<<<updated>>>Tube comparison: 6L6GC vs 6L6WGB - not sure where to post

[fdesalvo]

Like the title says, I'm not sure where to post this.  There doesn't seem to be a suitable subforum, so pardon the space debris if this is not the case!


Amp: 40w single channel AB763 - no verb/trem @ ~460vp
Tubes: Ruby 6L6GC-MSTR
          JAN Philips 6L6WGB, NOS/1980s
          *Next week a set of "Winged C" 6L6GCs will arrive
Guitar: Warmoth Mahogany/Maple neck super strat with TOM JB/Jazz (Currently building a tele which will have a Kinman singlecoil up front and a Bare Knuckles Abraxis in the rear).
Cab: Avatar 212, semi-open back, 2 aged V30s.
OD: G2D Cream Tone

You have to love adjustable bias and having test points makes things so much easier.  Over lunch, I had a blast trying both duets at various bias settings and was pretty amazed at the difference in tone and feel each set yielded with each adjustment.  

6L6GC-MSTR  
At 40ma, these tubes have a very broad tone - lots of deep lows, recessed mids, and bright highs stopping just short of that super sparkling tone which I was hoping to get out of the circuit.  Taking the humbuckers into consideration, I'll reserve judgment until I can plug in something with singlecoils.  Kicking on OD pedal yielded a punchy driven tone with a slightly scooped feel to the mids.

At 35ma, the tone is not much different than it was at 40ma.

At 25ma, however, the deep lows are only slightly augmented and the overall sound is more rounded with slightly softer highs and lows.  The midrange is much more apparent here, still keeping the basic tone of the circuit at 35ma, but with much sweeter overtones and a looser feel.  

With the OD pedal engaged, the tone was really sweet – nice chewy feel and lots of definition available, though a much rounder and less jagged tone than what was apparent at higher ma settings.

NOS JAN Philips 6L6WGB
There are lots of people that compare these tubes to a ruggedized 5881 because of its size and aility to reliably handle pv well in excess of 450v (470v max on the lot from the 80s).  Others note it’s mechanically identical to the 7581a, albeit in a much shorter envelope.  This thing looks like a juiced up 6V6 haha.

My bottom bias setting was ~31.5ma, which was at the short end of the bias pot.  I took it up to 36ma just for grins with no apparent retribution from the plates.

These are sweet!  The hollow midrange I experienced with the GCs is markedly less buried and is pushed to the left of center just a bit.  All the bottom and jangle seems to be there – all the tightness and definition are still in place, but mids are really sweet on this one.  In fact, with the OD engaged, the tone was open and raw on the lower strings with plenty of bark.  The higher strings were crystal clear and had great attack.  Loads of overtones clean – before I forget.

I wish I was able to overdrive these tubes with a bit more volume, but running these through 2 12” woofers was getting to be a bit much.  Rehearsal and stage volume would be amazing, I bet.

I built this amp for the Tele that’s still under construction – looking for a blues machine that can do the blackface thing.  However, with the JB/Jazz combo – I was pleasantly surprised.  The Jazz is a bit sterile IMHO and the JB is thin and flat clean, but I was able to get some chewy clean jazz tones from the neck – and with the OD engaged, the tone was really nice – especially with the WGBs.  Tomorrow I’ll crank it with a 12AX7 in the PI slot.

So this could technically salvage this thread from being posted here in vain – if I wanted more sparkle, should I have to make any circuit changes, or do you reckon it’s about the tubes from here on out?  I should really wait until I have the Winged Cs installed to ask, I suppose.  

[firemedic]

Very descriptive prose. "Reviews" such as this are real helpful when people (myself included) are casting about in search of new power tubes. Manufacturers' so-called reviews are so absolutely useless. Please post your findings on the SEDs as well.

[fdesalvo]

Glad it was able to help - I'll review them ASAP.

[sluckey]

That is a very descriptive sound comparison. Speakers will probably make a bigger difference in tone than any circuit mods of tube types. I'd hold off on too much modding until you get the tele ready if that's gonna be your main guitar.

One thing you can easily do to get more sparkle is to add a bright switch/cap to the volume control. This has a lot of effect at lower volumes and zero effect with volume pot maxed. You could almost break glass with a stock tele thru a super reverb with the bright switch on back in the '60s. A real screamer!

[fdesalvo]

Sage advice hehe. The Tele will have a hum in the bridge and single coil up front. Will try the bright cap just for S&G.  Haha doubt the. Doubt the volume will ever get past noon!

[tubeswell]

soundbytes?

[fdesalvo]

soundbytes?

Great idea. I do have a rig, but not much time :/

[DummyLoad]

NOS JAN Philips 6L6WGB There are lots of people that compare these tubes to a ruggedized 5881

in many cases, as this one, they are the same tube. some that have passed thought my hands have had both 5881/6L6WGB marked on the base.

