[JerryD6]

I've been reading the VMPS board for some time in researching the v60s to replace Infinity IRS Betas.

I was also an Infinity fan having owned the RS1bs for about 17 years, so I know exactly how you came to notice the RM-V60s and to think of them as a logical choice.

Yes, I think we both followed much the same path.

Also, thanks for the caution above about the RS meter. Mine is about 20 years old, so who knows if the current corrections are valid for it. Time for a new one.

[Tyson]

Or, if you have an Iphone, you could use the tools detailed below, which are much more accurate, and give you real time 20hz-20khz readings in full graph format:

http://www.audiocircle.com/index.php?topic=69443.0

RTA and FFT tools, fully calibrated to the iphone's internal mic.  Graphical display, and a huge amount of options to really fine tune your readings.  Pretty awesome for $30.

[Housteau]

Mine is about 20 years old, so who knows if the current corrections are valid for it.

What model is it?  Mine is also very old and it could be the same one.  If it is I can send you the correction factors.

[JerryD6]

Mine is about 20 years old, so who knows if the current corrections are valid for it.

What model is it?  Mine is also very old and it could be the same one.  If it is I can send you the correction factors.

The only number I see is the catalog no.  33-2050. It is an analog unit. If this seems right you can post the corr factors here or email if that is more convenient.

gdunn6@gmail.com

Thanks,
Jerry

[Housteau]

The only number I see is the catalog no.  33-2050. It is an analog unit. If this seems right you can post the corr factors here or email if that is more convenient.

You are in luck.  That is the one I have and an email is being sent.

[Housteau]

At CES I used a 3dB cut at 65Hz with a Q=1 to get maximum clarity in the upper bass range.  I suggest something similar for you.

That is a decent cut at a broad range, but it seems to do what I needed without sacrificing any weight or impact.  Right now I am listening with a -2.5db cut and that seems pretty good.

[JerryD6]

You are in luck.  That is the one I have and an email is being sent.

Thanks, I appreciate it.

[John Casler]

My DCX is one of the nice modified units and part of that mod is an improved digital in, ADC and DAC.  The digital in is very clean, but also fatiguing to my ears after a short while.  In all cases I have found that my DCX sounds best using the analog in and allowing it to use both of its own ADC and DAC together.  I reverified this last evening as part of my Benchmark vs Monarchy DAC tests.  My Proceed transport has several digital outs and they can all be used at the same time.  This makes comparisons a lot easier.

What did you use for a 6 channel volume control after leaving the D-OXO when you went straight digital in from the source?

[Housteau]

What did you use for a 6 channel volume control after leaving the D-OXO when you went straight digital in from the source?

My unit has the built in analog output board that acts as a preamp.  I bought it from Zybar and here is a list of all my mods as done by Mike Galusha.

- Linear Audio (Jan Didden) analog IO kit

- Frank Oettle SRC (Sample Rate Converter)/Clock/Input Receiver

- All electrolytic caps on DSP/DAC board replaced with Black Gate

- Voltage regulators on DSP/DAC board replaced with Oettle regs

- Digital input wired direct to transformer with RG-179 75 ohm coax and
terminated with precision 75 ohm resistor.

- DAC's upgraded to latest AKM AK4396 (this was a special one time thing - not sure if the chips can be easily obtained again)

- +/- 15V analog power supply lines have 100uH chokes and two of the caps
on the DAC/DSP board changed to 220uF create an LC filter. These are the
only two caps that are not Black Gate.

- "Felix" power conditional/filter between IEC and switching PSU. All
power wiring replaced with 18GA cryo treated teflon insulated wire.

- Install AudioQuest Silver NextGen 75 ohm RCA female socket.

There is a discussion on this thread about the preference of using the analog inputs over the digital ones:
http://www.audiocircle.com/index.php?topic=66503.0

In a much earlier posting Brian had noticed this too and mentioned that for some unexplained reason the DCX sounded best by allowing it to do the full conversion from analog - digital - analog.  This is what he wrote as an answer to my question about the quality of it used as a DAC:

The ADC/DAC section of the DCX2496 is a curious animal I don't think I've run into before.

It's obviously inexpensive.  Heard by itself by using the digital input fed from the digital output of my Krell transport, it sounds rather flat and uninvolving.  However, with the analog input engaged and fed from the analog output of my Wadia 27ix DAC with the digital volume control, it retains the lush sound of the Wadia pretty much without alteration.  Feeding the analog DCX input from the analog output of another player I use, the Denon 1300 DVDA player, you can clearly hear the difference between the Denon and the Wadia DAC's.

