Any Dynaco moders? 1& 2

[dynaco_dan]

Hi there;

If you own a Dynaco Pat-4 pre-amp you own a classic solid state pre-amp.

Very good value when new.

It has been the subject of, millions, ok, maybe oodles of modifications.

This has kept a well looked after pre-amp still quite capable of fine performance even 25 years later.

Certain to be bettered today, but, at a substantial increase in cost.

I have just come across some of my old notes, which has a simple sonic improvement at a very reasonable cost.

I assume you have the PAT-4's owners manual, for some help and the schematic, the desire to do the mod, a soldering iron, and patience.

The stock value for C-4 and C-16 is 50uf x 25 v elect.

Replace them with a 105'C - 100uf x 35 v or higher cap, watch the polarity, and also add a 0.47uf PolyP cap in parallel.

Another mod is to do a back to back with 2 - 105'C - 100uf x 100 v elect caps to replace the 0.47uf tantalum cap, also bypass these with a single .47uf PolyP cap.

One last tip for this session.

Use a 0.01uf polystyrene cap instead of or in addition to, for the bypass, but, moocha more money.

[Guest daveshel]

I attacked a PAT4 not long ago armed with a back issue of Audio Basics. I got through stage 1, taking the tone controls out of the curcuit. Stage 2 involved jumpering a four tiny 1 mdf electrolytic capacitors. The instructions mention that 2 of them are very hard to reach. I stared at them for a while and determined that ther were actually impossible to reach, and I never went forward. Stages 3 and 4 involve upgrading the components on the power supply and audio boards, and I'm sure I will eventually order parts and give this a try.

I don't have a lot of motivation on this project because I have an OmegaStar PAT5 modified by Van Alstine just a few months ago, and another FET3 PAT5 that is 20+ years old.

I have another PAT4 in addition to the one I have started modding. It plays but has a broken stop on the volume control. If anybody needs a project, I would be willing to sell that unit for $50 plus shipping.

[Guest rhollingsworth]

Hi there;

If you own a Dynaco Pat-4 pre-amp you own a classic solid state pre-amp.

Very good value when new.

It has been the subject of, millions, ok, maybe oodles of modifications.

This has kept a well looked after pre-amp still quite capable of fine performance even 25 years later.

Certain to be bettered today, but, at a substantial increase in cost.

I have just come across some of my old notes, which has a simple sonic improvement at a very reasonable cost.

I assume you have the PAT-4's owners manual, for some help and the schematic, the desire to do the mod, a soldering iron, and patience.

The stock value for C-4 and C-16 is 50uf x 25 v elect.

Replace them with a 105'C - 100uf x 35 v or higher cap, watch the polarity, and also add a 0.47uf PolyP cap in parallel.

Another mod is to do a back to back with 2 - 105'C - 100uf x 100 v elect caps to replace the 0.47uf tantalum cap, also bypass these with a single .47uf PolyP cap.

One last tip for this session.

Use a 0.01uf polystyrene cap instead of or in addition to, for the bypass, but, moocha more money.

Hello, Dynaco Dan. This is an old thread, but maybe you will see this.

I am not any kind of electronics expert (I know enough not to kill myself), and I like good sound, but I don't understand all the terms.

I have a PAT4 I built in 1975 that I would like to modify.

Your mod, "do a back to back with 2 - 105'C - 100uf x 100 v elect caps to replace the 0.47uf tantalum cap," has me confused. I don't see a 0.47uf value anywhere in the component list in my manual. Can you help me locate that?

Plus, when you say "bypass" I presume this means wire in parallel, correct?

And, what does "back to back" mean?

Many thanks,

RH

[jwjensen356]

I attacked a PAT4 not long ago armed with a back issue of Audio Basics. I got through stage 1, taking the tone controls out of the curcuit. Stage 2 involved jumpering a four tiny 1 mdf electrolytic capacitors. The instructions mention that 2 of them are very hard to reach. I stared at them for a while and determined that ther were actually impossible to reach, and I never went forward. Stages 3 and 4 involve upgrading the components on the power supply and audio boards, and I'm sure I will eventually order parts and give this a try.

I don't have a lot of motivation on this project because I have an OmegaStar PAT5 modified by Van Alstine just a few months ago, and another FET3 PAT5 that is 20+ years old.

I have another PAT4 in addition to the one I have started modding. It plays but has a broken stop on the volume control. If anybody needs a project, I would be willing to sell that unit for $50 plus shipping.

Can you make a comparison between the two PAT-5s that you have? Is your OmegaStar PAT-5 newly done over by van Alstine (meaning lots of new parts)?

John