ZOTL and RKV: The Search for Bass on the Sony R10
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Hirsch

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The Sony MDR-R10 tends to be very picky about amplifiers. I like the way it sounds with the Berning MicroZOTL a lot, with one exception: the bass. It’s not there. You can here where it should be, but there is no impact, and extension is not good. So, in a quest for bass out of the R10, and in light of Jan’s introductory offer on the RKV, Dusty Chalk and I put the RKV and the ZOTL on the same source, and did some comparative listening. The RKV had Mullard tubes, which Dusty feels sound the same as the stock Polamps. The ZOTL had Sylvania 12AT7WA’s (three-mica black plate) and 6SN7WGTA’s. The setup:

Sony DVP-NS500V SACD/DVD/CD player
Homegrown Audio Silver Lace interconnects
Virtual Dynamics Power 3 AC Cords
Monster HTS-2000 power conditioner
Sony MDR-R10 headphones
Grado HP-1 headphones
A couple of other headphones that merit discussion in a different post

My notes are with the R10, as my particular goal was to determine if the RKV would be a significant improvement over the ZOTL. We listened over the afternoon. Each of us would pick a track, which we would listen to for a period of time. We then switched headphones to the alternate amplifier, and listened again.

Music included:
Einsturzende Neubaten: Silence is Sexy
Sylvia Woods: Harp of Brandiswheire
The Stranglers: Meantime
Second Sight
Godhead: Power Tool Stigmata
Henry Kaiser: Those Who Know History are Doomed to Repeat it
Godhead: Nothingness
Cowboy Junkies: Open (SACD)
Yo Yo Ma, Edgar Meyer, Mark O’Connor: Appalachian Journey (SACD)

I’ll start with my bottom line (Dusty may well have reached different conclusions). The ZOTL and RKV are very similar amplifiers. Both are superb amplifiers. Neither one gets good bass response out of the Sony R10. Both are stunning with the HP-1. While I’m about to start picking at differences, in the overall scheme of things they are trivial, IMO. I wouldn’t ditch the ZOTL to buy an RKV. I wouldn’t ditch the RKV to buy a ZOTL. The ZOTL fits my personal preferences slightly better, but that may be simply because I’m used to it, while the RKV is more novel. The differences I’m going to point out are going to read as though they are more dramatic than they actually are…that’s the nature of this sort of review. I won’t reproduce all my notes, just those that seem to give a feel for the differences between the amps.

Reminder: the R10 does not produce bass well using either of these amps.

Track 2 on the Sylvia Woods album (In the Forest) has an interplay between harp, flute and acoustic bass. The RKV produced a better rendition of the bass, but neither was good, and with the ZOTL the bass tracked was almost missing in action. The harp seemed very detailed and well-articulated on the ZOTL. On the RKV, it sounded more artificial. Flute had excellent detail and air on the ZOTL. Good on the RKV, but less air.

The opening track to Einsturzende Neubaten has a very powerful bass presence. The RKV had better bass definition, as well as deeper bass. Hand drums went to the ZOTL, with better definition at the upper end. Drums on the ZOTL were precisely located, more so than RKV. The vocal on the ZOTL seemed to float against a black background. Clear, transparent, well defined. Vocal was also good on RKV, but did not stand out as much.

On Appalachian Waltz, the low acoustic strings were “glaring in their absence” on the ZOTL. Better on the RKV, but still missing the very bottom. RKV has very good tonality on the rest of the strings, but here the ZOTL was in its element. ZOTL had the mid to upper range of the strings dead on. Better sense of space, with strings more clearly articulated.

Second Sight, “Night Fires” has a nice introductory percussive crack. Impact was greater on the RKV, but definition was better on the ZOTL. There is both woodwind and synthesizer on the track. At times, with the RKV, I had trouble telling which was which. This was much easier with the ZOTL, which seemed to capture the fine tonal differences better.

Godhead’s Afterthoughts (Power Tool Stigmata) had some good bass that presented well on the RKV. It just wasn’t there on the ZOTL. There’s a percussion track that came across with good impact on the RKV, but hard to tell what it was. The percussion on the ZOTL had less impact, but more texture. By comparison, the RKV seemed to almost smear the detail of the percussive hits.

I could go on, but I think the general idea is there. The RKV has excellent bass, good midrange, but the very high end is rolled of. IMO a lot of spatial information is contained in the part of the spectrum that the RKV rolls off. The ZOTL had a clearer midrange and highs. Sense of space was better with the ZOTL, and imaging was clearer. The ZOTL seemed to be a faster amp, and was able to get at some fine detail that did not come through on the RKV. Important caveat repeat: I was using the R10, which is just about unequaled in its ability to retrieve fine detail and create a sense of space, IMO. Some of the differences I’m reporting simply won’t be there with other headphones.

