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PostPosted: Sat Dec 01, 2012 6:14 pm 
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Looking to get slightly more low end happening in my Triwatt build to warm it up. It sounds a little bit too bright with the Overdrive engaged - I'm playing it through a 2x12 cab closed back pine cab. I'm going to look into trying to roll off these high frequencies as well.

The build manual indicates that increasing the value of the coupling caps would boost the low end - if I've understood the schematic, the coupling caps are C15 & C16, am I correct?.
Any recommendations as to how large a value the coupling caps could be increased to?
What's the max value one would dream to increase them to?
Also, any other ideas on changes to warm up the tone a bit?


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PostPosted: Sun Dec 02, 2012 4:15 pm 
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Are you happy with the response when the OD is NOT engaged? C15,16 are indeed coupling caps but so are c2, c3, c4. only c4 is limited to the OD channel. I see C4 is 22n . you could try 47n or 68n. I don't have a Triwatt (yet;-) so probably l should leave it at that.. I'm sure others will respond.


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PostPosted: Tue Dec 04, 2012 4:27 pm 
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Yes, there are a lot of coupling caps as \stoo mentioned. How about the normal chanel with Bass turned up? Is that OK?

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PostPosted: Wed Dec 05, 2012 7:27 pm 
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On my last run through with the amp, I set all controls at noon and adjusted the treble and presence slightly from there and did not engage the overdrive - the clean sounds are good with those settings. With the overdrive engaged, the dirty sound is good as well but the bottom drops out slightly (which is natural as you start cranking up the gain). I'd like the overdrive to push a little more bottom end when it's engaged.

On an unrelated note, how warm should the power transformer get before it becomes a concern?

During my first extended playing session through the amp, I had the master volume at around 3-4 and power transformer was barely warm to the touch. I pushed the power section of the amp a little harder (noon) while playing for a couple of hours a couple of days ago and noted that it was warmer - not hot to the touch by any stretch but comfortably warmish let's say. Cause for concern?


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PostPosted: Wed Dec 05, 2012 8:41 pm 
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frethead wrote:
On an unrelated note, how warm should the power transformer get before it becomes a concern?

During my first extended playing session through the amp, I had the master volume at around 3-4 and power transformer was barely warm to the touch. I pushed the power section of the amp a little harder (noon) while playing for a couple of hours a couple of days ago and noted that it was warmer - not hot to the touch by any stretch but comfortably warmish let's say. Cause for concern?


That is not cause for concern. If you couldn't hold your hand on it, I would be concerned. It is overspec'd for this amp as well. No worries.

For more bass in OD mode, you could try a 47n cap off pin 6, instead of 22n, or put another 22n in parallel with the existing one & see if you like it.

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PostPosted: Wed Dec 05, 2012 9:34 pm 
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I will try the 22nF cap in parallel first I think - thanks for that.

Now, I need to build a cabinet for it.


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PostPosted: Sat Jan 12, 2013 2:21 am 
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FYI the recommended way to get more bass in a Hiwatt (hence also a Triwatt) is to replace the .001uF cap in the tone stack with a .022 or even .047.

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PostPosted: Sat Jan 12, 2013 8:38 pm 
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Would that be C6 or C8?
The objective was to get more bass when the OD was engaged. So we were looking at ways when only the OD switch was on.

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PostPosted: Sat Jan 12, 2013 11:00 pm 
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Correct. I find the sweet spot is when it's cranked and the power tubes are cooking, but I keep being asked to turn down. When I turn down, I bring the overdrive up to try and compensate for the power tubes not being worked as hard but I find the low end drops.

Perhaps I need to look into building an attenuator...


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PostPosted: Sun Jan 13, 2013 12:16 am 
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Did you ever try a 47n cap off pin 6?

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PostPosted: Sat Apr 13, 2013 2:11 pm 
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frethead wrote:
I will try the 22nF cap in parallel first I think - thanks for that.

Just remember that with all amps it's generally advisable to limit bass when running high gain, so that you don't get mushy or farty tones.

frethead wrote:
Also, any other ideas on changes to warm up the tone a bit?

