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PostPosted: Thu, Sep 06, 2018 10:04pm 
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Supah Stah
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psychodave wrote:
FourT6and2 wrote:
psychodave wrote:
It simply changes the impedance of the pot. I personally don’t like this since it makes the tone weird. I read the technical posts on SLO forum... ;)


Eh?

I like it. Tightens up the amp. Brings out the snarl. 68K is too low for standard/drop d though.



Years ago Mike and I were chatting about this and I ended up putting it on my BE clone. It definitely makes the amp tighter. I know people also throw a resistor across the gain lots on stock JCM800’s to change the pots impedance and tighten up the amp. I remember talking to Cameron about this and we both agreed it chokes the amp in a way I never care for. I’ll try find a video I made of that amp. I seem to remember turning that “feel” pot I had added.


Funny. Because I've seen it in in a few Camerons. ;) Not a pot. Just a resistor. I like it. You can compensate buy turning the gain up a bit. Keeps things tight and adds a bit of aggression. Put it on a switch and you can get the best of both worlds.

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PostPosted: Thu, Sep 06, 2018 10:15pm 
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psychodave wrote:
It simply changes the impedance of the pot. I personally don’t like this since it makes the tone weird. I read the technical posts on SLO forum... ;)


Yes true, it does change the impedance. However what its mainly doing is changing the cutoff frequency of the high pass filter.

The coupling cap (usually 0.0022uf in this spot), and the 1M gain pot, not only block dc between stages, and control the gain, but they also form a RC high-pass filter.

0.0022uf + 1M have a cutoff frequency of 72.34Hz

So if you add say the 82k across the 1M you get 75.79k

0.0022uf + 75.79k has a cutoff frequency of 954.52HZ


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PostPosted: Thu, Sep 06, 2018 11:56pm 
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CrazyNutz wrote:
psychodave wrote:
It simply changes the impedance of the pot. I personally don’t like this since it makes the tone weird. I read the technical posts on SLO forum... ;)


Yes true, it does change the impedance. However what its mainly doing is changing the cutoff frequency of the high pass filter.

The coupling cap (usually 0.0022uf in this spot), and the 1M gain pot, not only block dc between stages, and control the gain, but they also form a RC high-pass filter.

0.0022uf + 1M have a cutoff frequency of 72.34Hz

So if you add say the 82k across the 1M you get 75.79k

0.0022uf + 75.79k has a cutoff frequency of 954.52HZ


The 82k is in parallel with the shunt resistance only; the series resistance remains the same. So the cutoff freq depends on the setting of the gain 1 pot.

The resistive load (in this case, gain 1 pot and whatever resistor is in parallel with it) determines the AC load line and thus the gain of the preceding stage. So changing the resistive load (by adding some parallel resistance) will reduce the gain of the preceding stage.

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PostPosted: Fri, Sep 07, 2018 12:40pm 
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Guys, it does all three things at once. So it's a cool way to tune the stage and give players some additional means of EQ'ing the distortion itself. Put it on a switch and if you don't like it, you can always just not use it. But I find it comes in handy for really heavy, aggressive sounds. 2203/04 amps are not exactly "tight." But with this resistor or control, you can tune the feel of the distortion to match your level of aggression. For '80s cock rock? Meh. Don't need it. For more modern stuff, especially de-tuned guitars, it's helpful. I think a lot of people who have Chupacabras or Yetis ignore this push/pull. Engage the 82K on Gain 1 + bright switch to boost the mids (not the highs), then push Gain 2 up high with Gain 1 lower to keep the bright cap in play, and you will get some really angry, crushing, tight modern sounds...

Without a boost pedal.

A pot is more useful than a fixed value. Just a matter of making sure there's room to mount it. Otherwise, simple enough to literally solder one resistor across a pot lol. It's so cool how many of these famous mods are actually quite simple. Solder some diodes across the MV? Boom, built in distortion pedal lol. Solder a resistor across the gain pot? Boom, built in tube screamer. Throw a 4700pF cap across the gain pot with a switch and you've got an upper-mid gain boost that becomes variable with gain setting. Give it a cool name like "Annihilation" and you've got yourself an amp business. ;)

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PostPosted: Fri, Sep 07, 2018 1:06pm 
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^^ Agreed


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PostPosted: Tue, Sep 11, 2018 10:16pm 
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Hello, I didn't see any posts about it so I will mention that Friedman uses a bypass cap in parallel with the 100k load resistor of the cathode follower in many of his amps. It bleeds signal to ground. That is a big contribution to the smoothness of those amps, especially with the plate resistors being bypassed as well. Compare the Steve Stevens model schematic and clips to the JJ and BE and you should see and hear the difference some of those components make. I've seen 500pF up to 2200pF bypassing that 100k load R. You can use larger value grid stoppers at V1B and V2A to cut the brightness as well as the caps from coupler or input grid to ground, Plate R bypasses and caps from plate to cathode. The listed bypasses all send signal to ground, some directly and some through the power supply.


