Welcome Guest! To enable all features please Login or Register.

Notification

Icon
Error

Login


2 Pages12>
Options
View
Go to last post Go to first unread
SCompRacer  
#1 Posted : Friday, March 1, 2013 6:45:47 AM(UTC)
SCompRacer

Rank: Member

Groups: Member
Joined: 1/6/2012(UTC)
Posts: 305
Location: Plainfield, IL

Thanks: 11 times
Was thanked: 26 time(s) in 21 post(s)
Crude drawing, but if two B III's are connected to a single Legato in this manner, SE and balanced outs of Legato are in proper phase.

Single harness is for left channel DAC board; L channel phase correct, R anti phase. I'm not seeing or hearing increased output out of the dual BIII/ single Legato.

Edited by user Sunday, March 3, 2013 12:30:20 AM(UTC)  | Reason: Not specified

SCompRacer attached the following image(s):
singlelegato.jpg (38kb) downloaded 133 time(s).
left_harness.jpg (116kb) downloaded 132 time(s).
both_harness.jpg (73kb) downloaded 83 time(s).

You cannot view/download attachments. Try to login or register.
SCompRacer  
#2 Posted : Wednesday, March 27, 2013 7:57:22 PM(UTC)
SCompRacer

Rank: Member

Groups: Member
Joined: 1/6/2012(UTC)
Posts: 305
Location: Plainfield, IL

Thanks: 11 times
Was thanked: 26 time(s) in 21 post(s)
I am using two Placid HDBP power supplies to power my assembled as shipped Legato. Dual BIII's connected to Legato.

Jumpers J1 and J2 removed on Legato. Jumpers J3 and J4 installed so one HDBP powers the left channel, one powers the right channel and SE/headphone out. Sometimes when powering up for the first time, the right channel is garbled. It requires another power up for it to work. I tried another Placid HDBP I have, same thing happens.

Initially I shunted ~ 50mA for both R and L channel supplies. Pos and neg output set to 14.85v when warmed up, ~15 when first powered up. Now I am now shunting 90-100mA on the right channel/SE supply and sometimes I still don't get the right channel powered up on first power up. Voltage will read low on pos/neg for right channel supply when first powered up, like 7v, 5v, etc. Next power up I may get full voltage and mA.

Is their any difference with powering the SE stage from the left channel side versus the right? Anything I am missing?
Russ White  
#3 Posted : Friday, March 29, 2013 1:51:18 AM(UTC)
Russ White

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN

Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
Sounds like a power sequencing thing. All of the supplies need to come up at once.
SCompRacer  
#4 Posted : Friday, March 29, 2013 5:06:29 PM(UTC)
SCompRacer

Rank: Member

Groups: Member
Joined: 1/6/2012(UTC)
Posts: 305
Location: Plainfield, IL

Thanks: 11 times
Was thanked: 26 time(s) in 21 post(s)
Thanks for reply Russ.

When I wired the trannys I tired to keep the AC wiring close in length. That is closest tranny to furthest PS. There is ~ 2- 2.5 inches difference in AC wiring to Placid HDBP's. The DC wiring is shortest for the Placid HDBP running the extra load of SE section.

Primary wise I have three short harnesses off the line AC input connected to two trannys each.


Brian Donegan  
#5 Posted : Friday, March 29, 2013 6:09:07 PM(UTC)
Brian Donegan

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA

Thanks: 2 times
Was thanked: 141 time(s) in 134 post(s)
Originally Posted by: SCompRacer Go to Quoted Post
Thanks for reply Russ.

When I wired the trannys I tired to keep the AC wiring close in length. That is closest tranny to furthest PS. There is ~ 2- 2.5 inches difference in AC wiring to Placid HDBP's. The DC wiring is shortest for the Placid HDBP running the extra load of SE section.

Primary wise I have three short harnesses off the line AC input connected to two trannys each.




i don't think wire length will have any effect here, at least not with the problem you are having.
SCompRacer  
#6 Posted : Tuesday, April 2, 2013 5:43:17 AM(UTC)
SCompRacer

Rank: Member

Groups: Member
Joined: 1/6/2012(UTC)
Posts: 305
Location: Plainfield, IL

Thanks: 11 times
Was thanked: 26 time(s) in 21 post(s)
OK, just curious, does it have something to do with the relay on the Legato?

