I think the 'stealth mod' is easier if you're not used to SMD work. You're not having to attach wires to tiny pads, though I did end up having to bridge the C2 & C4 pads with scraps of wire; although I can bridge stripboard tracks without even trying, the PCB pads refused to link with just solder, after attempts to position a blob on the caps themselves ended up with them stuck to the iron. Surface tension is a wonderful thing, but it causes nervous tension. 
Output cap? 😕
Output cap? 😕
cpemma said:I think the 'stealth mod' is easier if you're not used to SMD work. You're not having to attach wires to tiny pads, though I did end up having to bridge the C2 & C4 pads with scraps of wire; although I can bridge stripboard tracks without even trying, the PCB pads refused to link with just solder, after attempts to position a blob on the caps themselves ended up with them stuck to the iron. Surface tension is a wonderful thing, but it causes nervous tension.
Output cap? 😕
i will probably work on the stealth mod as i've never worked with SMD. will visit a friend who owned a cellphone repair shop and let his guys remove R and bridge C.
any more suggestions on the output cap?
thanks in advance
Hi guys,
I have two less common questions asking about modifying the sonic impact.
1) I am using air core inductors from DIYparadise, are they directional, unlike toroidals which seem more mirror images of each other, these have an inner and outer layer.
2)Did anyone change the SMD diodes to schottkys like these?
http://www.referenceaudiomods.com/M...reen=CTGY&Store_Code=RAM&Category_Code=DIODES
It seems someone has used it with commercial success.
http://bestaudiomods.com/index.html
Happy Easter to everyone!
I have two less common questions asking about modifying the sonic impact.
1) I am using air core inductors from DIYparadise, are they directional, unlike toroidals which seem more mirror images of each other, these have an inner and outer layer.
2)Did anyone change the SMD diodes to schottkys like these?
http://www.referenceaudiomods.com/M...reen=CTGY&Store_Code=RAM&Category_Code=DIODES
It seems someone has used it with commercial success.
http://bestaudiomods.com/index.html
Happy Easter to everyone!
The Diodes used on the Sonic board are Schottsky diodes. Here is a link to the PDF Data Sheet
As to whether the diodes listed on the RAM site are any better, I don't know. But remember, these are the guys selling the $400 wooden volume knob. 😉 At least they aren't charging that much for the diodes! Any specs on those diodes?
As for the bestaudiomods site, isn't he the guy who got slammed so badly here awhile ago? I can't find the thread now, maybe it was removed.
Better diodes are probably better for the audio, but they mainly serve to protect the output transistors. It would be interesting to know if anyone has had success with different diodes.
Sorry angchuck, didn't mean to rain on your parade, just want to know what we are getting into before we leap.
As to whether the diodes listed on the RAM site are any better, I don't know. But remember, these are the guys selling the $400 wooden volume knob. 😉 At least they aren't charging that much for the diodes! Any specs on those diodes?
As for the bestaudiomods site, isn't he the guy who got slammed so badly here awhile ago? I can't find the thread now, maybe it was removed.
Better diodes are probably better for the audio, but they mainly serve to protect the output transistors. It would be interesting to know if anyone has had success with different diodes.
Sorry angchuck, didn't mean to rain on your parade, just want to know what we are getting into before we leap.
Thanks for the advise Michael. It was your website that got me into DIY a few months ago. 😀 Now i am hopelessly sucked into it.
It is addictive! 🙂
I had a look at the specs for the diodes on the RAM site. Both are made by Vishay. Only the MUS-160 gave switching times - 50ns, pretty fast. The other diode and the ON used by Sonic do not give switching times or show switching noise or rebound.
Thanks Chuck for pointing this out, it's worth looking into. I just bought a bunch of "soft recovery" diodes for a preamp project. Maybe something like that in an SMD could work well. But I may have to get a better o'scope to measure it!
