Burmester 911 mk3

[NorthStar]

Just for the Pleasure of the Music ...

---Burmester is German, and we all know that Germany makes some of the best audio gear and also musical instruments, and recording music labels, and cars, and all that steel Jazz ...

Enjoy this short video; only here in this thread, especially thinkin' 'bout you guys. :b

 

[joeinid]

Dank Bob,

Ich wünschte ich könnte das gesprochene deutsche Sprache verstehen.

 

[NorthStar]

---Dunno, but sounds good anyway Joe! :b

 

[garylkoh]

Gary,

The GAT uses a relay switched discrete resistor attenuator - only a single high quality precision resistor in series in an L circuit. The reason must be another for Joe's system. Should we consider that as the transformer reduces the signal voltage and the attenuator is located before the tube gain stage, the preamplifier will be working at higher levels, with a better signal to noise ratio?

That is another possibility. There should be a buffer before the attenuator so that source components will see a constant input impedance and a buffer after the attenuator so that the output impedance would be constant. The output tube buffer working at higher levels will certainly give a better signal to noise ration. Tube heater circuits commonly contribute 20dB or more of noise, and this is at a continuous level so that increased signal will improve the s/n ratio.

I have now seen that the 911mk3 has a gain of 34 dB. This can help the driving output circuits of the preamplifier as it it needs to supply a lower voltage to the amplifier,

That's pretty high - "standard" power amp gain is in the region of 26dB to 28dB.

the needed current being also lower. Most tube circuits can supply an high voltage, but measured distortion increases a lot when they have to supply currents above one miliampere.

and that is why a high input impedance in the amplifier is advantageous when a tube amplifier is used. The high input impedance ensures that the amplifier becomes a voltage drive instead of a current drive. I find that is also why SS preamps and tube preamps sound different. Tube preamps can be very low distortion when they drive high voltage and low current. SS preamps can be low distortion when they drive high current.

 

[Thf99]

Had entire Burmester electronics (Transport , DAC, Preamp, amp) and very good TT (Basis, Graham and Lyra Cart) ... I am a digital person now ...

If you can live with purely digital, that's great. Saves you a lot of dollars and maybe, hassle? As for me, after listening to the Davinci TT, I felt I must have it.

 

[SMcAudio]

Thanks Gary,

You are right once again. The Interocitor One is a great piece of gear. I love it!!!! I sincerely appreciate all your contributions here and in the world of Audio. Steve's Interocitor One let's me run my GAT in it's sweet spot allowing me run the volume scale in the 60's+ range of the scale that goes to 100 (I think). My 077 is superb but can be too good on these less than stellar recordings. My GAT plus Interocitor One lets me enjoy everything!

Hi Joe -

I have just returned home from an extended trip, so have only just now seen the latest bits of this thread. Thanks very much for your kind words about the Interocitor One - I'm glad you are enjoying it! Thanks also to Gary Koh for his explanations and support - a great resource, as always. Joe's situation put the Interocitor to very good use by employing the unbalanced-to-balanced conversion, *and* the impedance transform for his exceptionally-low-input-impedance amps. The galvanic isolation of the grounds is always welcome, of course, and the signal attenuation was also useful in this instance as it provided a better match between high-gain preamp and high-gain amps. A well-designed isolation transformer can be very helpful in a variety of situations, and this is a perfect example of some of its potential. As Gary has pointed-out, it is also worth trying it with your other amp / preamp combinations to enjoy the benefit of ground isolation, even if the impedance matching is not strictly necessary.

For those who may be interested, I am now working on a second model that will offer user-adjustable turns-ratios of 2:1, 1:1, and 1:2. This model will provide some useful flexibility in systems that do not require the 4:1 ratio of the original Interocitor. And speaking of the "Interocitor," I have decided to change the product name to "Flex-Connect." The name "Interocitor" was a bit of fun for me, as it comes from an old Sci-Fi movie called "This Island Earth." In the movie, the Interocitor is an advanced alien communications device (among other things) so I thought it would be fun to name my product after it. But this has proved to be problematic, so I have decided to be a bit more prosaic with my names. "Flex-Connect" is certainly more descriptive, if somewhat less fun ;-)

Thanks again, Joe - let me know if you have any further questions.

 

[joeinid]

Hi Steve,

It's great to see you here again. Thank you. I was getting some resistance from some of the "non-believers" (Ha!) but I kept an open mind. I am glad I did. I was having trouble deciding on which preamp to keep, now I don't have to. I can keep them both and pick the flavor I want based on my mood, music collection or source. I am also pleasantly surprised when I use the Interocitor One (soon to be Flex-Connect) between my CJ GAT and CJ Premier 350SA amp. The too high a gain from that system is annoying to me and the Interocitor One helps in that regard as well. I was ready to give up on that amp but I am having second thoughts on selling it at this point.

Please keep up the great work! I am a big fan now

 

[Rocco I.]

