Bottlehead Forum
Bottlehead Kits => Eros Phono => Topic started by: Plamen_T on June 07, 2016, 09:24:00 PM
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Hello all,
I have built an Eros tape head preamp and it played great for a while.
Now I have a different setup and don't need the Eros tape functions anymore.
My question is:
how to make an Eros Phono only out of Eros tape one? I mean to fully abandon the NAB/IEC tape EQ and convert the Eros to RIAA only?
I know, there is a similar topic but it discusses making the Eros both tape and phono capable. This is not my case though - I want to convert the preamp to RIAA only without NAB/IEC EQ.
Thanks in advance for any thoughts.
Cheers,
Plamen
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There are actually two versions for tape; I will assume you have the NAB/IEC one.
* Replace the 301-ohm resistor at R1 in the C4S board B side (OB goes to the EF86 plate, socket pin 6)
* Replace the 200K 1/4 watt resistor with 75K 1/2 watt (EF86 pin 6 to ground).
* Remove the switch, 5Meg resistor, 100K resistor, 0.47uF capacitor, and 2490 ohm resistor.
* Replace the 1070 ohm resistor with 10.5Kohm.
* Replace the 0.047uF cap with 0.030uF (3% or better).
* Add a 0.010uF cap (3% or better) from that same plate - socket pin 6, or probably T4 or T12 depending on which channel, to ground T5 or T11.
** Repeat for the other channel
Sorry, I don't have a built example to look at, just working from the schematic. So I may have gotten some of the terminal numbers wrong.
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Thank you very much Paul!
If any uncertainies arise I will get back to you.
Cheers,
Plamen