My new amp...let's wreck it

[tubenit]

when I play out of the amp, it feels and sounds extremely brittle from high mids all the way UP

I think the paralleled triode needs the values changed out ..... or to go back to a single triode? I think those values are creating some brittle tones for you.

And you may need some smoothing caps (plate to cathode) like we use on the TOS.

You might try that "enhance cap" again once more using around 82p - 120p across the LTPI entrance plate resistor?  It has been successful on every amp I've tried it on. Maybe you've changed enough that it would work now?

Originally it had a 500p there, but I "thought" I liked the higher value (.0022).....I could go back to 500p

You can have both by using a relay or mini-toggle and putting caps in series.

With respect, Tubenit

[jojokeo]

SG, this design isn't going to give you the overdriving preamp distortion lead tones you are seeking. But I do have a suggestion or two for you to where you don't have to scrap the whole thing. Atleast the poweramp section. If you're interested PM me and I'll get more specific because it will require several emails going back and forth and I'd also like to keep from having too many cooks offering too many suggestions & opinions confusing things further.
For now - I'm curious for you to try something please? Will you try using that last triode set-up exactly as the third triode is designed in the original schematic? You will therefore be cascading those last two gain stages but the last one is important to use the 10k cathode resistor unbypassed/without a cap on it. Don't forget to put a coupling cap & grid leak resistor between the two stages. Let me know.

[SILVERGUN]

I think the paralleled triode needs the values changed out ..... or to go back to a single triode? I think those values are creating some brittle tones for you.

I agree, but I'm unsure of the math,,,I read a little but it's confusing.....one thing I read was to cut the value of both the plate resistor AND the cathode resistor in 1/2.....but I did like having that bypass cap in there, AND Merlin talked about that "boost limiting resistor" that I have in series there and it did seem to work well at limiting the gain that I received from having that bypass cap,,,,,and made it desireable ( I just don't know how that affects the math either)...........also, it would be very simple for me to remove the paralleled "jumpers" from those pins, and try it again without the additional triode.

I like the idea of the smoothing caps and will take a look at that schematic.

My ears have been taking a beating, so I think some of these "enhancements" are blending together for me.....one mod into another (if that makes sense)
I am most grateful for the fact that you have stuck in there with me throughout this process....thank you again for taking the time from your to-do list
to watch over me and provide encouragement....I am listening

I have a friend who is a great player stopping by tonight and bringing his JCM800 head....we're going to put them side by side through the same speakers, and then I'll truly know where I am......I really wish I could get this damn 4 track to sound decent

[SILVERGUN]

SG, this design isn't going to give you the overdriving preamp distortion lead tones you are seeking.

I am starting to get that feeling, and that's OK...I have time, patience and motivation.....I HAVE TO get better at this.....sadly, it's one of the only real ways I have fun right now......this is something that I've waited a long time to do and I don't expect to get it perfect the first time

For now - I'm curious for you to try something please? Will you try using that last triode set-up exactly as the third triode is designed in the original schematic? You will therefore be cascading those last two gain stages but the last one is important to use the 10k cathode resistor unbypassed/without a cap on it. Don't forget to put a coupling cap & grid leak resistor between the two stages. Let me know.

Yes I will....maybe not tonight, unless my buddy doesn't show up,,,but I'll put it at the top of the list

I (almost) have all the parts to do an equivalent of this amp,,,so if it's replacing the preamp board, that's cool,,,if it's a totally NEW design, that's cool too
I'm not going anywhere, and I want you guys there when I figure this out.......we've only just begun

[SILVERGUN]

Big fun last night....my friend BOB stopped by wearing his rockstar leather jacket and carrying a Marshall JCM800 model 2205- 50 watt head (EL34s), and a very nice stock Gibson SG....I told him to hook up and play at stage volume and give me the real deal...he did, and here's the results:
- This amp has a great midrangy punch that immediately set it apart from the amp I am working on, and I was worried, because this setup really sounded awesome, and I knew he would be plugging into my amp soon.......he had the gain cranked to 8, the channel vol. on 8, and the master on 2, which after a little knob twisting,,,, I too was convinced that this was the best settings for his type of playing (Zep, Sabbath, VH, Guns and Roses, AC/DC, etc, etc)

