Fully ballanced valve preamps

[RobHolt]

Hi,



Train from Walthamstow Central? The MFA is very easy to carry....

Ciao T

Easiest route from here is bus to Stratford station then train to Dev's.

 

[3DSonics]

Hi,

Easiest route from here is bus to Stratford station then train to Dev's.

If there's space and if I get sat off for good behaviour I'll be over.

Ciao T

 

[Dev]

I was going to see Nick this weekend but he says things have become hectic. If our meet-up is off, do you have room for one more Dev?

Not problem Simon (and Thorsten), you are very welcome.

 

[bottleneck]

Did someone call?

Sorry guys, I haven't read the whole thread and looking at some of the loooooong posts, I'm not going to either. However, in the bake-off that S&M is referring to, Dean's Django TVC did indeed "crap all over" the Glasshouse pre.

sorry to hear that Dev - particularly because I reccomended it!

Hopefully you should be able to sell it on without too much loss.

In my own system, both Julian and myself thought it ''as good but slightly different'' to the TVC passive - and "not quite as good as the valve pre-amp" - but not a million miles off ...

I hate speaking for Julian, and am sure he will pipe up if he disagrees!.

This whole ''which pre'' thread shows the importance of a home dem about as clearly as anything could really..

 

[sideshowbob]

I thought the Glasshouse passive was quite poor into Dev's Rogue, it really did sound pretty distant and vague, even with the volume turned up. The Django TVC was a significant improvement.

With the Leak, the Glasshouse was fine, but then again IME Leaks really don't improve at all with an active pre (they have a very high input sensitivity and really don't need any additional gain even with a tuner or phono stage as a source).

My own preference is for no preamp at all if possible, but there are so many variables that this is useless advice as a general recommendation. It all depends. But the main job of a preamp is to provide a mono switch, and very few do that nowadays anyway.

-- Ian

 

[Dev]

sorry to hear that Dev - particularly because I reccomended it!

Hopefully you should be able to sell it on without too much loss.

In my own system, both Julian and myself thought it ''as good but slightly different'' to the TVC passive - and "not quite as good as the valve pre-amp" - but not a million miles off ...

I hate speaking for Julian, and am sure he will pipe up if he disagrees!.

This whole ''which pre'' thread shows the importance of a home dem about as clearly as anything could really..

No problem Chris, it's certainly not your fault. I think it's very much system dependent. As others have said, the Glasshouse is not good into the Rogue but it was much better feeding Ian's Leak. I assume it's due to the high input impedance of the Rogue.

 

[RobHolt]

No problem Chris, it's certainly not your fault. I think it's very much system dependent. As others have said, the Glasshouse is not good into the Rogue but it was much better feeding Ian's Leak. I assume it's due to the high input impedance of the Rogue.

It's normally low impedance inputs that kill the sound of a passive pre, together with high cable capacitance.
I'll bring some low capacitance cables just in case the MF ones you have are having an effect.

 

[julian2002]

yup,
what chris says however i though the tvc was a bigger dissapointment due to all the hype surrounding their ilk.
cheers


julian

 

[3DSonics]

Hi,

though the tvc was a bigger dissapointment due to all the hype surrounding their ilk.

Several usual traps.

1) TVC = principle not execution.

2) I currently endorse only one "TVC" of the two based on my specifications/designs and I severely disrecommend the third, even though it is marketed by one of my associates.

The "hype" relates to the simple fact that the one "technical" device which I recommend is the closest to a "wire" I have found so far. (forgive the cult of personality - but I claim the spot)

Many others have found the same.

Many others found different.

Many others have no clue.

According to Hassan ben Sabbah:

Everything is true
Everything is permissable

Ciao T

 

[sideshowbob]

According to Hassan ben Sabbah:

Everything is true
Everything is permissable

Actually, it's "Nothing is true, everything is permitted".

-- Ian

 

[3DSonics]

Hi,

Actually, it's "Nothing is true, everything is permitted".

Both versions have been recorded and actually, they say the same thing.

Ciao T

 

[sideshowbob]

Both versions have been recorded

Citation?

and actually, they say the same thing.

I disagree.