So can the R10 produce bass at all? Yep. As an afterthought, at the end of the afternoon, I plugged the R10 into the Grado HPA-1…and all the bass was there. Everything at the low end that had been plaguing the ZOTL and RKV was present and accounted for with the HPA-1. Not the ultimate solution, though, since both the RKV and ZOTL are better than the HPA-1 in the midrange and highs. The Melos SHA-1 also produces better bass than either the ZOTL or RKV, but again, loses out in the mids to both, and in the highs to the ZOTL. Neither of these amps were part of the day's comparison, though.

I’d love to biamp the R10 with the HPA-1 on the bottom and ZOTL on top. Since that’s not about to happen, the search for the right amp for the R10 is going to have to continue…
 
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88Sound

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Hirsch,

Thanks for the comparison!

I have been contemplating the RKV deal and want to know if you used the impedancer with the RKV during your audition.

I posted this question on the audiovalve web site:

Is the Impedancer required for low impedance headphones to sound their best with the RKV MK II?

I am specifically referring to Grado's (32 Ohms) but also wish to drive 40 Ohm, 48 Ohm, and 100 Ohm Phones.

This is the response from Helmut Becker, the designer of the RKV:

Quote:

the impedancer is for low impedance loads, example speakers or low ohm headphones and useful for an impedance range between 8 - 16 - 32 - and 64 ohms - switchable.

And when you use 100 ohm headphones, you can use the directly jackets by the RKV without impedancer.


Any thoughts?
 
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Hirsch

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88sound,

We did not use the impedancer (didn't have it). The RKV was able to drive the Grado HP-1 with no problem. Bass response of the R10 was problematical, but that was also the case with the ZOTL, which was designed to drive a 4 ohm load. I can't say whether the sound of the RKV would be improved by the impedancer or not, but I do know that the HP-1/RKV combo sounds great without it.
 
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zzz

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Same with W2002/HP4. However, I notice that at 11pm the problem is much less evident (my equipment is currently all at work, and it uses the same power network that has probably about a hundred CRT monitors and computers in it. late at night it gets better, although I prefer not to be here at that time
). I'm thinking about giving the Brickwall a try... But you have power filtering, so that probably doesn't apply to you.

One of the theories I toyed with is that even though W2002 and R10 are rated 32 Ohm, at bass frequencies impedance might drop to some lower values. Maybe that's not true; I have no way of measuring it. But say it holds. Then realise that the output power of a properly designed solid state amps is almost always nearly inversly proportional to the load impedance (hence the good bass response in that case), while for tube amps it's normally the other way around => poor bass performance.

Of course it's just a theory, I don't know if it has any resemblance with the truth...
 
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kelly

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Hirsch (and Dusty)

Thank you both very much for this much needed comparison. Hopefully this will stave off my curiosity for at least a little while.

The differences you describe were honestly about what I expected from what else I had heard about the microZOTL.

The only point that I made to Hirsch privately and that I'll make here is that while I haven't heard the microZOTL and it could indeed be even better, the soundstage of the RKV is very large and impressive. It's definitely a selling point of the amplifier. That it achieves this despite a slight high frequency rolloff to me says that there's something else going on. Maybe someone else can explain this but OTL amplifiers seem to often gain a reputation for their soundstages.

As for the Impedancer, I'm trying to get hold of one and will post about it if and when I can.
 
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Hirsch

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Quote:

Originally posted by zzz
One of the theories I toyed with is that even though W2002 and R10 are rated 32 Ohm, at bass frequencies impedance might drop to some lower values. Maybe that's not true; I have no way of measuring it. But say it holds. Then realise that the output power of a properly designed solid state amps is almost always nearly inversly proportional to the load impedance (hence the good bass response in that case), while for tube amps it's normally the other way around => poor bass performance.

Of course it's just a theory, I don't know if it has any resemblance with the truth...


In many speaker systems impedance does indeed drop with frequency. However, this doesn't even begin to explain the lack of bass on the ZOTL with the R10, unless I'm missing something. The ZOTL was originally designed as a speaker amp (for very efficient speakers), and has maximal power output into a four ohm load. Dropping impedance in a 40 ohm headphone shouldn't bother it a bit.
 
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zzz

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Ok, I guess I was wrong then. Maybe microZOTL measured specs are for a purely resistive load (which driver coils really aren't) and it just starts misbehaving a bit when asked to drive a low-impedance reactive load? I suppose measuring AC voltage with a 15-20Hz test tone could shed some light... But I figure that wouldn't help to cure the bass-deficiency problem in any way, so I will just shut up now
.

