DECWARE.....ZTPRE anyone have any expeiriance with one ?

Finally, to be sure we are looking at the same schematic, I am looking at the one shown on the last page of the manual.

Yes I think that’s the one Al pdf you have to rotate it twice, what I see that the cap sees is if the pot is at half way is a series and two parallel resistances, and yes as you say if full up it get’s closer to just 2 x parallel resistances.
Anyway whatever that cap is too small, and should be at least 1uf to take away the problem if close or full up on the VC.

Cheers George

viking62 said..."Gentlemen,I may just bite the bullet and purchase both the Prima Luna and the ZTPRE."

Sounds like a plan. Please keep us informed...8)

Hi George,

Yes, I’m pretty certain that what I said is correct.

The example you cited, resulting in the cap seeing 50K, applies if the pot is set at max. But since the amplifier with the 100K input impedance is connected to the wiper of the pot consider what would happen if the pot were set, for example, such that 10% of the pot’s resistance is between the wiper and ground, and 90% of the pot’s resistance is between the wiper and the point where the pot and the cap are connected.

With that setting the resistance between the point where the cap and the pot are connected together and ground (i.e., what the cap sees), assuming the same 100K input impedance of the amplifier, would be:

Cap sees: 90K + (10K in parallel with 100K) = 99.1K, not 50K

The rolloff of the resulting high pass filter in that example will be determined by the combination of 0.1 uf and 99.1K. The rolloff (and the corresponding phase shift) will occur at the point where the cap and the pot are connected together, and it will also occur at the wiper of the pot which in turn is wired to the output connector. The signal at the output connector and the signal at the point where the cap and pot are connected together will differ in terms of amplitude, of course, but not in terms of frequency response (putting aside the possible effects of cable capacitance and amplifier input capacitance on high frequencies).

Finally, to be sure we are looking at the same schematic, I am looking at the one shown on the last page of the manual.

Best regards,
-- Al

Gentlemen....I may just bite the bullet and purchase both the Prima Luna and the ZTPRE....cut heads for 2 weeks and return one. I do have access
to Clio and could perform an RTA  to really check that bottom end on both.I am checking into PM's return policy now.

I really do enjoy these types of discussions as I can get so many educated points of view...then again that's why we all love this "hobby" (addiction, habit, relapsing disorder) so much :}
Have a great day,

Kevin

almarg
The cap will only "see" the input impedance of the power amp when the 100K output level control is at or near max.

You sure Al, I see it like the cap seeing the "parallel" combination of what the volume control and poweramp impedance is combined, just like two paralleled resistors. As the pot goes to ground like the input of the poweramp would.

EG:
Pot = 100kohm
Amp=100kohm
Cap sees= 50kohm


Cheers George

Thanks, George. But actually it isn’t that bad. Note the presence of the 100K output level control. The cap will only "see" the input impedance of the power amp when the 100K output level control is at or near max. (Actually in that case it would see a heavier load than that input impedance since it would be paralleled with the 100K). And my suspicion is that under typical conditions the control would be set closer to the bottom of its range than to the top of its range.

So the resistance that forms a high pass filter in conjunction with the 0.1 uf would probably be comprised of the majority of the 100K, plus the parallel combination of the rest of the 100K and the input impedance of the amp. And if the control is used near the bottom of its range, that would amount to close to 100K overall.

Nevertheless, assuming the schematic reflects the present design, per some calculations I did prior to my earlier posts there would be upwards of 2 db of rolloff at 20 Hz even with no power amp connected and regardless of the setting of the control. Which already considerably exceeds the +/- 0.7 db tolerance of the 20 Hz to 20 kHz frequency response spec. There would also be phase shifts in the bottom octave that could very well be audibly significant. With the rolloff and the phase shifts especially likely to be problematical in a case like the OP’s, involving large speakers having excellent deep bass extension, and also for others who may be using subwoofers. (Compensating for the rolloff with the level control of a subwoofer would be a crude approximation at best, since both the amount of rolloff and the corresponding phase shift would vary as a function of frequency).

