Eico HF-14 build from scratch

Posted by banpuku (A) on March 25, 2015 at 06:11:13

Per my prior post about rebuilding a set of monoblocks, I am leaning towards a copy-cat build from scratch of the Eico HF-14. Why the Eico HF-14? A couple of reasons:

1. they are simple. this is my first venture into building an amp from scratch and I like the simplicity. I also have the less-is-better mentality.

2. these amps are made to run electrostatic speakers, like my Quad 63s. Per the service manual "The HF-14 has been designed to maintain its excellent characteristics under speaker load (including electrostatic types)." And further, "Stability is maintained on all speaker tabs with loads ranging from zero to infinity."

In studying the circuit, I see a few area that we can improve / eliminate circuitry (please see attached schematic. I would like your input on whether or not the highlighted areas are being addressed correctly.

1. The BLUE square represents a pot resistor R1 and resistor R2. I want to remove the pot completely. Q: should R2 also be eliminated?

2. The RED square represents an Octal Plug that is used to connect/drive/operate a pre-amp to this amplifier. I won't be using this octal plug at all. However, there is some text in the service manual that states the following: "a jumper between pins 2 and 3 (of the octal plug) effectively grounds one side of the filament winding. removal of the octal plug leaves the filament winding floating." Q: should I add a ground to the leg which is shown in YELLOW?

3. The GREEN square is a 0.03uf capacitor used for AC filtering. How can I improve on this? Anything is fair game, as I want this unit to sound as good as it can be.

4. Tube 4 is an EZ81 rectifier tube. Is the EZ81 a good tube for rectification? If not, any alternatives?

Your input would be greatly appreciated.

Pat

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Topic - Eico HF-14 build from scratch - banpuku 06:11:13 03/25/15 (24)

Less RISK ...... - drlowmu 13:25:41 03/25/15 (0)

If it were me, I would be looking at a PP EL84M or 6L6/KT66 design using SS soft recovery rectifiers - Timbo in Oz 13:04:13 03/25/15 (1)

RE: If it were me, I would be looking at a PP EL84M or 6L6/KT66 design using SS soft recovery rectifiers - Eli Duttman 14:46:34 03/25/15 (0)

RE: Eico HF-14 build from scratch - DAK 11:25:33 03/25/15 (0)

Is that really enough power? - Triode_Kingdom 11:25:11 03/25/15 (2)

RE: Is that really enough power? - banpuku 12:19:42 03/25/15 (1)

Keep in mind that the HF14 doesn't really do 14W... - Steve O 12:48:48 03/25/15 (0)

I realize specs aren't everything... - Steve O 08:57:01 03/25/15 (10)

RE: I realize specs aren't everything... - Eli Duttman 11:01:51 03/25/15 (9)

RE: I realize specs aren't everything... - Steve O 12:44:01 03/25/15 (8)

RE: I realize specs aren't everything... - Eli Duttman 13:19:22 03/25/15 (7)

Schematic for El Cheapo Grande? - Salectric 13:56:40 03/25/15 (1)

RE: Schematic for El Cheapo Grande? - Eli Duttman 14:26:39 03/25/15 (0)

RE: I realize specs aren't everything... - Steve O 13:34:27 03/25/15 (3)

RE: I realize specs aren't everything... - Eli Duttman 14:14:27 03/25/15 (2)

Negative Rails - Eli Duttman 17:44:18 03/25/15 (1)

RE: Negative Rails - Triode_Kingdom 16:52:25 03/27/15 (0)

RE: I realize specs aren't everything... - sony6060 13:30:03 03/25/15 (0)

RE: Consider Tublab's Simple P-P - sideliner 08:07:05 03/25/15 (0)

RE: Eico HF-14 build from scratch - sony6060 07:21:01 03/25/15 (4)

RE: Eico HF-14 build from scratch - banpuku 12:23:15 03/25/15 (2)

RE: Eico HF-14 build from scratch - sony6060 13:24:46 03/25/15 (0)

If you go with a 5AR4 in place of a 6CA4... - Steve O 12:54:46 03/25/15 (0)

RE: Eico HF-14 build from scratch - banpuku 07:30:53 03/25/15 (0)

Eico HF-14 build from scratch

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