[corndog71]

I'm sure the details are buried in this thread somewhere, but what size and brand of case did you use? 

Thanks, Mike

http://www.ebay.com/itm/3U-Black-Audio-Rackmount-Enclosure-DIY-Chassis-Case-10-19115B-/251031818592?_trksid=p4340.m185&_trkparms=algo%3DSIC.NPJS%26its%3DI%252BC%26itu%3DUA%26otn%3D5%26pmod%3D370238951697%26ps%3D63%26clkid%3D7464984291040949996


I have to warn you though that the bottom panel is steel and was not easy to drill holes into.  The rear panel is aluminum and was much easier.  I like how it all comes apart.  All assembled it's a freakin beast!



Here's a shot I took before mounting the gain pots to the back panel.

[Æ]

I have to warn you though that the bottom panel is steel and was not easy to drill holes into.  The rear panel is aluminum and was much easier.  I like how it all comes apart.  All assembled it's a freakin beast!

Nice case, but darn, how come so much for the shipping? It doesn't weight that much!

[RichG]

Hi Vinylb,
you are a funny guy by thinking about double decker bus If the double decker amp play they take me away also 

Original PS Caps are 10µF / 16V, i had replace them with 470µF / 25V 

Original Bootstrap / Filter Cap is 220µF / 4V, i had replace them with 220µF / 10 V.
I recommended to keep the capacity value of the Bootstrap / Filter Cap.

Please find some additional information about the input stage here :

http://www.thatcorp.com/datashts/Galo_THAT_Line_Dr_%20Rx.pdf

Especialy Page E13 / E14 describe which componets are used for the test circuit.

btw.. i will change the 100 Ohm resistors of the signal input path with some higher grade (e.g. TX Foli) stuff.

For me the bass has more bunch and the sound are more accurate. The music plays more free.

Regards
Marcus

Marcus. 
If you trace the PCB tracks carefully I think you will find that there is no bootstrap / filter caps as you suggest.  Tom has omitted these, probably with good reason.  The 220uF caps you changed are PSU decoupling caps.  Still might be worthwhile change.
The 10uF caps are in the signal path but you need to take great care with replacing these.  Standard electrolytic caps are very unlikely to improve on what is there and the longer leads are likely to cause issue with EMI pickup.  The sound will change, but for the better?  Tom has stated he was very careful on what caps he used here. A 470uf is way bigger than is needed.  I tried using a 4.7uF BlackGate in this spot but wasn't convinced it made things better.

[RichG]

The datasheet here has better detail of the input stage:- http://www.thatcorp.com/datashts/THAT_1200-Series_Datasheet.pdf

[corndog71]

Nice case, but darn, how come so much for the shipping? It doesn't weight that much!

That does seem high for ground shipping.  He must be tacking some on.  Not sure how that works.

[.Marcus.]

Marcus. 
If you trace the PCB tracks carefully I think you will find that there is no bootstrap / filter caps as you suggest.  Tom has omitted these, probably with good reason.  The 220uF caps you changed are PSU decoupling caps.  Still might be worthwhile change.
The 10uF caps are in the signal path but you need to take great care with replacing these.  Standard electrolytic caps are very unlikely to improve on what is there and the longer leads are likely to cause issue with EMI pickup.  The sound will change, but for the better?  Tom has stated he was very careful on what caps he used here. A 470uf is way bigger than is needed.  I tried using a 4.7uF BlackGate in this spot but wasn't convinced it made things better.

Hi RichG,
thank you for answer and share your finding, could you please elobarate your conclusion a little bit, because i guess you or i'm on the wrong track ?

Did you trace the PCB, how the capaitors are connected to the IC ? Some analogy to the Datasheet ?

Thanks,
regards
Marcus

[.Marcus.]

I must confess that i never trace the pcb circuit, but i will explain how are my findings :

The Tantal Chip near the That1200 i guess is connected to Pin 5 & 8 because the position is ideal, if you take a look in the datasheet you would find suggested Capacitor called "Cb", it is used as Bootstrap / Filter Cap.
This tantal chip is labled with Numbers 220 and 4 as suggested in the datasheet to use a 220µV / 3V cap here.
220µV / 4V make not sens in case of PS Cap, because 4V only ?
   
The area on the right side of the PCB i guess is to create the PS for the input stage by normal Z Diode Regulated topology. I had measure the voltage across the caps and find 14 V, they are used as decoupling this voltage.
I guess if you check the connection you would find that both That1200 Chip supply Pins 4 & 7 connected to this Tantal Capacitors.
The tantal chips are labeld with 10 / 16 what mean 10µF / 16V and make sense at this place.

If you change this tantals caps to smaller values (4.7µF) you maybe degrade the PS of the input stage !

I'm not expect any EMI Problem at this place, because is there a EMI Problem it would also impact the circuit path of the board, the pins are only increase the circuit path by some Millimeters.
Btw.. may be if you use a external wired gain pot they would more prone to EMI.

