bypass mode.  Just need to figure out how to jam a F6UEE in the space where the bypass switch is now (or some other method of getting 6PDT).  Piece of cake, right?

 

[qmp audio]

There will also be a header and shunt to select hard or soft bypass mode.

awesome idea

 

[horvitz]

I'm surprised it's only been a month since we were talking about this last.  Here's a look at the new version.

You can't see it, but just over the rear relays is a header and shunt which allows you to choose hard or soft bypass mode.
Regardless of the setting, it goes to hard bypass when the unit doesn't have power.
Below those relays is where you can select IC or unbalanced input.  I've got a switch coming which should fit in that spot.
The two relays near the top of the card manage the soft bypass.  They work in exactly the same fashion as the vintage unit.
Additionally, you can see the very dense resistor layout up front.  I think that's all the space!  No more of those small guys underneath, though.

Just a couple of small items left on the to-do list now.  Very close, though!

  Brian

 

[rob61]

1. Will these mods be available for v1 builds or will it require a new build?
2. Any plans for a divider switch so gains can be +/- 1 db or 2? Would that be hard to implement?

 

[horvitz]

1. Will these mods be available for v1 builds or will it require a new build?
2. Any plans for a divider switch so gains can be +/- 1 db or 2? Would that be hard to implement?

1 - It will require a new build, but I can offer a partial kit so you don't have to buy all the expensive stuff again.  The metalwork is all the same, so you can save that.  You'll also have to have a desoldering gun (and patience) to get all those switches out (lots of patience!).  Probably all the passive components will be replaced.  Unfortunately, even though there will be no change to the filter board, it won't fit the new layout so it will have to be rebuilt as well.  I'll do my best to make this as reasonable as possible for anyone who wants to do it.

2- Probably not.  I think I understand where it would need to go in circuit but I haven't tried it out.  I'll stew on this a little since I think it would be a really nice option but I hadn't wanted to change the front panel at all.  Doing 2 would make 1 more expensive since the metalwork would no longer be usable.

 

[horvitz]

All parts and PCBs have been ordered for the next round!  Should be available to order sometime in January.

 

[drgrateful]

Hi,

I would like to connect the output of the TB550a to an A/D converter having only RCA unbalanced inputs. Can I wire a cable as

XLR 2 --> RCA Tip
XLR 3 --> RCA Sleeve
XLR 1 connected to shield and left unconnected on the RCA side
XLR 1 bridged to XLR 3

It's scheme number 6 here: http://www.rane.com/note110.html

In particular, I am worried that bridging XLR 1 and 3 might harm the TB550a.

Thank you!

Matteo

 

[Majestic12]

Hi,

I would like to connect the output of the TB550a to an A/D converter having only RCA unbalanced inputs. Can I wire a cable as

XLR 2 --> RCA Tip
XLR 3 --> RCA Sleeve
XLR 1 connected to shield and left unconnected on the RCA side
XLR 1 bridged to XLR 3

It's scheme number 6 here: http://www.rane.com/note110.html

In particular, I am worried that bridging XLR 1 and 3 might harm the TB550a.

Thank you!

Matteo

You can make the connection unbalanced by connecting Pin 1 and 3 (Ground and Cold) at the xlr socket. Don't worry, there's no chance of damaging your EQ with this.

 

[horvitz]

Mr. Majestic beat me to it but yes, he's right.  You won't damage anything like this and it should work out.  Let's us know how it goes.

  Brian

 

[drgrateful]

OK, thanks, I am soldering my cable!

I suppose the same wiring applies also when going from the D/A converter output to the TB550a input. Correct?

Matteo

 

[horvitz]

Actually, on the input side, pin 3 is already connected to ground.  So, do it in the cable or let it happen on the EQ, it will be the same.

Just a note for other folks that on my v1.1 boards which I'm shipping now, this would not be the case!  It would have to be done in the cable.  There are some ifs and buts to go with that as well, so let me know if it comes up.

 

[Winetree]

I hope you can do right and make the partial kits to fix V1's very reasonable.
I helped financed this project with 2 V1's.

 

[horvitz]

To be honest, I haven't given it much thought since not a single person has expressed any real interest doing such an upgrade, except for one who hadn't even started building his v1 boards yet.  Are you having some particular issue with yours that you think would be addressed by the new boards?  Frankly, they are about 98% the same and you're looking at a LOT of work, and I'd hate for you to do all that work to no benefit.

 

[drgrateful]

OK, working fine! Here's my build:

http://s1071.photobucket.com/albums/u507/drgrateful/TB550A/

Cheers, Matteo

 

[emrr]

Seems like way too much work just to get stable bypass option on a V1.  Easiest path would be adding on a daughter board balanced receiver.  I may someday do that with a 1240 or similar.  Otherwise I just don't bother with the bypass. 

 

[horvitz]

Matteo, that is a wonderful and clean build!!  Very nice work, sir  8)

 

[okgb]

If V1 was designed to be as close to a real 550A  , then that's what you're getting
Since it's not a simple retro fit , I'm choosing to finish my v1 as is , and if I feel the need for the
v1.1 after having used the v1  , then I'll sell and rebuy . Still the only guy brave enough to take on
the mighty  550A  in kit form .