Modwright SWL 9.0SE Preamplifier

Seneca it is more sonically advantageous to have a circuit that inverts phase because it is a simpler circuit requiring more attention to circuit design. On the other hand a circuit that does not invert phase has extra sound-degrading circuitry. Many quality preamps for this reason do invert phase.

Dan Wright tells me that inverting phase is a natural consequence of a more purist (straight wire with gain) type of implementation with tubes stages. Dunno....lots of tube preamps do I guess. I believe Dan feels that an invert phase switch adds unnecessary switching/noise in the signal path. No big deal, really.

I believe one tube stage inverts the phase, and to have it revert back to the original phase in would take another stage (add'l cost, and add'l devices in the signal path) to correct.

Keep it simple, is what Modwright and various other mfgs wisely chose to do.

There are those that believe switching the speaker leads is better than using an electonic switch. Re: Tedmbrady's point about so many lines may be out of phase that phase reversal may be a moot point, well it depends on the recording. With that in mind, I have always wondered why so many pre's that tout the superiority of their dual mono designs don't include individual phase switches for each channel? Perhaps in the digital future it could be done automaticaly?

Hi guys, just tuning into this thread, so I had to read everything and get caught up.

First of all, the circuit inverts absolute phase because it is a simpler circuit - i.e. less gain stages impacting the signal. Aside from a cathode follower circuit, most SE designs will invert phase. Two inverting stages will give you a non-inverting output, but also requires what I feel in this case to be a redundant stage.

I very much appreciate everyone's input regarding the 9.0SE's performance and market reception. I actually polled a number of audiogon sellers who posted their 9.0SE's for sale, asking why they were selling. I found that in just about every case, it was a matter of spending quite a BIT more money and finding something that they preferred, system change to an integrated or balanced system, or they were looking for a unit that was more 'euphonic' or 'tubey' sounding.

One post made mention of our use of Solen capacitors. This is true in the power supply circuitry, but Sonicap and Sonicap Platinum caps are used in the signal path exclusively. I chose the Sonicaps because I felt that they were sonicly superior to every other capacitor available on the market. I experimented with paper in oil PIO types as well poly and film/foil types before settling on the Sonicaps.

The 9.0SE is voiced to be as neutral as possible, while still retaining the 3D soundstaging and holographic imaging of tubes. Circuit topology as well as tube type (5687) were key to this.

The 5687 tube is one of my favorites and is used almost exclusively in our designs. One of the strengths of this tube is that it was developed for the military originally and because of this, ALL 5687 tubes are Mil-spec. This means that there will be less variation between different mfrs. of 5687 tubes. Granted, 5687's from different mfrs. do sound different, but the degree of sonic difference is less than that for other popular triodes.

Returning to the issue of phase, the best way to achieve a non-inverting design is to use a balanced topology or use output transformers to create a balanced output. A balanced circuit provides both a (+) and (-) signal, without additional gain stages. In other words, both in-phase and out-of-phase signals are always present. This type of circuit can also offer phase switching.

Nothing comes for free however. Balanced designs are more expensive, because you are either doubling the circuit complexity and thus componentry, or you are using high-quality transformers and they are expensive.

The 9.0SE could not have been offered at the price that it is, if it was a balanced design. The owners manual explains that simply reversing the speaker cable leads at either amp or speaker end will correct for the phase inversion.

It is true that some recordings are in or out of absolute phase, depending on the recording process. So for some, the issue of absolute phase may be academic, for others it is definitely not.

Once again, I very much appreciate our customers support and the feedback of all who have contributed here. I try to stay abreast of all such discussions and take note, so that we can make our products the best that they can be.

Thank you,

Dan Wright
President, ModWright Instruments Inc.