Best regards,
-- Al

almarg
I see that the output tubes are coupled to the output connectors via capacitors having what to me is a very surprisingly low value of 0.1 uf

I just downloaded the latest I believe circuit.
And what Al has pointed out is quite bad, as if that preamp’s xlr output sees an input load of 20kohm the bass will be rolled of at -3db already at 80hz!!!! In other words you’ll have no low bass.

If it sees a Class-D amp which many have 10kohm input impedance, the bass will be -3db at 160hZ!!!! no upper bass either!!!

It’s rca output "could" be fine as they are isolated by the transformer coupling from outside amp impedance’s.

I suggest you don’t use the XLR output with any amp/s less than 100kohm input impedance.

Cheers George

1241...that PDP pre looks pretty nice and he is passionate about his product. Noticed the speakers in the background.

viking62 asked..."Taking all of this into consideration (And this goes out to everyone) what are your recommendations for a tube pre for this setup."

Have you thought/looked into the Primaluna Dialogue Premium preamp? It is not as sexy looking as the Decware but it sure is a music making machine of the highest order with superb reviews. Also, built like a tank..to last a lifetime. And a tube rollers dream!!! I own one and can not speak more highly of it...it's that good!!! Lots of great info online with great internal snapshots to look at to see what your money is buying you compared to other manufacturers. Good luck with your search.  

Br3098 8-4-2018
I have heard the new ZTPre "V6" design, paired with decware 6Wpc monoblocks and **decware speakers** [emphasis added], and I can definitively say that it is not rolled off on the bottom end.

To add to my previous response, it appears that none of the speakers shown at the Decware website would provide deep bass extension that is remotely close to what is provided by the OP’s Focal Grande Utopias. According to specs indicated in Stereophile the Focals incorporate a 15 inch woofer and an 11 inch mid-bass/lower midrange driver, and weigh 397 pounds. Completely different animals than the Decware speakers, and speakers that would clearly be far more revealing of bottom octave rolloff.

Regards,
-- Al

Thank you all for the input, I will continue with a little more research.

@jmolsberg, agreed, the MZ2 is incredible. I have 2 of them and need to sell one now that I have the Micro ZOTL Preamp. As someone who has owned both the MZ2 and ZTPre I can say the MZ2 is superior but is single ended not balanced. I did love the look of the ZTPre though.

I think Steve likes his Bass deep. Give him a buzz. 
LTA MZ2 is great! 

are you dead set on getting the ZTPRE ?

there are other options available for tube preamps.    one that comes to mind and has been mentioned in the forums is this site

http://aricaudio.com/tube_gear.php

Thanks for your input, Br3098. I see that the manual provided at the website which contains the schematic I looked at is dated 7/2016, and the schematic page within that manual states "last revision 5-14-2016." Perhaps the design has changed since then.

As I indicated earlier, the design illustrated in the schematic would result in deep bass rolloff that is inconsistent with the frequency response spec shown at the website, and would be audibly significant in the case of speakers capable of reproducing the bottom octave with reasonable accuracy.

Regards,
-- Al

I have heard the new ZTPre "V6" design, paired with decware 6Wpc monoblocks and decware speakers, and I can definitively say that it is not rolled off on the bottom end.  It's an excellent and unique dual mono preamp design.  If you need a tube preamp that has true balanced output this is the preamp for you.

Having said that, I have no idea how well this pre will work with your solid state monoblock amps.  I would suggest that you follow fourwnds advice and contact Steve Deckert at decware.  Steve is a stand up guy and a wealth of information.

I own a couple pieces of Decware equipment. Not the pre amp your asking about but I can say Steve has always been easy to reach on the phone and easy if not fun to talk with. Hit him up. 

FWIW, I would suggest the OP asking Steve Deckert, the owner of DEC, this question. He is the equipment designer there and I’d be very surprised if he made a mistake as simple as put forth in the above response. REALLY surprised.

