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ewizard

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    As a young boy I was always intrigued by music. Finally in 8th grade I acquired an acoustic guitar and some lessons offered at my school. That was juts the beginning. Fast forward 10 years and I am doing sound engineering and tech for sound companies through my company! All because my band broke up and I had all the equipment. I also teach guitar lessons to young students and my personal work focus is on providing sound for charitable organizations. I enjoy motorcycle racing, music, building guitars and amps as well as tinkering with other guitar electronics.

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  1. Did some more testing. Progress has been made! I was correct in my assumption that the .047 value in the feedback loop ( C58 ) Is too much. I figured initially that since it feeds the tone stack it would maintain bass. It does, but only that which is not controlled through the feedback loop. The feedback loop takes into consideration the value of that cap and what is not reduced or controlled in the feedback loop sails through and in this case made the bass strong, but also a little bit woofy. I was curious because I had bass, but it seemed to low in the mix and then once you got the bass to show up by knob twisting it was too boomy. I decided to place the C58 cap back to stock and make an earlier coupling cap .047 instead. This was a very fruitful choice. The bass was instantly solid and more even. I made C1 .047 and am still in debate as to whether or not it may still be too much bass? I also decided to play around with the choke circuit a little more. My biggest pet peeve with the amp was the high amount of fizzy top end. Seeing as how I seemed to keep going back to stock for most things I decided to put the R10 resistor back in it's spot. I left the choke installed knowing it would not change things much at all. Interestingly having the R10 resistor in it parallel with the choke reduced even more fizz without effecting the thump and tightness of the amp! I left it in place. It only slightly changes the bias voltage a little colder ( less voltage means longer tube life ) so I had to bump the voltage back up a little to keep the same bias point. Easy to do and it helped with my goals. At this point I am the happiest I have ever been with the amp and am in consideration of making only one coupling cap .047? I will wait and see. In my amp reducing the bias voltage has the effect of increasing highs and reducing a little bit of warmth. I have yet to try a colder bias to see if it will tame the bass that I am currently in question of. It has a very good balance right now with all knobs at the 12 noon position for tone, resonance and presence. Obviously different cabs will have a different sound, but it should be much more tuneable now. So to recap on what I have done: 1. Bias Mod is a must, I have an 870 ohm resistor in R68 to have a voltage range between 30-60 volts. 2. The choke mod is super easy ( although you must remove the Circuit board to install the choke ) and is highly recommended. Leave the R10 resistor in place and simply wire the choke around it. I would still move the standby circuit as noted in an earlier post. 3. A hybrid 5150 and 6505+ pre gain circuit works great. I simply changed C2 from the stock .001 to .022. This makes for a more solid and punchy sound while still having the saturation that the 5150 ii/6505+ is popular for. The original 5150 gain is too aggressive for me. 4. I placed a 10pf cap across R88. This tames just the very high end fizz. You can go higher, but I feel anything higher than 47pf may be too much? 5. The screen grid resistors is a must do if you want a warmer, less tight amp. Changing R203, R205, R207 and R209 ( the screen grid resistors ) is a great way to loosen up the amp and tame high end content. The stock value was 100 ohms. I went with 1K ohm resistors instead. 500 ohms would also be a good compromise. If you want to be able to run El34's in the amp you will need a value of 700 ohms or higher. This softened things up a bit, but when the choke goes in it tightens back up. 6. I placed .022 caps around C1 and C56 to make a total value of .047uf for those caps. This adds bass and thump, but perhaps too much? That is up to you. I think that with a standard 6 string at normal tuning this would be ideal, but if you have extended range instruments or use a drop tuning it may be a little much? I am considering removing the one located at C56? 7. The clean circuit is rather nice. I simply cut one leg of C27. This makes the clean channel truly a clean channel. The crunch channel stays the same though and you won't be able to switch back and forth. I don't mind this, but there is a way to fix that if you desire. 8. I removed the FX loop. It has it's shortcomings although from a performance standpoint is rather transparent. Lifting R79 and C49 so that you can place a wire from the master volume lead to the PI input will make the amp perform a little more normal. There is no longer any bleed when the volume is all the way down, the volume is more usable and perhaps a tiny bit of high end is tamed. I am contemplating putting it back in, but I do not like the bleed and I do not like the increase in level. Perhaps placing a 12AU7 would take care of the hair trigger volume that the amp has in stock form? I am looking at different tube FX loops to see other solutions. I would like to have an FX loop, but want it to perform better than this one. Time will tell. The Bias point as mentioned before is not a deal breaker for this amp. Whether it's hot or cold makes little difference. I found that mine, when ran hotter ( closer to -39 to -40 volts ), was a little warmer sounding and the highs were tamed, but it shortens tube life and may add too much low mids to the sound for others? Some like the colder bias where crossover distortion is introduced. Running a colder bias actually yields higher headroom and less power tube breakup. The trade off is that crossover distortion, if there is a lot of it, will make a truly clean sound not as easy to have.
