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VSSA Lateral MosFet Amplifier

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#1,841
presbel said:
Just fired up my VSSA 0mV on both 12mA VAS bias and 4V on 22ohms. There is hissing sound if you put your ear near the tweeter. It is just beginning to open up. Compared to my PP KT88 my tube amp sound better at first. But after 2 hours of listening the sound almost even with my tube amp. I Am using a temporary power supply with 30V-0-30VAC input. I ordered my SMPS800RE from Connexelectronics.
Click to expand...

PRESBEL thank you for sharing listening test, exited to hear your opinion between linear and smps.
Me myself am waiting for the last shipping from Andrej when the Semelab trans get delivered to Andrej.
But i have some to consider for you if i am right (I am not an engineer so bear over with me if i am not right).
You have ordered SMPS800RE which i think you would power both channels with. I have read a lot of times that because it is regulated and regulate on the return point from the load, it is best to use one for each amp (You can nearly get 2 times SMPS300RE for same prize).
Hope the info is alright.
Best regards Ricky
 
#1,842
Another VSSA is becoming alive. First half of hour of listening and already very promising...dead quiet, no hum, no hiss, just small green LED 😀
 

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#1,844
BYRTT said:
PRESBEL thank you for sharing listening test, exited to hear your opinion between linear and smps.
Me myself am waiting for the last shipping from Andrej when the Semelab trans get delivered to Andrej.
But i have some to consider for you if i am right (I am not an engineer so bear over with me if i am not right).
You have ordered SMPS800RE which i think you would power both channels with. I have read a lot of times that because it is regulated and regulate on the return point from the load, it is best to use one for each amp (You can nearly get 2 times SMPS300RE for same prize).
Hope the info is alright.
Best regards Ricky
Click to expand...

Hi Ricky,
Yes I will power the two channels with one SMPS800RE as of now I powered the 2 channel with linear PS. As far as I know SMPS800RE is not a regulated PS. Am not also an engineer only a hobbyinst. But I would like it compact as I will integrate a B1 buffer inside the case.
Here is my front panel.
 

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#1,849
chunek said:
Nice build, Supernet & Presbel!

I am still waiting 10ohm resistors and SMPS. Hopefully everything will be in tomorrow then can do OT during weekend!😀

This is my VSSA unit
An externally hosted image should be here but it was not working when we last tested it.
Click to expand...

Wow,Maybe is the angle of picture, but those terminals look way too close to those caps. Do you have enough room to connect power to those terminals?
 
#1,851
Now the power supply is done, the trafo is center tapped and PS is symmetrical + and -37V rails. 37V because still not under stress... VSSA is still not wanting to run. 60mV... drop across 22Ohm. What should I check then? Why should VSSA not run with voltage connected?
 
#1,852
A little shout out to vgeorge, who has reccommened me a DMM here present on my table and in the attached pic. Thanks! I made a fresh measurement with it on both modules across T1 & T2. After they've been on for two hours. 138mV and 141mV. Is that appropriate?
 

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#1,853
Renioo said:
Now the power supply is done, the trafo is center tapped and PS is symmetrical + and -37V rails. 37V because still not under stress... VSSA is still not wanting to run. 60mV... drop across 22Ohm. What should I check then? Why should VSSA not run with voltage connected?
Click to expand...
Hi Renio, please very short answers to next Q:
1. What is the voltage between TP1 and TP2?
2. What is the voltage between TP1 and GND?
3. Measure R19, R20 if they are 10 Ohm OK, if not replace them with Farnell - MCPWR10FTFQ0100 chip resistor 😉


Siberia said:
A little shout out to vgeorge, who has reccommened me a DMM here present on my table and in the attached pic. Thanks! I made a fresh measurement with it on both modules across T1 & T2. After they've been on for two hours. 138mV and 141mV. Is that appropriate?
Click to expand...
Is this voltage between TP1 and TP2? If yes, than OK. 😉

Guys please be very exact for the answers, otherwise we get a lot of posts for clarifying one simple issue. :cheers:
 
#1,854
presbel said:
Just fired up my VSSA 0mV on both 12mA VAS bias and 4V on 22ohms. There is hissing sound if you put your ear near the tweeter. It is just beginning to open up. Compared to my PP KT88 my tube amp sound better at first. But after 2 hours of listening the sound almost even with my tube amp. I Am using a temporary power supply with 30V-0-30VAC input. I ordered my SMPS800RE from Connexelectronics.
Click to expand...

Honour us all with some pics. With SMPS and elcos settled it will be even better. Congratulations. :up:

supernet said:
Another VSSA is becoming alive. First half of hour of listening and already very promising...dead quiet, no hum, no hiss, just small green LED 😀
Click to expand...
Congratulations, another amp in official chassis. :worship:

BTW price for this Alu case will be presented on Monday and than anyone interested can join GB. :up:

Junie said:
here's my progress:


An externally hosted image should be here but it was not working when we last tested it.
Click to expand...
Junie this is masterpiece. 😎
 
#1,860
Please check if T1 is BC560C (PNP), T2 is BC550C (NPN), T5 is KSA1381 (PNP), T6 is KSC3503 (NPN). Try to measure also another VSSA channel if it respond to TR1, TR2 rotation.
Also measure voltage drop on these resistors:
- R3, R4 is 0,1 V
- R5, R6 is 0,65 V
- R7, R8 is 15,6 V
 
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