[RCduck7]

I'm sure i want to try this when i read some positive comments of Dussun V8i and V6i owners that were using a tube preamp on the power amp stage.
I just want to find out what tube preamp could do nicely on the solid state V8i power amp section.
I a triode pre amp the way to go?
Or does anyone have experience with a passive preamp?
From what i read, a passive preamp makes the sound transparant uncolored and better for some it seems.
From what i read, a passive preamp can be a pretty cheap and easy DIY.
Anyone experience with using tube or passive preamps on solid state power?
Wich are recommended at not to exotic prices?
Is a passive preamp always without any form of remote control?

[rollo]

  Passive can be a blessing however are not for all applications. Impedance of the source say CDP must be low [ high= loss of extremes such as bass and top]. Below 100 ohms is desireable. The CDP also needs voltage at the output of 2V or better. The amp needs a low input sensitivity of lower than one volt to sound its best.
 There are transformer based, resistor based, LDR based[ Lightspeed] . Many choices for sure just make sure it suits your system.


charles

[toobluvr]

The amp needs a low input sensitivity of lower than one volt to sound its best.
 
charles

Just for clarity....
The amp input needs to be highly sensitive.....which is a low number.  The lower the number, the more sensitive the amp input is.

Other elements necessary for successful passive operation are:  short low capacitance IC,  robust source output,  low source output impedance,  high amp input impedance.

Even when you get all these things right you still may not like the passive sound.  Personally I don't.......especially if there are no tubes at all!  Passive operation yields detail and purity, but for me the cost -- a giveup of fullness, warmth, space, drive and dynamics -- is just too high.  Others like it, so YMMV.

[RCduck7]

I found my amp has a very sensetive volume, it goes to 12 and i manage to get it to 4 at the max, 5 is beyond normal listening.
Speakers are Hyperions and not that hard to drive.
The CD player is 2.3V sensitive.
Maybe of intrest, i also use the Dussun for the front channels in a surround setup.
I'm going from the L&R front preouts of a surround processor to one of the the Dussun line inputs.
The volume has to be a bit higher then normal on the Dussun to keep the same volume as my center and surround speakers.
The center and surround speakers are driven by a seperate multichannel amp.

I like the idea of fullness and warmth to the sound of tubes. Still, i would like to try a passive pre amp, still gonna have to look what type is suitable.

[rollo]

Well if ya want to try a passive unless you do a Penny & Giles stay away from transitor based passives. either a Stevens & Billington TVC [ origial Bent units], Bent Tap or transformer based TVC.
  Now the nw [ old] kid on the block is "Lightspeed" using LDRs and LEDs. $450 from Australia.

charles

[drphoto]

There's a fairly inexpensive 'autoformer' passive called the Sonic Euphoria that is supposed to be outstanding.

[RCduck7]

There's a fairly inexpensive 'autoformer' passive called the Sonic Euphoria that is supposed to be outstanding.

Sorry to come back to this thread so late. I have been bussy finding a way of getting pure power to my electronics and have been modifying the filters slightly in some of my speakers to mach in a surround setup. I looked for the Sonic Euphoria and reviews are promising, allthough did it have a remote control? Anyway, it seems the Sonic Euphria website doesn't exist anymore, and being from Europe (Belgium) i don't have clue where to buy this unit. Any information is welcome.
I also have been looking to tube preamps and i wonder, how do i know if i'm looking to a single ended triode design or something else?
This Vincent SA-T1 preamp for example would visually suit me my other gear well but what kind of tube design is it? specifications don't tell much it seems.
http://www.vincent-tac.de/en/product-types/preamplifiers/sa-t1.html

[RCduck7]

Well if ya want to try a passive unless you do a Penny & Giles stay away from transitor based passives. either a Stevens & Billington TVC [ origial Bent units], Bent Tap or transformer based TVC.
  Now the nw [ old] kid on the block is "Lightspeed" using LDRs and LEDs. $450 from Australia.

charles

Today i have been looking for mad for passive pre amps on the internet, the FT Audio LW1 is inexpensive and is well received but that was 8 years ago! Not sure what has come along in the meantime that can better it. There are also a lot of people that suggest to look for transistor based passives to not loose out on the richness in the sound.
I have also been looking on google for LDR based "lightspeed" passives but all i could find was DIY projects but no units sold by a manufacturer and no product reviews, at least no proffesional ones.
Any links to the LDR based??

[doug s.]

i would check out the diy paradise eva-2 ldr passive preamp - cheaper than the lightspeed, and offers remote control wolume & source switching.  i sue one between my tube preamp and deqx, and i love it...  check out my posts (and link to another thread) here:

http://www.audiocircle.com/index.php?topic=77811.msg767732#msg767732

doug s.

btw, i couldn't imagine ever not having a tube preamp in my rig...