Thanks
Regards
Marcus

[RichG]

Hi Marcus,

Sorry, I think I was a little confused with your post last night and we may well be talking about different caps after all.

It's a while since I did any work on this board, but I did take a picture of the BG caps in place:-



Prior to doing this I spent a couple of hours tracing the circuit and comparing to the data sheets. For the input stage I believe Tom has used the circuit shown if fig 14 of the datasheet I linked to. This is then followed by the IRAUDAMP7D reference design circuit with the addition of the pot across the input.

The caps I changed are the DC de-coupling caps between these stages - Tants have a certain signature when used as decoupling and I felt an improvement could be gained here.  As I said the improvement was minimal - perhaps a little smoother.  As I said, Tom was very picky about the cap used here.

I didn't consider changing the bootstrap caps or the PSU caps at the time as I felt the impact would be minimal at best.  It's interesting that you felt this was indeed positive.  It would be great if you could post a picture showing the caps you changed - I may well do some more investigation when I have the time.

Regarding the EMI - I can't help feeling that the main reason that people hear an improvement when swapping out the pots for fixed resistors is the reduction in noise pickup.  Perhaps if screened cable were used this would bring things closer.  Using through hole electrolytic caps for PSU coupling you may have issues relating to noise pickup and also the extra inductance from the leads.  SMD caps have a big advatage here.

I'm glad to see somebody else exploring the possibilities with mods of these boards.  Keep up the good work.

Cheers, Richard

[.Marcus.]

Hi Marcus,

Sorry, I think I was a little confused with your post last night and we may well be talking about different caps after all.

It's a while since I did any work on this board, but I did take a picture of the BG caps in place:-

Prior to doing this I spent a couple of hours tracing the circuit and comparing to the data sheets. For the input stage I believe Tom has used the circuit shown if fig 14 of the datasheet I linked to. This is then followed by the IRAUDAMP7D reference design circuit with the addition of the pot across the input.

The caps I changed are the DC de-coupling caps between these stages - Tants have a certain signature when used as decoupling and I felt an improvement could be gained here.  As I said the improvement was minimal - perhaps a little smoother.  As I said, Tom was very picky about the cap used here.

I didn't consider changing the bootstrap caps or the PSU caps at the time as I felt the impact would be minimal at best.  It's interesting that you felt this was indeed positive.  It would be great if you could post a picture showing the caps you changed - I may well do some more investigation when I have the time.

Regarding the EMI - I can't help feeling that the main reason that people hear an improvement when swapping out the pots for fixed resistors is the reduction in noise pickup.  Perhaps if screened cable were used this would bring things closer.  Using through hole electrolytic caps for PSU coupling you may have issues relating to noise pickup and also the extra inductance from the leads.  SMD caps have a big advatage here.

I'm glad to see somebody else exploring the possibilities with mods of these boards.  Keep up the good work.

Cheers, Richard

Hi Richard,
now things come to be clear, we talk about different mods

Many thanks for came up with some imteresting details and point to additional possible mod. These capacitors are used to DC de-coupeling between THAT1200 out and IRS2092 in ?

Please find a picture on page 159, there you could see the replaced caps.
I will provide a more detail picture later on.

Do you expect that it would be possible to identify change in the EMI behavior by comparing the "background noise" ?

regards
Marcus

[mboxler]

Thanks for the pics, corndog71.  I'm looking into a case that will hold 2 SDS-224's, a tranny, and a PS.  Looks like the size you bought will be a little tight for an extra amp.
I think I'll need something a few inches deeper.  I noticed one can buy a 12 series that is all aluminum...might make the drilling easier.  Decisions, decisions.

Mike
 

[dwk]

Thanks for the pics, corndog71.  I'm looking into a case that will hold 2 SDS-224's, a tranny, and a PS.  Looks like the size you bought will be a little tight for an extra amp.
I think I'll need something a few inches deeper.  I noticed one can buy a 12 series that is all aluminum...might make the drilling easier.  Decisions, decisions.

Mike
 

If you haven't already purchased your stuff, you might consider a Connexelectronics SMPS instead of the stock Class-D tranny/PS board. I have a setup using a pair of SDS-224s and a Connex supply which works well, and has a much smaller footprint than the stock setup. It is a bit more money, and you have to be a bit patient when ordering the SMPS, but I'm quite happy with the results.
 

[mboxler]

If you haven't already purchased your stuff, you might consider a Connexelectronics SMPS instead of the stock Class-D tranny/PS board. I have a setup using a pair of SDS-224s and a Connex supply which works well, and has a much smaller footprint than the stock setup. It is a bit more money, and you have to be a bit patient when ordering the SMPS, but I'm quite happy with the results.

Thanks...I'll look into it!  Which model did you purchase?

Mike

[krikor]

Thanks for the pics, corndog71.  I'm looking into a case that will hold 2 SDS-224's, a tranny, and a PS.  Looks like the size you bought will be a little tight for an extra amp.
I think I'll need something a few inches deeper.  I noticed one can buy a 12 series that is all aluminum...might make the drilling easier.  Decisions, decisions.

