Dynaco PAT 4 Pre-Amp ....Why is it Bashed??

Why not ask this question in a thread where people are bashing the Pat 4?

Because he asked it here. Are you worried about him over-consuming forum electrons?

Hey @ ml8764ag I guess you don’t have anything to say about the PAT-4. Me neither. But if the OP truly seeks an answer and had directed it to those actually making the claim perhaps he’d have a meaningful response by now. That is all.

 I am puzzled why there are so many negative comments being posted regarding this pre-amp sounding harsh and bright.
It sounds good to me...clear and detailed.

This is a common complaint leveled at a lot of solid state preamps, and often for the same reason. They tend to make a small amount of higher ordered harmonic distortion, which is interpreted by the ear as harshness and brightness. It is also common for the brightness to be interpreted as greater detail.


IME when the presentation is relaxed, smooth **and** detailed then you are making progress.

The PAT4 was a nice entry level preamp in its day, but these days the design would be considered antiquated, and you certainly would not want to operate one without at least changing out the power supply filter capacitors so as to prevent damage to the power transformer, and also so that it would be able to sound right.


The reason the preamp tends to sound bright is that it doesn't run quite enough feedback for the circuit to be able to correct for the distortion caused by the feedback. I know this sounds recursive but its not. To really do the job right you need a lot of feedback, and the PAT4 circuit lacks the needed gain that you would need to do that. So its a bit of a compromise. On paper its specs appear benign, but if you investigate deeper you'll find that the distortion is only spec'ced at one frequency. What is common with designs like this is that as frequency is increased, the distortion goes up with it (this is because it lacks the needed Gain Bandwidth Product to do otherwise, in case you're interested). IOW it makes a big difference as to what frequency the distortion is being measured. Brightness is a common complaint of designs that have this quality. 

IMO most of it is caused by marketing. The rebuilds Kenny Russell does will compete with anything available today. I deal with the same nonsense in the telescope industry. 

You can upgrade it piece by piece into something worthy.

Built one of those many many years ago along with an ST-150 power amp.  The PAT-4 was Dynacos first foray into solid state preamps and as such it lacked refinement that the later released PAT-5 had.  The PAT-4 initially received some good reviews as is sounded so different from its tubed predecessor.  Alas, in time different was not better.  There was an edge and lack of dimensionality.

I still remember soldering all those caps to the high cut filter assembly--arrrgh!  But maybe I understand why they included it now.

Man, you're dating me. In the mid 70s I built a PAT 5, then after reading a review, I had it modified by Van Alstein? It was then called a FET 5

Pat 4 is ancient history.

The PAT-4 was first introduced as a kit along with the Dynaco 400 SS amp. I built many of these on the side while i was working at Bendini building tube amps and i sold them as complete units. I remember back then that depending on who did the build that units could sound different from each other, i estimate that i built and sold over a 100.

Personally i never liked the way they sounded they had what i considered what was to become the classic SS sound that we lived with for several decades.

Anyone  know anything about Frank van Alstine? I have a chance to buy a Pat 4 restored by him and am wondering if that rings a bell with anyone here.

So it's spelled van Alstein?. And it has a sticker that says FET on it.

I am tempted to buy a Dynaco PAS3 and ST70 built by Kenny Russell.  Kenny's units are beautifully built and to the extent you can tell via computer, sound great.  Check out Kenny's webpage at: GetDynaco.com  .

This reviewer is very low key and I appreciate his reviews.

All new Dynaco PAS3 by Kenny Russell - YouTube

Dynaco ST70 update - YouTube

 

Anyone  know anything about Frank van Alstine? I have a chance to buy a Pat 4 restored by him and am wondering if that rings a bell with anyone here.

Frank has been doing this sort of work for decades here in town. Its likely not the stock circuit. Frank has his own stuff he often installs in older Dynaco chassis.