[mhconley]

I had originally used this thread to ask a series of questions about bi-amping my VR-4 Gen III HSEs.  Then I read through the bi-amping sticky and decided to post... In the words of the immortal Emily Litella, "Nevermind."

Now I'm on to asking for recommendations for amplifiers to drive the midrange-tweeter module on my speakers.  I currently have DIY ICEpower 1000ASP monoblocks driving the entire speaker in a bi-wire configuration so I have two full sets for speaker cables on each side.

I'll keep the ICEpower monoblocks to power the woofer module.  They put out 1000W into 4Ω and 500W into 8Ω.

How many watts would you recommend to drive the midrange-tweeter module?  Any recommendation on specific amps?  I'd like to use tube monoblocks but I'm open to anything?

I am budget conscious and a very capable DIYer.  Some I'm considering include Dynaco Mark III, various Chinese amps, and possibly even DIY from kits or schematics.

All comments and recommendations are most welcome.

Thanks,
Martin

[mhconley]

I’ve made a decision to build a pair of new Dynaco based monoblock kits to power the upper cabinet on my VR-4 Gen III HSEs. I’ll be using my DIY 1000asp based monobloocks to power the bottom cabinet.  They put out 525 Watts into 8 ohms and 1100 into 4.  I need to choose between a Mark IV with 40 Watts, a Mark III with 60 Watts or a tubes4hifi m125 with 125 Watts.  Which of these three amps would you recommend?

Thanks,
Martin

[mhconley]

Wow, the sound of crickets in here is deafening... regardless, I'll try one more time...

I posted this earlier in the bi-amping sticky:

From Albert Von Schweikert:
3.  The "secret" to achieve "killer" sound quality is to ensure that the amplifiers have exactly the same input sensitivity.  The amplifier with the lowest numerical rating, i.e. 100mV is much more sensitive than an amplifier with a rating of 500mV - the higher the number, the lower the sensitivity.  You'll need to reduce the higher sensitivity by using a series input resistor.  This can be installed inside your amplifier, directly at the RCA female jack leading to the input stage. If this sounds a little scary, then build an adaptor to house the resistor outside the amp.  If you contact Michael Percy at www.percyaudio.com, he will advise you on what you'll need to get from him.  Usually, a female RCA jack, a male RCA plug, a high quality metal film resistor, some plastic sleeving, and a short piece of high quality hookup wire is all that is required.  Basically, you're inserting the resistor between the "hot" connection from the female RCA jack to the male RCA plug, and then using hookup wire to connect the ground leads.  The entire assembly can be only a few inches long and installed into a plastic or Teflon sleeve to prevent short circuits.  This adaptor is inserted into the signal path between your preamp and the most sensitive amplifier. As you can infer from this description, the adaptor is used in between your interconnect and the input jack of the amplifier.
Michael Percy sells these parts for less than $100 for everything you'll need, and he'll also help you select the proper value of resistor to match the sensitivities.  Although this simple technique may sound like a "Micky Mouse" setup to "sophisticated" engineers that design chip OP AMPS and sell electronic crossovers to the PA industry, it is a very "pure" form of passive matching that will stomp the crap out of any electronic crossover I have ever tried.

If I know the input sensitivity and gain of each amp - how do I calculate the resistor value?

Specifically, I am looking to use my DIY ICEpower 1000asp based monoblocks (2.96V input sensitivity) on the LF cabinet with a pair of VTA m-125 monoblocks (1V input sensitivity) on the HF cabinet. From Albert's statement above the m-125 is more sensitive than the 1000asp so I need to add a series resistor to its input. Since I am building the m-125 from a kit I want to add the resistor inside the amplifier. What value will I need?

Thanks,
Martin

[Escott1377]

Martin -

I am not sure you will get there w/ math.

I say that b/c I run a very similar set up w/ the jr's.

You can make a resistor ladder and play around w/ different values.  I played around w/ some different attenuator values and ended up w/ a 7 dB attenuator after lots of listening.

CI Audio makes a device that is passive and will allow you to adjust your gain to match the level for both amplifiers.  It is not cheap.