--DL 

[fdesalvo]

I just tried two diff bright caps - 250/500pf.  500 takes the cake - this is exactly what I was looking for!

With this current config (WGBs) the amp is so woody sounding with my Jazz - this humbucker has never sounded so good!  All the sparkle and chime I wanted are there, as well!  I have no desire to even listen to the SEDs now haha.  I am perfectly satisfied and content (at the moment?). 

NOS JAN Philips 6L6WGB There are lots of people that compare these tubes to a ruggedized 5881

in many cases, as this one, they are the same tube. some that have passed thought my hands have had both 5881/6L6WGB marked on the base.

--DL 

I just read this, as well.  I've read that the older versions of the WGBs are synonymous with the 5881.

[Willabe]

Didn't PRR say that the later NOS JAN 6L6GB's probably had 6L6GC guts in them?


                    Brad     

[fdesalvo]

OK - I can't believe how great this amp sounds and feels.  The last AB763 variant I built had the voltage divider in place before the PI, despite the amp having no trem or reverb and I thought the amp did a really solid clean, though it was a bit sterile.  The tone controls were largely ineffective, save the treble pot. 

This new one feeds the PI directly from the .001uf cap off V1's plate resistor (Thanks, Sluckey) and it has this indescribable magic that I have never been able to attain in any amp I've owned, be it purchased or scratch built.  Maybe I finally got the circuit right.  Maybe my soldering iron cooked the caps and resistors in such a way.  Maybe the layout is responsible.  Maybe it’s the tubes.  Maybe it’s all of these layers each contributing to the sonic lasagna that is this amp.  The tone controls actually work - and with the mid cranked, the center of the sound stage fills our beautifully - and the amp doesn't lose that blackface magic! 

The guitar feels alive in my hands and the tone has solid bottom end with the perfect balance of mids and top end shimmer.  Even the JB, which I characterized and thin and flat, sounds great clean.  This is the first amp I’ve ever enjoyed hearing a bridge humbuckers played clean through.  And it loves my OD pedal! 

This is also the first amp I’ve ever played that sounds amazing dry – normally I wouldn’t be caught dead without reverb or a little delay adding ambience.  The harmonics and overtones riding along the fundamental tones are outstanding!  I’ve never been a neck humbucker guy, but this amp sounds great when I roll my volume back a little.  Tons of smoky and bouncy jazz tone!  I can’t wait to hear it with single coils!

I’m going to run my delay through the front end right behind my od pedal tonight.  If it sounds good, I’m selling my Boogie Deuce II without thinking twice.  With a little high density foam, this amp will fit right inside of it's flight case.

[fdesalvo]

OK, I need to replace my bias range resistor - I need a lower mA range.  

I installed the winged c's just now and was able to lower the mA to ~ -49.xxmA - a little hotter than the 70% dissipation rule, I reckon. No red plating evident, so I fired up the amp.  

Compared to the WGBs, the sweet spot up the amp has moved further up the volume dial.  Honestly I'm putting the NOS Philips back in - they are so much richer sounding with every bit as much depth and fullness.  Maybe it's my bias pot's range that needs adjusting, but I just can't justify the hype under the conditions I've tested these in this evening.

The mids are more subdued at the same eq settings and the rudeness I was enjoying with my od pedal was largely absent.  The touch sensitive and woody nature of the amp was also absent.  Your mileage may vary and at stage volume, all bets are off for both tubes.  Tomorrow is rehearsal, so I'll be able to play this amp with the volume around 10 - 11 O'clock as opposed to 7/8.  I'll update again after.

If I'm looking to move my bias range about 10mA lower, what suggested size should I source for my bias range resistor?  Is there a rule of thumb, of do I finally need to learn Ohm's law?    

[HotBluePlates]

The bias circuit doesn't directly obey ohm's law, because the diode rectifying a.c. and a cap trying to filter that to d.c. complicate the math significantly. The best approach is to figure if a given resistor needs to go up or down in value, and experiment.

My other suggestions:
- If you want to change tone through tube swaps, changing your first preamp tube will make the biggest impact.
- A circuit or component value change (or a speaker change) will nearly always make a bigger impact than a tube swap. And except for maybe speakers, you'll probably save money.

[fdesalvo]

The bias circuit doesn't directly obey ohm's law, because the diode rectifying a.c. and a cap trying to filter that to d.c. complicate the math significantly. The best approach is to figure if a given resistor needs to go up or down in value, and experiment.

My other suggestions:
- If you want to change tone through tube swaps, changing your first preamp tube will make the biggest impact.
- A circuit or component value change (or a speaker change) will nearly always make a bigger impact than a tube swap. And except for maybe speakers, you'll probably save money.

Thanks for your reply - I definitely lost my faith in the magic tube theory - although these NOS Philips are making me consider otherwise!  Looks like I need to knock my bias range resistor down a little.