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VSSA Lateral MosFet Amplifier

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Lazy Cat

Lazy Cat

Member
Joined 2007
Luke said:
yep its demanding, smt is not diy friendly IMO.
LC, I now have 4 channels of this amp that don't work, any chance you can send me a real schematic with some test points and voltages?
From what I can tell, I read some instructions to modify the board, I cant find it now, but what I did was short both bases with a jumper to ground. Now all I get from the second pair of modules is heavily distorted sound.
Click to expand...

There's not many VSSA down, they're quite tough, not so easy to leave the game.

There's one finished VSSA in a chassis selling for the cost of the materials built by me. It is working perfectly and you can find it here ;)
 
L

Luke

Member
Joined 2001
Lazy Cat said:
There's not many VSSA down, they're quite tough, not so easy to leave the game.

There's one finished VSSA in a chassis selling for the cost of the materials built by me. It is working perfectly and you can find it here ;)
Click to expand...

You clearly a marketing guy, not so much support:)
Tell you what, give me what I paid for my oscillators including the caps and I will consider it.
BTW, how many are going?
 
Esperado

Esperado

Banned
Joined 2011
esperado.fr
Luke said:
I read some instructions to modify the board, I cant find it now, but what I did was short both bases with a jumper to ground. Now all I get from the second pair of modules is heavily distorted sound.
Click to expand...
Why don't-you had read the first post of this thread ?
http://www.diyaudio.com/forums/vend...lateral-mosfet-amplifier-151.html#post3314786
And i believe you had instructions with your modules.
We are all here to help-you. Please, describe your problem with precision, your cabling and what you did.
 
L

Luke

Member
Joined 2001
Esperado, followed the instructions to the letter. I did short the bases to ground, but the input transistors are ok. My wiring is a little messy due to the nature of the case and small space.
I can only assume its oscillating, one went for a while and then cooked. On LC instructions i used inductur on output. I ordered new input cable with shielding, I made new less capacitive speaker cables.
I got distortion in two channels, heavy distortion. Today I tried one channel again, only it seemed to work better, then no bang or smoke, one channel died, speaker seems ok, it's very odd. I have built enough amps to expect smoke from either the speaker or amp module:)
Now C2 on this module is very hot.
I think I give up for now, maybe later I try and build the through hole boards if there is ever a group buy.
 
Esperado

Esperado

Banned
Joined 2011
esperado.fr
Luke, VSSA is supposed to be very stable, if cabling is made properly, and whatever output cables (with zobel network). I don't understand.
How can-you fire several bad working amps ? When you mount them, the rule is to connect only one to the power supply (with protective resistances), tune-it until quiescent, offset and stability are ok, test the sound, and, when (and only when) it is OK, do the same with his brother. Then remove the protective resistances, reverify and you are ready.
If you give-up, i can't help you. If not, let-us take the amps one by one and figure out what happens. The SMD version will always be better (and more stable) than the through hole one, because less surface, shorter wires and good passive components.
Can-you show us a photo of the amp and a cabling schematic ?
Don't give-up: this amp is a gem. And a lot of builders had no problems: we will cure yours.
 
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Lazy Cat

Lazy Cat

Member
Joined 2007
Luke said:
You clearly a marketing guy, not so much support:)
Tell you what, give me what I paid for my oscillators including the caps and I will consider it.
BTW, how many are going?
Click to expand...

Proposal to you was just because that you see it is working properly. So far I got three VSSA back to repair, so less than 1% reclamations, all gone because of user misuse, one even connected to wrong polarity.
Look Luke I was not beside you when connecting and powering up, so anything wrong could happen. This amp is so trivial that it should work also with all three trimmers completely in wrong positions, there would be some DC offset and wrong bias but it should play anyway. To be successfully wrong with all four VSSA PCB-s attempts there's only one explanation, systematic mistake repeated every time. Please consider carefully your building procedure and you may find a mistake somehow crawling in somewhere. :up:
 
pinnocchio

pinnocchio

Member
Joined 2010
quebecdiy.forumactif.com/
Hi Nick77,

I tried just about anything to get them in North America but the min. order Qty is 300 and they won't budge (I'm talking about Mouser, Digikey, Allied, etc...). I was only able to source them from Farnell in UK with their Export department. Cost a pretty penny and not worth the 70$ it costed me not to mention duties and other taxes (for two PSUs).

I would go with an equivalent in the CDE (Cornell Dubelier) or Nichicon. I believe those were 30mm diameter with 10mm pitch (please double check) so you could use some of the following:

http://www.digikey.ca/product-detail/en/LGW2D152MELB45/493-8525-ND/1966867

381LQ152M200K042 Cornell Dubilier | Mouser

Hope this helps

Ciao!
Do
 
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pinnocchio

pinnocchio

Member
Joined 2010
quebecdiy.forumactif.com/
Esperado said:
As VSSA has good caps aboard on their rails, are-you sure it is worth to change SMPS caps ?
L.C. had not changed them on his First One, if i'm not mistaken. I believe he had made a listening comparison ?
Click to expand...

I did several listening sessions with SMPS original caps (on VSSA) and with the proposed changes and there was a huge impact, especially on the bass rendering and dynamics but this could have just been due to a much larger capacitor reserve compared to the original, almost double the original (820uF vs 1500uF).

Not to mention it will be more reliable in the long run (compared to Samwha and the likes).
 
N

Nick77

Member
Joined 2009
pinnocchio said:
Hi Nick77,

I tried just about anything to get them in North America but the min. order Qty is 300 and they won't budge (I'm talking about Mouser, Digikey, Allied, etc...). I was only able to source them from Farnell in UK with their Export department. Cost a pretty penny and not worth the 70$ it costed me not to mention duties and other taxes (for two PSUs).

I would go with an equivalent in the CDE (Cornell Dubelier) or Nichicon. I believe those were 30mm diameter with 10mm pitch (please double check) so you could use some of the following:

Invalid Request

381LQ152M200K042 Cornell Dubilier | Mouser

Hope this helps

Ciao!
Do
Click to expand...

Crazy helpful thank you!
 
K

kimon

Member
Joined 2011
kimon said:
After one year or so, I finally managed to built two VSSA channels.Calibration was a demanding procedure , but at the end I got 120mV between TP1 and TP2 and <2mV DC offset at the output.Next time I switched the amplifier on, DC offset was around 50-60 mV,both channels.I trimmed it with much difficulty down to 2-3 mV.After that,when the amp was turned on again ,the DCoffset climbed to 160 mV in one channel and to 330 mV in the other.Rotating TR1 and TR2 had no effect.I have to say that, by mistake,I tried to measure voltage during the initial calibrating procedure with the DMM set on diode check mode!Could this have made some damage to the transistors?Or have I destroyed the trimmers?Anyway,apart of DCoffset,the amp shows no sign of audible distortion and is completely silent with no input signal.Right now I am listening to it through a pair of Q 1010i speakers, source is a PAL Tivoli radio and the sound is really pleasant.
Click to expand...

Success at last!Thank heavens there was no damage,only the combination of personal rush,a stupid personal mistake and of an out-of-order DMM,as I discovered after returning home from vacations.During calibration I switched on only one channel ,but I measured DC output at the switched off channel !:headbash:The damaged DMM showed completely false readings, hence the whole mess!Now VSSA works okay and the calibration procedure was quite easy.LC, you have designed a really tough and good sounding little beast!:worship:
 
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