[RCduck7]

i would check out the diy paradise eva-2 ldr passive preamp - cheaper than the lightspeed, and offers remote control wolume & source switching.  i sue one between my tube preamp and deqx, and i love it...  check out my posts (and link to another thread) here:

http://www.audiocircle.com/index.php?topic=77811.msg767732#msg767732

doug s.

btw, i couldn't imagine ever not having a tube preamp in my rig...

Thanks for the link, a good volume control to an amp is the purest i have been told, not really sure to use tubes or not, i shall investigate.

[RCduck7]

i would check out the diy paradise eva-2 ldr passive preamp - cheaper than the lightspeed, and offers remote control wolume & source switching.  i sue one between my tube preamp and deqx, and i love it...  check out my posts (and link to another thread) here:

http://www.audiocircle.com/index.php?topic=77811.msg767732#msg767732

doug s.

btw, i couldn't imagine ever not having a tube preamp in my rig...

Well, this Eva 2 ldr with remote looks intresting and it seems many are happy about them, except with some recordings it can sound a little raw for some, but this is what passive pre amps is about i suppose.

Doug s, since you can't miss a tube pre amp in your rig, i think for me and maybe for you it could be worthwhile to use a tube buffer between the EVA 2 and the power amp.
Something like this...
http://pacificvalve.us/YaqinTB.html
If i understand well it should get rid of the pre amp but offer tube sound with the passive ldr wich controls the volume.
Best of both worlds right?Any thoughts?

[jtwrace]

I would suggest the Dodd Buffer.  You can purchase together or diy.

http://doddaudio.com/diy.aspx

[doug s.]

Well, this Eva 2 ldr with remote looks intresting and it seems many are happy about them, except with some recordings it can sound a little raw for some, but this is what passive pre amps is about i suppose.

Doug s, since you can't miss a tube pre amp in your rig, i think for me and maybe for you it could be worthwhile to use a tube buffer between the EVA 2 and the power amp.
Something like this...
http://pacificvalve.us/YaqinTB.html
If i understand well it should get rid of the pre amp but offer tube sound with the passive ldr wich controls the volume.
Best of both worlds right?Any thoughts?

i like tube buffers, i have a few.     i have never tried the yaqin, but you can get the earlier cd-1 & cd-2 direct from china for ~$100 shipped.  (i haven't checked the pricing on the cd-3).  while these are fine between s/s tuna and preamp, or between dac & preamp, my results w/them between s/s preamp and amp are such that, while better than not using them, they are not a substitute for a good tube preamp, imo.

ymmv,

doug s.

[RCduck7]

I decided and i just ordered the EVA 2 with volume control at diyparadise. I'm from Europe so it might take a while to arrive. I might try a tube buffer to in the future but i first wanna see how the EVA 2 works out.

[Steve]

I decided and i just ordered the EVA 2 with volume control at diyparadise. I'm from Europe so it might take a while to arrive. I might try a tube buffer to in the future but i first wanna see how the EVA 2 works out.

Hi RC and Gents,

A little more information may be helpful for future considerations.

Different types of passives have different problems that must be considered and addressed, just like active preamplifiers. First, just to be safe, I am addressing passive preamplifiers without a cathode/source follower. (Cathode/source follower eliminates volume control from seeing IC capacitance. However, it does have its own problems such as output capacitance size etc.)

One of the biggest problems is that since passives have little or no gain, the gainstage is located somewhere else, which I will address now and towards the end of this post.

We know CD players have analog gainstages, which are far from optimum, even tube stages. There simply is not enough room to design an optimum highest quality tube analog gainstage in a cd player. (I have not seen a SS design either.)

A.  Using a passive preamp with selector switch and discrete resistors create problems with matching impedances.

First, the input impedance (Z) needs to be high enough not to load the source and cause distortions, and

Secondly, not cause bass loss because of small output coupling capacitor size.

This is not a huge problem with CD players using SS gainstages as large coupling capacitors allow for fairly small passive preamplifier input impedances. However, CD players with tube circuits often times have very skimpy size capacitors, so the total passive preamp's input resistance needs to be much higher or the coupling capacitor size needs a substantial increase.

Thirdly, the higher the input impedance (Z) of the passive preamplifier, the higher the output Z will be for a given volume (and at midpoint resistance) which attenuates the high frequencies more than lower resistance passives.

Important: The output of the passive preamplifier directly "sees" the interconnect cable (IC) capacitance, so IC capacitance is very important.

So if the passive preamplifier has too little resistance, the bass will suffer. If too high resistance, then the highs will suffer. ICs capacitance is very important.


B.  Next, although transformer (magnetic) type volume controls may look simple, they are really not. We have:

Hysteresis losses
Leakage inductance
Distributive capacitance/winding capacitance

Frequency response problems. For great highs, the requirements of inductance are low, with less core material (iron), low distributive capacitance (DC) and leakage reactance (LR). However, for great bass response, we need the opposite, more core material (iron), high inductance, which unfortunately means more DC and LR.