Edited by user Tuesday, April 2, 2013 5:43:53 AM(UTC)  | Reason: Not specified

Russ White  
#7 Posted : Tuesday, April 2, 2013 5:40:17 PM(UTC)
Russ White

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN

Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
No - it is more about the time sequence of the various supplies coming up. It's just a theory, as I am not sure how your rig is set up.
SCompRacer  
#8 Posted : Tuesday, April 2, 2013 10:29:38 PM(UTC)
SCompRacer

Rank: Member

Groups: Member
Joined: 1/6/2012(UTC)
Posts: 305
Location: Plainfield, IL

Thanks: 11 times
Was thanked: 26 time(s) in 21 post(s)
This pic is accurate for power supply and tranny placement. Originally had two ver 3.1 Legatos but wanted discrete output, SE and headphone back. That is when I decided to power single Legato with two HDBP supplies. Jumpers J1 and J2 removed, J3 and J4 installed.

Using switch on back of IEC/filter (not pictured) to power unit on. Line in off IEC/filter is 14 gauge black/white. Three 16 gauge black/white leads soldered to line in 14 gauge leads. Each pair 16 gauge leads attach to two trannies each, one 15va and one 30va.

30va trannies mounted across upper part of angle aluminum. Looking at it first closest 30va it powers HDBP at right. Second 30va powers HDBP at left.

UserPostedImage
SCompRacer  
#9 Posted : Wednesday, May 1, 2013 3:50:14 AM(UTC)
SCompRacer

Rank: Member

Groups: Member
Joined: 1/6/2012(UTC)
Posts: 305
Location: Plainfield, IL

Thanks: 11 times
Was thanked: 26 time(s) in 21 post(s)
The fix for post # 2 was to just increase the output of the Placid HDBP that powers the right channel and SE (middle) section of my Legato. It shunts 100-105mA now but doesn't get hot enough to worry about. The right channel has powered up properly every time since I upped the current. The HDBP powering the left channel only is still shunting ~ 50mA and the left channel has never failed to power up.

Edited by user Wednesday, May 1, 2013 3:52:55 AM(UTC)  | Reason: Not specified

avr300  
#10 Posted : Wednesday, May 1, 2013 6:09:48 PM(UTC)
avr300

Rank: Member

Groups: Member
Joined: 6/17/2008(UTC)
Posts: 921
Denmark

Thanks: 1 times
Was thanked: 70 time(s) in 69 post(s)
This is rather interesting. Way before my "ripple on output" threat (and before I modded the Placid) I experienced almost the same behaviour - only difference to yours is that I'm powering a single Legato (with buffer) with only one Placid HD.

I have set my HD to shunt around 100mA @+-12V.

When I power up, the negative rail always gets to -12, but the positive hangs ~5-7v.

I have narrowed the problem down to one channel. When powering the left channel it works. When powering the SE section it works. But when powering the right channel, excessive current draw at the positive rail occurs holding it down.

Now, here comes the really interesting part. Due to the nature of the shunt supply, it can safely survive a shot on the output. When the problem is present, if I quickly short the positive (5-7v) rail to gnd and release the short - it ALWAYS comes up as expected. 10 out of 10 times.

All el-caps on the problematic channel has been lifted to rule out a semi shorted cap, no difference.

The problem isn't the Placid HD. It lays somewhere in the Legato.

Now, what can cause the one channel to behave as described ?
avr300 attached the following image(s):
cut.JPG (38kb) downloaded 32 time(s).

You cannot view/download attachments. Try to login or register.
thanks 1 user thanked avr300 for this useful post.
dsolodov on 3/4/2014(UTC)
Russ White  
#11 Posted : Wednesday, May 1, 2013 6:37:48 PM(UTC)
Russ White

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN

Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
The only thing that would cause it would be that the circuit is drawing more current then you think. :) Check the shunt current at the positive rail. It must be at zero when this occurs.

I am sure you probably did this, but you have to remember measure the shunt current with the load connected.

There is also the possibility of a problem (bad FET?) with your Legato, but I have never seen this occur.

Edited by user Wednesday, May 1, 2013 6:38:58 PM(UTC)  | Reason: Not specified

Russ White  
#12 Posted : Wednesday, May 1, 2013 6:40:48 PM(UTC)
Russ White

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN

Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
What I would do to get to the bottom of your issue, is power the circuit with a series regulator (like LCBPS) and measure the actual current draw of each rail for each channel.

That will help you narrow down where to look. :)
avr300  
#13 Posted : Wednesday, May 1, 2013 6:51:24 PM(UTC)
avr300

Rank: Member

Groups: Member
Joined: 6/17/2008(UTC)
Posts: 921
Denmark

Thanks: 1 times
Was thanked: 70 time(s) in 69 post(s)
Right away I'll do.

