Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Shack on April 10, 2019, 05:59:05 pm
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I see the demos of these amps and it seems they get that sweet crunch without pedals...I plan on turning a Princeton reverb build into such an amp, using the tweed bassman platform. I will have a preamp tube socket left over, and I have a 6.6k OT in there so I can use 6V6 or 6L6 tubes. Steve Carr builds amps that sound awesome too, but there isnt any schematics to any of these amps. Can someone point me in the right direction? I wont start until I figure out what it is I want to do.
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Someone did one for a Route 66. Search " Root 666. Should come up.
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Shack,
Dr. Z Amps and Friedman Amps are fairly different. There a few schematics floating around including a Z Wreck which looks intriguing. I have owned a number of Z amps and they are very simple and have rich tones. Some of the amps like the EMS, Z Wreck DB4, SRZ are high gain crunchers.
I also have a Friedman JJ-100, now there is crunch. There is a schematic and layout for a Friedman Smallbox 50 in the library.
If you are looking for a Friedman style high gainer then Fowlers #39 Modified Plexi is the fire breather that quite entertaining. I just finished mine and I really like it.
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Thanks.....I know all these amps are different and I also know that I am listening to demos that guitarists way better than I are playing , but the rich clean sounds and awesome crunch is something that my clones of Fender and Marshall are just barely shy of, I still have yet to build one with its own dirty sound, and I just love to study schematics.
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i have had success using pentodes as v1, one amp uses a 6u8s with the pentode into the triode into the 6v6. but my favorite crunchy amp which sounds very marshallish uses a ef86 a 12ax7 and 6v6 single ended but you could add a different power section if you need it louder than 5 watts. what i did was use a 5e3 deluxe as inspiration one channel has the ef86 and a volume, the other channel inputs into half of a 12ax7 with a volume they combine and get amplified again with the other half of the 12ax7. there is a simple treble cut tone control , the volumes are interactive like a 5e3. plugging into one channel gives you a normal fendery tube amp sound but the other channel screams with both volumes turned up high. i love that freaking amp. i think the secret is the pentode preamp gives you a similar to power tube distortion so it has that cranked cruncky sound. i am sold on the pentode preamp tubes, even a 6sj7 rocks hard but has tons of harmonic character . try it you will like it. to me 12ax7s sound generic, i prefer a 6SL7 to a 12ax7 all day they just sound super thick and rich to me.
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I recently built a Pink Taco, massive gain & super loud for a 2xEL84 amp. I did find a schematic and verified all I could from a bunch of pictures I found. I made a nice layout also that I will share if you are interested. The amp turned out to be more than what I wanted, just too much gain on tap. Im more of a blues crunch type of player & this amp was way beyond that.
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I recently built a Pink Taco, massive gain & super loud for a 2xEL84 amp. I did find a schematic and verified all I could from a bunch of pictures I found. I made a nice layout also that I will share if you are interested. The amp turned out to be more than what I wanted, just too much gain on tap. Im more of a blues crunch type of player & this amp was way beyond that.
Joe6v6,
I would be interested in that Pink Taco plan if you don't mind. I might have parts for something like that.
Thanks,
Brian V
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Here is the schematic I found and the layout I put together. The layout is minus the effects loop and has a tube recto vs diodes. Also a few other changes, no sag resistor & the elevated heater connection. . Joe
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Here is the schematic I found and the layout I put together. The layout is minus the effects loop and has a tube recto vs diodes. Also a few other changes, no sag resistor & the elevated heater connection. . Joe
Thanks Joe,
It will be on my todo list
BV
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I recently built a Pink Taco, massive gain & super loud for a 2xEL84 amp. I did find a schematic and verified all I could from a bunch of pictures I found...
Any idea what the big gold chassis mount 20k 25W resistor is doing? https://www.musiker-board.de/media/pink-taco-pt20-guts-1-1280x719.24818/full
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Any idea what the big gold chassis mount 20k 25W resistor is doing?
I think it lowers the voltage being supplied to the effects loop. ?
