[BUILD] TBDD

[horvitz]

Another one lives!  Awesome  8)  Nice noodle  ;D ;D

 

[horvitz]

A bit of good news!  It's been a long delay, but the TBDD-rack PCBs are finished and approved.  I'll be ordering them today.  We can look to ship in mid-July.

Between now and then, I'll get together the BOM and wiring guide for you all.  I plan to offer the PCBs and an optional mini-kit with all the hard to buy parts.  Unless there is some overwhelming demand (at least 25), full kits will not be available for this one.

 

[fazeka]

That is a BUNCH of good news, for the rack-lovin' TBDD people, anyway.  ;D Sign me UP!

Thanks!!

 

[fred]

It's very good news!! Sign me up aswell!!!! ;D

 

[horvitz]

Just added TBDD-Rack PCB sets and Mini Parts Kits to the store.  BOM and Wiring Guide in just a couple of days.  Hopefully I can get some pictures soon too, but my camera broke.  There are just three parts kits right now, but the rest will be available by the end of the week.  Enjoy!

 

[fazeka]

Hi,

Just ordered two sets of the parts kits and PCBs! Can't wait!  ;D

Chris

 

[electrisizer]

thing is alive and sounds veeery cool  8)

demo

original: https://app.box.com/s/1yp6ve5ixknenlitffgd
TBDD on keys + git stem (knob 4, 100%wet): https://app.box.com/s/8obi5t70z5iz9r5rcwt0

thats real 3d sound

thanks horvitz!!!

 

[horvitz]

Awesome!!  ;D

That's a darn cool little groove, too.  Well done.

 

[kante1603]

thing is alive and sounds veeery cool  8)

Klasse Alter,die Dinger sind einfach endgeil!

Love mine,

Udo

 

[fazeka]

Got something in the mail today... 

 

[rob_gould]

I've got a really strange problem with this unit.  At first I was only testing in mono, and everything appeared to work OK.  I could hear lovely chorus even when the unit was uncalibrated.

When I tried to calibrate it, I noticed that there was a big mismatch between channels, and I couldn't get a steady output on the right hand side feeding the unit with test tone.

I noticed that I had accidentally put two THAT 1246s on the right hand side, and two THAT 1646s on the left hand side, instead of one on each side.  Aaargh!

So I swapped two chips round so now IC101 and IC201 are THAT 1246 and IC114 and IC214 are THAT 1646.

Unfortunately, now it seems that there's another issue.  On power on, the output seems to be steady, but when I turn up the gain on the test tone coming from my DAW, the meter goes crazy and dances about.  The sound through the speaker is a variable speed of clicking, about once or twice per second.  I can hear the correct audio coming from the left hand side though it's distorted.

Just to make sure I haven't got some weird feedback loop through my DAW, I've gone straight in with a synth and the result is the same; clicks on the RHS and a low volume, distorted version of the source on the LHS.

By swapping the 1246 and 1646 chips round I've worked out that the source of the distortion is one of the 1246 chips, so that takes care of that.  I'll order a replacement.

But where is this clicking noise coming from? 

The clicking matches what appears on the meter, it appears in both mono and in stereo mode and it only comes out of the right channel.  It also is the same whether the unit is in soft bypass or with one of the chorus modes engaged.  Of course, when the unit is off (hard bypass) the correct audio is passed straight though.

Any ideas anyone?  I presume the next stage is to start swapping chips between LHS and RHS one at a time, but I'll like to have an action plan wather than just wading in.

Cheers

Rob

 

[jplebre]

The sound through the speaker is a variable speed of clicking, about once or twice per second.

this would be the clock. One of the chorus chips.
have a look at the clock cancel step on the callibration procedure, or maybe there is a filtering cap gone wrong somewhere when the chips were inverted?

 

[rob_gould]

The sound through the speaker is a variable speed of clicking, about once or twice per second.

this would be the clock. One of the chorus chips.
have a look at the clock cancel step on the callibration procedure, or maybe there is a filtering cap gone wrong somewhere when the chips were inverted?

Thanks, I'll have a poke around. 

I did actually swap the chorus chips themselves MN3007 and MN3101 and the problem remained on the right hand side, so at least I know those chips are OK.

I'll double check the calibration procedure again too.