The transformer must have a balanced tonal response. A transformer can be bass heavy or high frequency heavy.

The problem of resonant circuit(s) development as the transformer interacts with the interconnects (IC)/load capacitances. Too high of load resistance results in ringing, and two low of load resistance over damps and may also over load the source component.

Any time the source or load capacitance/IC is changed, the required damping resistance needs to also be changed for optimum performance.

Finally, what is the quality of the analog gainstage placed somewhere else instead of the preamplifier? In otherwards where did the preamplifier gainstage go? In the CD player, the quality is poor. If in an integrated amplifier, it depends upon the quality

1. of the circuit,
2. of the power supply design. How much low frequency musical information is passed from stage to stage with phase shifting etc.

So things are more complex because either type passive preamplifier is more sensitive to the IC capacitance than a typical gainstage preamplifier. It is rare for a passive device to be truly accurate.

Lastly, the designer and parts quality is important as to the quality of a passive preamplifier.

Cheers.

[RCduck7]

Steve,

I do not have the technical knowledge that you do, but i understand about the big lines of what you mean.
I knew it is a bit of a risk ordering the EVA 2 or any other passive for that matter, i understood there has to be a very good synergy between components with passives to sound their best.
I only looked at some basic matching requirments regarding passive pre amps with the other components before i ordered.
Does the same issues also occur with a good potentiometer? Isn't a potentiometer the purest thing you can do or does it have the same issues, or other issues?
Also, if a passive amplifier with my components does sound as the bass suffers or the opposite, the highs suffer, can a (small) modifiction or something be done about the problem?

Thanks the info.

[Steve]

I only looked at some basic matching requirments regarding passive pre amps with the other components before i ordered.

Hi RC,

Yes you are doing just about all you can do, just give it a try and see how it sounds. 

Does the same issues also occur with a good potentiometer? Isn't a potentiometer the purest thing you can do or does it have the same issues, or other issues?

Yes, a potentiometer has the same issues/problems as a switchable volume control I mentioned in my last post. One must be careful of the resistance, sound quality, and the IC capacitance comes into play; so if possible find the lowest possible capacitance that also sounds the best.

Also, if a passive amplifier with my components does sound as the bass suffers or the opposite, the highs suffer, can a (small) modifiction or something be done about the problem?

I doubt it as the resistors, potentiometer, transformer would probably have to be changed or modified.
But it could be close to accurate with one noticing only fairly small (semantics always get in the way) loss of highs, snares might lack some "snap" etc, or bass lacking along with thin voices.

Hopefully the pre you ordered will fill the bill nicely. 

Good luck RC and all the best.

[RCduck7]

Ok, the EVA 2 has arrived but i have a problem, the following post is an existing one that i allready posted on the EVA2 topic on the "cheap and Cheerful" forum...

Since i received my EVA 2 that i ordered from DIY paradise i was impressed by the music the moment the unit was switched on, apart from the hum i can hear through the speakers when the music is not played loud or at silent passages.
I have this the moment a source is connected to the EVA, i tried a few.
I'm not sure if i will still have this hum when i connect the EVA to other power amps, i didn't try yet but i didn't have "hum" with an active pre amp to my amp.
A friend told me that a passive pre or volume control has to be very good build to not have hum.
Do i have a faulty or not good tweaked EVA? Anyone have those problems? Or is the EVA2 made for low Watt class D amps and not so for power monster class A/B amps with lots of power and big transformers inside?
Anyway, i have to test some more or think of different options becausse i can't live with the hum.

[RCduck7]

Ok, i know more now...

Well, this friend told me it was the EVA while my first thaught that it was the power amp.
Guess what, it is the power amp!
When i use the Dussun V8i integrated as a power amp, if i'm right it is the same as the volume is way up to the max of the V8i, then i can hear hum without the EVA connected.
I also tried an other active preamp, again hum, so i'm sure it is the power stage of the V8i, propably becausse the amp has big transformers inside, capable to 1200 Watt for each channel and i guess while this is a good thing it can generate a bit of hum i think.
I did have reduced hum when i connected my sources to the V8i and went from the "line out" of the V8i to the EVA and then to the power amp section.
I also tried to connect the EVA between pre an power stage of the V8i and there was almost no hum, but i don't intend to use the pre of the V8i together with the EVA, i like the sound of the EVA as it is as a stand alone to a power amp.
I also want to try out a tube buffer stage soon between the EVA and the Power stage of the Dussun it might kill a bit more hum to in the process.
But for now i'm happy connecting the line out of the V8i to the EVA, i can live with that.
My confidence is restored in DIY products.