Grounded Grid TRANSCENDENT line stage

widi · 9th September 2011, 06:31 PM

Hi Friends,
I purchased second hand a Grounded Grid, transcendent stage line, and I am very happy with it.
But I want to improve the volume control and have bought second hand, a step attenuator 41 Acoustic dimension, say it is very good, cuention is that it is 100k and the volume control on my preamplifier is 50k.
You can make any modification in the preamplifier to work well with step attenuator 41 Acoustic dimension?.
Deputy schematic and parts list of the preamplifier.
Thanks in advance
Greetings to all.

Vinylsavor · 9th September 2011, 06:40 PM

Hi!

You can replace the 50k volume control with the 100k unit. No other changes necessary. It will work fine.

One thing which might be useful is add a 1M resistor from the 'wiper' (output of volume control) to ground. This ensures that the grid is always referenced to ground also in case the switch looses contact.

Best regards

Thomas

widi · 9th September 2011, 06:47 PM

Thanks for your advice, Vinylsavor, I will make what you say, I thought you had to adjust the input gain of the preamplifier

Vinylsavor · 9th September 2011, 06:53 PM

Hi!

The volume control in that circuit has no effect on the gain of the preamp (except for it's own effect when setting the volume of course).
Your sources will see an easier load. Some might even sound better with the higher load impedance, if they have a high Zout.

Best regards

Thomas

widi · 9th September 2011, 07:11 PM

Thanks again, Vinylsavor, a new question.
Improved sound, if you replace all the resistors, metal film, for kiwame resistance, and resistance VISHAY DALE resistance?

DF96 · 9th September 2011, 07:45 PM

That must be the 'grounded grid' preamp where none of the grids are grounded! Instead an LTP is unbalanced by turning half into an SRPP-like circuit with local feedback. There is a chance that these two different distortion-cancelling mechanisms will work against each other by each destroying the very balance which the other assumes.

It might sound nice, but its not a grounded grid.

Vinylsavor · 9th September 2011, 07:57 PM

Hi!

Quote:

Originally Posted by widi

Improved sound, if you replace all the resistors, metal film, for kiwame resistance, and resistance VISHAY DALE resistance?

I'm not really a parts roller, so I'm the wrong person to ask

If you want this really to improve, try a different circuit, like a 26 linestage or other DHT as discussed in the 26 preamp thread.

Or if it shall be a bit simpler with a indirectly heated triode, try the line section of my octal preamp:

VinylSavor: The Octal Preamplifier Mk2: Circuit Update

Just a single triode in the signal path per channel

Thomas

Jogi · 9th September 2011, 08:16 PM

I also have this preamp; and changed it quite a bit to improve sound. You can try to put in a better heater supply, I took a module from Machmat, but maybe the circuit from Rod Coleman works as well. Big improvement..
Then of course the output caps are sensitive to changes, I took Jensen Copper foil to get a little more warmth.
And changing the three 22µF electrolytics near the tubes for film caps is another worthwhile tweak.
Best tubes i tried were Siemens E82CC triple micas from the 60ies.

But honestly, the DCB1 built from a group buy in this forum is much better in every respect, and doesn't need tweaking or expensive caps or resistors.
Thomas suggestion to try another circuit, especially the 26 preamp, is another good advice.And should be fun to build too...

cheers
Juergen

Jogi · 9th September 2011, 08:23 PM

I also have this preamp; and changed it quite a bit to improve sound. You can try to put in a better heater supply, I took a module from Machmat, but maybe the circuit from Rod Coleman works as well. Big improvement..
Then of course the output caps are sensitive to changes, I took Jensen Copper foil to get a little more warmth.
And changing the three 22µF electrolytics near the tubes for film caps is another worthwhile tweak.
Best tubes i tried were Siemens E82CC triple micas from the 60ies.

