The Dynaco audio equipment was, and still is, a very high quality and reasonably priced alternative in the audiophile market. Deciding what to buy comes down to several choices. For preamps the PAT-4 and PAT-5 both provide excellent performance for the cost.

PAT-4

This was the first Solid State (transistorized) Dynaco preamp. It offers great phono performance and multiple inputs. The PAT-4 has more filter options than the PAT-5 for serious FM or AM radio listening. It also offers the ability to listen with headphones without an external amplifier, something the PAT-5 does not provide. As to modifications to improve performance the PAT-4 is easily upgraded. The Bass and Treble controls are a unique design that are electrically out of the circuit when centered.

PAT-5

This was the second and third generation Solid State units. The PAT-5 has two distinct versions, the later used Bi-Fet I.C. technology as an improvement over the original PAT-5 Bi-polar I.C. design. Both offered the same feature set in controls. They provided a switch to bypass the Bass and Treble controls and Speaker switching functions. The headphone jack is driven by the external amplifier. They offered two Phono inputs which could be optimized for different phono cartridges. The early PAT-5 can be updated to the Bi-Fet technology that offered lower noise levels although it would take very sensitive ears to tell the difference. Modifications are a little more complex but still reasonably priced.

Choices 

Both the PAT-4 and PAT-5 were offered as kits or factory assembled units. Factory units are designated as "A" models (PAT-4A, PAT-5A) and are much less common than the kits. Were they better? Not if the builder did a good wiring job as all the circuit boards were assembled and tested at the factory. They do command a higher price as they are less common but not "RARE" as many sellers lead you to believe.

So, take your choice based on the features of each unit, performance is very close with some specs better in the PAT-4 and some better in the PAT-5.

Prices

PAT-4 in good condition $75-100, tested and refurbished $150 & up.

PAT-4A add 20-40%

PAT-5 Non bi-fet in good condition $100-150, tested and refurbished $225 and up.

PAT-5 bi-fet add 20- 30%

"A" models add 25% 

The TUNERS

Two tuners were offered by Dynaco, the FM-5 and the AF-6 with the AF-6 adding an AM tuner. Again both were offer as a kit and factory "A" models. The quality of both was determined by the front end which was not built by Dynaco. I have had some excellent tuners, many very good tuners and a few that were not so good. The FM sections on both have a "DYNATUNE" circuit that provides automatic fine tuning and frequency lock. Be aware that the circuit utilizes the tuning lamps in the circuit functions. If the lamps burn out the circuit will not function correctly. It should also be noted that the dial lamps use  "festoon" style lamps that are very difficult to locate. Several sources exist for LED replacements in white or colors. The photo shows an FM-5 with blue lamps. Modifications are also available to improve performance on these units. Again, take your choice, FM only or AM/FM.

Prices

FM-5 in good condition $100-150, tested and refurbished $150 & up

AF-6 in good condition $125-175, tested and refurbished $175 & up

Add 20% for an "A" model

Modifications and Upgrades

All of the Solid State units are getting old and the electrolytic capacitors are in need of replacement to provide original performance and renewed reliability. Most will also require cleaning of the controls and switches. You should expect to have this done to restore the original performance. The cost will be determine by the extent of repairs. You should look for  service  by Dynaco specialists as the cost will be lower due to their experience and parts cost. Figure about $100 for a refurbishing for the PAT units and a little less for the tuners. More if you use a local shop.

You should have the dial lamps on the tuners replaced with LEDs as they should last a lifetime so it is a one time cost. Figure $30 minimum for this.

Upgrades to these units include power supply capacitance increases and replacement of the signal path capacitors with high quality polypropylene capacitors. Early PAT-5s can be upgraded to the bi-fet design at a reasonable cost, $75-100.

We provide several options for refurbishing and upgrades to these units as do others, please see our Store for more info.

Link to our JMR BLUE modifications