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Dynaco Pat 4 Upgrades

Full Upgrade

Replace all electrolytic capacitors, using non-polarized units where available (usually the pass through electrolytic’s , bypass electrolytic’s are replaced with non-polarized units size permitting.  These capacitors get very large as most available are high voltage units.  Low esr capacitors are used in other replacements)

Use larger filtering capacitors for the power supply section ( original calls for 700 – 700- 800 I use 1000 – 1000- 2200 or larger.

Replace all carbon comp resistors with lower noise film types. (Standard carbon pack resistors when they age can introduce noise, though small in amount each, the more you have in small signal applications the more chance you have to introduce noise. Remember early microphones and for 100 years the microphone in your telephone handset was a carbon compaction type. Compressing carbon changes resistance and is one of the reason resistors can go our of tolerance when they get old.)

Use shielded leads from phono inputs to selector switch and from output board to output jacks (It can be argued that due to the short length and high impedance this is not needed. But in chasing down floor noise in any system that has been designed well, every effort must be made to keep noise out.  Phono inputs are the smallest signals in the pre-amp and the out put section the highest. By shielding these we can reduce some of the noise.  Any one noise reduction modification may not seem to reduce noise much but it is additive.  As you make any part of the system better, i.e.: noise reduction, distortion reduction etc. you allow other lower level noise and reduction to be heard. )

Rebuild phono, tape head and special feedback loop using 1% metal film resistors.  Capacitors replaced as needed (This is the section that reproduces the RIAA equalization, tape head equalization and the special equalization. The capacitors are already high quality and usually do not need to be replaced but will be replaced as needed. The resistors will be changed from carbon composition to film types and 1% tolerance to insure that the phono stage equalization will be stable for years to come.)

Rebuild Phono input PEC, allowing high level, ceramic, and low-level phono carts (This is the small PEC circuit at the input jacks on the backside of the pare-amp. This allows three different kinds of phono cartridges to be used on the phono input.  These can change value over time and change the pr-amp input characteristics seen by your phono cartridge and changes the sound you hear.)

Use modified Star grounding. ( using multi-stranded copper wire, all input and out put jacks on the rear panel, as well as rear panel, and thus all the chassis, is brought back to the power supply ground at one point. It is a modified Starr system as with out a larger rewiring of the unit, it is not possible to have one ground and that tied to one point on the chassis.

 

Basic Upgrade

Replace all electrolytic capacitors, using non-polarized units where available (usually the pass through electrolytic’s , bypass electrolytic’s are replaced with non-polarized units size permitting.  These capacitors get very large as most available are high voltage units.  Low esr capacitors are used in other replacements)

Use larger filtering capacitors for the power supply section ( original calls for 700 – 700- 800 I use 1000 – 1000- 2200

Replace all carbon comp resistors with lower noise film types in the Phone section only. (Standard carbon pack resistors when they age can introduce noise, though small in amount each, the more you have in small signal applications the more chance you have to introduce noise. Remember early microphones and for 100 years the microphone in your telephone handset was a carbon compaction type. Compressing carbon changes resistance and is one of the reason resistors can go our of tolerance when they get old.)

Use shielded leads from phono inputs to selector switch and from output board to output jacks (It can be argued that due to the short length and high impedance this is not needed. But in chasing down floor noise in any system that has been designed well, every effort must be made to keep noise out.  Phono inputs are the smallest signals in the pre-amp and the out put section the highest. By shielding these we can reduce some of the noise.  Any one noise reduction modification may not seem to reduce noise much but it is additive.  As you make any part of the system better, i.e.: noise reduction, distortion reduction etc. you allow other lower level noise and reduction to be heard. )

Use modified Star grounding. ( using multi-stranded copper wire, all input and out put jacks on the rear panel, as well as rear panel, and thus all the chassis, is brought back to the power supply ground at one point. It is a modified Starr system as with out a larger rewiring of the unit, it is not possible to have one ground and that tied to one point on the chassis.

 

 

 

 

 

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