  2. Some more info. So I wanted to play around some more with seeing how this amp really ticks. I can tell you for fact that it's the local negative feedback in the last stage before the tone stack that makes this amp what it is. You can really tweak this thing a lot just in that stage alone. However it really only sounds good in near stock form. The local negative feedback is pretty unique, but isn't unlike a cathode follower. Although the signal comes off the plate ( typically high impedance ) it greatly reduces distortion in that stage, increases bandwidth while also flattening response and creates a lower impedance driver to push tone stacks, or effects loops. I decided to eliminate the feedback loop to see how the amp sounded. Holllllly hellllll there is a lot of saturation, lots of bass and the highs are about demolished. So the feedback loop is absolutely essential for this amp to work. It also has the effect of compression ( also similar to a cathode follower ). I would say the difference between the local negative feedback circuit and a CF circuit are that the CF circuit makes the amp a little warmer while the LNF circuit seems to extend and flatten the tone. I didn't stop there. I realized that the feedback in the LNF can be altered and even tone shaped. So I increased the feedback by using another 1meg resistor parallel to the current one in the loop essentially making 500k. Low and behold it reduces the distortion even more and increases bass and reduces highs. The problem is that it significantly reduces the level of the amp. It wasn't exactly the sound that you wanted either. A bit mushy as you had to increase the pre gain to get saturation back and by then it sounds highly saturated but loose and just not appreciable. The next thing I did was to decrease the feedback gain. I didn't have anything larger than 1meg and new that much less feedback wasn't going to improve anything, but for the study, I had to try. The LNF stage is unbypassed ( no cap around the cathode bias resistor ), so I knew I could get more gain there. A 22uf polarized cap should do the trick to fully bypass the cathode resistor. What does it do? Well it further increases saturation ( because of less effective feedback ) which makes sense, but it also reduces frequency control adding emphasis to certain frequencies. It also has the effect of making the level of saturation vs compression too distant. The saturation is really there and it's so un-compressed that it just seems off. The less feedback the more open loop gain which means more volume, less frequency control and less compression. Of course too much feedback and the other components in the circuit effect the frequency response greatly beyond what the loop can control. I Knew there was one more way I could effect tone in just the loop portion of the stage. I removed the Cathode bypass cap and I am now back to stock. If I place a cap around the feedback resistor ( which is R88 for reference ) I can increase the highs in the feedback loop thereby reducing them. I ultimately ended up using a 10pf ceramic cap around R88 to just tame the really high end fizz. I didn't have a good selection of other low pf value caps, so my options were limited. I would say that 10pf is as low as you would desire and 82pf is perhaps going to be too much? A 47pf with a resistor to control it's effect may be the sweet spot? But wait, there's more! Looking at the circuit I saw R24. This is as far as I can tell nothing more than a low/cut shelf with the effect of setting the gain of the channel into the tone stack. 47K is pretty low in value really so it should be a pretty decent change in level right? Well it does take some level away ( perhaps 2-3db, so not a whole lot ) but removing it also increases bass. For me it was too much of a difference. I wouldn't mind having the level increase, but the bass was a little too much, but only just a little. It may be ideal for others to remove R24? The R/C network next to R24 which is C59 and R94 is technically a High Pass circuit, however in conjunction with R89 it forms a low pass circuit instead. Cutting one leg of C59 increases mids and highs unfavorably to me. I suppose you could mess with R89 to further tweak the channel? My bet is that lowering the resistance from 470k will increase level, but may also effect tone a bit? I have yet to try that though as I am happy with the amp right now. I also decided to see what removing C19 would do. Leave it alone........ It helps the lead channel a lot. My thought was that it would allow a slightly bigger sound at lower gain settings; NOPE. It sounds fuzzier, but that's just it; it sounds fuzzier all the time too. The entire lead channel is nearly perfect as it is. I in the end have only placed a 10pf cap around R88 and I am now debating removing the extra .022 cap I placed in parallel to C58 and moving it to C57 instead. In retrospect The .047 value in the feedback loop probably effects the lows too much. I have yet to test that.