---Burmester is German, and we all know that Germany makes some of the best audio gear and also musical instruments, and recording music labels, and cars, and all that steel Jazz ...

Enjoy this short video; only here in this thread, especially thinkin' 'bout you guys. :b

Musicians
Allan Taylor: vocal, guitar
Michael Koschorrek: guitar, lap steel guitar, tremolo guitar, dobro, electric guitar
Ralf Gustke: drums, percussion
Hans-Jörg Maucksch: fretless bass, electric bass
Dieter Burmester: electric bass
Michael Kleinhans: tuba

 

[microstrip]

Hi Joe -

I have just returned home from an extended trip, so have only just now seen the latest bits of this thread. Thanks very much for your kind words about the Interocitor One - I'm glad you are enjoying it! Thanks also to Gary Koh for his explanations and support - a great resource, as always. Joe's situation put the Interocitor to very good use by employing the unbalanced-to-balanced conversion, *and* the impedance transform for his exceptionally-low-input-impedance amps. The galvanic isolation of the grounds is always welcome, of course, and the signal attenuation was also useful in this instance as it provided a better match between high-gain preamp and high-gain amps. A well-designed isolation transformer can be very helpful in a variety of situations, and this is a perfect example of some of its potential. As Gary has pointed-out, it is also worth trying it with your other amp / preamp combinations to enjoy the benefit of ground isolation, even if the impedance matching is not strictly necessary.

For those who may be interested, I am now working on a second model that will offer user-adjustable turns-ratios of 2:1, 1:1, and 1:2. This model will provide some useful flexibility in systems that do not require the 4:1 ratio of the original Interocitor. And speaking of the "Interocitor," I have decided to change the product name to "Flex-Connect." The name "Interocitor" was a bit of fun for me, as it comes from an old Sci-Fi movie called "This Island Earth." In the movie, the Interocitor is an advanced alien communications device (among other things) so I thought it would be fun to name my product after it. But this has proved to be problematic, so I have decided to be a bit more prosaic with my names. "Flex-Connect" is certainly more descriptive, if somewhat less fun ;-)

Thanks again, Joe - let me know if you have any further questions.

Steve,

Thanks for your help. Just one detail: when you refer to turns-ratios are you addressing voltage ratios ? The Interocitor literature refers to 4:1 impedance conversion for driving long interconnects . Does it mean a impedance or voltage ratio?

 

[SMcAudio]

Hi Microstrip -

The "4:1" refers to the transformer input-to-output turns ratio. It is this ratio that provides the impedance transform, along with the decrease in output voltage and increase in output current. In this case, the Interocitor One / Flex-Connect has an input impedance of about 40K and an output impedance of about 200 Ohms, which gives it the ability to drive very-low-input-impedance amps like the Burmester 911 MK3. Joe's system - like most, in my experience - has a considerable surplus of gain, so the -12dB attenuation of the 4:1 ratio model does not pose any problem, and in fact is useful in matching his preamp and amp. When running long interconnects (say 4M or more) I find it beneficial to have a low source impedance and, hopefully, a balanced connection. The Flex-Connect provides this facility for systems that may not have it.

 

[microstrip]

Hi Microstrip -

The "4:1" refers to the transformer input-to-output turns ratio. It is this ratio that provides the impedance transform, along with the decrease in output voltage and increase in output current. In this case, the Interocitor One / Flex-Connect has an input impedance of about 40K and an output impedance of about 200 Ohms, which gives it the ability to drive very-low-input-impedance amps like the Burmester 911 MK3. Joe's system - like most, in my experience - has a considerable surplus of gain, so the -12dB attenuation of the 4:1 ratio model does not pose any problem, and in fact is useful in matching his preamp and amp. When running long interconnects (say 4M or more) I find it beneficial to have a low source impedance and, hopefully, a balanced connection. The Flex-Connect provides this facility for systems that may not have it.

Steve,

I see - the 2 kohm impedance of the Burmester shows as 4 x 4 x 2kohm = 32 kohm, an excellent impedance for most preamplfiers.

There is also another very interesting application for your Interocitor One - driving subwoofers in high quality audio systems. Some of the best subwoofers have low input impedance and if you drive the main speakers full range you have to have this load in parallel with the amplifier input impedance. Using the Interocitor One will prevent the subwoofer from affecting the sound quality of the system. Happily usually subs have a very high gain, the attenuation will not be critical.

 

[garylkoh]

Steve,

I see - the 2 kohm impedance of the Burmester shows as 4 x 4 x 2kohm = 32 kohm, an excellent impedance for most preamplfiers.

There is also another very interesting application for your Interocitor One - driving subwoofers in high quality audio systems. Some of the best subwoofers have low input impedance and if you drive the main speakers full range you have to have this load in parallel with the amplifier input impedance. Using the Interocitor One will prevent the subwoofer from affecting the sound quality of the system. Happily usually subs have a very high gain, the attenuation will not be critical.

micro, yes. That is a great application for the Interocitor. Steve Williams uses the Musical Fidelity tube buffer between his preamp and his JL Audio subs to perform this impedance matching. I'm sure that the Interocitor would work as well, if not better. This is yet another application for Interocitation.

