SimpleSE R17/27

fandersen · 4th September 2010, 08:32 PM

Assuming the same rating (i.e. 560ohm 5W), will different types of the cathode bias resistors (R17/27) affect the sound quality? For example wire wound, metal film, metal oxide, etc.

Ty_Bower · 4th September 2010, 11:01 PM

It shouldn't. Those resistors are just carrying DC. The idle current through the tube passes through that resistor, but any AC (audio) signal should be going through the bypass capacitor, C12 or C22.

Metal film would be a poor choice for this position. Metal film types tend to catch fire and burn if you happen to exceed their power handling limit. This resistor needs to be able to dissipate a fair amount of power. Metal oxide types are often rated flameproof, but again you need to ensure you've got sufficient power handling capability. KT88 type tubes can draw a lot of current, and you really need a minimum 5 watt rating for the cathode resistor. It might be difficult to find that in a metal oxide type.

fandersen · 5th September 2010, 04:34 AM

Thanks Ty,

This was a bit of a hypothetical question. I didn't think the cathode bias resistor affected the sound buy I'm not the electrical engineer

I did instal 5 watt wirewound resistors and everything is working fine. Just trying to learn more

4th September 2010, 08:32 PM	#1
fandersen diyAudio Member Join Date: Jan 2010 Location: Victoria, BC	SimpleSE R17/27 Assuming the same rating (i.e. 560ohm 5W), will different types of the cathode bias resistors (R17/27) affect the sound quality? For example wire wound, metal film, metal oxide, etc. __________________ Flemming

5th September 2010, 04:34 AM	#3
fandersen diyAudio Member Join Date: Jan 2010 Location: Victoria, BC	Thanks Ty, This was a bit of a hypothetical question. I didn't think the cathode bias resistor affected the sound buy I'm not the electrical engineer I did instal 5 watt wirewound resistors and everything is working fine. Just trying to learn more __________________ Flemming

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Mark Levinson ¹27.5	Taifun	Solid State	101	14th March 2011 09:57 PM
Adjusting Pioneer A-27	hifileslie	Solid State	5	4th February 2011 07:05 AM
Accuphase C-27	Onvinyl	Analog Line Level	4	25th February 2009 04:27 PM
To Fix T 27 Tweeter?	Tony.ca	Multi-Way	0	19th May 2004 03:42 PM
type 27 pre	exurbia	Tubes / Valves	14	26th December 2003 04:01 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read

4th September 2010, 11:01 PM	#2
Ty_Bower diyAudio Member Join Date: Mar 2007 Location: Newark, DE	It shouldn't. Those resistors are just carrying DC. The idle current through the tube passes through that resistor, but any AC (audio) signal should be going through the bypass capacitor, C12 or C22. Metal film would be a poor choice for this position. Metal film types tend to catch fire and burn if you happen to exceed their power handling limit. This resistor needs to be able to dissipate a fair amount of power. Metal oxide types are often rated flameproof, but again you need to ensure you've got sufficient power handling capability. KT88 type tubes can draw a lot of current, and you really need a minimum 5 watt rating for the cathode resistor. It might be difficult to find that in a metal oxide type.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)