- We switched him over to my amp and the difference was obvious,,,,we now had much broader low-mids/low freq. response, but the 6V6s were not handling the load, and were breaking up very easily (which was the original intention for using them).....so I decided right away to switch them out for EL34
- I put EL34s in there and re-biased to 35mA, and the result was very real......now we had more headroom, clarity throughout the spectrum, and although this amp didn't have the mid punch of his amp,,,,,,my amp DID have something that his didn't......it stood right up to one of the best rock amps out there, and that felt GREAT!
- We experimented with different value bypass caps, and settled on these:
4.7uf on V1a; 4.7 on V1b; 1uf with the boost limiting resistor still in series,,,,,and that was the clear winner.....it got rid of a lot of the mud that Tubenit was trying to tell me all along.......I thought it was going to kill the bass response, BUT it didn't and that's a lesson learned
- With the vol. on 3, treb. 7, mid 5, bass 6, presence 10, we found the sweet spot, where it would bark, bite, growl, sing, and especially feedback into harmonics, which he enjoyed as much as I do....
- I broke out the Variac and lowered the input Vac to 105 and it brought the B+ down to 395Vdc....I rechecked the bias and adjusted it HOT to 51mA, and that combination was a pure winner.....he got a huge grin on his face and wanted to place an order right then and there
- Although I originally liked the sound of his amp better,,,,after some adjustments we both actually preferred the sound and potential of mine

-The volume was very similar with both amps and he said he could use mine onstage...
- I asked him for comments, critisizm and he asked for a little more gain ...which made me laugh out loud because it has a ton of gain

- So from here I'm going to continue to voice the amp based on these findings and just try to narrow it down to a great sound with THIS circuit....
I'm going to try jojo's cascade suggestion, tweak the tone stack values, install PPIMV, and basically STOP trying to get this amp to sound totally different than it was intended..................I can wait to get "MY SOUND"

- When finished I will label this amp the "HOME-WRECKER", sell it to Bob, and use the money for parts to move further along towards the dream...

- He asked me for an amp that will "put some blonde PU$$? on (his) lap",,,,,so that's where HIS head is.....and I can appreciate that,,,mine will be trying to figure out how to get an amp to do that...........Now that would be a marketing slogan

[tubenit]

Glad you are making progress with the amp and you & your friend are enjoying it. I appreciate knowing the lower value cathode caps did help with transparency and clearing up some mud (at some level) in the TW design & topology. Thanks for sharing that.

Will you try using that last triode set-up exactly as the third triode is designed in the original schematic? You will therefore be cascading those last two gain stages but the last one is important to use the 10k cathode resistor unbypassed/without a cap on it.

I think Jojokeo is giving some good advice to try. This is a reasonable approach. I like the 10k without a cap on the 4th stage cathode idea.

Something to consider regarding Jojokeo's sound advice.........

I will say that my D-style inspired amps typically will use 100k and/or 250k pots in the OD section.  Having said that, I actually have some very low values to ground in those pots. Particularly going into the OD section of a D-style amp (which would be the 3rd gain stage, I may have a "trim" pot that is only 22k-27k to ground?

I am thinking the 3rd gain stage may need a fairly low resistor to ground value and then you can bump up the value in the 4th stage.   In other words, maybe try a 68k-120k resistor to ground on the grid into the 3rd gain stage and then try that 220k into the 4th stage.  I am thinking using 220k into both of those will be too much gain and even bring possible oscillation?

Maybe Jojokeo can comment on that approach?

Work with Jojokeo on the topology and values. He has alot of experience and knowledge about designs & mods. And I think he may have a much better understanding of the direction that you're wanting to go & the tone you're after.  (which I am guessing is different than the D-style amps?)

With respect, Tubenit

[jojokeo]

I just stopped in for a quick read and update and everything sounds real positive. I'm outta time so I printed out the latest schem w/ comments so I can go over later today. Great feedback SG & info as always T!

[SILVERGUN]

Will you try using that last triode set-up exactly as the third triode is designed in the original schematic? You will therefore be cascading those last two gain stages but the last one is important to use the 10k cathode resistor unbypassed/without a cap on it.

I think Jojokeo is giving some good advice to try. This is a reasonable approach. I like the 10k without a cap on the 4th stage cathode idea.

