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Old 8th January 2013, 10:21 PM   #2301
12B4A is offline 12B4A  United States
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Quote:
Originally Posted by djn View Post
Is that also true with LED lightspeed volume controls?
Yes, I don't see why my statement would not be true in that case. A mechanical contact is removed from the path but the signal is still developed across a semiconductor that is not electrically isolated from the source or from the following stage.

Anyway, I'm with Andy. I do all my attenuation digitally.
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Old 9th January 2013, 07:06 AM   #2302
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Hi folks,

Thank you for information about the tubes especially for Andy and Mogglia who share their experience with the tubes they recommend. Very inspiring. It's also inspire me to try other DHT tubes as well, especially the triode one.

After I read some of the former info in this thread, I also realized that sooner or later I must face investment on filament bias. Either for upgrade for the system (better performace) or fixing the hum problem which usually came from the heater. So maybe I will try 46, 26 or 10Y in further days. Right now still focus with my RE144 preamp project......
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Old 9th January 2013, 07:32 AM   #2303
tyo94 is offline tyo94  Indonesia
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Quote:
Originally Posted by Vinylsavor View Post
Hi!



I regard the volume control as one of the most delicate parts in the entire system. When I tried transformer or autoformer volumecontrols the first time I never went back to resistive volume controls. That's already almost 15 years ago. This is not related to DHTs but preamp design in general. Although I prefer DHTs generally, I would take a IDHT linestage with a great TVC any time ober a DHT with a resisitve volume control. They need some care though. IME best driven low impedance through a step down transformer. For example 10Y thorugh LL1660 wired 4.5:1 into a Slagle TVC is awesome. Equally good the Tribute lineouts with the secondary implemented as volume control

Best regards

Thomas
Hi Thomas,

Thanks for you explanations. I am clear now about volume control issue. Yes, it's not about DHT issue. It's more about the signal path issue. Lucky me, some weeks ago I just bought Tribute AVC from swap meet. I plan to replace the blue 100K ALPS in my preamp.

By the way, I see some difference approach here as I saw TVC and AVC implementation. I saw TVC and AVC got so low impedance value such as 10K or 33 ohm. Will be any siginificance problem when an AVC replacing a potentiometer as is?

Regarding your comment before, about Tribute lineout with secondary acts as vol control. Does it means you combine lineout trany with volume control at the output path?
How is the sound impression compared when the volume control installed as conventional way?

Last edited by tyo94; 9th January 2013 at 07:50 AM. Reason: addition
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Old 9th January 2013, 09:01 AM   #2304
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Quote:
Originally Posted by Vinylsavor View Post
Hi!
I regard the volume control as one of the most delicate parts in the entire system. When I tried transformer or autoformer volumecontrols the first time I never went back to resistive volume controls. That's already almost 15 years ago. This is not related to DHTs but preamp design in general. Although I prefer DHTs generally, I would take a IDHT linestage with a great TVC any time ober a DHT with a resisitve volume control. They need some care though. IME best driven low impedance through a step down transformer. For example 10Y thorugh LL1660 wired 4.5:1 into a Slagle TVC is awesome. Equally good the Tribute lineouts with the secondary implemented as volume control

Best regards
Thomas
Hi Thomas

yes you hit the nail. Nowadays Linestages didn't need such high gain and to increase the gain of the Phonostages to the level of a CDP (region of +6dBu / ~ 1.55Vrms).
Another thought, why not implementing the gain of the Linestage into the Power Amplifier and use a TVC as stand-alone Volume Controller like in Studios?

BR
Joao
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Old 9th January 2013, 01:02 PM   #2305
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Hi!

Quote:
Originally Posted by tyo94 View Post
I saw TVC and AVC got so low impedance value such as 10K or 33 ohm. Will be any siginificance problem when an AVC replacing a potentiometer as is??
You cannot replace a potentiometer with a TVC in every case. I found lower impedance TVCs to generally sound better. Many sources cannot cope well with TVCs even those rated as 10k impedance.