-- Ian

 

[3DSonics]

Hi,

Citation?

Principia Discordia among others.

More critically, there is excellent evidence that HbS never uttered "Nothing is true, everything is permitted", however a basic precept of the Ismaeli at Alamut was: "There is no haram. Everything is halal." which is closer to "all is true everything is permitted" than to the opposite.

I disagree.

How can you?

Either extreme automatically becomes equal to it's polar opposite as the circle closes.

If nothing is true truth stops existing and therefore automatically everything becomes true.

All the following statements are actually equal...

Nothing is true, everything is permitted
Everything is true, nothing is permitted
Nothing is true, nothing is permitted
Everything is true, everything is permitted

in that they negate any formal law and require the individual to reassume responsibility.

Ciao T

 

[Dev]

It's normally low impedance inputs that kill the sound of a passive pre, together with high cable capacitance.
I'll bring some low capacitance cables just in case the MF ones you have are having an effect.

I think the input impedance of the Rogue is 200k. The Glasshouse pre was fitted with 100k to match it as best as we could and the DACT pre which sounds a lot better is 50k. We can try and find logic in this tomorrow.

 

[3DSonics]

Hi,

I think the input impedance of the Rogue is 200k. The Glasshouse pre was fitted with 100k to match it as best as we could and the DACT pre which sounds a lot better is 50k. We can try and find logic in this tomorrow.

It has been my experience that about the highest impedance permissable for a passive preamp is 10K, any higher and unless your cable has no capacitance to speak off degradation sets in drastically. Using 1K is definitly better but few sources can drive taht kind of load.

I found that going down to 100 Ohm MASSIVELY improved things, which gave rise to my own style of "buffered input passive preamp", in other words using a Buffer (BUF03 from AD was very good) followed by a 100 Ohm multiturn wirewound pot per channel.

Ciao T

 

[Dev]

Put simply T, are you saying that with 200k input impedance, I'm better off forgetting about a passive and looking for an active instead? (as S&M has suggested a number of times). Or are you saying that the output impedance of the pre should be as low as possible regardless of the input impedance of the Rogue?

I thought the input impedance of the amp and the output impedance of the pre must match for best results.

 

[Dynamic Turtle]

Either extreme automatically becomes equal to it's polar opposite as the circle closes.

If nothing is true truth stops existing and therefore automatically everything becomes true.

All the following statements are actually equal...

Nothing is true, everything is permitted
Everything is true, nothing is permitted
Nothing is true, nothing is permitted
Everything is true, everything is permitted

in that they negate any formal law and require the individual to reassume responsibility.

Ciao T

Responsibility of what exactly?

 

[anubisgrau]

pardon my stupid question, but is the output impedance of TVC preamps fixed or is it somehow related to the impedance of the source? f.e. my ATCs have the input impedance >10kohm meaning (if it is correct that it is advisable to match component impedances with a look-up factor of at least 200) that the matching preamp should have at least 50ohm output impedance? what is the output impedance of TVCs such as django or music first?

 

[Dynamic Turtle]

Another stupid question! Am I right in thinking there is another ATC - Airtight Corp Japan, or something, that make pre-amps, or is it the same ATC that makes studio monitors???

DT

 

[3DSonics]

Hi,

Put simply T, are you saying that with 200k input impedance, I'm better off forgetting about a passive and looking for an active instead?

Nope. Forget the input impedance, it is inconsequential, except for it's capacitive component, which (IIRC the Rogue has a 12AX7/ECC83 as input) is quite significant.

What I am suggesting is that under no conditions should the impedance of the attenuator/pot be any higher than 10Kohm for passive Pre, preferably lower.

Or are you saying that the output impedance of the pre should be as low as possible regardless of the input impedance of the Rogue?

Yup. That's the size of it. Of course, by lowering the impedance of the attenuator you increase the laod on the source and 10K is about as low as most sources "like"....

I thought the input impedance of the amp and the output impedance of the pre must match for best results.

Absolutely not, doing that garantees the poorest possible results ANY TIME. The output impedanc eof the preamp (passive or not) should be 1/10th or less of the worst case load.

Ciao T