Yeah, I put this mod on the top of this list right now.....I want to try it before I insert the PPIMV, so that I don't confuse results

I am thinking the 3rd gain stage may need a fairly low resistor to ground value and then you can bump up the value in the 4th stage.   In other words, maybe try a 68k-120k resistor to ground on the grid into the 3rd gain stage and then try that 220k into the 4th stage.  I am thinking using 220k into both of those will be too much gain and even bring possible oscillation?

I understand 100% and will leave the (variable grid leak resistor) 250K pot before V2a, and put one before V2b, and attempt to dial in a great "blend " of gain by adjusting those 2 values........
Thanks again for the idea to use that approach, it gives me the "mad scientist" feel that I am now embracing.....and trying not to abuse

When I get a chance I will update both JPEG and SCH shematics

Next steps: (possibly tonight)
1) Cascade V2 a+b per jojo's advice and experiment with grid leak resistor values
2) Tweak tone stack
3) Install PPIMV

[tubenit]

OK, I looked up the settings that are my "favorite" tone on the D'Mars ODS.  This favorite tone is more of an overdriven sustaining clear tone than a high gain tone. I am intentionally avoid grit/grind and looking for smooth sustain.  So I presume you're going for something with more grind, but at least, this illustrates the concept. And I can easily dial in almost endless sustain in the same amp but with different settings on OD drive and OD level .

OD trim (50k set at "6.5") = 49k to ground   prior to 3rd gain stage
OD drive  (250k set at "4") = 29.4k to ground   prior to 4th gain stage
OD level  (250k set at "3.5k") = 18k to ground   post 4th gain stage

These settings are such that there is no volume difference between the clean and OD channels (at the volume I like to play). Just a difference in tone, overdrive and sustain.

PPIMV (favorite setting for volume) is 66k to ground.

My guess is that you will want more gain and volume than I do? And if so, simply up the values. Anyhow, this gives you a reference point to be thinking thru this.

With respect, Tubenit

[SILVERGUN]

Nice....thanks T,
I always appreciate your playing and tone and I definitely hear what your talking about there...I have been enjoying your soundclick page since I came aboard the forum,,,,,and you're right....I would want more gain and grind in my amp, and I'm actually still sitting on a TOS board that I WILL eventually build (it'll just be a TOS TURBO OD)....this TW thing sidetracked me, but I'm glad I did it because it is such a simple circuit, and lends itself well to experimentation...

Here's the projected schematic for tonight's work for you and jojo to look over and make sure I'm translating what he's suggesting for the cascade mod:

[tubenit]

Schematic looks good to me. I think that could be a very nice amp.  Hopefully, Jojokeo will add his perspective. I think he's got a better grip on the tone that you're probably after.

I would be tempted to also try a .02 - .047 coupling cap into the LTPI instead of the .1.   However, that may not be needed & could be tried at another time.

With respect, Tubenit

[jojokeo]

I'll quickly say sound advice from T on the grid leak resistors. You may want to solder in a 22k - 47k or something between ground and bottom lug which allows you to turn pot completely down. Not a must but keep you from gounding the signal out. By the low .002uF coupling caps btwn them it would be easy to parallel these quickly to adjust the frequency of signal getting through too giving more low mids, etc.
Lastly, try a higher value on the V2b's cathode also such as going as high as 39k like Soldano does on his SLO 100 amp. The reason is to give you a feel for what this does as being a soft clipper effect.

Looking forward to results...an maybe a listening test one of these days????

My other suggestions are more radical from a circuit design point to what you're doing right now (meaning changing the circuit as it currently is set-up and requires a partial re-build of the front stages) but since the amp's already wired up the way it is, these last adjustments are easy to do while in it's current configuration. It may or may not need further reconstruction at this point and the only way of knowing is manipulate that circuit?

In reading your prior email about Bob's visit, which was quite entertaining BTW, you talked about how his amp sounded. You too could easily manipulate yours to sound pretty much exactly the same way fairly easily. That's the great fun of these simple circuits using tag strips/eyelet & turret boards...so easy to re-design things for anything you want it to be. Same thing when using vero board when I'm building effects pedals. The old painstaking way of making circuit boards is long gone.

[SILVERGUN]

I'll quickly say sound advice from T on the grid leak resistors. You may want to solder in a 22k - 47k or something between ground and bottom lug which allows you to turn pot completely down. Not a must but keep you from gounding the signal out. By the low .002uF coupling caps btwn them it would be easy to parallel these quickly to adjust the frequency of signal getting through too giving more low mids, etc.
Lastly, try a higher value on the V2b's cathode also such as going as high as 39k like Soldano does on his SLO 100 amp. The reason is to give you a feel for what this does as being a soft clipper effect.