  3. it is near the pre gain pot for the clean/crunch channel.
  4. There is a way to make the clean and the crunch be more in line with each other, but i'm not interested in that. I am more of a 1 channel guy. But if I'm going to have an amp with at least 2 real channels, I want two real channels. As far as I'm concerned the amp in stock form was a 2 channel amp. The clean was about useless. Now at least the clean is clean and the crunch is crunch. So perhaps still really a 2 channel amp, at least you can decide between full clea or a crunch and a lead channel. Instead as before where it was a crunch and a lead channel.
  5. Again some more noteworthy Information. I decided to play with the clean channel now. It has this nasty box like , nasally sound when the pre gain knob is turned down below 5. I have always known that the amp employs a high pass circuit that surrounds the pre gain knob. It basically allows some mids and highs to sail past the pre gain knob at all times. So when the knob is turned down you are still getting strong signal from the upper frequencies. It is what makes the clean channel not so clean. I decided to eliminate that part if the circuit. The result, very nice! Removing C27, or simply cutting one leg and lifting it away makes it so all signal must pass through the pre gain pot. This means that even with low pre gain settings there is nothing sliding past it. Basically you now have a true clean channel. The clean channel is well designed and has a fender like sound to it. Very round and punchy. The post gain can be turned up all the way and the channel will still be quiet and clean with low pre gain settings. I like it. I have a 2.5 channel amp now. So there is a down side. The crunch channel of the amp is more usable, but you won't be able to have a clean and crunch you probably want? The level difference between the two is going be too much. At this point you either have a crunch or a clean channel, don't plan on having both at your disposal. The only real upside to cutting C27 is that each one is more usable, hence the 2.5 channel amp. You can have lead and clean, or lead and crunch, but not all three.
  6. Some new info about the 6505+. There is some questions about the effects loop in the 6505+ head. It is not friendly to rack type effects units and is meant more for pedals. This is fine and all, but many people usually end up with added hum and some form of change in tone not related to the effect itself. The nature of the loop lends it to be susceptible to noise and is picky about some other things. Another small complaint about the 6505+ head is that it does not bode well for bedroom level playing and even if you turn the post gain all the way down while in the lead channel, you can still hear the channel coming out through the speakers. Many believe this is inductance from the FX tube picking up signal from the lead channel. I can tell you that is not the case. My discoveries are as follows. I had suspected that the FX loop was the bulk of some issues in the amp in terms of sound. It is, but only minimally. The FX loop on it's own ( with nothing in it's path ), be it bypassed or not is rather transparent actually. It does add a small amount of high end and adds to that nasal bark of the amp. The design is such that even when the FX loop is bypassed, it is still actually almost entirely in the signal path. My first test was to see if the FX loop tube was the cause of the bleed from the lead channel when the post gain was all the way down. I simply pulled the V3 FX loop tube and turned the amp on. The amp will of course not pass signal because the recovery stage of the FX loop is what feeds the PI to the amp. Well I still got bleed into the amp and I could hear the lead channel still! It is not the V3 FX loop tube responsible for the bleed. My next task was to bypass the FX loop entirely. Pretty easy really. Simply pull one lead of R79 so it's free of pin 7 on V3 and then remove C49. Now simply patch a short wire from V3's pin 7 and splice into the connection at C49 that goes towards the PI tube of V4. The channel switching of the amp for lead to crunch will not work unless the tube is installed and I am not to sure why? It shouldn't matter, but it does. I would desire to leave the tube any way to preserve the current draw from the PT. You could at this point use different tubes like a 12AU7 to impact the draw on the heaters and see if it alters tone? So what happened when I removed the FX loop entirely? The amp was rejuvenated! A little more fizz was eliminated and there seemed to be a small amount more low end. Although minimal as the changes were ( the FX loop was rather transparent ) there were some pluses. The on off switch of the post gain for the lead channel was eliminated and is actually usable now. So now you can have bedroom level playing without total tone obliteration. The bleed into the PI was basically eliminated. This is thanks to lifting ( I believe ) R79 so that signal no longer passes through the crazy network of resistors and caps in the FX loop. I don't really ever use FX anyways and the horrible nature of this amps FX loop left me little desire to even keep it. I left it out as I can now have a very acceptable sound with all tone, presence and resonance knobs at the 12 noon position. I can run the post gain up to 2 and still be at a level that is just above bedroom playing status and the amp in general is more evened out. I should also note that I paralleled .022 caps to C56 and C58 essentially making them both .044mf. this adds a small amount of low mids. This is not as noticeable as I thought it would be. I bet that the signature tone of the amp starts earlier in the preamp? Here is a rundown of what was done and the effect it had. 1. Removed the FX loop tube V3 to discover it is not the source of bleed into the PI from the lead channel. 