I would say go cathodyne, and use the other half to boost the signal before the PI since the cathodyne has slightly lower than unity gain. You'll also want the anode voltage as high as possible on the cathodyne PI to keep your headroom up. If you don't already read "The Valve Wizard" site, there are a few good points to be careful of with the cathodyne PI shown on this page.
Sorry guys, I shouldn't have gone there. I wasn't going to, but I was full of energy early this morning. haha
Yes, I'm using a valvewizard inspired cathodyne in my current P-P EL84 amp. I also just got his pre-amplifier book; good reading so far.
some good answers, thank you
but the above quote shows I have been misread, or misunderstood
just a short last note to SS 'debate'
1. I suppose we were talking distortion 'device(s)'
and I think a couple of the latest mosfet designs beats everything
if you abandoned SS devices 3 years ago, you may not know anything about it today
2. yes, mosfets are still the same 'crap' today as they were yesterday
but the understanding of how to handle them have improved
or lets say the inside knowledge have become 'wider known'
3. on the power amp side, tube output is probably still the winner
but for effect devices, no sir, I dont think so
or you are a true wizard building exstremely hot stuff no normal mortal can hope to own
well, better let that one rest
If you have seen mosfet devices used in a high gain, high distortion, guitar preamplifier with good results please post it or a link.
3. on the power amp side, tube output is probably still the winner but for effect devices, no sir, I dont think so or you are a true wizard building exstremely hot stuff no normal mortal can hope to own
well, better let that one rest
I'm not doing anything with this design that hasn't been done before. There are many, many guitarists with bigger, all tube amplifiers than what I have outlined here.
Actually, they're not. There have been many incremental improvements in mosfets in the last few years. This is really apparent in the things we tube guys like such as gate capacitance and high voltage capability. 900 volt 10 amp fets are now catalog items.
The cathodyne may have a slight edge in gain over an LTP. In a guitar amp they each contribute a different sound when pushed into distortion. The LTP in a Marshall does contribute to the amps distortion signature. It's up to the builder to get the sound he wants.
I guess I suffer from the "I can't stop screwing with it" syndrome. It's fairly easy to tweak a guitar amp to get a certain sound at a certain volume level. It's also fairly easy to get tired of that sound in a few days.....then the cycle repeats.
The DSP boxes let you create a new sound any time you get bored with the old one. Some sounds are realistic, and some are kinda lame, but it is a cool tool to go exploring with. I have been trying to put that kind of flexibility in a tube amp.
Peavey has a software simulator that is really cool. If it would work as well as the hype suggests I would buy it, but the reviews seem to say otherwize. The software is called ReValver and it lets you call up the schematic of a tube amp (only peavey amps) and tweak parameters like resistor and cap values, and even change tube types. Cool idea, so I think I will try to build a hardware version. That will keep me busy for a while.
I haven't tried it on the 12AX7 yet. Forum member SY explored the 12AX7 in this respect a few years ago. He was working from a HiFi perspective and reported excellent results.
I explored using CCS loading and mosfet buffering with cheap TV tuner tubes while working on an amp for the $100 guitar amp challenge. The 12AX7 seems to work best at low currents like 1 mA. This leads to plate load resistors in the 100K range. The loading of the next stage considerably reduces the gain. The actual voltage gain of the typical RC coupled 12AX7 guitar amp stage is in the 30 to 40 range.
This can be increased to near 90 by the use of a CCS load and a mosfet buffer. Doing this raises the impedance of the plate circuit into the megohm range. This can lead to cross coupling between stages, hum pick up and oscillation.
The amp I built for the $100 challenge used 3 ECC85's and 2 UL84's to loosely emulate a Marshall 18 watt circuit. At first I had CCS loading and mosfet buffering on all 4 gain stages. There was too much gain causing instability, oscillation and microphonics. In the final working circuit I removed all the mosfets except for the follower driving the tone stack and cut out 1 gain stage. There is now 3 gain stages with a gain control between the first and second stage. The tone stack / master volume is now between the third gain stage and the PI (LTP), the amp is completely stable and can be dialed between mellow to metal.