Looking forward to results...

WOW ...lit it up again!!!!

Wired it up point to point (cause I ran out of board), just like I drew it up and WHAM!!!.....face melting, lava spewing, blonde on your lap, smokin' hot TONE.....
This is just a preliminary report,,,,BUT----GREAT BALLS OF FIRE----

I'm sill tweaking grid leak pots, and so far I've only raised the 3rd-4th stage coupling cap to .0047,,,and V2b cathode at 33K,,,,,but I just had to let you guys know what we've done here is INCREDIBLE!!!!.....stay tuned...MORE LATER

[jojokeo]

  Nice character drawings (multi-talented)!!!
IF you have a tiny bit of high end roll off needed, insert small value grid stopper going into 3rd stage first, then maybe 4th stage's input 2nd. By the Miller effect & input capacitances this will roll off a bit of high end for you (just a little theory of why). Also with grid stoppers you help prevent blocking distortion too when used later in signal chain.

Lowering the 100k slope resistor in tone stack may give you a slightly fatter sound/signal as you experiement w/ the tone stack. But every value change made to the tone stack affects the freqrency response of your controls. If you need more low end from the stack increase the middle cap from .02 to .047 or more likely 0.1uF. Not sure what you're liking or maybe lacking right now in this area but two considerations for the tone control tweaking for you w/out guessing. One last note is that these will mostly cause only a change in control settings but not necessarily be like a "leave it or remove it" type of deal like what you've been doing. Meaning instead of Bass set to 6 and Mid set to 5 as before, you may get the same response now w/ Bass set to 3 and Mid set to 4 at the same high volume? But at lower playing settings you may need more bass signal on tap which you'll have available then. So what I'm trying to say is that you can always decrease control settings but it's much harder to increase bass frequency for example if it's not there in the first place and you want the best sweep/range of your controls for various playing levels. Hope this helps? Just a reminder as you are likely aware already but on final tweaking it's best when using actual speaker(s) and/or guitar(s) you'll end up using OR use various guitars & speakers if going for more universal/versatile (you said earlier that you were using a crappy speaker just laying around?)

[tubenit]

increase the middle cap from .02 to .047

1+   That's what I do and usually use .03

With respect, Tubenit

[SILVERGUN]

IF you have a tiny bit of high end roll off needed, insert small value grid stopper going into 3rd stage first, then maybe 4th stage's input 2nd. By the Miller effect & input capacitances this will roll off a bit of high end for you (just a little theory of why). Also with grid stoppers you help prevent blocking distortion too when used later in signal chain.

Cool,,,I didn't even think of ADDING a grid stopper at either one of those locations, but I will experiment with that next.....
I was looking at the 820R going into V1b as a possible candidate to change, but wasn't sure of what effect it would have...

I tried tweaking the tone stack and noticed exactly what you guys are saying...no huge changes, but just different "ranges" in the tone pot settings...
I'll go to the .03 on the mid. cap

At this point the amp is a 50 watt distortion pedal....so with that comes hiss, and feedback, but I'm glad we took this route, because I feel like I'm at the top of the mountain, as far as gain (OD) is concerned, and now I can work my way back and start addressing issues....
I'm also glad it went this way because I feel like I was able to "voice" the amp before adding that last gain stage and now we're just amplifying/overdriving  what was already a good sound...

Here are the biggest problems I need to address next:
1) I have to do something about the preamp volume , and I'd like to do it before I install the PPIMV so I'm not mixing results (will the V1b grid stopper effect the vol. control much?)....I will really concentrate on this tonight and go back in the posts and try to follow what you guys were telling me about pot values ( I tried replacing the 1M vol. pot with a 500K, and when that wasn't an immediate improvement, I put the 1M back and moved on)
2) There is a "screechiness" in the strings when I slide my hand up or down that has been there all along but is just more pronounced now that we have more OD/volume...standard "pick slide" type screech that just seems to really jump out at me.....( I realize that comes with the distortion territory, but I wonder if it's a certain frequency that we can cut).......and maybe it's got something to do with my guitar which has a Seymour Duncan JB,  no tone control/cap and just has a 500K vol. pot (Bob's stock SG sounded better)
3) Just noise in general...adding that 4th stage has amplified the bad as well, so I will need to go back and re-flow some solder, check lead dress, check ground connections, and wire paths, plus make some permanent components out of those grid leak pots on V2a+b......etc,etc,etc

If you couldn't tell from my last post,,,I am extremely excited about the sound coming from this amp now!......even through this "crappy" Line6 labeled Celesetion I am using......Bob said the speaker sounded OK to him, so I guess it's not the worst

[llama]

It's Alive!  Alive!......