2. Completely bypassed the FX loop by removing R79 and C49 and then patching a short wire between pin 7 of V3 to the side of C49 lugs that goes to the V4 PI tube. 3. Removal of effects loop eliminates 99% of bleed from lead channel into the PI and power amp. 4. Removal of FX loop makes the channel post gain knobs ( especially the lead ) actually usable and bedroom level playing in now possible with no real loss in tone. 5. Removal of FX loop does tame a small amount of highs and evens out the tone a little more. The FX loop was actually very transparent, however it's design was susceptible to issues when used in some circumstances ( not all ). 6. I paralleled .022 caps to C56 and C58 to find only a small increase in low mids. Not as much girth as I hoped. I believe that the bulk of the tone shaping is earlier in the preamp. 7. One other thing I should note is that the crunch/clean channel is REALLY bassy now. It has a lot of girth added to it. I believe that the FX loop is what tamed it down to begin with. The lead channel already lacking in the LOW end girth in comparison to the crunch channel, probably was left alone in the FX loops R/C network? I am a one channel guy anyway. I got the amp for one reason and one reason only. This issue may not be of concern for most?
  7. The new board only allows 2000 characters..... there is more. A rundown of what I did: 1. Replaced C2 with a .022 cap. The stock value was .001. This adds girth to the lead channel. 2. Replaced the stock Screen Grid resistors with 1k 5watt ceramic resistors. The stock value is 100 ohms. The higher value means less highs and spongier feel. 3. Set the R68 resistance to get the bias pot range between 30-60 volts at the test points. I have 870 ohms at the moment. You will have to find the value you will need. lower value means lower voltage. I set my bias at 45 volts. This is a little low and allows crossover distortion. I like it here. You can set to your liking as long as the tubes don't red plate at performance volume. Remember the lower the voltage you run them at, the shorter your tube life will be. The higher you run them, the longer you r tube life will be at the expense of crossover distortion. 4. Replaced R210 with a Mercury Magnetics choke for the 6505 series amp. Simply wire it in. You must however move the standby switch to be in the B+ secondary side. Cut the wire from the F1 jumper and place the standby switch between there. 5. Cut one leg of C158 which is the Fx recovery bypass cap. It adds highs and is not really needed. I won't get into the specifics on how to make these changes as I feel that if you don't know what I'm talking about or how to go about doing them, you probably shouldn't be trying to. As always perform these tasks at your won risk. have fun and rock on. All that being said. The very first mod I dis was the Bias mod. It did help, but not enough. I tried going to the 5150 spec. This was not the trick either. Then I decided to do a more detailed and exacting approach. So with the bias mod intact I did the 5150 mod. again to see what I liked about it. I found the big change was at C17. Thta change is what makes the 5150 that amp and the ii series what they are. The C2 cap basically allows to shape the EQ for the rest of the preamp. My finding was that C2 is a great place to add bottom end if you want to keep the smoother grind of the ii series amps. The C158 is totally up to the user. It really is not a deal breaker. It adds highs ( or at least allows highs to pass ) and I find it to be not needed. The Bias circuit is sensitive to the biggest thing you can do to to the feel and change in sound to the amp. The Screen grid resistors are truly where it's at. The stock value is a meager 100ohms. This is fine, but it makes for a very stiff and highly processed sound. Great for djent or other very tight music. For the in between it is very un-inspiring and emotionless. With the 1k screen grid resistor you get some looseness and of course the high end and fizz is diminished. I wanted an mp that was tight, but still had emotion and feel. So the SG resistors to mee made the amp a little too loose. This is fine as I knew I could tighten it back up. I had wanted to do a choke mod for some time and this was the perfect excuse. There is some varying ideas on what a choke does. Many say it simply changes the feel of the amp. What that means is up for debate? Loose, tight, spongy, more or less bloom, all that are different was of describing the sound and feel in one word. I find that the amp is looser with higher henry ratings and tighter with lower henry ratings. The highs are really the most effected with the henries of the choke. The higher the rating the more the highs are effected. Less highs get through with a high henry choke. This makes for a looser sound while a low henry choke allows more highs through meaning a more neutral difference in the power supply which means a tighter sound all around. The choke adds tightness to the unaffected frequencies. Remember the choke is not actually a resistor and does it's job through inductance. There is less resistance than the resistor that it replaces which means a more robust supply voltage. This adds to the amps headroom and tightness. The lows become tighter and less flubby while allowing more of it to be there. The highs are resisted by inductance and like a capacitor it is shunted out of the amp. The power supply has less ripple and hum meaning a cleaner, firmer supply of power. This counter acts to some degree the sag introduced by the higher value screen grid resistors. The choke alone will do little to change the overall sound of the amp. It reduces the fizz and highs minimally, but it is in it's feel that it changes. The amp will become tighter all around and the cleans cleaner, while the dirty channel stays basically same while eliminating flubby lows and fizz. For me it set the amp right where I wanted it. The amp has feel and emotion while still being very tight. I may even go to 2k on the screen grid resistors?