Just for technical giggles, have a look at the two waveforms on the upper right of this page: waveforms
If you look at the top and bottom of the square wave you will see the inductor ringing that the diodes are meant to clamp. Getting rid of that ringing without adding any other noise might help the audio. But that ringing is pretty high, around 5MHz. Not much of it is likely to get thru the output filters, if the filters are any good. (That's a whole other can of worms)
I had a look at the specs for the diodes on the RAM site. Both are made by Vishay. Only the MUS-160 gave switching times - 50ns, pretty fast. The other diode and the ON used by Sonic do not give switching times or show switching noise or rebound.
Thanks Chuck for pointing this out, it's worth looking into. I just bought a bunch of "soft recovery" diodes for a preamp project. Maybe something like that in an SMD could work well. But I may have to get a better o'scope to measure it!
Just for technical giggles, have a look at the two waveforms on the upper right of this page: waveforms
If you look at the top and bottom of the square wave you will see the inductor ringing that the diodes are meant to clamp. Getting rid of that ringing without adding any other noise might help the audio. But that ringing is pretty high, around 5MHz. Not much of it is likely to get thru the output filters, if the filters are any good. (That's a whole other can of worms)
I read, in this thread I think, that there could be a problem area of solder on the SI T-amp board which would need heated to ensure it made a better connection.
I remember some mention of increased resistance on the input power lines if this was not taken care of.
Does anyone remember this advice?
I'm kicking myself I didn't make a note it at the time.
🙁
Datawolf
I remember some mention of increased resistance on the input power lines if this was not taken care of.
Does anyone remember this advice?
I'm kicking myself I didn't make a note it at the time.
🙁
Datawolf
Stealth mod variations
I notice 2 variations in the 'stealth mod' recipe:
Method A
If soldering the input caps direct to the pads of C3 + C4, the items L1 + L2 are removed.
Method B
If soldering the input caps to the boards pot connector, C3 + C4 pads shorted amd R01 + R02 are removed.
Why the difference?
Are they both correct?
I want to use Method A so I want to be sure.
Also, I'm modding 2 amps in dual mono block configuration.
I intend using the left channel of both amps.
Do I need to 'disable' the right channel to minimize noise etc.?
Are there any grounding issues i should be aware of?
I notice 2 variations in the 'stealth mod' recipe:
Method A
If soldering the input caps direct to the pads of C3 + C4, the items L1 + L2 are removed.
Method B
If soldering the input caps to the boards pot connector, C3 + C4 pads shorted amd R01 + R02 are removed.
Why the difference?
Are they both correct?
I want to use Method A so I want to be sure.
Also, I'm modding 2 amps in dual mono block configuration.
I intend using the left channel of both amps.
Do I need to 'disable' the right channel to minimize noise etc.?
Are there any grounding issues i should be aware of?
Re: Stealth mod variations
Hi Mr Wolf, as far as I know there is only one 'Stealth' mod (method B), so called due to the fact that it "sneakes in ahead of the input filter" as a certain Mr Mardis puts it.
L1 & 2 are the inductors that form part of said filter.
R01&02 are removed because the pot becomes your bridge to ground....I'll let an EE explain that one!
The other versions either jump in and simply replace the on-board caps C3&4 or jump in at the input resistors (R1&2) if you want to replace those as well.
Hope that makes everything as clear as mud!
Lee
datawolf said:
Hi Mr Wolf, as far as I know there is only one 'Stealth' mod (method B), so called due to the fact that it "sneakes in ahead of the input filter" as a certain Mr Mardis puts it.
L1 & 2 are the inductors that form part of said filter.
R01&02 are removed because the pot becomes your bridge to ground....I'll let an EE explain that one!
The other versions either jump in and simply replace the on-board caps C3&4 or jump in at the input resistors (R1&2) if you want to replace those as well.
Hope that makes everything as clear as mud!
Lee
Re: Re: Stealth mod variations
R01 and R02 are removed because bridging the pads of the original input capacitors would leave them on the wrong side of the new input caps (connected to the pot wiper), with a DC path to ground on the chip input pin.
Original:
"Stealthed"
It's explained better somewhere, but essentially you'll end up amplifying a few volts DC along with the signal or the amp will shutdown or overheat, bad things whatever.