Read here if you want to know if Deckert just might know something about this issue:

http://www.decware.com/paper20.htm

And this is "dumbed down" for we who play the music not MAKE the music.

I owned the ZT Pre for a while and it was just OK. It wasn’t long before I started looking for another preamp. I just recently got a new Linear Tube Audio Micro ZOTL Preamp and holy crap it’s good. It makes the ZTPre sound like it was made to work with a Bose clock radio.

Taking all of this into consideration (And this goes out to everyone) what are your recommendations for a tube pre for this setup.

Given the reasonably high input impedance of your amps, even if that value is only half of the specified 75K when they are used in bridged mode (which is very conceivable), and their slightly above average gain, you have a very wide range of possibilities. Given that the sensitivity of your speakers is also somewhat above average (apparently specified as 95 db/1 watt/1 meter) I would just suggest avoiding line stages having highish gains, above say 10 or 12 db or so. Especially if you are using digital sources.

Good luck. Regards,
-- Al

Al...Thanks for pointing that out, didn't even think to look at that. There is no way I am giving up my bottom octave. This is the age old problem of trial and error with changing components. Buy it, dump it, take the hit...buy it, dump it, take the hit. Deware has no dealers so I can't even give a dealer a deposit to try it out for the weekend. One would think however with the schematics posted, Steve Deckert would have been called out on this in his forums.Taking all of this into consideration (And this goes out to everyone) what are your recommendations for a tube pre for this setup. As a side note I really did like the idea of being able to set the output gain to my liking.

Excellent comments by Larry, as always.

Also, I took a look at the schematic for the ZTPre, which is included in the manual provided at the Decware site. I see that the output tubes are coupled to the output connectors via capacitors having what to me is a very surprisingly low value of 0.1 uf, the caps being in series with 100K pots (potentiometers) that are provided on the rear panel, apparently to allow the preamp’s overall gain to be adjusted.

A 0.1 uf capacitor has an impedance at 20 Hz of about 79.6K, which will produce a significant deep bass rolloff in conjunction with the 100K impedance of the pot. That is particularly likely to be apparent given the excellent deep bass extension of your speakers. And depending on the setting of the pot and the input impedance of your amp (specified as 75K, although it isn’t clear if that applies to its unbalanced inputs or its balanced inputs or to the bridged mode you are using), the resulting rolloff may be worsened significantly.

In saying this, I am of course assuming that the schematic is accurate. And for that matter I don’t see how the schematic and the claimed frequency response spec of 20 Hz to 20 kHz +/- 0.7 db can be reconciled.

Regards,
-- Al

Larryi...excellent point about the in home trial. Decware does offer 30 days for trial and 10% restocking fee, so that would be about a $470.00 hit just to try it out. I would assume that they are so confident that you will keep it that they are right up front about the restock fee.I also have a Mcintosh 225 that has no on/off switch...so I am very used to unplugging it each time.I did have the opportunity to try an Audion pre amp with the CA400's and it sounded wonderful.

I don't have any experience with the Decware linestage, but, I do have a few suggestions on what to consider in your choice of linestage.  From a practicality standpoint, I always turn off tube gear when it is not in use.  But, because solid state gear, particularly amps, take an extremely long time to warm up and sound their best, I would leave such gear on even when it is not in use.  There might be problems with using a tube linestage with a solid state amp that is left on all the time because of the possibility that the tube gear will emit loud noises/pulses when being turned off and on; if one can mute the linestage for turn on and turn off, that might to be a problem, so that is something to look into about your prospective purchase.

I hope that Decware will allow you to audition their linestage with your amp.  While an audition is really important for ANY purchase, it is particularly important when one is trying to match a tube linestage to a solid state amp.  I have found that, even when the match is theoretically fine (i.e., low enough output impedance from the linestage, short interconnection cable), the result can be quite unpredictable (more unpredictable than the other hybrid approach of solid state feeding tube amp).