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KenTripp   
Posted (edited)

Joe Rasmussen, Custom Analogue Audio, JLTi

8pm Wednesday 17th May, visitors welcome.

Willis Room, City of Whitehorse Offices
Maroondah Highway (Whitehorse Road), Nunawading
Melway Map 48 Ref G9
Contact: 9437 1249

 

This month the club is very privileged to have an audio enthusiast travel all the way from Sydney to present at the club. Joe Rasmussen is known among the DIY audio fraternity as the "Father of the Buffered Gainclone" His collaboration with the late Allen Wright, led him to develop several projects starting back in 1975 with a "hybrid tube amplifier" In 2001 their work saw them develop upgrade modules for the first generation Sony SACD players.

 

Joe will be presenting at the club his latest upgrade projects. The JLTi Oppo level 4.2+ACB, is a highly modified Oppo-105D fitted with no less than eight modules. Each having a specific task - Master Clock - DAC Clock - Terra Firma power supply - all designed and developed by Joe at Custom Analogue Audio. "Ultimate Digital playback deserves Ultimate Stability! This is about the importance of clocking CD players and digital playback, a new standard of performance. How to make digital sound more like good vinyl".

 

His collection of equipment that will fill the room with sound, will include two amplifiers, a prototype "Beyond Triode" amplifier - A New Type of Tube Amplifier, and a DIY 40 Watt "Transconductance Amplifier" This solid state unit will be brought along for a bit of fun. Designed to output 'current' it will be demonstrated with his Elsinore Mk6 speakers. Compatible with this amplifier they can be driven from any source impedance and hence does not rely on the 'damping factor' of the amplifier. The "Beyond Triode" amplifier encompasses thirty years of experience and developments rolled into one design. The prototype unit a Yaqin MC-100B, has been upgraded to give a great boost in the 'Permeability' of the output transformers, which then translates into an extreme level of resolution.

 

To round off the equipment list for the night, two versions of the JLTi Phono Stage will be presented, a single box unit, and the new Deluxe Phono Stage. The Deluxe version is a two-box unit with a 'beefed up' design in the gain and buffer stages plus a massive separate power supply with extreme filtering that reduces power supply noise.

 

What Joe Rasmussen has achieved by taking a good quality product, amp or CD player, and lifting its performance to more than just one level, but several, makes music sound just lovely - Just Listen To it.

 

Nick Karayanis

Program Co-ordinator

 

Ken Tripp
Wise and Wonderful Webmaster
Melbourne Audio Club, Inc.

http://www.melbourneaudioclub.org.au

Edited by KenTripp

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KenTripp   
20 hours ago, Whites said:

This should be a great meeting.

 

@KenTripp let us know how it goes.

 

It should be indeed. I'll keep you posted.

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evil c   
Any updates on this meeting?

Joe gave us a detailed intro on his design philosophy, refreshingly different to conventional audio rules and let his system do the talking.
Sounded incredibly detailed and dynamic, and his Elsinore speakers produced predigious bass far exceeding that expected for such a compact bass driver.

I, and many others were excited by what we heard and Joe was very much in demand at the end of his demonstration.

He does sell those speakers in a kit form with drivers etc. requiring sourcing of a cabinet build.


Sent from my SM-G900I using Tapatalk

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Keith_W   

I was seated next to Evil C in this meeting. When Joe said that "damping factor is a myth", I looked at Evil C with raised eyebrows. He said, "open your mind!!". I have to admit that Joe's explanation made a lot of sense. But damping factor is so entrenched in the hifi world that I have a problem changing my thinking. He's probably right though. 

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evil c   
I was seated next to Evil C in this meeting. When Joe said that "damping factor is a myth", I looked at Evil C with raised eyebrows. He said, "open your mind!!". I have to admit that Joe's explanation made a lot of sense. But damping factor is so entrenched in the hifi world that I have a problem changing my thinking. He's probably right though. 

I have the benefit of ignorance compared to guys like you Keith, makes it easier to be more open minded .
One of the most important things I've learned all these years - how little we really know !

Sent from my SM-G900I using Tapatalk

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KenTripp   
Posted (edited)

Damping factor is not so much a myth but more or less irrelevant for any speaker system with a passive crossover network.

 

Some pics from the night (not my pics)...

 

jrequip.jpg

jrjoe.jpg

jrxovers.jpg

jryaqin.jpg

Edited by KenTripp

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16 hours ago, KenTripp said:

Damping factor is not so much a myth but more or less irrelevant for any speaker system with a passive crossover network.

 

 

Damping factor is not irrelevant for the vast majority of loudspeakers available today. The amount of damping factor required varies considerably, but, with an 'easy' 8 Ohm speaker, a damping factor or around 20 is usually plenty adequate. It has always been possible to design a speaker that can be current driven, it's just that, since the year dot, every speaker made has been designed to be driven by a Voltage source. IE: A low output impedance. 

 

The difficulty with using a speaker designed to be driven by a current source, is that it may perform sub-optimally with a Voltage source. Same deal with the amplifier. Since the vast majority of speakers are designed to be driven by Voltage sources, then most of those speakers will perform sub-optimally with a current source. ESLs would be one of the worst choices for a current source amplifier. 

 

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KenTripp   
2 hours ago, Zaphod Beeblebrox said:

 

Damping factor is not irrelevant for the vast majority of loudspeakers available today. The amount of damping factor required varies considerably, but, with an 'easy' 8 Ohm speaker, a damping factor or around 20 is usually plenty adequate. It has always been possible to design a speaker that can be current driven, it's just that, since the year dot, every speaker made has been designed to be driven by a Voltage source. IE: A low output impedance. 