[tubenit]

so with that comes hiss, and feedback,

Shielded cable in the right places.

Try moving wires safely with non-conductive chopstick. Sometimes that will significantly change hiss or hum. You may possibly be able to dramatically lower noise doing that (sometimes)?

Try different tubes.

Try "enchance cap" (again) across LTPI entrance plate resistor. I actually found this to not just eliminate high end "hash" BUT instead it actually increased blooming where notes tend to blossom and open up more with greater sustain. It may work just great this time after these recent changes?

Try snubbing caps 220p-390p range on the 3rd & 4th gain stages from plate to cathode.

Remember on changing the 1M to 500k, that you can put a resistor going into the non grounded side terminal of the 500k pot.  The idea of the 500k is to "mentally" have the volume on "7" instead of "3".  It's more of a mental thing really in that regard IF you're using a resistor into the 500k. Hope that makes sense.

With respect, Tubenit

[jojokeo]

Remember on changing the 1M to 500k, that you can put a resistor going into the non grounded side terminal of the 500k pot.  The idea of the 500k is to "mentally" have the volume on "7" instead of "3".  It's more of a mental thing really in that regard IF you're using a resistor into the 500k. Hope that makes sense.

This is making a voltage divider along with the pot which lowers the overall signal down even when the vol is full up/on, but also cuts out some highs too w/out a treble bleed/bypass cap on it to make up for it (if you need the highs back?). This will lower your preamp volume you've been complaining about and you are dropping signal in a permanent way as we've said earlier in this post and similar to the split plate load techinique remember? If the resistor is designated R1 and the pot is R2 then the formula for voltage out (when the pot is on 11) is Vin x R2 / R1 + R2.

Noise level...where have you run the center tap of your heater wiring? Anything further you will need to show a good picture of the complete inside of the chassis? A doctor can't treat a patient unless they make a trip to the office.

[SILVERGUN]

Even more fun today...went into work on one of my days off (which I never do, unless it's to be with this amp)
Got lucky today and it was a big one:
-I soldered a 50K trim pot in series wtih the 820R grid stopper coming off of the vol. wiper to V1b and went all the way up to 51K and it just plain sounded better...
-I had also put a 10K trim pot as a grid stopper before the 4th stage V2b and dialed that to 2.7K
That combination was awesome and it got rid of some of the preamp "spank" I was talking about early in the build, and added a great feel to lead playing, plus a slightly "vocal" mid voice that just kills....
-Got a little crazy and replaced the 250K grid leak pot before the 3rd stage (V2a) with a 1M!......I could dial that all the way up and it just got better.....I couldn't believe the killer distortion and the fact that it wasn't really getting muddy or lost, but REALLY filling out the low mids/bass....BAM!!......left it at 800K!
-Those 3 tweaks has this thing sounding more and more like the 1st VH album tone (+ extra dirt),,, I know a lot of people have tried a lot of things to get close to that sound, and I believe that you could dial in those 2 grid leak pots and nail it ...........
the amp still sounds good when you turn the guitar vol. down, but I wouldn't really call it clean anymore, but's it's got a nice "crystally" pushed grit, that would definitely cut a mix

-So, since I was starting to bleed from my ears,,,, and I didn't want to do anything else different to the preamp.....................
I FINALLY INSTALLED THE PPIMV---AND IT IS A WINNER!!!!!---it aint coming out!!
It sounds good throughout the entire range of the pot, BUT still sounds best at full volume, with the control all the way up (of course it does)........but there are plenty of useable settings from 3-8, with everything from bedroom vol. to a decent practice vol.......
YES, it does thin out at the lower settings but who cares...it still sounds good and it's the only MASTER that I've tried that actually retains the aggression of the preamp.