That's why I would never use a TVC at the input of the linestage or as a stand alone attenuator, unless you are sure all your sources can drive the inductive load. That's why I put the TVCs at the output of teh linestages, so all sources are decoupled from this rather difficult load.


Quote:
Originally Posted by tyo94 View Post
Regarding your comment before, about Tribute lineout with secondary acts as vol control. Does it means you combine lineout trany with volume control at the output path?
How is the sound impression compared when the volume control installed as conventional way?
Hi!

I have built 10Y linestages both ways. In the article below I posted a listening report from someone who compared both:

VinylSavor: 10Y Line Preamplifier Follow Up

Best regards

Thomas
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Old 9th January 2013, 01:35 PM   #2306
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Quote:
Originally Posted by 12B4A View Post
Yes, I don't see why my statement would not be true in that case. A mechanical contact is removed from the path but the signal is still developed across a semiconductor that is not electrically isolated from the source or from the following stage.

Anyway, I'm with Andy. I do all my attenuation digitally.
Thanks 12. I had to laugh though. While I was reading your response I remembered I bought a Prometheus a number of months ago and dropped my plans to build a LightSpeed.......

I would really like to try the 26 preamp. I had a John Hogan 300B for 7 years. The drive tube was the 26 and it sounded fantastic. I have the Pete Millete Low-Mu pre amp now, but would like to compare the 26 with it and the 12B4.
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Old 9th January 2013, 01:38 PM   #2307
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Quote:
Originally Posted by Joao@AltheaMusica View Post
Hi Thomas

yes you hit the nail. Nowadays Linestages didn't need such high gain and to increase the gain of the Phonostages to the level of a CDP (region of +6dBu / ~ 1.55Vrms).
Another thought, why not implementing the gain of the Linestage into the Power Amplifier and use a TVC as stand-alone Volume Controller like in Studios?

BR
Joao

If you did that, wouldn't you just end up with a three stage amp....or possible a 4 stage amp?

I quad-amp my system so my line stage/pre amp needs to be separate.
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Old 10th January 2013, 08:16 AM   #2308
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Quote:
Originally Posted by Vinylsavor View Post
That's why I would never use a TVC at the input of the linestage or as a stand alone attenuator, unless you are sure all your sources can drive the inductive load. That's why I put the TVCs at the output of teh linestages, so all sources are decoupled from this rather difficult load.
Hi Thomas

I forgot to mention. Thanks for the correction. And yes I agree that lower impedance of AVC / TVC sounds better.

BR, Joao


Quote:
Originally Posted by djn View Post
If you did that, wouldn't you just end up with a three stage amp....or possible a 4 stage amp?
I quad-amp my system so my line stage/pre amp needs to be separate.
Yes what is the problem with a 3 stage phono - which reaches the signal level of a CDP - and with a 3 stage power amp?
In general it's the same as you have a lower gain phono and power amp and a separate line stage. I Like Thomas mentioned, dealing with impedances you can lower the impedance of the AVC / TVC (for example 60Ω output of the source > 600Ω TVC > 10K input impedance of the amplifier). You'll find this in studio gear!

BR, Joao
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Old 19th January 2013, 12:56 AM   #2309
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Hello guys,

Can you please critique my HT PS circuit below. Corrections and suggestions are most welcome. I am new to this and trying the best I can to learn in order to prepare myself to build the Type 26 preamp. Apologies for the quality of the pic.

Raw DC supply for the filaments coming soon after I completed this.
Thanks and regards,

Abe

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Old 19th January 2013, 03:47 AM   #2310
eboz is offline eboz  United States
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Quote:
Originally Posted by amandarae View Post
Hello guys,

Can you please critique my HT PS circuit below. Corrections and suggestions are most welcome. I am new to this and trying the best I can to learn in order to prepare myself to build the Type 26 preamp. Apologies for the quality of the pic.

Raw DC supply for the filaments coming soon after I completed this.
Thanks and regards,

Abe

Click the image to open in full size.
Hi Abe,

20uF is rather high for the first C with the AZ1 rectifier. I would use a max of 3uF here for best results. Just increase the secondary voltage of your transformer and you will have better regulation this way.

-MW
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