WestminsterLab Re-imagining Amplification

[mxk116]

Thanks a lot! Brilliantly clear, well thought of and very helpful. The hight of the front & rear EVPs are the same, correct?

Yes, the EVP's I used are all the same height. The felt covered versions I used are ~ 1 1/4" tall (they do compress a bit depending on the load they are bearing). There is a version with rubber on the top and bottom. That version might be slightly taller.

 

[Robifabs]

Robifabs,

Cable lengths depend on how you configure your bridged pairs. Two methods.

Method one: Use two pairs of discrete XLR cables driven directly from your pre-amplifier outputs. Cable set one is standard phase and cable set two inverted phase. This constitutes one channel. Left or right of a bridged pair, four interconnects make up both channels. In that case, the interconnect length is whatever you choose from pre-amplifier to amplifier.

The next thing needed is the "ground bridge wires" connecting the grounds of each left and right channel pair of amplifiers. Generally, we offer them in 20'' lengths unless for some reason, you do not place the amplifiers side by side which is usual and customary. Longer lengths can, of course, be provided.

In bridged mode, your speaker cables' hot and ground legs are connected to the + binding post of each amplifier pair. No special speaker cable modification is needed.

Method Two:
When using only one set of standard phase interconnects (left and right), connect each channel's left and right cables to the lead amplifier. We then supply two, one each for left and right bridged channels inverted phase interconnects to accomplish the bridging between the amplifiers (also approx. 20" in length).

We can also discuss why and how we decide between these options. For now, suffice it to say that both work splendidly and accomplish the goal of perfectly bridging each channel without fuss or complication.

I am running to an out-of-office meeting but will post a schematic of both methods later today, illuminating how Westminster elegantly accomplishes the goal.

On shelving for your application, carbon fiber is always a suitable material, although it is a bit overkill. Either 1/2" MDF or fabricated sheet plexiglass will work perfectly, providing a stable platform for the top set of amplifiers and the needed clearance. Since we have a machine shop stateside, we can fabricate this for you, and you can purchase a set of bridged amplifiers at no cost.
Note: The Reis is not highly susceptible to air and floor-borne vibration, especially when not placed near your speakers. MX116 has his Reis placed between his powerful Magico S5s; therefore, I suspect the extra steps taken with isolation to be beneficial.

Fun fact: Angus originally designed the Reis for bridged operation. Unlike many amplifiers available for stereo and monoblock operation, the Reis was optimised from day one to be electrically perfect when using a single or a bridged pair of monoblocks.

Thanks a lot Gary. Amazingly helpful!

 

[Mobiusman]

The improvement from removing the JL F113's and replacing them with the tunable SW's was something I could comprehend, but the actual benefit was priceless.. Add to that the bridged REI's was more than I ever projected was possible!

 

[viola]

Thanks a lot Gary! That helps a lot indeed.
The challenge I would have then, would be to add a thin enough shelf in my existing rack, to make the staking work within the available hight of my shelf. Does anyone have an experience with carbon fiber or any thin materials, robust and non resonating enough that I could potentially use to create that additional shelf? It would be resting on the main shelf and benefit from the decoupling of the main stack structure. No perfect but good enough if I don't create new vibrations with the additional shelf I guess... Just thinking up-loud guys. Thanks in advance for any contribution

Robifabs,

One relatively inexpensive but effective approach would be to construct a platform of 18mm baltic birch plywood for the side supports with a 10mm baltic birch (or 6mm panzerholz) top attached to the two sides. The baltic birch top could be glued to the two baltic birch sides. The panzerholz top, although better than baltic birch for resonance control (which is already very very good), cannot be easily glued but would have to be attached by screws. Panzerholz is much more readily available in Europe than in the US, but it can still be obtained in the US through a gentleman in North Carolina. www.usaudiomart.com/details/6ed 49892564-panzerholztankwood/ Obviously, you could use any wood for this type of open platform, but baltic birch (or panzerholz for the top) would be the best from a resonance and performance perspective.

I use a panzerholz stand that is suspended above a maple platform with appropriately sized springs to support my two Rei mono blocs, and I have been very pleased with the results. This spring suspension approach, however, increases height which would likely be problematic given your height constraints.

 

[Robifabs]

Thanks viola! Very good insights. And here I Europe we can rather easily source Norvegian birtch “multipli” (multi-layer) so I will certainly pursue your reco. Will keep you guys posted. Thanks again to all contributors

 

[viola]

Thanks viola! Very good insights. And here I Europe we can rather easily source Norvegian birtch “multipli” (multi-layer) so I will certainly pursue your reco. Will keep you guys posted. Thanks again to all contributors

One other thought: if you or a friend has a table saw (or router), it would be relatively easy to cut a rabbet notch in the top of the 18mm thick side supports with a depth equal to the thickness of the top piece, leaving about 6mm of the side support uncut on the outside. That way, the top would fit nicely into the rabbet notch and this would provide a more secure joint than simply gluing the top to the side. Alternatively, you could also source some inexpensive small metal 90-degree angle supports that could be screwed into the insides of the top and sides.