- I played more "casual" guitar today then I have in 7 years since I "retired", because the amp is a joy to play,,,,and it probably sounded like I was auditioning for a VH tribute band.......I'm thinkng about it

[SILVERGUN]

Noise level...where have you run the center tap of your heater wiring? Anything further you will need to show a good picture of the complete inside of the chassis? A doctor can't treat a patient unless they make a trip to the office.

I've got 2- 100K resistors (artif. CT) coming right off of the indicator light housing  AC tabs to a ground tab 1/2 inch away

I think my noise issues are a combination of issues, incuding, but not limited to:
Temporary pots still wired in as grid leak resistors (and just hanging over the side of the amp)
Wires from tube sockets (added gain stage) overlapping and crossing...
Possible cold solder joints where I "rushed in" multiple mods...
Amp being opened up and me sitting within 1 foot of it while playing...
Temporary mini (bias type) pots wired directly to tube pins as grid stoppers...
A lack of shielded wire in critical locations.......
A crappy guitar cable...that is usually on the floor over the AC input cable...
An old un-shielded/un-insulated Variac in my AC input path...
PPIMV basically just done point to point in mid air, and hovering over board (I wasn't convinced it was going to work for THIS amp...(man was I wrong)
A workbench area that is surrounded by flourescent lighting....

I need to clean up my bench , and then clean up this board , and then talk about noise........after I'm done tweaking

[sluckey]

I've got 2- 100K resistors (artif. CT) coming right off of the indicator...

100Ω would work much better.

[jojokeo]

Those wires & pots definitely make a difference to that noise for sure. Glad to hear the PPIMV is a winner there and seems like you're getting the classic EL34 crunch going.

[SILVERGUN]

I've got 2- 100K resistors (artif. CT) coming right off of the indicator...

100Ω would work much better.

I think they are 100R and I just forgot (I know they are supposed to be).....it was a month ago that I put them in there, and I am getting old........thanks for looking out!!
But I will check them because I have made mistakes before.......

Hey,,,WHERE did you get that ohm symbol???....I want one

[SILVERGUN]

Those wires & pots definitely make a difference to that noise for sure. Glad to hear the PPIMV is a winner there and seems like you're getting the classic EL34 crunch going.

Yeah,,,I won't know where I stand until I straighten this stuff up...

The EL34's were definitely the way to go with this one.......I didn't realize until I heard that JCM800

PPIMV surprised me....

[sluckey]

Hey,,,WHERE did you get that ohm symbol???....I want one

Alt 234

[jojokeo]

where's the rest of the symbol key strokes?

[sluckey]

These?

[jojokeo]

Thanks sluckey™

[SILVERGUN]

+1 

Sluckey for President 2016 

[SILVERGUN]

Updated JPEG schematic to include weekend updates....(sorry for the cut and paste BS, but it's simple)
PPIMV really smoothed this amp out and I much prefer it on 5 than 8, but that's only 'cause my ears are old...8 does sound better

[SILVERGUN]

Here's a pic of the best drummer I ever had the honor of sharing the stage with ('89-'97) this pic is from New Years Eve 1995...this amp was partially inspired by his influence on me
When you hear me say that my ears are old / bad,,,it's all his fault....he used to break the biggest sticks you can buy on his snare because he liked the pop he would get when he would catch a piece of the rim.......
I couldn't figure out how to post this in a PM,,,so here it is,,,,he belongs on this thread with THIS amp

Mike Belton 1967-2009

[jojokeo]

I meant to ask, what's with the 51k resistors after the wipers of the PPIMV? Dropping more high end?

[SILVERGUN]

I meant to ask, what's with the 51k resistors after the wipers of the PPIMV? Dropping more high end?

I was gonna mention that....I put them in there because they were in your schematic from Mission Amps...(33K to 100K,,,it says....so I just threw 51K in there without any thought)
I tried it with and without them and it seemed to sound better without them, but I'm still a slave to the schematic, so I left them in...

[SILVERGUN]

I don't know....can anybody tell me where all of this noise is coming from???

[llama]

Use a lower ISO setting. This may be done by decreasing the shutter speed or increasing the f-stop settings, allowing the photographer to use a lower ISO. A lower ISO means decreased sensitivity of the image sensor, and so smaller electrical currents--the cause of ISO related noise--are not recorded.

Amp looks cool BTW - a bit messy though.

[Stankfut]

I think he was being facetious

[llama]

i was!

Thanks for the pic, Silvergun.  I'm a few steps behind you as a mad scientist.  More of an ill-contented Scientist. 