But honestly, the DCB1 built from a group buy in this forum is much better in every respect, and doesn't need tweaking or expensive caps or resistors.
Thomas suggestion to try another circuit, especially the 26 preamp, is another good advice.And should be fun to build too...

cheers
Juergen

widi · 9th September 2011, 08:54 PM

Thanks for your feedback Jogi.
But not what you mean when you say, (But honestly, the DCB1 built from a group buy in this forum is much better in Every Respect, and Does not Need tweaking caps or resistors or expensive).
Forgive my ignorance, but it's not the DCB1.
Thanks again to everyone.

9th September 2011, 06:40 PM	#2
Vinylsavor diyAudio Member Join Date: Feb 2002 Location: Lindau	Hi! You can replace the 50k volume control with the 100k unit. No other changes necessary. It will work fine. One thing which might be useful is add a 1M resistor from the 'wiper' (output of volume control) to ground. This ensures that the grid is always referenced to ground also in case the switch looses contact. Best regards Thomas __________________ http://vinylsavor.blogspot.com/

9th September 2011, 06:53 PM	#4
Vinylsavor diyAudio Member Join Date: Feb 2002 Location: Lindau	Hi! The volume control in that circuit has no effect on the gain of the preamp (except for it's own effect when setting the volume of course). Your sources will see an easier load. Some might even sound better with the higher load impedance, if they have a high Zout. Best regards Thomas __________________ http://vinylsavor.blogspot.com/

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9th September 2011, 06:47 PM	#3
widi diyAudio Member Join Date: Sep 2006	Thanks for your advice, Vinylsavor, I will make what you say, I thought you had to adjust the input gain of the preamplifier

9th September 2011, 07:11 PM	#5
widi diyAudio Member Join Date: Sep 2006	Thanks again, Vinylsavor, a new question. Improved sound, if you replace all the resistors, metal film, for kiwame resistance, and resistance VISHAY DALE resistance?

9th September 2011, 07:45 PM	#6
DF96 diyAudio Member Join Date: May 2007	That must be the 'grounded grid' preamp where none of the grids are grounded! Instead an LTP is unbalanced by turning half into an SRPP-like circuit with local feedback. There is a chance that these two different distortion-cancelling mechanisms will work against each other by each destroying the very balance which the other assumes. It might sound nice, but its not a grounded grid.

9th September 2011, 08:16 PM	#8
Jogi diyAudio Member Join Date: Jan 2008	I also have this preamp; and changed it quite a bit to improve sound. You can try to put in a better heater supply, I took a module from Machmat, but maybe the circuit from Rod Coleman works as well. Big improvement.. Then of course the output caps are sensitive to changes, I took Jensen Copper foil to get a little more warmth. And changing the three 22µF electrolytics near the tubes for film caps is another worthwhile tweak. Best tubes i tried were Siemens E82CC triple micas from the 60ies. But honestly, the DCB1 built from a group buy in this forum is much better in every respect, and doesn't need tweaking or expensive caps or resistors. Thomas suggestion to try another circuit, especially the 26 preamp, is another good advice.And should be fun to build too... cheers Juergen

9th September 2011, 08:23 PM	#9
Jogi diyAudio Member Join Date: Jan 2008	I also have this preamp; and changed it quite a bit to improve sound. You can try to put in a better heater supply, I took a module from Machmat, but maybe the circuit from Rod Coleman works as well. Big improvement.. Then of course the output caps are sensitive to changes, I took Jensen Copper foil to get a little more warmth. And changing the three 22µF electrolytics near the tubes for film caps is another worthwhile tweak. Best tubes i tried were Siemens E82CC triple micas from the 60ies. But honestly, the DCB1 built from a group buy in this forum is much better in every respect, and doesn't need tweaking or expensive caps or resistors. Thomas suggestion to try another circuit, especially the 26 preamp, is another good advice.And should be fun to build too... cheers Juergen

9th September 2011, 08:54 PM	#10
widi diyAudio Member Join Date: Sep 2006	Thanks for your feedback Jogi. But not what you mean when you say, (But honestly, the DCB1 built from a group buy in this forum is much better in Every Respect, and Does not Need tweaking caps or resistors or expensive). Forgive my ignorance, but it's not the DCB1. Thanks again to everyone.

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