Lets smoke a FET ;-)
Russ White  
#14 Posted : Wednesday, May 1, 2013 6:58:12 PM(UTC)
Russ White

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN

Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
yes if you have one that bad it may smoke once it gets unfettered current. :) But hey then you will know what to replace. :)
avr300  
#15 Posted : Wednesday, May 1, 2013 7:03:15 PM(UTC)
avr300

Rank: Member

Groups: Member
Joined: 6/17/2008(UTC)
Posts: 921
Denmark

Thanks: 1 times
Was thanked: 70 time(s) in 69 post(s)
Great humour... I like it :-)

Shields down!
avr300  
#16 Posted : Wednesday, May 1, 2013 8:10:16 PM(UTC)
avr300

Rank: Member

Groups: Member
Joined: 6/17/2008(UTC)
Posts: 921
Denmark

Thanks: 1 times
Was thanked: 70 time(s) in 69 post(s)
No smoke detected.

Surely it is as current problem. I did shunt to little. I'll try to balance it, enough to startup and no more than the heatsinks are up to remove.

Thanks Russ. Always a pleasure.
SCompRacer  
#17 Posted : Thursday, May 2, 2013 12:18:56 AM(UTC)
SCompRacer

Rank: Member

Groups: Member
Joined: 1/6/2012(UTC)
Posts: 305
Location: Plainfield, IL

Thanks: 11 times
Was thanked: 26 time(s) in 21 post(s)
Originally Posted by: avr300 Go to Quoted Post
This is rather interesting. Way before my "ripple on output" threat (and before I modded the Placid) I experienced almost the same behaviour - only difference to yours is that I'm powering a single Legato (with buffer) with only one Placid HD.



I had the same issue with a single BIII/Legato build and IIRC used your advice to bump the current up. I have an extra Legato since I removed one from my dual mono build. Also had an extra HDBP. What I described happened with the spare Legato/HDBP too so if a fault is there it would have to be identical. I suppose I could move jumpers on the Legato and try powering left channel and SE section with HDBP currently used for left channel and see if same thing happens when it is shunted at 50mA.

Starting a single BIII build for a friend so pretty soon I'll have no extra parts.
avr300  
#18 Posted : Thursday, May 2, 2013 3:30:48 PM(UTC)
avr300

Rank: Member

Groups: Member
Joined: 6/17/2008(UTC)
Posts: 921
Denmark

Thanks: 1 times
Was thanked: 70 time(s) in 69 post(s)
Originally Posted by: SCompRacer Go to Quoted Post

I suppose I could move jumpers on the Legato and try powering left channel and SE section with HDBP currently used for left channel and see if same thing happens when it is shunted at 50mA.


It was now I did it.

Problem is, that I have to shunt such a large an amount of current to be able to start up the thing, that the steady state shunt current afterwards tends to be to much for the heatsinks (and for my comfort).

"Inrush" current in the fets ??? (no).

BTW, with the LPBPS the Legato starts up as designed, using aprox 190mA @ 12v. I have set up the Placid to ~300mA, with this it doesn't start every time.

Edited by user Thursday, May 2, 2013 3:31:27 PM(UTC)  | Reason: Not specified

Russ White  
#19 Posted : Thursday, May 2, 2013 7:38:23 PM(UTC)
Russ White

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN

Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
If the Placid is really doing 300ma, then the Legato will start up as expected. The legato is itself a kind of constant current source. the only way for it to pull a rail down is for it to be using more current than it should be.

You need to measure things when you get your anomaly. Post those measurements and we can find your solution. :)
avr300  
#20 Posted : Thursday, May 2, 2013 8:29:06 PM(UTC)
avr300

Rank: Member

Groups: Member
Joined: 6/17/2008(UTC)
Posts: 921
Denmark

Thanks: 1 times
Was thanked: 70 time(s) in 69 post(s)
I just need to wake up! d'oh!

The output voltage was to low, somehow this condition kept down the positive rail.

Changing this to +-14.8v shunting 270mA it just works flawlessly.
Rss Feed  Atom Feed
Users browsing this topic
GuestUser (2)
Similar Topics
* solved *Dual Mono Single Legato Can't Null DC Right Channel (Legato Discrete I/V Stage)
by SCompRacer 3/11/2016 7:10:31 AM(UTC)
Buffalo 3se dual mono single legato 3.1. (Buffalo DAC)
by astro888 2/27/2013 9:04:44 PM(UTC)
2 Pages12>
Forum Jump  
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.