Converting to 6973 tubes.

Tube-specific discussions

Moderators: CurtissRobin, zaphod_phil, rock_mumbles

geoff 1965
Occasional poster
Occasional poster
Posts: 488
Joined: Mon 01/04/16 3:52 pm

Re: Converting to 6973 tubes.

Postby geoff 1965 » Thu 01/26/17 5:04 pm

i've got a lite2 which i tweaked"voiced" to my preference,the stock values of the coupling caps were too bright&thin for me so i put .022's post phase inverter and .015 & .012 in the preamp and these el84's are"singing" definately not muddy or fizzy!
when mullard made the el84 & el34 they had a patent on them so you guys in the states came up with the beam tubes 6V6,6L6 etc so they did'nt have to pay mullard royalties.i've looked at the specs for the 6973 and it's pretty close to the el84 but i have'nt heard one in an amp,in fact i've never seen one here in the U.K.
good luck with your project,i've got a voltage drop "gremlin" popping my brain cells!
0 x

Trapland
Unrated
Posts: 7
Joined: Thu 01/05/17 5:44 pm

Re: Converting to 6973 tubes.

Postby Trapland » Fri 01/27/17 1:18 am

geoff 1965 wrote:i've got a lite2 which i tweaked"voiced" to my preference,the stock values of the coupling caps were too bright&thin for me so i put .022's post phase inverter and .015 & .012 in the preamp and these el84's are"singing" definately not muddy or fizzy!
when mullard made the el84 & el34 they had a patent on them so you guys in the states came up with the beam tubes 6V6,6L6 etc so they did'nt have to pay mullard royalties.i've looked at the specs for the 6973 and it's pretty close to the el84 but i have'nt heard one in an amp,in fact i've never seen one here in the U.K.
good luck with your project,i've got a voltage drop "gremlin" popping my brain cells!

A good example it any of the videos of the supro 1624 dual tone. Ive owned 2 and am amazed how much the overdrive sounds like an el34. . No sure why I sold them but I think it was to fund a vintage Marshall.

If I get this running, I will for sure post clips.
0 x

User avatar
JMPGuitars
Super Duper Admin
Super Duper Admin
Posts: 1211
Joined: Tue 09/18/12 8:00 pm
Location: South Central, MA
Contact:

Re: Converting to 6973 tubes.

Postby JMPGuitars » Fri 01/27/17 8:26 am

Trapland wrote: Ah yes. The sweet spot for EL84 perhaps. Or maybe for el84 in this design. Capable of higher voltage and requiring it are very different. But I am of the opinion that lots of voltages (in the PA) can sound good, maybe different, but good. Off the top of my head, 2 of my favorite Marshalls both running Siemens el34 run 340 and 485 VDC on the plates.

My plate voltage with no signal is 303, lol. Having said that, I have no intention of running el84s, but if y'all want to do the "fer instances" assuming el84, it could be informative.
Yes, 340ish is the sweet spot for this specific circuit running EL84s. As CurtissRobin pointed out, an amp with 360 would have a much different sound, though the voltage would still be fine. A 20v variance on the plate can alter the tone significantly.

To put it terms of sound- too high a voltage gives less overdrive and more headroom, too low and you get ugly distortion and less headroom. You're 40v lower than the sweet spot, so I would bet that's why you're getting the undesirable tone you're describing.

That being said, I'm ALL for experimenting and changing tubes, and I would love to hear what your amp sounds like with 6973 tubes in it. BUT this raises a concern. Why is your plate voltage so far out of spec for this circuit? Are your other voltages where they should be? (The only way to answer this is by comparing it here: http://18watt.com/storage/Voltage-Chart.htm and posting your voltages in this thread)

To get the best potential tone out of the 6973s, the voltages need to be correct across the board, and then make adjustments in the power section to bias the 6973s, and adjust for tone.
0 x
'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright
Web Design - DolceVittoria.com
Guitars / Amps / Effects - JMPGuitars.com


Return to “Tube Talk”

Who is online

Users browsing this forum: No registered users and 2 guests