Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Smack => Topic started by: jlschweiger on February 28, 2012, 04:58:57 PM

Title: Adjustments for tube rolling?
Post by: jlschweiger on February 28, 2012, 04:58:57 PM

Forgive this basic question, but if I were to substitute a different set of tubes for the originals (say 7119 PQ) would adjustment of the active loaded hybrid tube/solid state shunt pot be needed any time the tubes were changed?  Thanks for any replies!

Title: Re: Adjustments for tube rolling?
Post by: Grainger49 on February 28, 2012, 10:33:31 PM

John,

A good safe question. 

Tubes have equivalents and almost equivalents.  The "almost" needs circuit adjustments.  In the case of the tubes mentioned on the product page, 5687/7119/7044, these are all drop in replacements.  That is, no circuit adjustments needed.  There are probably others that might need a cathode or plate resistor change, maybe both and some that need different heater wiring schemes.

I hope this helps.

Title: Re: Adjustments for tube rolling?
Post by: Doc B. on February 29, 2012, 06:20:36 AM

Yeah 7119s plug right in without any changes and the PQs sound great. That's what I use in mine.

Title: Re: Adjustments for tube rolling?
Post by: Dwight on July 31, 2012, 08:22:19 AM

Hello tube rollers

Can I also use a E182CC as replacement without modification of the circuit?

Is there eventually a list of tubes that can be used for the Smack without modification?

I searched the manual for this info but did not found anything.

Thanks in advance and Kind Regards

Philipp

Title: Re: Adjustments for tube rolling?
Post by: Paul Joppa on August 27, 2012, 06:13:03 PM

The E182CC is obviously not an exact replacement, since it has a mu of 25 vs. 17 for the 5687. It may or may not be close enough to work - we have not tested other tubes. The heater current is a bit lower, so if you try it check the heater voltage to be sure it's OK - you may need to increase the resistor in the power supply. Then check the tube pin voltages and report any that are off by more than the usual 15%, and I'll assess the consequences and possible cures.

When checking this, I noticed that the power supply circuit shows 12AU7 tube heaters - those should be 5687 types! Sorry for the typo.

Sorry this reply is late; sometimes I just don't see posts until a few weeks later.