So with the analog inputs, I would call the ADC/DAC of the DCX2496 "tonally neutral".  If I were using it as a DAC only, I'd probably hire one of the many modders who improve the analog output with quality parts and wiring to enliven its sound.

[Housteau]

Or, if you have an Iphone, you could use the tools detailed below, which are much more accurate, and give you real time 20hz-20khz readings in full graph format:

http://www.audiocircle.com/index.php?topic=69443.0

RTA and FFT tools, fully calibrated to the iphone's internal mic.  Graphical display, and a huge amount of options to really fine tune your readings.  Pretty awesome for $30.

This is the first I have see anything about this.

[Tyson]

Just get a 3.5mm mini-plug to RCA stereo adapter and plug the headphone jack of the Iphone into an input jack on your preamp.  I got a 12 foot cable from Amazon to do just that.  Then, the FFT application has a pink noise generator - turn it on and set the readout to be a 2 second or a 4 second delay, and take a look.  It was a real eye opener for me, considering that I'd put considerable time and effort in with the Radio Shack SPL meter, and hadn't gotten anywhere new a good, flat response. 

The 1/3 octave spacing that I had previously for test tones was just not granular enough to get a good reading.  With the FFT, you don't get twenty data points like you get with the 1/3 octave tones.  You get anywhere between 200 and 16,000 data points.  Plus, having a DCX (like you do), it was a snap to start making adjustments in real time and getting the EQ and crossover settings "really" dialed in. 

I also downloaded a program called "speaker pop" from the same group, which allows you to determine the phase of each set of drivers.  I found out that the amps driving my mids and highs invert polarity, but my bass amps do not.  So, I just flipped the polarity settings in my DCX to correct for that, and viola! much better sound.  Easy peasy.

[JerryD6]

The Studio Six is a very nice site. Makes me want to get an iPhone. The RT60 software looks interesting as well.

[John Casler]

What did you use for a 6 channel volume control after leaving the D-OXO when you went straight digital in from the source?

My unit has the built in analog output board that acts as a preamp. 

Got it.

I remember that thread now.

Wonder why all the conversions "sound" better. 

Theoretically the cleaner path would have the advantage to accuracy, but as we all know it is "ALWAYS" system dependant.

What is interesting and also not well explored is placing an analog device (like a tube amp or dac), in front of an ADC.

Does that ADC take the analog signal (with tube charachter and all) and convert same to digital in a way that can be reassembled by the DAC on the other side?

Your, Brian's and George's evaluations suggest that "may" be the case.  However it is a sample based on the "preamp" section of the modded D-OXO.

I would wonder if the stock incarnation might show similar or differently.

Obviously the most economical route would be to not have an expensive preamp and DAC preceding the D-OXO, and a high quality 6 channel preamp (such as a good Pre/Pro with 7.1 analog ins).  Then the weaker link would be the DAC in the D-OXO.

It will be interesting as more and more of these reach the field what begins to unfold.  If one need not have an expensive Preamp and DAC on the front end, it would certainly allow for a nice mod to the D-OXO's DAC and a good Pre/Pro with analog in and good volume control.

Interesting. . . .

[Housteau]

Your, Brian's and George's evaluations suggest that "may" be the case.  However it is a sample based on the "preamp" section of the modded D-OXO.

I would wonder if the stock incarnation might show similar or differently.

It will be interesting as more and more of these reach the field what begins to unfold.  If one need not have an expensive Preamp and DAC on the front end, it would certainly allow for a nice mod to the D-OXO's DAC and a good Pre/Pro with analog in and good volume control.

Actually. Brians observation was with a stock unit.  He posted that before he had a modified unit.

Boy, you are right on how nice it would be if the DAC in the D-OXO was better.  How simple a system could be, just a transport, the digital out from a server, or the line out from a phono preamp is all that would be needed in adition to the D-OXO.  However, making things that easy just might be against the rules somewhere .

[PLMONROE]

Dave, if the DAC in your modified DCX is the same as mine (and it may or may not be - you would have to ask Mike) you are going to have to go beyond 4K to best it - IMHO.

Paul

[Housteau]

Dave, if the DAC in your modified DCX is the same as mine (and it may or may not be - you would have to ask Mike) you are going to have to go beyond 4K to best it - IMHO.
Paul

I am not sure if ours are the same, but the digital system seems very good.  It must be to be so transparent.  I will so more testing, but so far for me this digital system has sounded best with both the ADC & DAC working together using the analog in.  It has not sounded as nice breaking into the middle and just using the DAC half by itself.   