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Thanks, that makes sense, given the opamp on the fx loop board :icon_biggrin:
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I have built last week a small combo SE amp that REALLY ROCKS. I use to play my guitar straight into my amps (not even a tuner......but maybe I should use one :laugh: ) . What a hassle plugging and unplugging everything and having to find the right spaghetti in the bunch of them, and I find that the use of pedals modify a bit the amp's tone.
To make a long story short I desired to build a small practice amp (f....loud after all) that would give me lots of crunch at low volume. I looked at many schems: Marshall, Soldano, Top hat (yes indeed) Hiwatt, Sound City and more to finally build a rocky combo with 4 stages of gain that drive a single 5881. No tone stack: a pre and a post. That s it that s all. If you visit the Rob Robinette site you will find lots of hints to achieve a nice crunchy tone. I must admit it helped me a lot.
Colas
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I recently built a Pink Taco, massive gain & super loud for a 2xEL84 amp. I did find a schematic and verified all I could from a bunch of pictures I found. I made a nice layout also that I will share if you are interested. The amp turned out to be more than what I wanted, just too much gain on tap. Im more of a blues crunch type of player & this amp was way beyond that.
Joe6v6,
I would be interested in that Pink Taco plan if you don't mind. I might have parts for something like that.
Thanks,
Brian V
Looks to be a low powered JCM800 is all w/ extra components taming high end and some gain... ie - two cascaded triodes > CF > tone stack > pi > pa
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I recently built a Pink Taco, massive gain & super loud for a 2xEL84 amp. I did find a schematic and verified all I could from a bunch of pictures I found. I made a nice layout also that I will share if you are interested. The amp turned out to be more than what I wanted, just too much gain on tap. Im more of a blues crunch type of player & this amp was way beyond that.
Joe6v6,
I would be interested in that Pink Taco plan if you don't mind. I might have parts for something like that.
Thanks,
Brian V
Looks to be a low powered JCM800 is all w/ extra components taming high end and some gain... ie - two cascaded triodes > CF > tone stack > pi > pa
Joe, good to hear from you. What are you building these days?
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Joe, good to hear from you. What are you building these days?
Ive been up to quite a few things, ive always got an amp or 2 underway and a couple more in the back of my mind. For the last year or so I went on a Dumble type excursion, which was nice but I have built plenty of simpler amps that work better for me. Dont get me wrong they sound wonderful & have made their way to much better musicians than me. Too many knobs for me. My quest for tone took a big leap forward with a 2 amp setup of a 5e3 and a Tweedle D. To me they compliment each other and blend together so well & with an a-b-y box theres plenty of dynamics there. . . The last amp I completed was a Lightning, and on a recent visit here I stumbled across Sluckeys schematic & layout for the Deluxe Lite which is what I am in the early stages of construction now. So ive been keeping busy & still love building amps. . Joe
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Too many knobs for me
:laugh:
that's my build criteria, if it's more than four I'll provide a couple names for someone else to build it :icon_biggrin:
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Hola, todo bien ?
Wanna build an amp with lots of crunch ?
Easy, very easy.
1. Choose the type of amp you want: SE, PP, the type of power tubes you prefer and get the trannies accordingly.
2. Build the power supply section. Copy the Marshall one let s say the 2204., if PP.
3. Don t fool around with tone stack, line in/out, reverb or other similar shit like hi lo inputs treble boost switch or play-for-me switch.
3. GET TO THE POINT NOW: FIND THE CRUNCH !
hook up the 4 sections of the first 2 12ax7 in cascade and PLATE DRIVE the LTP . You' ll add a cathode follower if you want, when you find the crunch. The CF wont collaborate to your goal.
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4. Concentrate your effforts on the CATHODES
of the 12ax7.
Example: 2k7 / .68 , 1k5/25, 33k and 820. There are your 4 cathodes that will work for you.
5. Add a master volume !!!!!!! No MV no crunch.
Forget about post phase inverter MV with dual ganged pots and wiring that never ends. The last plate of the preamp into a 1 meg and to the Pi or direct to the tube if SE.
KEEP IN MIND that distortion/overdrive/crunch hate low frequencies. Put a .0022 coupling cap somewhere between the preamp halves. I did not write .022 but ten times smaller. You ll need at least one voltage divider. I love the 470k on the outer leg of the 1M master volume. You ll need grid leaks ( to get voltage at the cathodes).