I sent my jr's in to VSA for the Gen IV upgrade and when they came back as 8 ohm across the speaker and I'll be damned if the problem just kind of fixed itself, so no more attenuators.

If you are able to calculate mathematically, please share as I never was never able to do so.

Good luck - I know I did not answer your ? specifically, but when it works, it sounds really good.

BTW - my bottom cabinet uses a pair of Wyred 4 Sound mAmps and my top cabinet uses a set of Primaluna Dialogue 7 mono blocks.

Eric

Wow, the sound of crickets in here is deafening... regardless, I'll try one more time...

I posted this earlier in the bi-amping sticky:

If I know the input sensitivity and gain of each amp - how do I calculate the resistor value?

Specifically, I am looking to use my DIY ICEpower 1000asp based monoblocks (2.96V input sensitivity) on the LF cabinet with a pair of VTA m-125 monoblocks (1V input sensitivity) on the HF cabinet. From Albert's statement above the m-125 is more sensitive than the 1000asp so I need to add a series resistor to its input. Since I am building the m-125 from a kit I want to add the resistor inside the amplifier. What value will I need?

Thanks,
Martin

[mhconley]

Martin -

I am not sure you will get there w/ math.

I say that b/c I run a very similar set up w/ the jr's.

You can make a resistor ladder and play around w/ different values.  I played around w/ some different attenuator values and ended up w/ a 7 dB attenuator after lots of listening.

CI Audio makes a device that is passive and will allow you to adjust your gain to match the level for both amplifiers.  It is not cheap.

I sent my jr's in to VSA for the Gen IV upgrade and when they came back as 8 ohm across the speaker and I'll be damned if the problem just kind of fixed itself, so no more attenuators.

If you are able to calculate mathematically, please share as I never was never able to do so.

Good luck - I know I did not answer your ? specifically, but when it works, it sounds really good.

BTW - my bottom cabinet uses a pair of Wyred 4 Sound mAmps and my top cabinet uses a set of Primaluna Dialogue 7 mono blocks.

Eric

Thanks for the input. I've considered a passive preamp like a Lightspeed Attenuator but really don't want to add another box with its associated cables, no matter how small.

I could temporarily wire in a good quality stepped attenuator, find the correct setting, then measure its resistance and replace it with a good quality resistor of the same value.

I've been Googling for days trying to find a mathematical formula but have been unsuccessful so far... someone has to know. This isn't rocket science - just electrical engineering.

EE was my toughest course; I barely squeaked through with a C- 23 years ago. I'm a very visual learner and found I just could not visualize what was happening. Pure math all the way through higher order differential equations was a breeze; EE was not. 

Your Wyred4Sound amps are very similar to my DIY monoblocks and your Primaluna's are very similar to the VTA m-125 I am considering. I am sure your setup sounds very nice.

Thanks,
Martin

[Escott1377]

I have an EE from Clemson

[mhconley]

Ressurecting my old thread...

I am currently biamping my VR-4 Gen III HSE speakers using a pair of 17W 300B PSET monoblocks on the upper modules and my 1000W ICEpower 1000ASP based monoblocks on the bottom. The amplifiers are connected to my YS-Audio Audio Experience balanced A2 preamplifier. I am using XLR from output 2 to the class D amps and RCA from output 1 to the tube amps. I measured pink noise separately on the tube/top module and class D/bottom module and found the bottom end to be about 10db louder than the top end. I currently have a cheap passive preamp (Nobsound Little Bear MC2) to attenuate the bottom end. The setup sounds pretty damned good to my ears. I purchased a pair of 10db Sescom SES-IL-10DB XLR Male to XLR Female Inline Attenuators to use in place of the passive preamp.

Any issues with this solution? Comments are most welcome.