Try different tubes, such as Mullard 12AX7s in the preamp (even the current production fake Mullards will do the trick). KT66s in the power stage will also fatten up the whole sound.

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PostPosted: Sun Apr 14, 2013 8:58 am 
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"Try different tubes, such as Mullard 12AX7s in the preamp (even the current production fake Mullards will do the trick). KT66s in the power stage will also fatten up the whole spectrum.."

Great suggestion.

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PostPosted: Sat Jan 11, 2020 4:54 pm 
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zaphod wrote:
FYI the recommended way to get more bass in a Hiwatt (hence also a Triwatt) is to replace the .001uF cap in the tone stack with a .022 or even .047.


Would that be C6 or C8?

Just looking to beefen up the lows since I still find them to be on the weak side. Could be due to my lower playing volume. Still, it doesn't hurt to try some stuff out.

Thanks in advance!


Last edited by Gertjan2411 on Tue Jan 14, 2020 1:34 pm, edited 1 time in total.

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PostPosted: Sun Jan 12, 2020 10:24 am 
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Change C6 to 47n

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PostPosted: Tue Jan 14, 2020 1:40 pm 
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Thanks Stephen! That did the job.
I ordered a 22nf and a 47nf cap.
Ended up using the 22nf since the 47nf was a bit too much.
Figured it would be overkill in a band mix at loud volume.

I also ended up changing the PI to a AX7 tube which I prefer opposed to the AT7. Sound a little fuller/more aggressive. It's giving me more sustain without adding crunch. I guess this is also due to the fact that I don't play very loud. It's giving me more compression at lower volume I guess.


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PostPosted: Tue Jan 14, 2020 1:48 pm 
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:thumbsup: :thumbsup:
Great!

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PostPosted: Tue Feb 04, 2020 2:52 pm 
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Just thinking out loud/random food for thought: from working with DIY hifi/stereo playback (as opposed to guitar-specific electronics), I've found that bass perception doesn't always mesh with reality. In particular, I've both experienced and seen a lot of subjective comments from people perceiving a reduction in bass when moving from component A to component B, when in reality, there is actually more or at least improved bass. There is a notion that as bass tightens up, it can be perceived as being reduced. Said another way, even if the bass doesn't go deeper or bass frequency amplitude isn't increased, if the bass is better "controlled", then it may "feel" reduced.

...Or maybe that's all just audiophile nonsense. :)

I feel like I've read anecdotal accounts of Hiwatts actually being used as bass amps?

Still, I'm curious what the modeled/predicted frequency response from a Hiwatt look like compared to other guitar amps. It would also be interesting to see measured frequency response plots from Hiwatts versus other amps through the same speakers and level matched. I guess you'd have to take multiple readings with the tone knobs in various locations.


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PostPosted: Tue Feb 04, 2020 4:22 pm 
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Matt, I have to agree. I run AVA pre and power amps (SS) into Salk Songbirds. The 'Birds define the bottom end so well I don't realize how "loud" the bass is until I step outside and hear the thumpin'!
Also, some people don't realize at low volumes, to sound right to a lot of people, bass has to be boosted, i.e. using the "loudness" switch or the low band control of an equalizer. Ain't psycho-acoustics strange :bugeye:

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PostPosted: Thu Feb 06, 2020 11:52 am 
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Two response graphs for you to peruse!


STANDARD TRIWATT TONE STACK C6 at 1n

Attachment:
Hiwatt _std.JPG
Hiwatt _std.JPG [ 67.74 KiB | Viewed 419 times ]



TRIWATT TONE STACK WITH C6 at 47n

Attachment:
Hiwatt _c6_47n.JPG
Hiwatt _c6_47n.JPG [ 63.39 KiB | Viewed 419 times ]

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PostPosted: Thu Feb 06, 2020 3:18 pm 
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Stephen,

Thank you for posting those. Is that modeled or measured data?

What do the different colors represent?

If it's easy for you to generate those kinds of plots for your other amps, I'd be interested in seeing them!


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