 

The difficulty with using a speaker designed to be driven by a current source, is that it may perform sub-optimally with a Voltage source. Same deal with the amplifier. Since the vast majority of speakers are designed to be driven by Voltage sources, then most of those speakers will perform sub-optimally with a current source. ESLs would be one of the worst choices for a current source amplifier. 

 

 

By irrelevant I meant the ever increasing values for quoted amplifier DF because the great equalizer is the series resistance of the sizable inductor in series with the bass driver, hence the passive reference. So it doesn't matter if the quoted DF is 80, 800 or even 8000 as the actual DF will in all cases be lucky to make double digits.

 

 

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Well I still belive in dampening factor between amp and speakers but I also understand once it gets above 100 there is little change in effect. I felt that Joe's system (Melbourne Audio Club demo) was electrically under-damped but accusticly properly damped. That's just my impression of the sound.

 

I would personally like to thank Joe for going to such a huge effort for that demo night. He brought down a pile of gear, went to a lot of trouble and got us all thinking about well established dogmas. He certainly rattled the cages but like unlike Bond I'm stirred but not shaken. 

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KenTripp   

It was a good night, one of the better ones we've had. The industry would be a lot better if there were more guys like Joe.

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1 hour ago, KenTripp said:

 

By irrelevant I meant the ever increasing values for quoted amplifier DF because the great equalizer is the series resistance of the sizable inductor in series with the bass driver, hence the passive reference. So it doesn't matter if the quoted DF is 80, 800 or even 8000 as the actual DF will in all cases be lucky to make double digits.

 

 

 

You have just opened a big ole can of worms. I have a great deal to say about this matter and will be doing so very soon. Stay tuned. 

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KenTripp   

No worms. Just facts. Awaiting with bated breath for the great deal.

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Posted (edited)
On 2017-5-27 at 10:01 PM, Keith_W said:

I was seated next to Evil C in this meeting. When Joe said that "damping factor is a myth", I looked at Evil C with raised eyebrows. He said, "open your mind!!". I have to admit that Joe's explanation made a lot of sense. But damping factor is so entrenched in the hifi world that I have a problem changing my thinking. He's probably right though. 

 

He is.

 

The "myth" part is around increased damping factor leading to generally increased performance....    increasing damping factor leads to the response of the speaker/amplifier combination being independent of the speaker impedance.....  and this might seem like increased performance, depending on the specific situation.

Edited by davewantsmoore

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joz   
On 5/27/2017 at 10:01 PM, Keith_W said:

I was seated next to Evil C in this meeting

 

Lucky you, everyone else had worked it out.

Must have been the last seat yea?

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Martykt   
29 minutes ago, joz said:

 

Lucky you, everyone else had worked it out.

Must have been the last seat yea?

 

Well it is the second closest seat to the sweet spot so in a way a smart move by @Keith_W...... :P 

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Who has done the test in reference to dampening factor with the same speaker and using similar spec amps but with different dampening factor?  

 

 

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18 minutes ago, Addicted to music said:

Who has done the test in reference to dampening factor with the same speaker and using similar spec amps but with different dampening factor?  

 

 

 

Lots of people. Including me. Like many things in life, it really does depend greatly on the speaker. Try it yourself. Insert a 1 Ohm resistor in series with your speakers. With 8 Ohms speakers, that means your damping factor is 8. Now try the same thing with an 8.2 Ohm resistor. Now you have a damping factor of 1. With certain speakers, the effect is not huge, whilst with others, the difference can be very substantial. A bunch of VERY BIG generalisations follow:

 

* ESL speakers will show a falling HF response, with increasing damping factor.

* Those speakers with a very resistive impedance (Maggies, for instance) will show very little difference from the mids to the highs. Bass will be affected (flabby). Speakers with conjugate networks in the crossovers should fare better than those that do not. 

* Sealed enclosures will be less affected than bass reflex.

 

Again, these are generalisations. They may not be true for all instances. That said, I will state again, that the vast majority of speakers are designed to operate from a Voltage source (aka: a damping factor of greater than 20 or so). 

 

 

 

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Posted (edited)
2 hours ago, Addicted to music said:

Who has done the test in reference to dampening factor with the same speaker and using similar spec amps but with different dampening factor?  

 

Yes.

 

Above a certain 'damping factor' the speaker will be driven the same.   As you lower DF the response of the speaker changes.    You'll get various results depending on the particular speaker....  which is part of the reason why amplifiers with a reasonably low output impedance (high damping factor) are the standard.

 

If the speaker driver/crossover is made to be immune to the change in response due to low damping factor....   or if the speaker is designed with the changed response as an integral part ....  then there's no problem, quite the opposite.

Edited by davewantsmoore

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KenTripp   
1 hour ago, Zaphod Beeblebrox said:

Again, these are generalisations. They may not be true for all instances. That said, I will state again, that the vast majority of speakers are designed to operate from a Voltage source (aka: a damping factor of greater than 20 or so). 

 

People using valve power amps must have a very limited range of speakers to choose from.

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Posted (edited)
41 minutes ago, KenTripp said:

 

People using valve power amps must have a very limited range of speakers to choose from.

 

Nope. Not all valve amps possess very high output impedance figures. Earle Weston's beauties possess commendably low output impedance figures. It's all down to the output transformers and there's none better than Earle's. Don't forget: Most valve amps utilise a tapped output transformer, enabling the user to select a lower impedance tap, which means a lower output impedance. Check out this baby:

 

http://www.westonacoustics.com/service5.html

 

A damping factor of greater than 10, whilst not spectacular, is probably adequate for most loudspeakers. However, MOST importantly, that damping factor is specified from 20Hz ~ 20kHz. Very few solid state amp manufacturers cite such a figure, because it is likely they cannot offer such a damping factor at high frequencies. Impressive stuff. 

Edited by Zaphod Beeblebrox

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gemini07   

So.

 

What was the actual sound like?

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