BTW, did you try using speakers with it? Just curious.
 
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the same at the headphone jack as it is at the speaker posts? Could it, for example, pump a whole watt out of the jack if there were some headphones that could use that much power?


Same question for the McCormack, etc..?
 
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kelly

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zzz
I'm not sure how the R10's bass mystery could be tied to impedance. Hirsch has no such problem with the Grado HP-1 which has a similar impedance rating. Then again, I know impedance varies at different frequencies so maybe the HP-1 and R10 are more different in the low frequencies than we would assume. It will be interesting to see what the Impedancer (or similar devices) would do for him regardless.

I have another theory--that the R10 is just naturally a little bass shy and only somewhat "dark" amps like the Grado amps do such a weak job of reproducing the high frequencies that it only seems that the bass is better.
 
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Hirsch

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Quote:

Originally posted by kelly
I have another theory--that the R10 is just naturally a little bass shy and only somewhat "dark" amps like the Grado amps do such a weak job of reproducing the high frequencies that it only seems that the bass is better.


SHA-1 isn't dark, and gets good bass response. Also, RA-1 gets good bass, and that's not dark by any stretch of the imagination. We've got to look somewhere else I think.
 
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Hirsch

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Quote:

Originally posted by zzz
BTW, did you try using speakers with it? Just curious.


I don't have any really efficient speakers, but I have tried it, and the sound, if kept at low volumes, is really good. My ZOTL has also be modified by Berning to have preamp outputs, and it's an excellent single input preamp as well.
 
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Quote:

Originally posted by Hirsch
I don't have any really efficient speakers, but I have tried it, and the sound, if kept at low volumes, is really good. My ZOTL has also be modified by Berning to have preamp outputs, and it's an excellent single input preamp as well.


One question about this--if you use the ZOTL as a preamp with a good quality and somewhat neutral amplifier, the summed sound will be lacking a certain amount of bass since that is the ZOTL's comparative weakness, right?

It strikes me that if a preamp is to be used that it is critical that this component be of extremely high quality--perhaps higher quality than the amplifier. Having never owned a real preamp myself, this is just what I gather from HeadFi--is this a bad assumption?
 
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Quote:

Originally posted by kelly
It strikes me that if a preamp is to be used that it is critical that this component be of extremely high quality--perhaps higher quality than the amplifier. Having never owned a real preamp myself, this is just what I gather from HeadFi--is this a bad assumption?


I'm convinced you're right about this. I'd never really thought about it before, but reading Tuberoller's thread from a couple months ago about how switching to a tube preamp makes more of a difference than switching to a tube amp made me think and start experimenting with various preamps (passive and active; I've settled on a nice active preamp).
 
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Hirsch

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Quote:

Originally posted by kelly

One question about this--if you use the ZOTL as a preamp with a good quality and somewhat neutral amplifier, the summed sound will be lacking a certain amount of bass since that is the ZOTL's comparative weakness, right?

It strikes me that if a preamp is to be used that it is critical that this component be of extremely high quality--perhaps higher quality than the amplifier. Having never owned a real preamp myself, this is just what I gather from HeadFi--is this a bad assumption?


Well, I do know that the ZOTL isn't normally bass shy, either with headphones or as a preamp. This issue appears peculiar to the R10, and isn't necessarily the ZOTL, as the RKV exhibits it also. I once tried using the ZOTL as a preamp, driving an Acurus 200x3 amp (well, 2/3 of it anyway). Speakers were KEF 101.1, which is a 4" driver and dome tweeter. Bass was tight, deep, well-defined, and there was lots of it (more than you would expect a small monitor to be able to produce). I couldn't find a hidden subwoofer anywhere
 
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Hi Hirsch,
It's too bad you didn't have the impedancer thingy with the RKV. I never really considered the KKV primarily because it seems so restricted in terms of the phones it is likely to be compatible with. I was also leery about sticking on some separate device to alter the signal, as I wonder about performance degradation. Wouldn't you be better off if the impedencer was built-in to the circuit as in integral part of the RKV?

Did I miss it, or did you try the SHA-1 with the R10? Having tried both the ZOTL and the Melos SHA-Gold/Maestro with the R10, I found the Melos to have subjectively "more" prominent bass, but still the R10 is no bass monster.

Don't know if you've considered this but I'll throw a curve ball at you-- why not give the EMP a spin with the R10s? When I had my HD600 (I know *totally* different phone), I found the combo to have absolutely whomping bass. Perhaps that would carry over to the R10.

Also, if you are curious about EMP, PM me I have a special tip for you.

markl
 
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