 

[horvitz]

Yeah, unfortunately those THAT chips are a little wimpy.  Putting one in the wrong socket will show it a voltage somewhere where it isn't expected so I'm not surprised that one got cooked.

Regarding the click, when you look at the calibration again, what do you see on the BBD bias voltage?  Is it steady?  I've seen a bad compander (the SA571NG) blurp out DC every few moments.  You would be able to see that at the bais test point.  Hopefully your DMM is fast enough to see it, if that's the case.  If I had to swap something left to right to see if the problem follows, I'd start there.

 

[rob_gould]

Yeah, unfortunately those THAT chips are a little wimpy.  Putting one in the wrong socket will show it a voltage somewhere where it isn't expected so I'm not surprised that one got cooked.

Regarding the click, when you look at the calibration again, what do you see on the BBD bias voltage?  Is it steady?  I've seen a bad compander (the SA571NG) blurp out DC every few moments.  You would be able to see that at the bais test point.  Hopefully your DMM is fast enough to see it, if that's the case.  If I had to swap something left to right to see if the problem follows, I'd start there.

The bias voltages are steady at -7.50V measured on a Fluke 177 meter.

I've swapped the SA571s anyway and the problem remains on the RHS.

Because this issue exists in soft bypass mode, which parts of the circuit can be eliminated?  I remember you advising someone earlier in the thread that if the issue exists in soft bypass, a lot of the circuit can be ruled out as problem free...

Thanks!

 

[horvitz]

Because this issue exists in soft bypass mode, which parts of the circuit can be eliminated?  I remember you advising someone earlier in the thread that if the issue exists in soft bypass, a lot of the circuit can be ruled out as problem free...

This is very true.  Most of the circuit is out when in soft bypass.  In basically goes like this:

input->input mode (mono/stereo)->blend->output

A good experiment would be to send a test tone to the right input and put it in mono mode.  That takes the right input and sends it to both channels.  In this case, does the clicking exist on the left?  If not, we know that the problem is after the input mode select.  If it does, it's there or before.

 

[rob_gould]

Because this issue exists in soft bypass mode, which parts of the circuit can be eliminated?  I remember you advising someone earlier in the thread that if the issue exists in soft bypass, a lot of the circuit can be ruled out as problem free...

This is very true.  Most of the circuit is out when in soft bypass.  In basically goes like this:

input->input mode (mono/stereo)->blend->output

A good experiment would be to send a test tone to the right input and put it in mono mode.  That takes the right input and sends it to both channels.  In this case, does the clicking exist on the left?  If not, we know that the problem is after the input mode select.  If it does, it's there or before.

So, the test is tone to the right input only.  Left input is completely disconnected.  Mono mode engaged.

Through the right hand side comes the clicking noise.  Through the left hand side comes clean tone.  So the problem is after input mode select.

Two observations :

1 - As I raise the gain of the tone, the clicking gets faster.  At zero gain it's a slow click.  As I make it very loud the clicking mutates into almost a constant noise.

2 - Patching around I have noticed that if I removed the right hand output connection the clicking stops.  If I put the unit in stereo mode and feed a signal into the left and out from the left, the unit effectively works properly on the LHS only. 

Or to put it another way, I can put it into mono mode, feed a signal to the RHS and then hear chorus on the LH output with the RH output disconnected.

 

[horvitz]

OK, so we're getting down to it then.  On the right side, the only remaining ICs are 113 (TL074) and 114 (1646).  You already swapped the 1646, so we know that's ok.  Try changing 113/213 and see if the problem goes with it.  If not, it's some individual component and we'll have to trace the signal through the last bit to see where it's happening.

 

[rob_gould]

Well, I swapped ic113 and 213 and the problem didn't go. So I though t I'd just quickly swap the THAT1646s again and whaddayaknow, the clicking moved to the other channel. So I'm embarrassed to say that I must somehow have confused myself when initially moving things round to troubleshoot.

This makes sense really, both a 1246 and a 1646 were in the wrong position so it's plausible that both would have ended up fried.

I'll place an order for a replacement of each and keep my fingers crossed!

Thanks for your help Brian.

 

[kante1603]

Fingers crossed here too Rob,this chorus is one of the best ever!

Good luck,

Udo.