Mike
 

Mike, for the money I don't think you can beat the Par-Metal all aluminum enclosures.  Got mine from them via Ebay which saved a few more bucks.  Plenty of room, easy to drill and disassembles easily for working on the panels.

Here's a shot of my SDS-470 monoblocks.  Plenty of room for a second amp board in each enclosure.

[mboxler]

Mike, for the money I don't think you can beat the Par-Metal all aluminum enclosures.  Got mine from them via Ebay which saved a few more bucks.  Plenty of room, easy to drill and disassembles easily for working on the panels.

Thanks...

Which model/size are they?  I agree, looks good for two amps!

Mike 

[krikor]

Which model/size are they?  I agree, looks good for two amps!

I went with the 16x12x4.  Not sure what part number that is and just the standard finish.  See below from when I first mounted up the boards and xfmr.

The 12x12x4 Par-Metal chassis will work, but I went with the 16x12 to give myself a little more room in laying out the components and keep the power supply farther from the amp board.  Also allows for other possible upgrades in the future (power supply, volume control, etc.).  Chassis doesn't come punched for anything unless you special order it as such (costs extra). 

I've found them pretty easy to drill though I haven't gotten to the back panel yet.  Just finished laying out the base plate for my mono SDS-450 amps. Did them mirrored since they'll be positioned side-by-side or behind the speakers. This actually made it easier to lay out and drill the second amp... just clamped them bottom to bottom and drilled through the first (only two of the power supply screws had to be relocated since that board is not symmetrical).








I also drilled out the footer holes a little larger to accommodate some 1/4" shaft spikes I had on hand... I was only going to use three but found the amp too tippy with the big xfmr off to one side, so there's an extra hole at the front middle.

[.Marcus.]

I will provide a more detail picture later on.

Regards
Marcus

[vinylb]

Krikor, I agree, par-metal cases are very good value for money and I too purchased mine on ebay, had a change of heart on color and called them up and they added a few bucks for black. I dont have all the tools, drill bits available, in fact very limited tools so It was a bit of  a pain to drill the correct sized holes. It did provide a sense of accomplishment and pride when I was done, albeit rather "mCgyver style" with some of the holes

So its about $85-100 for par-metal and drill own holes or $225 with everything done for you but you have to hunt for extras and kinda locked into Tom's non household standard screws and limitations of the rear plate and close proximity to the ps board.

Oh btw I did pick up flag disconnects and the allen key for those small little screws at ACE hardware. Allen key is not very helpful because of the small size its already stripped a little so it was a mission to get those screws in. I also moved the ps board back to its original location - all this talk of heat got me nervous. Maybe water cooling is the next mod ? I dont think so, at least not for me....ok to put that in a PC but not my hi-fii stuff.

[RichG]

Hi Richard,
now things come to be clear, we talk about different mods

Many thanks for came up with some imteresting details and point to additional possible mod. These capacitors are used to DC de-coupeling between THAT1200 out and IRS2092 in ?

Please find a picture on page 159, there you could see the replaced caps.
I will provide a more detail picture later on.

Do you expect that it would be possible to identify change in the EMI behavior by comparing the "background noise" ?

regards
Marcus

Thanks Marcus.

Are these the caps you've changed?  Looks like quite a fiddly job



Getting some higher quality caps on the PSU rails close to the chips is probably a good idea. I think I'm going to have to open mine up again and have a play.  While doing the changes did you do any direct listening comparisons between modded and normal boards?

Checking for EMI is not trivial, it may have a direct influence on audible noise but is likely to be more subtle and manifest in other ways.  A very fast and sensitive scope or analyser is probably needed, which I don't have.

The caps I changed for BGs were indeed the DC blocking between 1200 and 2092. 

BTW the data sheets for the 2092 and iraudamp7d make for interesting reading:
http://www.irf.com/technical-info/refdesigns/iraudamp7d.pdf
http://www.irf.com/product-info/datasheets/data/irs2092.pdf

cheers

[vinylb]

K well I am all done, plugged her in and she sounds really good. BUT I do have some issues i need to address:

1. changing from unbalanced to balanced produces a buzz and music comes through from unbalanced
2. increasing gain pots decreases the volume - what the .... maybe I have them backwards?

Going to check connections. Any other suggestions?

[mboxler]

K well I am all done, plugged her in and she sounds really good. BUT I do have some issues i need to address:

1. changing from unbalanced to balanced produces a buzz and music comes through from unbalanced
2. increasing gain pots decreases the volume - what the .... maybe I have them backwards?

Going to check connections. Any other suggestions?

Good job!

1)  Can you easily disconnect the toggle switch from the amp?  This should be the same as balanced.  Still get the buzz?

2)  This is hard to describe.  Can you take a picture of the pot...I should be able tell you if it's wired correctly.

Mike