Thanks,
Martin

[mhconley]

I tried two different sets of 10db attenuators, the Sescom ones I mentioned in my last post and a pair of MCM ones from Newark.com. They don’t work. While they did cut the bass modules by 10db they introduced some odd interference / noise / muffling of the high end. I don’t know how since I had them on the cable to the amps driving the woofer modules. Must have been some kind of issue inside the preamp between the two outputs. I know the attenuators mess with output impedance. Maybe something there. In any case the Nobsound Little Bear MC2 passive preamp is working wonderfully. I’m going to try measuring the resistance through the preamp and add resistors directly to the input of my DIY bass amps. For now just enjoying the wonderful music emanating from my beloved VR-4 Gen III HSEs.

Martin

[mhconley]

Last update, I promise. I have decided to permanently leave a passive volume control between my preamp and ICEpower amps on the bottom cabinet of my speakers. I replaced the cheap little Nobsound Little Bear with a relay based passive. The sound emanating from my speakers is mesmerizing. I’m spending hours each evening listening to all kinds of music. The 300b PSET amp on the upper cabinet is bringing a quality to female vocals, acoustic piano, and both acoustic and electric guitar missing when they were biwired on the ICEpower amp. I am a very happy camper!

Martin

[LesterSleepsIn]

That sounds fantastic but a bit of a tangle with the powercords and the the ICs, no? Any chance for a photo?
Or better yet, why don’t you pack it up and haul it all over to my house so that I can give a listen? Fall colors are starting to change but perhaps bring snow tires. I’ll make lunch.

All best,
Lester

[leif8660]

Martin -

I am not sure you will get there w/ math.

I say that b/c I run a very similar set up w/ the jr's.

You can make a resistor ladder and play around w/ different values.  I played around w/ some different attenuator values and ended up w/ a 7 dB attenuator after lots of listening.

CI Audio makes a device that is passive and will allow you to adjust your gain to match the level for both amplifiers.  It is not cheap.

I sent my jr's in to VSA for the Gen IV upgrade and when they came back as 8 ohm across the speaker and I'll be damned if the problem just kind of fixed itself, so no more attenuators.

If you are able to calculate mathematically, please share as I never was never able to do so.

Good luck - I know I did not answer your ? specifically, but when it works, it sounds really good.

BTW - my bottom cabinet uses a pair of Wyred 4 Sound mAmps and my top cabinet uses a set of Primaluna Dialogue 7 mono blocks.

Eric

Hi Eric,
If your speakers are coming across at 8 ohm's something is seriously wrong lol.  It is a ruler flat 4 ohm speaker

[mhconley]

That sounds fantastic but a bit of a tangle with the powercords and the the ICs, no? Any chance for a photo?
Or better yet, why don’t you pack it up and haul it all over to my house so that I can give a listen? Fall colors are starting to change but perhaps bring snow tires. I’ll make lunch.

All best,
Lester

It's actually not too bad. I only have the amps between the speakers so the only thing between the speakers are the xlr and rca cables coming from my preamp, speaker wires and power cords.



Martin

[mhconley]

Breaking my promise...

I am thinking of making some changes to my bi-amp setup. I'm seriously considering of replacing my Audio Experience balanced A2 preamplifier with a miniDSP SHD: https://www.minidsp.com/products/streaming-hd-series/shd

This will allow me to:

• balance the lower cabinet / ICEpower monoblock pair and the upper cabinet / PSET monoblock pair using volume correction on the outputs and get rid of the passive volume controller I'm now using for that task
• get rid of my separate DAC and Raspberry Pi Volumio streamer
• use Dirac Live room correction.

I have several questions...

My VR-4 Gen III HSE speakers have acoustic fourth order crossovers at 150 Hz and 2.6 kHz. As there are separate binding posts on each cabinet I assume the bottom "crossover" is simply a 24db per octave low pass filter and the upper crossover incorporates a 24db per octave high pass filter along with the 2.6 kHz crossover between the midrange and tweeter. Is this correct?

The miniDSP SHD can be used as an active crossover. Is there any benefit to using a 150 Hz 24db low pass filter to the ICEpower monoblocks feeding the lower cabinets and a 150Hz 24db per octave high pass filter to the PSET monoblocks powering the upper cabinet? And, if I do this, could I modify the upper cabinet/remove the lower cabinet passive crossovers in the speakers?

Thanks,
Martin