Hiraga The Monster...

[fdegrove]

Hi Jam,

I have built a few tube preamps 12AX7's and 6DJ8's, sounded good but I needed better bass.

Good for you.

Who stole the bass? Who stole the music?

There is no reason whatsoever for tubes to have worse bass performance.

Silly speakers do abound though...and I can still slam their *** off with tubes given a fair chance.

Maybe I can convince you to the tube area?

If you are prepared to take that route expect your electrity bill to be halved, your enjoyement of music to be doubled and be prepared to change your view of speakers too...

It's a philosophy,

[jam]

Frank,

I used to use transmission line subs that were flat to 17 Hz, just could not get the control I needed even with a large power supply. Midrange and highs were great though.

Why don' t you post your favourite tube preamp schematic and we could start a new thread and you might convince me to build one.

It has to be balanced though.

Cheers,
Jam

[SvErD]

Originally posted by fdegrove
Hi,

In case anyone has scans of the original publications by "L'Audiophile" I'd be happy to assist in translation work.

As Pierre pointed out, this and most other circuits by this team depend heavily on certain parameters for sonic bliss.

Passive components, layout, wires everything was painstakingly thought out.
They were lightyears ahead of the commercial designs of those days and I still go through some of the articles for reference.

Let me know if I can help, I hold most of these publications anyway....I am a bit surprised by this nostalgia though.

Ciao,

Thanks Frank, I do have the original transistors, but it would be nice to know if there were some hidden gold nuggets in the orignal articles. They are here: http://www.gmweb.btinternet.co.uk/hiraga.htm#index

[Steve Eddy]

Originally posted by fdegrove
And they didn't like the battery PSU on its' own either...no,no, they bypassed all that lead.

Hmmmm. That's not how I read the article. If you're referring to the one originally posted at the top of the thread.

The way I read it, they were using all that power supply capacitance to try and deal with the ripple caused by the AC supply. To wit:

<i><b>It can be very clearly seen, starting at 50Hz, that when one decreases the fre_quency, the charge frequency, which is obviously that of the mains, is not sufficiently fast to feed the power supply filter capacitors. One would think that a capacitance of half a Farad, or even 1 Farad, would be sufficient to alleviate this slowness, but this is not so, and a modulation signal is found on the power supply which, similar to a piece of gelatine, fluctuates according to the signal.</i></b>

He doesn't seem to realize that increasing the amount of capacitance increases the ripple current which just loads down the transformer even more.

It seems he prefers the battery-only option with regard to sonics, but prefers the AC supply with regard to practicality.

<i><b>Of course, in this solution, the power supply noise rises considerably, by 30 to 40 dB. However, in spite of this, the Monster remains an amplifier without rival, even if it loses in "luminosity" compared to its operation on batteries and without a mains supply.</i></b>

I mean, what is there to bypass across a battery anyway? It's pure DC and doesn't have any ripple voltage or higher frequency noise that you'd need to shunt to ground.

So what's there to bypass?

se

[SvErD]

Originally posted by Steve Eddy
I mean, what is there to bypass across a battery anyway? It's pure DC and doesn't have any ripple voltage or higher frequency noise that you'd need to shunt to ground.

So what's there to bypass?

se

A car battery has a quite high ESR so a cap will lower the impedance of the supply. Look at what the car-audio people does.

[UrSv]

Originally posted by SvErD



A car battery has a quite high ESR so a cap will lower the impedance of the supply. Look at what the car-audio people does.

The Monster did indeed use large amounts of caps even with battery. The largest set-up used a large amount of 68.000 uF caps but also a Gold-Cap style cap normally used for battery back-up in low power consumption gear. That cap was rated 0.5 F at 12 V but run at a slightly higher voltage (close to 13.5 V). I listened to them all when there was a Swedish company (Tesserakt) selling most of the variations. It was very nice playing on large Onkens, Dauphin horns and/or T5000 tweeters. Mated with the subject of another thread - the Kaneda La Solstice.