[7x57]

If you can still find them, adding a Scan-Speak vent or two can make your sealed enclosure seem 50% bigger and the bass quality will be very similar to a good transmission line and the bass cutoff will be extended. I have used one to make a Marshall guitar amp into a bass guitar amp, along with the addition of an American made Eminence Beta 10A bass guitar speaker with HUGE magnet in place of the cheap trashy Chinese Celestion speaker with DINKY magnet. The speaker cabinet was too small for the bass guitar speaker, but the Scan-Speak vent and addition of Acousta-Stuf damping material (available from Parts Express) solved the problem. Because VMPS speakers such as my RM-1's have no dust cap, there is a resistive air leak between the pole piece and voice coil such as a Scan-Speak vent would provide, but maybe not to that level of leakage. Adding the Scan-Speak vent makes it so, and transmission line type resistive dampening is the result, and the bass will be very tight. This is a personal thing, and not a mod that everybody will like. The old Dynaco A25 was a poster child for what a resistive flow vent can do. They were made by Dynaudio to the tune of almost a million units worldwide.

[7x57]

I should also state what my actual bass extension measurements were after making my several modifications to my RM-1 speakers. It affects mainly the bass, as the midrange and tweeter are still stock factory setup as of 2001 when I ordered the speaker kit. The speaker cabs had the optional soundcoat treatment. Using the Stereophile Test CD2 track 16 bass decade 1/3 octave warble tones for signals, the bass is -1dB at 40Hz, -3dB at 31.5Hz and -6dB at 25Hz when set to 0dB at correlated pink noise of track  15. When sound level meter set to 0dB of uncorrelated pink noise of track 15, the bass extension is +1dB at 40Hz, -1dB at 31.5Hz and -4dB at 25Hz at my sitting listening position ear height. Output at 20Hz was around -15dB or maybe even less. Meter set to C weighting and slow response and my meter was tested with a sound level meter calibrator and found to be within 0.5 dB of calibrator output. The 25Hz signal was tested at several locations around my listening chair and found to be quite consistent, unlike the higher frequency bass signals. 5dB of rolloff over 2/3 of an octave seems quite good to me. If I remember correctly, with my Vandersteen Model 2Ci speakers tested in a similar manner in the same positions, the frequency response was flat at 40Hz, -6dB at 31.5Hz and it fell on its face at 25Hz and I heard practically nothing. The RM-1 thus goes about 5Hz deeper in the bass than a Vandersteen 2Ci, which is regarded as good in the bass region and they are at a similar price and size point. Amp was C-J MF-2250 solid state with low impedance bipolar transistor outputs in both cases and flat to 2Hz, preamp is PV-14L with similarly flat response and JFET buffered low impedance 200 ohm output impedance into a 100K ohm input. I should also state that I bought the 8 ohm version kit as I was also using mono tube amps at the time I bought the speakers, but they are out of service for many years now (blew a power transformer) and due for a rebuild this coming winter, as I want them as steady auxiliary heat source for our Montana winters. They give poor bass response with the Vandersteen 2Ci, but work great with the little Polk RT5 speakers that I have on my television. I modded the Polk speakers and got them flat to 50Hz by adding resistive foam flow plugs in the ports, adding Acousta-Stuf damping material, and replacing the crossover 10uF electrolytic cap with a 6.6uF film cap, filling in a measured gap in the lower treble that had the speakers lacking in definition and involverment. Bass guitar lines are much better defined and extended lower in frequency, being -6dB at 40Hz, which is good as most E-Bass notes are 45Hz and higher. I never was a fan of undamped bass reflex speakers, and adding resistive flow ports and quite a bit of damping material is the old cheapo route to quasi-transmission line bass response. My Altec Lansing VS-4121 multimedia computer satellite/subwoofer speakers have a similar underdamped bass reflex subwoofer, and the humped wolf note bass response was flattened, tightened and extended by simply wadding up a paper towel and stuffing it in the vent, which makes it about a 2-cent Scan-Speak vent equivalent. Fiberglass, open cell foam, open cell paper and fabric can all be experimented with as resistive flow vent material. Styrofoam cups with many pinholes punched in them have been used as well, or you can use a hole saw in a sealed enclosure and use hardware screen on both sides of the hole with fiberglass sandwiched in between the screen like the old Dynaco A25.