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Dynaco PAT 4

40.133.181.113

Posted on January 15, 2025 at 13:58:30
joetech
Audiophile

Posts: 67
Joined: June 27, 2006
A friend gave me a Dynaco PAT 4 some years ago. I have used it off and on over the years but mostly it just sits on a shelf. I am thinking of getting a power tube amp or maybe a SS power amp kit or updating a 8w tube amp kit I built several years ago.
Regardless, I broke out my old turntable and plugged that into the PAT4 and used the headphone out. Sounded OK but the volume was low even with the volume knob all the way up. I tried two different headphones, both easy drivers at only 64 ohms. The cartridge has an average output of 4.7 mV and the specs on the phone input say ma of 10mV. There is a low, cer and high input on the phono on the back. Only the low even worked at all.
I am thinking of getting the upgrade kits from Akitika (upgrademydynaco). In the meantime, is this normal?

 

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From page 5 of the PAT-4 manual..., posted on January 15, 2025 at 15:11:37
1973shovel
Audiophile

Posts: 10252
Location: Greenville SC
Joined: February 25, 2007



...it would appear that your headphone's impedance, at '64 ohms' is too low for the PAT-4, and apparently you require the "matching transformer" mentioned in the manual.

 

RE: Dynaco PAT 4, posted on January 16, 2025 at 07:44:10
bare
Audiophile

Posts: 1882
Joined: April 14, 2009
Welll Dyna co Pat 4 was in a word: Junk. The update my dynaco kits Works well. I did the fuyll Monte upgrade years ago. Made a big difference.

Don't bother with the Phono upograde one tho :-) A diy Le pacific standalone phomne is a whole planet better.

Seriously suggest doing the ~7$.. "Reduce PAT-4 Distortion by 10X (DRD4)-$7.00" FIRST as it makes THE biggest improvement.
... then... decide if you want to go further.

Don't waste time /$$ on NOS Potentiometers ..I did, and along with the NOS supplier discovered that the Seriously Low Quality pots Cheap Ass Dave Hafler
chose to use. Self deteriorate! ...sitting in sealed packagings.. on the parts shelf for 50+ years ! As in 'new' NOS proved worse than my used ones.. repeatedly !

That said; I replaced My'updated' Pat 4 with a Dact type stepped attenuator 20$ (Ali express) as passive pre..and a DIY 'Le pacific' Phono stage.
For sounds quality NO Dynaco /Hafler even approaches.. True.
Good luck.

 

RE: Dynaco PAT 4, posted on January 16, 2025 at 08:23:08
mg16
Audiophile

Posts: 1057
Joined: October 18, 2001
Contributor
  Since:
March 11, 2021
Look for a Pat-5 bifet.
A very good sounding preamp for the money.
I owned at Pat-4.
When I built a Pat-5 Bifet kit, back in the 80's,(Bought from Stereo Cost Cutters), I became a believer in how much a preamplifier can affect sound quality.
Phono and line.
mg16

 

Remember the origin of the PAT-5 BiFet?, posted on January 16, 2025 at 13:22:26
E-Stat
Audiophile

Posts: 40054
Joined: May 12, 2000
Contributor
  Since:
April 5, 2002
It was Frank Van Alstine at Jensen's Stereo who modified PAT-5s using lower noise RN60D resistors, tantalum and polystyrene signal capacitors, stiffened the power supply and...replaced the LM301 op amps with newer LF356 models which used a combination of bipolar and JFETs. Bypassed the tone control circuits altogether.

I used one of his FET-5s in the late seventies replacing a Citation 11. Was pretty darn good but the SP-6 that followed was significantly better.

There is a similar story to how Van Alstine modified the Stereo 400 into the Double Dyna which was later adopted by Dynaco as the Stereo 416 including the optional external capacitor bank for the power supply. I took that approach to an Audire power amp at the time with great results. Taught me a valuable lesson as to the qualitative and dynamic advantages of extremely stiff power supplies.

 

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