[llama]

I had the opportunity to visit Silvergun's Laboratory last night.  I thought i knew what gain sounded like.  I've been playing guitar for over 20 years.  I thought my AX84HO had high gain....I now know why they call it the brown tone.  I almost shat myself.  Killer Distortion and Singing Sustain.  This Trainwreck killer is something.

Silvergun impressed me with his understanding of what you guys have been teaching him in this post.  He kindly left his chassis open with the temp mods in place so i could hear the differences with the changes.  I heard the difference in his amp with bypass caps in and out, as well as the variable grid leak resistors, Holy Gain Dial-In Batman!  Thanks Silvergun-  Your Awesome!

I didn't hear any DC noise on the pots for his grid leaks, could he tie them in as knobs?  I would guess, as a nube would, that if he placed a small value resistor in series with the pot he could change the gain effect on the fly.  Could that be used in place of a gain control?

But, I'm sure that if it could be done, it would have, by now...

-LLama

[SILVERGUN]

Probably the coolest thing that Llama and I did was to take the 12DW7 (7247) tube from his AX84HO and try it in my V1 position...(see attachment)
The way that this tube is configured with mixed triodes was something I was totally unfamiliar with........it allowed me to try a lower gain (12AU7) in the second gain stage while retaining the stock (12AX7) in the first stage.....(for those who are unfamiliar, THIS tube has both types of triodes in a single tube package,,,,,so I didn't have to put in a separate tube socket to try separate triodes and experiment with different gain values in those stages)
Are there many other tubes configured this way??

Well, much to my surprise, it worked perfectly with that tube in that position and allowed my (preamp) volume control, to actually have a useable range from 0-10, with 3 being a nice lowered gain sound, and dialed up to 8, right back to the the insanity I've come to know and love...( before this experiment, there was no reason to turn the control past 3, because all it would do was introduce more noise,,,,,OD was maxed at 3).....that revelation alone was worth the price of admission for Llama stopping by .

I had left all of the temporary mods in place so that I could expose Llama to "the mad scientist" approach of tweaking, and it's now time to make some things permanent, clean up the board, and then start looking at noise reduction.

If I can get something recorded I'll post it.............I have even more confidence in the amp after hearing Llama's comments  

[tubenit]

it worked perfectly with that tube in that position and allowed my (preamp) volume control, to actually have a useable range from 0-10, with 3 being a nice lowered gain sound, and dialed up to 8, right back to the the insanity I've come to know and love...( before this experiment, there was no reason to turn the control past 3, because all it would do was introduce more noise

Thanks for sharing that!  Great experiment and creativity in that.

With respect, Tubenit

[jojokeo]

  SG has a hype-boy!

Damn it all to hell...I've finished my schems for my latest creation but it was slanting towards the Plexi's CF>PA sections-direction. Now I'm starting to re-think my original idea of making both in the same amp. Damn you and thank you SG.

[SILVERGUN]

Now I'm starting to re-think my original idea of making both in the same amp. Damn you and thank you SG.

Your East Coast R+D dept. (me and llama "the hype guy") says do the double preamp thing.....that way you can make it double bad-ass,,,that's better than single every time.......we both agree on that
Tubenit was asking about the possibility of stacked boards in a recent thread.......if you build it like that, you could build 2 separate preamp boards, and if it turned out to be unnecessary, just remove the one you like least and build another amp out of it
4 total preamp tubes (2 for the Wreck and 2 for the Plexi).....+1- EF 86 if you must
4 Channel amp with clean Wreck, turbo Wreck, pushed Plexi, lava Plexi

The Wreck tone controls don't make a ton of difference, so if you could just live with the tone stack bypass (PAB type - permanently), you could eliminate those controls ( I saw on your thread where that was a concern....i.e...# of controls)

I don't know .......sometimes I feel like a dumb little kid trying to tell his dad how to fix the family car

I'm also still not convinced that they sound different enough to justify the time...?