 

[SMcAudio]

Yes, the subwoofer application is another interesting possibility, both in terms of ground isolation and impedance matching - thanks for the suggestion.

I have to admit that I am still a bit unclear on the actual input impedance of the Burmester 911 MK3 amplifier. The best information I've been able to turn-up says "22.9kOhms Unbalanced, 1.88kOhms Balanced." Which is odd, since I would expect to see each leg of the balanced XLR input with an equal value. The amp is designed to be driven balanced, but is supplied with an RCA-to-XLR adaptor, so perhaps something in the adaptor is responsible for the apparent discrepancy? Of course 1.88KOhm is unusually low and would present a problem for many tube preamps, and even a few solid-state units, if this figure is correct. Could you explain how you are coming-up with the 32K figure?

Thanks for your feedback.

 

[SMcAudio]

This is yet another application for Interocitation.

Ha! Thanks, Gary - I love it ;-)

 

[joeinid]

Ha! Thanks, Gary - I love it ;-)

+1

 

[microstrip]

Yes, the subwoofer application is another interesting possibility, both in terms of ground isolation and impedance matching - thanks for the suggestion.

I have to admit that I am still a bit unclear on the actual input impedance of the Burmester 911 MK3 amplifier. The best information I've been able to turn-up says "22.9kOhms Unbalanced, 1.88kOhms Balanced." Which is odd, since I would expect to see each leg of the balanced XLR input with an equal value. The amp is designed to be driven balanced, but is supplied with an RCA-to-XLR adaptor, so perhaps something in the adaptor is responsible for the apparent discrepancy? Of course 1.88KOhm is unusually low and would present a problem for many tube preamps, and even a few solid-state units, if this figure is correct. Could you explain how you are coming-up with the 32K figure?

Thanks for your feedback.

I also found it odd and some posts above in this thread member AudioExplorations kindly offered to measure it. I supplied a simple receipt (post #589) and he did the hard job, getting a value of 2k for the balanced input impedance and 1k for the unbalanced - the current official WBF value for 911 mk3 input impedances. I just multiplied the measured 2k by the square of the ratios of your Interocitor One.

Ok, the moment of truth...

Balanced:

Va = 1.441
Vb = 0.134

Rin = 2.051 kOhm

Unbalanced:

Va = 0.633
Vb = 0.058

Rin = 1.009 kOhm

All I need now is getting an Interocitor One for my system ASAP

 

[SMcAudio]

Ok - got it. Thanks Microstrip. And thanks for providing a definitive answer for the input impedance - it's nice to know for sure. If you decide you can't live without the Interocitor / Flex-Connect, just let me know.

Cheers!

 

[audioarcher]

Hi Steve,

I attended the demo of your new preamp at the PNWAS meeting. Your preamp was very impressive. It sounds very transparent to the source. The Flex-Connect is a good idea and makes matching equipment that does'nt mix possible.

I have a question that is a little off topic. I am wondering if a preamps volume control position effects the output impedance? If the volume control is wide open would the output impedance be lower?

Thanks,

Sean

 

[SMcAudio]

Hi Sean -

Thanks for your kind words about the VRE-1C. I'm glad you were able to attend the PNWAS presentation, which I really enjoyed - a good time was had by all!

Your question about volume controls opens something of a "can of worms" - a complete answer would be rather lengthy. However, the simple answer is "no," at least in most cases. The reason is that most preamps are designed so that the amplification circuitry comes *after* the volume & balance controls, which means that the output impedance of these designs is fixed - changing the volume setting does not affect it. Having said that, I hasten to add that, while "most cases" covers a lot of the market, there are plenty of exceptions, especially in the realm of passive designs. In a pure passive design, either resistor-based or transformer-based (TVC), the volume setting does directly affect the output impedance, albeit in very different ways, depending on the specific design type. And then there's the whole question about what might be happening to the *input* impedance - yikes! Well, that's another story...

Let's leave it there for the moment and just say that, if you have a typical active preamp, the answer is most likely no and you need not worry about this particular question. I hope his helps.

 

[audioarcher]

Thanks for the response Steve.

I do use an active preamp but my setup is a little different than ordinary. My speakers are Innersound Kayas. They use an active crossover with a bass amplifier built in to power the woofers in this hybrid electrostat design. This active crossover also has a volume control but only one input. I have more than one source and also need a balance control so I use an Aesthetix Callisto tube preamp into the crossover. I noticed that my dynamics were a little soft so I played around with the setup to solve the issue. Eventually I found that if I turned the volume almost all the way up on the Callisto and lowered the volume on the crossover to compensate my dynamics improved quite a bit. That is why I asked the question.

Best Regards,

Sean