Bottlehead Forum

Bottlehead Kits => Eros Phono => Topic started by: mwaller on May 12, 2016, 08:21:49 AM

Title: Resistor upgrades for Eros?
Post by: mwaller on May 12, 2016, 08:21:49 AM

I've read a number of posts indicating that various resistors can be replaced for improved sound. 
Many people swear by the TX2352 resistors...
Which resistors are most critical to the sound, and what components are considered the best replacements?
Thanks,
Mik

Title: Re: Resistor upgrades for Eros?
Post by: mwaller on May 13, 2016, 07:36:58 AM

I've read that the 47K input load resistor and 47K (2W) output tube plate load resistor are critical to the sound. 
How about the 27K (1W) resistor attached to the cathode of the output tube?
Thanks,
Mika

Title: Re: Resistor upgrades for Eros?
Post by: Paul Joppa on May 13, 2016, 10:01:30 AM

The 27K is bypassed with a large electrolytic, so the resistor has little effect. That cap will have more effect. The 75K and 10.5K in the RIAA filter are probably important. We have used good quality metal film resistors, so effects will be small.

Title: Re: Resistor upgrades for Eros?
Post by: mwaller on May 16, 2016, 01:13:31 PM

Quote from: Paul Joppa on May 13, 2016, 10:01:30 AM

The 27K is bypassed with a large electrolytic, so the resistor has little effect. That cap will have more effect. The 75K and 10.5K in the RIAA filter are probably important. We have used good quality metal film resistors, so effects will be small.

Thanks for the reply!  Regarding that 100uF /160V bypass cap - what voltage rating is actually required in this application?  Is a 50V cap ok, or do you really need the 160V rating?
Thanks,
Mika

Title: Re: Resistor upgrades for Eros?
Post by: Doc B. on May 16, 2016, 01:31:49 PM

I'll suggest studying the schematic if you are going to make these modifications. From the schematic you can see that the voltage at the cathode of the 6922 is 27174 ohms x .0038A = 103V.

Title: Re: Resistor upgrades for Eros?
Post by: mwaller on May 16, 2016, 01:52:16 PM

Quote from: Doc B. on May 16, 2016, 01:31:49 PM

I'll suggest studying the schematic if you are going to make these modifications. From the schematic you can see that the voltage at the cathode of the 6922 is 27174 ohms x .0038A = 103V.

Thanks for the explanation. I'll have a closer look.
Mika

Title: Re: Resistor upgrades for Eros?
Post by: mwaller on May 16, 2016, 04:22:30 PM

Quote from: Paul Joppa on May 13, 2016, 10:01:30 AM

The 27K is bypassed with a large electrolytic, so the resistor has little effect. That cap will have more effect. The 75K and 10.5K in the RIAA filter are probably important. We have used good quality metal film resistors, so effects will be small.

What brand / type is the stock 100uF 160v cap?  Mine doesn't have any mfg markings.  Thanks!
Mika

Title: Re: Resistor upgrades for Eros?
Post by: Doc B. on May 16, 2016, 04:26:29 PM

We use Nichicons.