[jojokeo]

4 total preamp tubes (2 for the Wreck and 2 for the Plexi).....+1- EF 86 if you must
4 Channel amp with clean Wreck, turbo Wreck, pushed Plexi, lava Plexi

The Wreck tone controls don't make a ton of difference, so if you could just live with the tone stack bypass (PAB type - permanently), you could eliminate those controls ( I saw on your thread where that was a concern....i.e...# of controls)

I like the sound of turbo wreck and lava plexi. I would've said that about the tone stack where it is in relation to it's set-up & design. The later in the preamp the better the control factor and often the difference btwn more of a rock sound, definition, & control to blues sounds. That would be a great blues amp like a tweed w/ pronounced mids and early break-up the way it is. (didn't we discuss this already?). I think you might be better served by cascading the first two stages, then tone stack and finally recovery and soft clipper. Better control, definition, and likely better tone too. This was what I was going to suggest much earlier on. If you're happy with it then why change it? But...if you're willing to re-build Frankenstein with Abbey Lutely's brain instead of Abbey Normal's then... in the name of science you will be compelled by your destiny to acheive your tubular zenith. 

[tubenit]

What's the update on this amp?   Everything wired in?  What's the noise level at idle?

Any closer to having a sound clip?

With respect, Tubenit

[SILVERGUN]

It's sitting there waiting for me to get back to it.....after the hurricane, my company was inundated with flooded welding machines, which present a huge problem for us, because theorhetically, once a unit is submerged in water, it "shouldn't" be used again, due to corrosion and insulation breakdown.....BUT, it's our job to dry some of them out, and try to get people back to work... so it's been some long days.

The amp is nowhere near "done"...now that I've gotten this far, I have to read more to learn what I'm actually doing....I realize, by listening to guys on this forum, that there is A LOT more to learn.....I haven't stopped thinking about it for one day, and have changed my mind about 10 times as far as what my next move will be... I am completely addicted to building and have to fight the urge to build everything I see and hear...
I have downloaded all of the material from Sluckey's website and am reviewing all of it to try to broaden my horizons...

Here's what I'm thinking today about the amp on my bench:
- I was in re-introduced to a guy who wants to sit in with me to try to find an amp design for him....I really want to build a "holy grail" amp,,,and while searching through schematics, I saw that the AA864 Bassman has a VERY similar design to this Twreck,,,so I am considering converting this to a single channel (normal) version of that amp to get him taken care of....it shares a lot in common with the AB763 LITE that Sluckey has on his website,,,,so I'm thinking it would be an easy road, and a lot of the guesswork has been taken out of it for me.

My intention is to "roll back" this amp, in sections, so he'll be able to hear the differences, and decide for himself if he wants to go all the way back to the AA864, or if there's something in the wreck design for him. I invited him to sit with me for the day and make the changes, and play through each stage, to see where he would want to stop.......I'm thinking about putting the Bassman preamp circuit on another temp. board so that at some point we'll just be able to jump all the way over to that sound by just wiring it in. (not sure if that's easier than making all the component value changes on this board)

If he decides he wants to do it I'll probably go for it, in hopes that it will enlighten me about the differences in designs/sounds....I will try to get a clip recorded before I make the changes.

AND, in the meantime, my curiosity about doing a Dumb OD type amp has grown,,,,a TOS,,,a 5 watt,,,a Stout,,,a pentode preamp........

AND, I still have to keep my wife happy!.....she hurt her back so I've been taking the brunt of the housework.

Thanks for asking and caring and helping me through all of this....I'll be back to writing updates SOON

[jazbo8]

SG,

Just gone through this fascinating thread, very informative indeed. The way you are tweaking the design, part values is admirable and I think well suited for a tube breadboard like Tubelab's: http://www.tubelab.com/The_Tubelab.htm. Looking forward to read more about your experiments.

Jaz

[phsyconoodler]

a guy over at the amp Garage asked about paralleling V2 in a 'wreck.I think with some tweaks to the bypass caps on V1 and the gain control,a fat sounding V2 might be really cool sounding.
 I'm definitely putting it on the list for my next experiment.
We have way to much here on the Hoffman forum,don't we?

[SILVERGUN]

I tried paralleling V2a into V2b, with no real noticeable results (for me),,,,but I was looking for waaay more gain......cascading V2a into V2b really lit this amp up, and I'm so happy jojo thought to tell me to try it.......great way to make use of that unused triode

JoJo and Tubenit each get 33% on this build......all I did was throw parts at it  (but thats worth 34%)

Thanks jazbo,,,,that's very interesting ....at one point during my build my amp kinda looked like that

[phsyconoodler]

I'm going to get an amp up and running in the next week or so and try out some of those mods.
Thanks for sharing your experiences!