I mean, what is there to bypass across a battery anyway? It's pure DC and doesn't have any ripple voltage or higher frequency noise that you'd need to shunt to ground.

So what's there to bypass?

I have been reading for ages about the chemical process in batteries causing noise and that the high ESR makes a pure battery PSU slow and sluggish. I thought that was common knowledge. Maybe I was wrong.

[Steve Eddy]

Originally posted by SvErD
A car battery has a quite high ESR so a cap will lower the impedance of the supply.

Guess it depends what you consider "high." I'm currently using some 7Ah SLAs which have a rated internal impedance of a little over 20 milliohms. And the higher the capacity of the battery, the lower its internal impedance.

What's 20 milliohms when you consider the fact that people are building Gainclones with 10 times that much resistance tied to their outputs?

Look at what the car-audio people does.

Car audio's a whole different ballgame. Car audio amplifiers use switchmode power supplies which are drawing current in pulses of typically between 50-100kHz (and we're just talking about the fundamental, not the harmonics).

The so-called "stiffening" capacitors are ostensibly intended to overcome the series inductance of the 12 volt lead running from the front of the car back to the trunk where the amplifiers are.

se

[Steve Eddy]

Originally posted by UrSv
I have been reading for ages about the chemical process in batteries causing noise...

EVERYTHING causes noise. Every length of wire or conductor causes noise. Every resistor and capacitor causes noise. Even when there's no current flowing. Raise the temperature or the current and you get even more noise. Transistors cause noise. Vacuum tubes have gobs of noise.

You think AC power supplies are noise-free? Think again. And personally, I'll take the benign, random noise of a battery over the kind of noise that AC power supplies can produce any day.

...and that the high ESR makes a pure battery PSU slow and sluggish.

This whole "slow" and "sluggish" thing is one of those weird metaphysical misunderstandings that seem to crop up all too often.

The impedance of the power supply has nothing to do with the "speed" of the circuit it's powering. The "speed" of a circuit describes how quickly it can change from one state to another (slew rate for example). And that's determined by the circuit itself, not the power supply.

The impedance of the power supply manifests itself in two basic ways, neither of which has anything to do with the "speed" of the circuit.

The first is the voltage drop that results from the supply impedance. The higher the impedance, the greater the voltage drop and the lower your supply voltages which means that your circuit will clip a bit sooner than otherwise.

But if you need X amount of power, all you have to do is increase the power supply voltage. That's what Final had to do with their dry cell powered amplifier. Dry cells have a much higher internal impedance per cell than SLAs, so Final had to string up 18 1.5 volt D cells in series to get a rail voltage of 27 volts in order to achieve a 10 watt power rating.

The second is that the supply impedance adds to the amplifier's output impedance. And when you drive a load which doesn't have a constant, flat impedance (such as a loudspeaker), you'll get a less than flat frequency response.

But if low output impedance is of such importance, no one would touch a tube amplifier with a 10 foot pole seeing as they routinely have output impedances 100 times greater than the 20 milliamps of the SLAs I'm using.

So unless all one cares about are absolute objective specs rather than how the system sounds, I don't see what the big fuss is about.

se

[peranders]

Originally posted by UrSv
Gold-Cap style cap normally used for battery back-up in low power consumption gear. That cap was rated 0.5 F at 12 V but run at a slightly higher voltage (close to 13.5 V).

Wasn't the use of a backup cap an obvious case of bad engineering? Nowadays there are types which can deliver current but in those days these type of caps were only good for CMOS backup.

[UrSv]

Originally posted by peranders

Wasn't the use of a backup cap an obvious case of bad engineering? Nowadays there are types which can deliver current but in those days these type of caps were only good for CMOS backup.

I think it was rather a way to impress but to some extent it did add a little capacity to the cap bank. To me it seemed like a bad idea at that time and it still does, especially with those caps meant to deliver low currents and running over spec.