• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Vacuum State RTP3C

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#68
Looking at the RTP3C schematic I noticed the LM329 is bypassed to ground with a 1uf capacitor. I guess the intention is to lower the input impedance to the 6922 at high frequency therefore shorting any possibility of interference noise that might cause oscillation. The thing is this 1uf will load the lm329 that preventing it from working properly.

I've built a similar 2sk146//6922 cascode using lm329 for voltage reference and bypass it with a 1uf Wima cap. In listening there is a lack of airiness, highs seem rolloff. Like there's a veil between me and the music. I found out the hard way that lm329 does not like capacitive load. After I yank the wima, the veil removed but noise floor increases causing soundstage to become more 2D and bass fullness reduced. For experiment, I replaced the lm329 with a resistor and a bypass cap (oscon). This restored the sonic balance n noise floor. Comparing to the lm329 with bypass, the later seem to offer more dynamic contrast and ambient information. Again this I suspect is the lower noise floor of the lm329 combo.

I did a search on some voltage regulator design where lm329 is used as a voltage reference for the error opamp. There is always a RC filter following the lm329 for providing a resistive load, input impedance matching for the opamp, and to reduce the lm329 noise.

Any one out there share a similar experience? The next thing I'm going to try is probably adding a RC filter to the lm329.
 
#69
swordsman said:
Looking at the RTP3C schematic I noticed the LM329 is bypassed to ground with a 1uf capacitor. I guess the intention is to lower the input impedance to the 6922 at high frequency therefore shorting any possibility of interference noise that might cause oscillation. The thing is this 1uf will load the lm329 that preventing it from working properly.

I've built a similar 2sk146//6922 cascode using lm329 for voltage reference and bypass it with a 1uf Wima cap. In listening there is a lack of airiness, highs seem rolloff. Like there's a veil between me and the music. I found out the hard way that lm329 does not like capacitive load. After I yank the wima, the veil removed but noise floor increases causing soundstage to become more 2D and bass fullness reduced. For experiment, I replaced the lm329 with a resistor and a bypass cap (oscon). This restored the sonic balance n noise floor. Comparing to the lm329 with bypass, the later seem to offer more dynamic contrast and ambient information. Again this I suspect is the lower noise floor of the lm329 combo.

I did a search on some voltage regulator design where lm329 is used as a voltage reference for the error opamp. There is always a RC filter following the lm329 for providing a resistive load, input impedance matching for the opamp, and to reduce the lm329 noise.

Any one out there share a similar experience? The next thing I'm going to try is probably adding a RC filter to the lm329.
Click to expand...

Thanks for your comments. I note in the LM329 application sheet none of the suggested circuits has a capacitor across the chip. Unlike the case of - say - the LM317 - there is no specific recommendation for a capacitor across the regulated voltage.

Alex
 
#70
Looking at the vacuum state website and some comments spread, the use of a mat02 is recommended over the use of a jfet...

But which type is best suited?

selection AH / CH / EH or FH ? Which is recommended and what is the effect of a different choice???

Dirk
 
#72
lm329-rtp3

swordsman said:
Looking at the RTP3C schematic I noticed the LM329 is bypassed to ground with a 1uf capacitor. I guess the intention is to lower the input impedance to the 6922 at high frequency therefore shorting any possibility of interference noise that might cause oscillation. The thing is this 1uf will load the lm329 that preventing it from working properly.

I've built a similar 2sk146//6922 cascode using lm329 for voltage reference and bypass it with a 1uf Wima cap. In listening there is a lack of airiness, highs seem rolloff. Like there's a veil between me and the music. I found out the hard way that lm329 does not like capacitive load. After I yank the wima, the veil removed but noise floor increases causing soundstage to become more 2D and bass fullness reduced. For experiment, I replaced the lm329 with a resistor and a bypass cap (oscon). This restored the sonic balance n noise floor. Comparing to the lm329 with bypass, the later seem to offer more dynamic contrast and ambient information. Again this I suspect is the lower noise floor of the lm329 combo.

I did a search on some voltage regulator design where lm329 is used as a voltage reference for the error opamp. There is always a RC filter following the lm329 for providing a resistive load, input impedance matching for the opamp, and to reduce the lm329 noise.

Any one out there share a similar experience? The next thing I'm going to try is probably adding a RC filter to the lm329.
Click to expand...

hi,

i use my rtp since 10 years now and i built it from start with a 9V battery supply instead of the 329, and it was an impreovement to change to 2 pcs of 4,5v batteries instead the small 9v and they last several years-maybe a quick fix
 
#73
lm329-rtp3

swordsman said:
Looking at the RTP3C schematic I noticed the LM329 is bypassed to ground with a 1uf capacitor. I guess the intention is to lower the input impedance to the 6922 at high frequency therefore shorting any possibility of interference noise that might cause oscillation. The thing is this 1uf will load the lm329 that preventing it from working properly.

I've built a similar 2sk146//6922 cascode using lm329 for voltage reference and bypass it with a 1uf Wima cap. In listening there is a lack of airiness, highs seem rolloff. Like there's a veil between me and the music. I found out the hard way that lm329 does not like capacitive load. After I yank the wima, the veil removed but noise floor increases causing soundstage to become more 2D and bass fullness reduced. For experiment, I replaced the lm329 with a resistor and a bypass cap (oscon). This restored the sonic balance n noise floor. Comparing to the lm329 with bypass, the later seem to offer more dynamic contrast and ambient information. Again this I suspect is the lower noise floor of the lm329 combo.

I did a search on some voltage regulator design where lm329 is used as a voltage reference for the error opamp. There is always a RC filter following the lm329 for providing a resistive load, input impedance matching for the opamp, and to reduce the lm329 noise.

Any one out there share a similar experience? The next thing I'm going to try is probably adding a RC filter to the lm329.
Click to expand...

hi,

i use my rtp since 10 years now and i built it from start with a 9V battery supply instead of the 329, and it was an impreovement to change to 2 pcs of 4,5v batteries instead the small 9v and they last several years-maybe a quick fix
 
#78
You may not be aware that the author recently passed away. I think his company was a sole trader status, so there may no longer be a company to order the book from. Joe Rasmussen handled business in Australia I think and he has been an active member on these boards. Try looking at his JLi amp webpage to see if he can help.

Shoog
 
#80
Shoog said:
You may not be aware that the author recently passed away. I think his company was a sole trader status, so there may no longer be a company to order the book from. Joe Rasmussen handled business in Australia I think and he has been an active member on these boards. Try looking at his JLi amp webpage to see if he can help.

Shoog
Click to expand...

Thanks, I was aware of Allen's passing. I should have been more proactive about ordering it when I asked him my questions earlier in the thread.
 
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