HERE YOU GO , You are now getting the tone you want. You can fine tuning it with other resistors or cap values,, add a CF , a tone control knob or even full tone stack if you like loosing your time !!! You can add peanut butter on top of that: hi lo switch, 220k plate load and so on.
Colas
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LOL......I guess that sums it up....thanx Colas :icon_biggrin:
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Hello guys. I resume this topic because was the only where I found information and schematics about the Pink Taco. I build it using a couple PT/OT I had around from many years. I've a couple of question for you gurus:
- my OT have a reflected impedence of 10K (both for 8 and 16 Ohm output) that is a little higher than the 8K requested for a couple of EL84PP, common cathode (looking to the majority of datasheet). What is your opinion for a Pink Taco application?
- my PT have a 290Vac output that, bridge rectified and filtered gives around 400Vcc (with no charge). It seems the EL34PP couple requires between 250-300Vcc (both Va and Vg2) working in class AB. I don't find information about the voltages of the Pink Taco. Have guys had the opportunity to measure or see a voltage chart of it? Suggestions? Do you think the 400Vcc with no charge drops to an accettable value when I put in place the yubes?
Really many thanks for your help.
Ivan (from Italy)
PS The schematic I used is the above mentioned in the post ;-)
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Someone did one for a Route 66. Search " Root 666. Should come up.
^this^
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Thanks tubesweel. I found the Root 666, but it's based on a PP of KT66 and not EL34, like the Pink Taco. I saw in this topic that Joe6v6 have built one
and I wondering if him or someone reading is able to share the B+ voltage values of the Pink Taco.
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Your PT should be fine for a Pink Taco type amp with EL84s. Modern EL84s (e.g. JJ) can take fairly high voltages.
Also, with cathode bias, the relevant voltage is anode-carthode, not anode to ground, so the actual voltage the rube sees is lower than the HT voltage.
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Hello everybody. My PT is near to be finished (in attachment the last version after a guitar session). The sound is quite good, but not so harsh as I expected, specially at low volume.
May be the cause are the B+ voltages I setted changing the resistors in the original schematic (the output voltages of my PT seems to me too high)? My R10 (after the rectification diodes, on the far right on the picture, not fixed yet) is 150 instead 22 Ohm, and the R11 (between B+ of OT center tap and B+ of power tube screen) is 1500 instead 470 Ohm. At the end the B+ (at idle) values are:
- 351 Vdc for the OT center tap (and the plates of EL84)
- 330 Vdc for the screen of EL84 (the cathodes are 10.5 Vdc)
- 298 Vdc for the 12AX7 Phase inverter
- 260 Vdc for the 2x12AX7 of the preamp stage
Are these values correct, in your experience?
Another strange thing is the very light effect of the tone stack. Only the mid knob seems working well, while the bass/treble knobs introduce a slight modification only moving from min to max.
What about a switch to bypass the tone stack to have more distortion at low volumes?
Many thanks for your precious suggestions. :help:
Greetings from Italy :icon_biggrin:
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Your voltages are fine. You have too much/many voltage dividers. Starting at V1 you have split plate load resistors which drops signal output to 54%. And then you have another with R19 & R16 both being 68K each. This drops more than another 50% because these values are too low causing extra load on top of the extra 50% reduction.
Suggestions of what I'd do and are more "normal" for an 18watt type build:
1) replace R19 with a jumper wire and replace R16 with 1M or 470K.
2) C24 usually makes things too bright but you may need this because of of C8 and C27 reducing high end?
3) remove R30 & C26 and replace with a jumper wire.
4) Jumper R7 & remove R59
5) Replace R35 with 100K
6) Do not go higher than 1K resistors for the screens to EL84s
7) Make R39 1k to 1.2K for pi tail resistor
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Many thanks, jojokeo, and WOW, a lot of suggestions.
The only doubt is that I moved from a schematic that, in this thread, was mentioned as the Fridman Pink Taco one.
The result is a very nice sound at high volume, but not the same at low volume.
Do you think that your suggestions change the tone also at high volume? In which direction?