Lostcause said:
R01 and R02 are removed because bridging the pads of the original input capacitors would leave them on the wrong side of the new input caps (connected to the pot wiper), with a DC path to ground on the chip input pin.
Original:
An externally hosted image should be here but it was not working when we last tested it.
"Stealthed"
An externally hosted image should be here but it was not working when we last tested it.
It's explained better somewhere, but essentially you'll end up amplifying a few volts DC along with the signal or the amp will shutdown or overheat, bad things whatever.
Question cleared up!
A picture is worth a thousand words, at least! How did you manage to post such large pictures? I have never had them accept the larger size. Are they done as jpeg?
Roger
A picture is worth a thousand words, at least! How did you manage to post such large pictures? I have never had them accept the larger size. Are they done as jpeg?
Roger
Circuit credit to Panomaniac.
These forums give the choice of posting a limited-size attachment (hosted here) or hot- or cold-linking to your own webspace images (any size that doesn't annoy people) with the [ img ] or [ url ] tags.
These forums give the choice of posting a limited-size attachment (hosted here) or hot- or cold-linking to your own webspace images (any size that doesn't annoy people) with the [ img ] or [ url ] tags.
Pictures?
Got it. The web page owner would have to approve of this or there could be unhappy people out there. Saving links in archives assures that half of them will be dead in a year or so. Posts like yours would be totally meaningless without the pictures. It would be best to keep it all together. What needs to be done is to get the forum to allot more space somehow.
Roger
Got it. The web page owner would have to approve of this or there could be unhappy people out there. Saving links in archives assures that half of them will be dead in a year or so. Posts like yours would be totally meaningless without the pictures. It would be best to keep it all together. What needs to be done is to get the forum to allot more space somehow.
Roger
Re: Pictures?
What needs to be done is to get people to learn how to use proper image compression techniques 😉 Photoshop has a wonderful "Save for web..." feature or you can always download the Gimp for free and do the same thing. You can post decent 1024x768 jpegs if you compress them properly.
sx881663 said:
What needs to be done is to get people to learn how to use proper image compression techniques 😉 Photoshop has a wonderful "Save for web..." feature or you can always download the Gimp for free and do the same thing. You can post decent 1024x768 jpegs if you compress them properly.
For schematics there is almost nothing better than 2 or 4 color gif. Images considerably bigger than a computer screen can fit into the 100k attachment limit.
However, cpemma was not using the attachment system of the forum but his own web space to store the images, that way they become automatically displayed without clicking on them. www.imageshack.us may come very handy as it provides free image hosting.
However, cpemma was not using the attachment system of the forum but his own web space to store the images, that way they become automatically displayed without clicking on them. www.imageshack.us may come very handy as it provides free image hosting.
photos are very very helpful
i have done the version 3 stealth mod suggested by Michael Mardis but i have difficulties to understand the following:
1) is C10 the cap among the 4 inductors?
2) what value to replace it?
3) replacement of c10 cap needs to solder on top and bottom of the PCB?
4) how and where to add stiffening caps?
your help much appreciated.
i have done the version 3 stealth mod suggested by Michael Mardis but i have difficulties to understand the following:
1) is C10 the cap among the 4 inductors?
2) what value to replace it?
3) replacement of c10 cap needs to solder on top and bottom of the PCB?
4) how and where to add stiffening caps?
your help much appreciated.
cpu8088 said:
YES
As big as will fit in the space. I use a 680uF Panasonic FM series.
Wherever it will fit. Be careful with polarity. A bigger cap might fit on the bottom.
Add in parallel with the incoming 12V. As close to the board as you can.
There are diagrams here and on my site (I think)
cpu8088 said:
If you mean with a single-cap replacement, you don't need to physically solder the leads on both sides of the board, make a decent joint on one side and the solder will wick through the holes and link both sides. 😕 Besides, the cap should be close up against the board, space permitting, so the iron won't go in. 😉
To fit between the coils where the original is, 8mm dia is the biggest that fits, eg, for Panasonic FC/FM 680uF 16V you need the "long" series one EEUFC1C681L/EEUFM1C681L , not the 10mm diameter versions without the 'L' suffix.
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