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Next to my SF Twin to give some size perspective. This is a HUGE sounding cab.



I've been playing with the thing for the last few days, and it definitely has more preamp gain than my 4 holer (I sat the 504 on top of this cab and tried them back to back).

Even with the master down around 9:00, and using the channels separate and OD off, I can't put the preamp volume up past 8:00 or so before medium to heavy-ish barre chord strumming starts adding a little hair to the tone. I can get up to about 11:00 on my 4 holer before this happens. It does it on both bright and normal input, so I don't think it's a pot issue.

I am sure I did something wrong. I am leaving on a trip for a few days, so I won't get to mess with it until I get home. .


FWIW, I am using a Mullard ECC81 in the PI, and have tried a bunch of different 12AX7s in the rest, including new production as well as NOS/used.

It is a great sounding amp though! My Superfuzz KILLS through this thing!

I still need to order some KT66s for it!

Bear in mind that it takes quite a bit less effort to overdrive 6V6s than EL34s. And the Triwatt's voltages have to be a little lower as well, to accommodate the 6V6s. So that may be affecting things. It gets cleaner with the KT66s, since they have to be driven harder before they break up, somewhat more like EL34s.

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Great tones come in small glass jars!

That's what I was thinking. I am gonna order some KT66s for it!

The overdriven tone is pure Hiwatt..... Something I can't practically use with the larger amps.

Phil, can I try EL34s in this thing? I recall that the OT impedance is different, but it seems that KT66s and EL34s run in similar voltage ranges.

I'd sure like to see that done.

You'd have to 'mismatch' the OT to a different speaker load to change the reflected impedance to more suit the EL34. This OT is 50Watts and 8K primary. The best you could do is to plug 8 ohm speakers in and set the impedance switch to 4 ohms so it reflects 4K back to the EL34s.

You'd have to change the bias resistor to and rebias of course.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I might give this a try. I'd prefer a tad more headroom than I am getting with my Triwatt. I think KT66s would be perfect, but don't have any. I have a bunch of EL34s......

What would you suggest for the bias resistor? I am thinking around 27k maybe?

Well, I threw in a pair of EL34s and checked bias (left the stock bias resistor)). On the KT66 setting, I didn't have nearly enough adjustment in the pot to get them in range, but in the 6v6 side, I was able to get them in the ballpark (450volts 33MA dissipation). It sounded just like my 4 holer

It is definitely the 6V6s overdriving that I am hearing.

For giggles, I biased the 6v6s a little hotter (26ish), and they cleaned up nicely, but I am not sure what kind of life I'd get out of them.

I am gonna order a pair of KT66s for this thing..... I think it will be perfect!

Way Too Cool!

What impedance did you set the OT at and how did you mismatch the spekaers /Impedance.

With the EL34, how loud was it in comparison to your 4 holer?

I think the JJ 6V6 can take the heat better than some.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I set the output impedance to 4 ohms into an 8 ohm load.

I didn't crank it all the way up, but it definitely had similar headroom to my 4 holer.

It wasn't a whole lot louder than the 6V6s, but definitely had more headroom.

I have the 6V6s back in it now.

BTW, I took it over to my friend's music store today to try out a Line 6 M13 stompbox modeler (which is pretty damn impressive), and the Triwatt got rave reviews. It was nice to hear it in a different acoustic environment

OK, now that the meat and potatoes are done with this build, it's time to do the rest of the fixins.

I'd like to have some type of FX loop in this thing for running delays and mods.

I am looking at this one http://www.skipzcircuits.com/TBFX.html, (FWIW, I used his power scaling kit in my Marwatt and it is great) which can be switched in and out of the circuit. I think the newfangled footswitch relay system in my Triwatt might be what the doctor ordered on this one.

I have only owned two amps with loops, and I am not familiar at all with them and how they fit into the circuit.

Can any of you guys give me any advice on what would work best and where to break into the circuit with a Hiwatt/Triwatt?

Fit a pair of switching jacks in series between the MV pot's wiper and the input cap of the following stage and you should be good. It's so handy that Dave Reeves put in an extra preamp stage after the MV, and before the PI, as this provides a perfect recovery stage.

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Great tones come in small glass jars!

Wow....Small-Freakin-World Syndrome. I checked out www.skipzcircuits.com & they're located ~25 miles from my home and within a few minutes of where I work.

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That's it? I'll try it when I get home. Thanks Phil!

Phil, can you give me the specific spots (tube pins) to break this into the circuit?

Thanks!

Just break between the wiper of MV pot VR7 and 22k resistor R17. You would need to place a 1M resistor between V3 Pin 7 and ground, to keep the grid biased to 0V, when an FX unit has been placed in the circuit. You may also want to place an isolation cap (0.1uF say) between the return jack and R17 if any of your pedals don't have a cap on their output.

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Great tones come in small glass jars!

Thanks Phil! I'll try it tonight! BTW, I picked up a pair of Shugang KT66s, and they just arrived today. Any bias suggestions to start with?

Just bias them to around 40mA-ish, and tweak to taste. They like being warm biased.

BTW I forgot to say you may need to play around a bit with the cap in front of R17. If the value's too large, the tone may get mushy in the low end. Too low, and you may lose some low end. So may like to try some different values, like 0.022uF, 0.047, 0.01uF, with a few different guitars, and see which value you like best overall.

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Great tones come in small glass jars!

Phil,

I put the KT66s in, and the lowest I can get the bias is a smidge under 41 with the pot at it's limit.

I played it for a bit, and the KT66s are exactly what it needed IMHO. Big, clean and chimey.....

Hmmm that's strange. I actually used a pair of Shuguangs in the Triwatt prototype and they biased fairly nicely near the middle. Did you remember to flip the 6V6/KT66 switch? Sorry, if that's a dumb question... Anyway, like I said Shuguangs sound good running a little warm.

Glad to know you got the sound you're looking for.

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Great tones come in small glass jars!

LOL.... I did flip the switch, and even tried switching to the 6V6 setting, but it was at 52!

Maybe my pot value is off a bit. It does sound great though.

Now I need to mod my tube retainers to fit those huge bottles!

Well, I've been tweaking my Triwatt. I wimped out and installed the Skipzcircuits TB FX loop. It works great. I tried to make it footswitch bypassable with a second relay, but it was way too noisy. It is actually very transparent and doesn't load down the signal. My delays sound awesome.

I also wanted to clean up the preamp a bit more, so I changed the non boosted plate and cathode resistors on V2 to 220K/2K2 respectively and the 560k cathode resistor on V3 to 1.8M. I am not sure if I am gonna keep it like this, but so far, I really like it with my pedals and Gibsons.

Now, I'd like to get more dirt from the OD at lower volumes, so I am gonna play with the cathode bypass cap/resistor values on that side of V2 next.