  8. So I decided I wanted to improve upon this already amazing machine. I felt that the 6505+ was a bit too tight with a little bit too much high end and of course it's signature nasal characteristic was too much for me. My goal was to loosen the amp up a little and give it more feel, while reducing highs and fizz to make the amp more neutral. The nasaly bark the amp had was also going to hopefully be tamed out as well. I think I have the perfect remedy if this is what your looking for. So just to point out, the BIAS Mod is not enough alone to get what most are probably actually looking for. I feel the BIAS Mod is a must ( actually a requirement if you do some of these mods ). The first thing to do after going back to stock was to change out the screen grid resistors. The stock values of 100 ohms., makes the amp very stiff and bright. The lower the value the more highs and the the tighter the amp feels. The higher the value the lower the highs and the looser the amps feels. I went with the classic 1k 5watt route and that did the trick for me. It tamed a bit of the fizz, butt now the amp was too loose. For reference you can go as high as 5k if you like, while 1k-2k seems to be fairly standard. Many modern amps are sticking them fairly low to tighten the amp up and get that modern sound I think? The screen grid for reference is R2003, R2005, R2007 and R2009 in the attached schematic. So now that the amp was loosened up and the highs tamed, it was time to tighten it back up a little and even the EQ out a little more. This modification requires you to change the BIAS resistor in order to get the range into the correct area. The resistor you have to change is R68 and is located on the BIAS pot board. I ended up with 870ohms if I remember correctly. It may be different for you depending on what screen grid resistor size you go with. You want to change it and get the voltage to be between 30-60 volts when you move the BIAS pot. When I changed the screen grid resistors I had something like 100 volts at the test points, which will instantly make the tubes red plate!!!!!! The next major thing was doing a hybrid 5150 spec change. C17 is the big one that really changes the characteristic of the amp. The 5150/6505 spec here is a .022 cap with a 470k resistor in parallel. This is what really gives the amp that mean distortion. The other half of the 5150 spec is C2. The 5150 has a .022 while the 6505+/ 5150 II has a really small .001. The former is what gives the amp more balls. I simply left C17 stock ( 470pf ) and changed C2 to the .022 that the 5150 has. This added some girth to the sound, while retaining it's smoother distortion. You can get more balls if you want by using a .047 in the C2 position. I Think that it's the 470k resistor in the 5150 that gives it that aggressive distortion. The cap at C17 is in series with the C6 .022 cap and when added with another .022 cap ( like in the 5150 ) would add up to a .044 cap value. This cap is partially bypassed by the 470k resistor. I have yet to test this out, but my guess is that the resistor isn't even needed at the C17 position. The coupling cap at C6 voids any need for another before the gain pot. Any other cap or resistor in that part of the circuit is going to be for tone shaping and gain staging. The next thing on my list was removing the bypass cap on the FX recovery tube which is C158. The value of .0047 allows highs to pass through and is really not needed. It adds to the fizz and high end of the amp. It is nice if you want your FX to sparkle a little more though. I don't think there is any need for it honestly. I simply cut one leg and pulled it up a little. This is a mod that can be done super easily. Next I played with the tone circuit slope resistor and the popular Mid pot bypass resistor. The slope resistor is R28 and in stock form is set at 47k. The lower the value the more lows you get, but then you also start to loose some mid range sweep. The popular range for this resistor is between 68k and 33k. I think that 47k is fine and hits right in the middle ( obviously ). I also did a modification that moves the mid range tone control sweep to a lower frequency range. Basically you place a 47k resistor in parallel with the current 47k resistor at R95. This to me proved to be not worthwhile. It makes the effective resistance of the mid pot around 10k and makes it change frequencies that are lower. I, in the end, ended up leaving the tone stack alone and leaving it stock. The 33k resistor at R28 was too bassy. Any higher and it just brought the nasal sound back. So now I had an amp that was about 90% of the way there. It was still loose sounding, the highs were still a bit much and I didn't have the feel I was really looking for. I still