[eduke55]

Tube rolling can give some interesting results. Especially if you can acquire some great NOS tubes. I recently added a NAT Preamp and the sound is amazing. Very usual design and built like a tank, but has a remote, great gain, and as I said earlier, sounds wonderful.

[serlvz]

Disclaimer: I had help with this answer

Both the DVA M225 and DVA M750 require true differential inputs --  as long as we mean the same thing here. These amps require an XLR connection where (a) both the hot and cold signals are driven, (b) the hot and cold signals are inverted versions of each other, and (c) the ground connection is actually connected to the source's signal ground. In some cases (c) won't be required. Fortunately, this is how the majority of line-level equipment with XLR outputs is configured today.

Also, to clarify any possible confusion, both the DVA M225 and DVA M750 will produce output with sources that don't meet (a) and (b). However, they won't reap the benefits of the bridged configuration these amps use, and so they won't sound as good nor make the same power.

I am planning on ordering a pair of M750(s), imminently.
I use a Bryston BP-26 preamp. It has a pair of XLR balanced outputs. How would I know if they are true differential outputs? I don't want to compromise the M750's performance.

Scott

I found this, and though it doesn't use the term true differential inputs or whether the ground connection is actually connected to the source's signal ground, it looks like I may be good.

Still it would be good to have someone in the know verify that.

 Balanced Outputs: As with the input XLR jacks, pin 1
is ground, pin 2 is positive and pin 3 is negative. These
outputs are capable of driving 30 volts into any load of
600 ohms or greater. Do not short any of these three pins
together!

[eduke55]

Should be fine. I have a friend who drives Bryston amps with the same BP=26 preamp. No issues.
Waiting on a NAT Magnetic preamp that should be a big improvement over my current Benchmark LA4. Will post impressions soon.

[morganc]

That question was answered elsewhere ie differential and yes your pre will work well. 

[TomS]

I am planning on ordering a pair of M750(s), imminently.
I use a Bryston BP-26 preamp. It has a pair of XLR balanced outputs. How would I know if they are true differential outputs? I don't want to compromise the M750's performance.

Scott

I found this, and though it doesn't use the term true differential inputs or whether the ground connection is actually connected to the source's signal ground, it looks like I may be good.

Still it would be good to have someone in the know verify that.

 Balanced Outputs: As with the input XLR jacks, pin 1
is ground, pin 2 is positive and pin 3 is negative. These
outputs are capable of driving 30 volts into any load of
600 ohms or greater. Do not short any of these three pins
together!

I owned a BP26 preamp for quite a while, great piece for sure. James Tanner, in the Bryston circle, can answer your question definitively and is very responsive there. My understanding is that the BP26 is single ended internally and inverts the positive to derive the minus signals in and out. In other words there are not 2 full active signal paths, one plus and one minus, which is required to be true differential. James can confirm that but I believe it's been asked and answered before in their circle if you search. I had no trouble mixing balanced and single ended signals with the BP26.

[strat95]

Should be fine. I have a friend who drives Bryston amps with the same BP=26 preamp. No issues.
Waiting on a NAT Magnetic preamp that should be a big improvement over my current Benchmark LA4. Will post impressions soon.

Hey eduke, can you share what you like/dislike about the Benchmark LA4?

[eduke55]

Well, there is nothing wrong with the Benchmark LA4. It works very well and ergonomically it is one of the better preamps I have ever owned. It doesn't have any particular sound signature and seems to work well with several amps I had. What it does lack and the NAT magnetic has, is more a connection with the music. There is more of everything that makes home audio listening very enjoyable. I had forgotten how important a preamp is to audio system, especially if you have analog sources. I had a Counterpoint 3.1 and a MFA Magus previously, and the NAT Magnetic brings back that extra "magic". Notice I preferred tube preamps, and after many integrated amps between them and the Magnetic, this was a good choice. The tube preamps I have owned had separate power supplies and that may account for a lot of the extra "magic". I know there are plenty of solid-state preamps out there, and if I tire of tube preamp short comings maybe I'll investigate them.

[strat95]

Well, there is nothing wrong with the Benchmark LA4. It works very well and ergonomically it is one of the better preamps I have ever owned. It doesn't have any particular sound signature and seems to work well with several amps I had. What it does lack and the NAT magnetic has, is more a connection with the music. There is more of everything that makes home audio listening very enjoyable. I had forgotten how important a preamp is to audio system, especially if you have analog sources. I had a Counterpoint 3.1 and a MFA Magus previously, and the NAT Magnetic brings back that extra "magic". Notice I preferred tube preamps, and after many integrated amps between them and the Magnetic, this was a good choice. The tube preamps I have owned had separate power supplies and that may account for a lot of the extra "magic". I know there are plenty of solid-state preamps out there, and if I tire of tube preamp short comings maybe I'll investigate them.

eduke, thanks for explaining your thoughts.

[serlvz]

I owned a BP26 preamp for quite a while, great piece for sure. James Tanner, in the Bryston circle, can answer your question definitively and is very responsive there. My understanding is that the BP26 is single ended internally and inverts the positive to derive the minus signals in and out. In other words there are not 2 full active signal paths, one plus and one minus, which is required to be true differential. James can confirm that but I believe it's been asked and answered before in their circle if you search. I had no trouble mixing balanced and single ended signals with the BP26.

I started a thread in the Bryston forum. James Tanner replied and told me "Hi - email Mike on this please - mpickett@bryston.com". So, I did. When I get some info I'll report back here.

[serlvz]

Yes, that would be a nice addition, I'm sure. A bit pricey for me, and that would still leave the issue of high passing my main monitors. Also, I'm using a MiniDSP 2x4HD to implement and EQ dual subwoofers. The MiniDSP is connected to the P6's dedicated sub-out and is not in the signal path to the main speakers. Lots of flexibility in the P6, which makes it more difficult to replace.

I believe you can use the MiniDSP 2x4HD to send a "high passed" signal to the main speakers.

[BadDNA]

I believe you can use the MiniDSP 2x4HD to send a "high passed" signal to the main speakers.

In theory, yes. I have considered how I could do that, but there are several reasons I don't.
1. I do not want the mains to receive a DSP'd signal from a "Cheaper" device such as the 2X4HD, and since the P6 handles the hi-pass I do not need to do that.
2. If I did wish to route the mains via the 2X4HD, I would then need to spend more money to purchase the single-ended to XLR converter box since my M225's only except balanced connections.
3. The system just sounds fantastic as is!

[serlvz]

I do not want the mains to receive a DSP'd signal from a "Cheaper" device such as the 2X4HD, and since the P6 handles the hi-pass I do not need to do that.

I have often wondered about exactly that.

For a while I was considering using a miniDSP to derive a LF signal to a sub and letting my mains get the filtered remains. Decided not to, but for several other reasons.
Still, always wondered if that signal passed on to the subs would in some way be degraded.

[figcon]

The AVA Fet Valve is a great preamp and a perfect match for the DVM M225's. A little off subject perhaps, but does anyone know how the two gain levels in the Fet Valve pre are implemented? If high gain, is there an additional gain stage, or if low gain, some sort of reduction in the circuit, like resistors?

[avahifi]

Low gain mode is a simple resistive voltage divider. Nothing exotic.
Frank