Extra Triode?

[fusionbear]

Just curious, I searched and couln't find anything on this topic. I've noticed some builders will use an extra triode in a circuit by using it in parallel. Has any one done this with V2 in the express, or has any one done this in V1 before going to the tone stack. Has it been tried a failed or is this something someone hasn't tried?

[nickt]

Just curious, I searched and couln't find anything on this topic. I've noticed some builders will use an extra triode in a circuit by using it in parallel. Has any one done this with V2 in the express, or has any one done this in V1 before going to the tone stack. Has it been tried a failed or is this something someone hasn't tried?

Don't know if this helps but I built a Lightning and used the parallel input tube same as the Matchless. Never really liked the amp until I set it up for optional single or parallel input. Surprise surprise - the single sounds MUCH better and now I like the amp.

Perhaps this doesn't apply in the wreck's case for V2 but certainly I'd be reluctant to hard wire a parallel stage for V1.

One thing that might be interesting is using the spare stage as an unconnected cathode follower at V1. An unconnected CF has the effect of making the current draw from the power supply constant for that tube. (basically reduces PS induced hum) Haven't tried it myself but there's some info on it at John Broskie's site http://www.tubecad.com/

Another thing - think someone used the extra stage as the PI to drive a 5E3 style power section - can't remember where I saw this.

cheers
Nick

[rhinson]

you could also make it a cathode follower as the 4th stage, pre the p.i. like the concorde does. rh

[tele_player]

One thing that might be interesting is using the spare stage as an unconnected cathode follower at V1. An unconnected CF has the effect of making the current draw from the power supply constant for that tube. (basically reduces PS induced hum) Haven't tried it myself but there's some info on it at John Broskie's site http://www.tubecad.com/

I'd love to read about it - could you narrow it down a bit, so I might not need to wade through all the other stuff there?

[nickt]

One thing that might be interesting is using the spare stage as an unconnected cathode follower at V1. An unconnected CF has the effect of making the current draw from the power supply constant for that tube. (basically reduces PS induced hum) Haven't tried it myself but there's some info on it at John Broskie's site http://www.tubecad.com/

I'd love to read about it - could you narrow it down a bit, so I might not need to wade through all the other stuff there?

Now you're an optimist !!

You're lucky to get "tubecad" retrieved from the dark recesses of my addled memory. Tell you what - you start at the latest and I'll start at the earliest and we'll see who finds it first

[gearhead]

There have been a few threads on this subject. One is:

https://tubeamparchive.com/viewtopic.php?t=3287

The search function is not like google. Need to put an "and" between search words. Had me stumped for a while myself.

Do a search on "parallel and triode" and you can dig into all the other threads.

[txbluesboy]

When I first finished my Express I had all kind of noise and unstability problems, besides taking the tone caps off the board and putting them directly on the pots, to reduce the amount off wire in the amp, I paralled V1A&B then moved V1B's Duties to The unused part of V2. I too, got this from experience with Matchless Amps which sound awesome in my opinion. It helped a lot in taming the noise, and I think sounds real good. I now think that Trainwrecks need a lot of usage before they settle down and work really well. There were several times that I told myself " Tomorrow I'm going to tear that Express down and make something else out of it" but I put if off and kept trying different tubes in it and playing it until it now sounds really good I think. However I dont have a real Expressto compare it to.

[sliberty]

Don't know if this helps but I built a Lightning and used the parallel input tube same as the Matchless. Never really liked the amp until I set it up for optional single or parallel input. Surprise surprise - the single sounds MUCH better and now I like the amp.

How would you characterize the differences in tone? I have a stock circuit Spitfire clone (very similar to a Lightening), and wonder how the change would affect my amp.

Also, do you have a schem or layout fragment that shows what you are switching?

[jaysg]

I'm building a Liverpool at the moment. I have made some provisions to try the unused half as a second input to the PI. With el84's, it should be enough to drive the power amp.

[El_Martin]

Hi!

I had two ideas:
1. use it as an alternative third stage with local feedback to get earlier overdrive (start pounding on me for leaving the TW path...
2. installing an EF86 to drive the unused triode, then into the pi

oops, and here's another idea: use it for an active tonestack
either the old Gibson way or the newer Peavey style. At least the Gibson schem needed only one triode.

Since I'm not satisfied w. the hum yet and there are some layout issues, I didn't bother the search function. Dunno if either of these ideas is pure and utter bs...

I can't stand unused triodes in my diy amps...I paid for them

Ciao
Martin

[bigtone96]

I used the spare triode to parallel v1 on my clone, and I used my high input to use both side, and the low to use only one. I got the idea from 18 watt.com. I found it thickens the tone alot. I play strats mainly, and to me it is more suited to single coils than a humbucker. I plug my LP into the low input.

[novosibir]

The biggest benefit of paralleling triodes - also named 'composite triode' - is the reduction in hiss to about 70% compared w/ a single triode. The gain only marginally will be enhanced.

See also KOC's TUT Vol. V - pages 1-40/1-41

But it's interestingly in respect to additional harmonics, when you'd keep the 100K plate resistor and the 1.5K...2.7K cathode resistor as common resistors for both! Look here:

http://members.aol.com/sbench102/dax7.html

Although - by my experience - it's still sounding most familiar w/ the single triode.

Larry

[dartanion]

I implemented a switchable CF using the extra triode my 18watt Liverpool build, which smooths out the tone at higher volumes.

Parallel triodes is pretty sweet too. It definitely sounds different than single triode mode on my 18watters. Single really gives it that classic Marshall tone whereas the parallel is a bit grittier and more harmonically complex.

[nickt]

Don't know if this helps but I built a Lightning and used the parallel input tube same as the Matchless. Never really liked the amp until I set it up for optional single or parallel input. Surprise surprise - the single sounds MUCH better and now I like the amp.

How would you characterize the differences in tone? I have a stock circuit Spitfire clone (very similar to a Lightening), and wonder how the change would affect my amp.

Also, do you have a schem or layout fragment that shows what you are switching?

In my case I found the paralleled triode to be less controllable from the guitar volume. I'm an amp/lead/guitar kinda guy and didn't like what the parallel did to the tone. Basically less variety was available and tone dropped out completely with volume turned down on my strat.

The schemo below is a hackup of the 18watt Lite II input stage and shows the switching as I've done it (only 1 x 1M resistor)

[tomrasdf]

If I felt the need to put that triod to use, I'd probably throw in footswitchable tremolo, the bias voltage modulating type. You could mount the circut in the huge tracts of land in the southwest corner of the chassis so aw not to pollute the tested layout. Speed and depth controls could be mounted on the back of the chassis. Just a thought.