wanted a tight amp, but I wanted it to have a little more touch to it. In stock form the notes literally flew off the fretboard with no real emotion. At this point the amp was a little too spongy and would work great for blues and rock, but it would have a tough time with djent ( for lack of a better term ). The next big trick and real big improvement was to install a choke. A choke, at least for how it's used in amplifiers, is essentially a really big inductor. It has the characteristics of a capacitor in that it filters out rectifier noise and like a resistor it has a resistance. Chokes have three ratings of real concern. It's Ma rating ( how much current it can handle ), it's resistance and it's inductance which is rated in Henries.. Chokes can be used in a couple places of the power supply for different results and desired outcomes. In our case there is only one place it will go. R210 is the resistor that we are interested in. This resistor alone has more to do with the feel of the amp, but also sets the voltage for the for the tube plates and power tube screen grids. The resistor alone does nothing to filter out hum and creates sag. When you hit power chords or other heavy chords, it causes a large voltage swing to flow through that resistor. The resistor does just that and the result is a sag in power to that section of the amp. This makes the amp spongy and have a bit of bloom to the sound. This is great if you like that. To tighten it up you can use a lower value resistor if desired, provided it doesn't allow the amp to run outside of it's designed range.. Or you can install a choke here. The choke has a high enough resistance to keep the amp in a safe operating range that actually increases clean headroom and since the choke is not actually a resistor it doesn't sag, so you get more oomph as well. The choke does however have inductance which has a couple neat effects. The choke resists the flow of electrons, but it does it differently for different frequencies. It does very well at allowing lower frequencies to flow freely and without resistance, but it has much higher resistance to higher frequencies and blocks them out. The Henries rating of the choke determines how much of the highs will get filtered out. The choke I used was a Mercury Magnetics choke made for the 6505/5150 series amps. It is a 250 Ma, 10 Henries and 140 oms ( I believe ) resistance choke. There is more to the choke mod than meets the eye. It will tighten the amp up in a couple ways. It makes the low end tighter, but allows there to be a little more of it and as mentioned cuts out highs. This will further eliminate the fizz. This is dependent upon the henries of the choke though. The lower the value the more highs that get through and the tighter the attack. The higher the henries the less the highs that get through and the looser feeling the amp will have. 10 henries seems to be a fairly magic number, while 3 is on the low end and 10 being more to the high end. Different people have different ideas of what the henries will do. Some think that the higher that value the tighter and vice versa. My experience thus far is that larger values means looser feel and less highs. In either case there are two ways to install the choke. You can do it in parallel to the R210 resistor. This will give you a hybrid of the two of course. Basically you get the filtering of the choke ( reduced hum ) and a little bit a sag ( but less than the resistor alone ). You can simply cut the old resistor out and solder the two leads from the choke in it's place. You can also if you desire, place the resistor before or after the choke and get the spongy feel while also reducing highs. I have a less destructive remedy that allows you to easily switch back and forth as desired without removing the resistor. To do the choke mod you have to move the standby switch into the B+ HT secondary supply . If you don't, you get a loud pop when you flip the standby on or off. Essentially all you do to move the standby switch, is to cut the PT B+ secondary legs, which is the wire that connects to F1 on the circuit board and place it between there. This now frees up the J5 and J6 leads that the standby switch was once connected to. If you solder the leads of the choke to J5 and J6 then all you have to do a place a wire in parallel around R210. This shorts that connection and allows you to switch it in or out if you want. This will introduce the sag back into the supply making the amp bloom more, but you will again have slightly lower headroom. Using just the choke alone means that you can get the clean channel to clean up better and it also makes the lead channel have a little more oomph and girth to it.
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