50W 12xxx spec preamp, not enough gain

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Carbia
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Re: 50W 12xxx spec preamp, not enough gain

Post by Carbia » Tue Feb 23, 2016 11:52 am

Even with impulses, you probably noticed that the gain is more that the gain you're hearing live :wink:


About sounding more VH1... 50w vs 100w is one important difference. With 100w the bass is tight and the amp sounds less compressed and bigger.

About the excesive brightness... I don't have bright cap on my '71 Super Lead and I like it, but it depends on the amp. A friend of mine has a '76 that sounds great with 4n7 bright cap and a '70 that sounds horrible with 4n7 and great with just 100pF.

Later I'll record an small clip with my '71 to let you see how much gain it has. I will record with a LP with minihumbuckers (sorry, no humbuckers in da house) but you can make yourself and idea.

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Re: 50W 12xxx spec preamp, not enough gain

Post by fhn_lopes » Thu Feb 25, 2016 12:59 pm

Nice Carbia, please do It!! I'd love to hear your amp.

I had those Redwirez impulses, very nice, but the clips I did were very faithfull gainwise, strange... As I said, it's not VHI but it has enough gain for me anyways... maybe recorded it will be oversaturated... will know only if I manage to record it the correct way.

When you say bright cap you mean the bypass cap over the mixer resistors or the cap across the volume pot?

I'm using 470pf for the mixer bypass and 4n7 at the volume pot... the amp has 2 bright channels, one is "stock" 2k7/.68 rk/ck, 500pf mixer bypass, no cap across vol pot.... the other is 12xxx 820/.68, 470pf mixer bypass (didn't have 500pf arround) 4n7 across Vol pot. Both channels have 22n coupling after 1st stage.

I like the tone now, even a bit brighter, it's not bothering me with a Les Paul... I have to fix my strat though and test if it's going to be too bright for her.... it's not playable right now :lol: :lol: :lol:
76' JMP 50w w/ 71' metro board
93' Fernandes SSS strat
93' Fender Japan HSS Strat
4x12 w/ 2x 25w rola creambacks /2x 25w m75 Scumbacks

5150Watts
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Re: 50W 12xxx spec preamp, not enough gain

Post by 5150Watts » Thu Feb 25, 2016 1:27 pm

motrock wrote:
Last little trick... set amp to 8ohms and plug in to 16ohm cab. That adds extra.
Is that safe to do?

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Re: 50W 12xxx spec preamp, not enough gain

Post by jnew » Thu Feb 25, 2016 1:35 pm

Amp on 8 ohms into 16 ohm cab is fine. Been doing it for years

The bright cap I'm talking about is the one across the Volume pot.
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5150Watts
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Re: 50W 12xxx spec preamp, not enough gain

Post by 5150Watts » Thu Feb 25, 2016 1:42 pm

So what causes the extra sizzle when you do this?

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Re: 50W 12xxx spec preamp, not enough gain

Post by jnew » Thu Feb 25, 2016 1:55 pm

It decreases headroom and let's the power section saturate and compress very nicely.
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Re: 50W 12xxx spec preamp, not enough gain

Post by Carbia » Thu Feb 25, 2016 2:43 pm

And roll off some highs IMO
Last edited by Carbia on Fri Feb 26, 2016 3:06 am, edited 1 time in total.

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Re: 50W 12xxx spec preamp, not enough gain

Post by Carbia » Thu Feb 25, 2016 3:02 pm

Here is my 71:
https://soundcloud.com/josecarbia/71-super-lead

It's a LP Deluxe. The amp is vol bright 10, vol normal 0, treble 10, mid 10, bass 0, presence 5

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Re: 50W 12xxx spec preamp, not enough gain

Post by 5150Watts » Thu Feb 25, 2016 3:12 pm

I just tried it on my 2203. It does sound better.

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Re: 50W 12xxx spec preamp, not enough gain

Post by jnew » Thu Feb 25, 2016 3:17 pm

Yeah, shaves off any harshness in the highs and takes out some boominess in the lows.
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Re: 50W 12xxx spec preamp, not enough gain

Post by motrock » Thu Feb 25, 2016 9:31 pm

I agree on the 8ohn trick. Thanks btw jnew! ;-)

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Re: 50W 12xxx spec preamp, not enough gain

Post by jnew » Thu Feb 25, 2016 9:32 pm

:thumbsup:
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Re: 50W 12xxx spec preamp, not enough gain

Post by jculb69 » Mon Feb 29, 2016 7:57 pm

I just tried the 8ohm tap w/16ohm speaker on my 50watter. I'm amazed at how much better it sounds! I wish I had done this years ago. Thanks!

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Re: 50W 12xxx spec preamp, not enough gain

Post by fhn_lopes » Mon Mar 07, 2016 6:14 am

Did the mods, and the 8ohm trick. Really nice but still feels too bright and too bloomy at the low end, but the punch and the depth are way bigger now... If I set the bass pot closer to 0 I can get a tighter sound but it kills a bit of the "body" of the whole tone, it affects not only the bass response, that's interesting.
I'm seriously thinking of adding a pot instead a 100k resistor at the NFB, the changes in overall tone are brutal.. this deserves more love :lol: :lol: I can dial an EVH tone that's usefull for that alone but I need a "more controled" tone for my band (national pop rock). Also thinking of removing the bright cap as the gain increase wasn't so big...
Here's a clip I recorded with my cellphone... everything on 10 except channel 1 volume... guitar is a LP classic (not a VH guitar) with a BKP VHII in the bridge position.
Sorry about my terrible playing and the crappy cellphone audio. The volume was a bit above bedroom level so it's highly atenuated. I can hear nunaces I didn't have before, I'm enjoying this now :vh:

https://youtu.be/_m_cxrAsSTM
76' JMP 50w w/ 71' metro board
93' Fernandes SSS strat
93' Fender Japan HSS Strat
4x12 w/ 2x 25w rola creambacks /2x 25w m75 Scumbacks

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