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PostPosted: Wed, Sep 12, 2018 8:29am 
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CoffeeTones wrote:
Hello, I didn't see any posts about it so I will mention that Friedman uses a bypass cap in parallel with the 100k load resistor of the cathode follower in many of his amps. It bleeds signal to ground. That is a big contribution to the smoothness of those amps, especially with the plate resistors being bypassed as well. Compare the Steve Stevens model schematic and clips to the JJ and BE and you should see and hear the difference some of those components make. I've seen 500pF up to 2200pF bypassing that 100k load R. You can use larger value grid stoppers at V1B and V2A to cut the brightness as well as the caps from coupler or input grid to ground, Plate R bypasses and caps from plate to cathode. The listed bypasses all send signal to ground, some directly and some through the power supply.



Yeah, some are even lower 100pf, 220pf, 330pf, etc. Some people remove these because they don't like the smoothness. Most Jose style amps don't have them, although some have one in different spots, such as a 1nf after the first stage to ground.


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PostPosted: Wed, Sep 12, 2018 10:31am 
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Could anyone here tell me what value the first dropping resistor (feeding the PI node) is or list the entire dropping string in the CCV power supply? I don't see the first one in gut shots, but the others appear to be 10K.


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PostPosted: Wed, Sep 12, 2018 12:35pm 
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CoffeeTones wrote:
Could anyone here tell me what value the first dropping resistor (feeding the PI node) is or list the entire dropping string in the CCV power supply? I don't see the first one in gut shots, but the others appear to be 10K.


10k


[47uf pre node] - 10k - [47uf cath follower node] - 10k - [100uf PI node] - 10k - [100uf screens] - Choke - [100uf Main]


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PostPosted: Wed, Sep 12, 2018 1:11pm 
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CrazyNutz wrote:
CoffeeTones wrote:
Could anyone here tell me what value the first dropping resistor (feeding the PI node) is or list the entire dropping string in the CCV power supply? I don't see the first one in gut shots, but the others appear to be 10K.


10k


[47uf pre node] - 10k - [47uf cath follower node] - 10k - [100uf PI node] - 10k - [100uf screens] - Choke - [100uf Main]

Thank you.


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PostPosted: Wed, Sep 12, 2018 3:25pm 
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CoffeeTones wrote:
Hello, I didn't see any posts about it so I will mention that Friedman uses a bypass cap in parallel with the 100k load resistor of the cathode follower in many of his amps. It bleeds signal to ground. That is a big contribution to the smoothness of those amps, especially with the plate resistors being bypassed as well. Compare the Steve Stevens model schematic and clips to the JJ and BE and you should see and hear the difference some of those components make. I've seen 500pF up to 2200pF bypassing that 100k load R. You can use larger value grid stoppers at V1B and V2A to cut the brightness as well as the caps from coupler or input grid to ground, Plate R bypasses and caps from plate to cathode. The listed bypasses all send signal to ground, some directly and some through the power supply.


Yup, I'm aware. I don't much care for the Friedmans I've played. Too smooth. Too dark. Too much high-end rolled off. I like a more aggressive, angry sound. Just without the harsh high-end fizz and the "beamy" presence like you have your ear right up on the speaker grill cloth.

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PostPosted: Wed, Sep 12, 2018 4:47pm 
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CoffeeTones wrote:
CrazyNutz wrote:
CoffeeTones wrote:
Could anyone here tell me what value the first dropping resistor (feeding the PI node) is or list the entire dropping string in the CCV power supply? I don't see the first one in gut shots, but the others appear to be 10K.


10k


[47uf pre node] - 10k - [47uf cath follower node] - 10k - [100uf PI node] - 10k - [100uf screens] - Choke - [100uf Main]

Thank you.


:aww: i saw
90uf main
choke
90uf screens
20k
180uf PI


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PostPosted: Wed, Sep 12, 2018 4:54pm 
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nico22 wrote:
CoffeeTones wrote:
CrazyNutz wrote:
CoffeeTones wrote:
Could anyone here tell me what value the first dropping resistor (feeding the PI node) is or list the entire dropping string in the CCV power supply? I don't see the first one in gut shots, but the others appear to be 10K.


10k


[47uf pre node] - 10k - [47uf cath follower node] - 10k - [100uf PI node] - 10k - [100uf screens] - Choke - [100uf Main]

Thank you.


:aww: i saw
90uf main
choke
90uf screens
20k
180uf PI


Yeah, thats the thing, there are different versions. Those 180uf's that he used at one point will make little difference from 200uf, or 220uf.

Looks like he even used one of those 180uf's for the elevated heaters, which is WAY overkill.

In my opinion, he got a super good deal on a big lot of those 180uf, and just used them everywhere he could. Just speculation.


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PostPosted: Mon, Sep 17, 2018 9:33am 
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Hello again. Can anyone explain the purpose of the box cap and resistor connected to what appears to be the cathode of the power tube in the CCV? I have not had access to the CCV but have seen those components in a few pictures. :confused:


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