Whether the CCS will work for you with a 12AX7....only you can tell, but it is worth a try.
not high gain, only distortion effect
I think its relatively new to use high power mosfets in effect devices
its probably been too easy to use IC's etc
they are considered SS solid state, I guess
there might be one or two brands/devices only
and there are a few new and more special effect devices that might surprice you
one I think is digital, to rub it even more
but not DIY, sorry
I'm picturing Nigel Tufnel raving about a new in-guitar tube preamp he's been hired to rave about; then a video clip of a guitar player on stage shredding his way toward the climax of his penultimate solo when his guitar starts smouldering from the preamp tubes about to catch the nitro'd swamp ash on fire. The guitar player notices smoke pouring from the gap between his pickups and the pickguard, and gets a concerned, then a panicked look on his face. But just before it bursts into flames, some insulation melts off a 300 volt B+ wire inside which touches the bridge assembly and electrocutes the guitar player with a 136 decibel BLAAAT through the amp and a brilliant Roman Candle explosion. The crowd goes nuts!..Todd
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The typical Fender LTP that I'm used to has a gain of about 30 I believe. I totally agree, it can and must be tweaked for the ear of the builder. I was just very happy with the cathodyne in my amp build, and the LTP sounded like crap when I tried it for about 10 minutes.
Count me in for this syndrome too. Just today, after about 2 months of not fiddling with my amp, on my drive home from work I was thinking about ordering some new main B+ caps (big dual cap cans) to clean up and shrink the loop for the 5th time! It just popped into my head without warning. hahaha
hahaha.... I think I have a seasonal version of the syndrome. As soon as summer arrived I turned my focus to mountain biking, motorcycling and for the next week, fence building. I got a big OPT that my Dad had (used to be the OPT for the Traynor that I scavenged, quad EL34) and I'm eager to get it into my Fender Super Reverb that has twin 6550's instead of 6L6's (plates are up around 700V) to see how it sounds loaded down a bit more and opened up. The OEM Fender OPT got pretty warm with those 6550's, but it will be happy with quad 6V6's in my new amp... but I digress.
Hi Stormrider,
Not sure if you want this feature, just suggestion. Seeing as your tone stack is right at the end of the preamp line, you may want to look at some tone shaping control after V1 or V2. Depends if you are into scooping or bumping mids going into subsequent stages of distortion. Or you might want to be able to adjust to taste.
I know you are looking for modern metal, but maybe to have an option to switch out stage 4&5, you would still have plenty of drive in a somewhat cleaner version? you know for power ballads n stuff.
Not sure if you want this feature, just suggestion. Seeing as your tone stack is right at the end of the preamp line, you may want to look at some tone shaping control after V1 or V2. Depends if you are into scooping or bumping mids going into subsequent stages of distortion. Or you might want to be able to adjust to taste.
I know you are looking for modern metal, but maybe to have an option to switch out stage 4&5, you would still have plenty of drive in a somewhat cleaner version? you know for power ballads n stuff.
Was it useful, or any feedback on my approach? I wish I had a good microphone, I'd play some Pantera and Slayer for you to hear it. I'll be seeing my Dad next weekend so maybe I can borrow one of his.
Your amp looks like it has a lot of functionality built in, and that's awesome. I don't have the need for a two channel amp, because if I need a cleaner sound or more vintage overdrive I can switch over to my Fender. Otherwise I would be going in a similar direction as you did. The fact you used quad 6V6's instead of a more typical 6L6 or EL34 pair makes it even more cool, different.
Clips and build pics would be sweet
Clips and build pics would be sweet
Your amp looks like it has a lot of functionality built in, and that's awesome. I don't have the need for a two channel amp, because if I need a cleaner sound or more vintage overdrive I can switch over to my Fender. Otherwise I would be going in a similar direction as you did. The fact you used quad 6V6's instead of a more typical 6L6 or EL34 pair makes it even more cool, different.
Clips and build pics would be sweet
Thanks
The goal was to cover as much ground as possible with this amp because I don't have any other amp with an overdrive stage, and my Fender with twin 6550's eats speakers (and your ears) when you push it into overdrive. The quad 6V6's (JJ's) really sound great.
Thanks
I have a cheapo Fender Champ600 I bought before they upped the prices. I modified it for more overdrive, and swapped the stock speaker for a Jensen 6". I will probably switch the preamp back to more of a 5F1 style for a little more clean headroom. Someday I was thinking about rebuilding it into a new cabinet to house a 8" speaker. Sounds pretty good, either way. I need to get my Ibanez set up, as my Jackson's action is set too low to really sound good running clean or slightly overdriven...
Nice! I have my cousin's Vibro-Champ at my place right now and I tried one of my JJ 6V6's in it, wow, what a difference! If you've never tried a JJ I would highly recommend it. Opens the amp right up.
I need to find an old 1x10" or 12" combo to scavenge for my next project (high sensitivity pre-amp with single ended 500V pentode power amp, likely a 6550).
I sold my Gibson Marauder to my brother so I've only got my Yamaha right now and the action is brutally high on it since the neck is way too stiff and I can't get enough relief to kill low-action rattles. I have all the parts I need to build a new guitar but that one has been on hold for 4 years. I need to get it done.
I need to find an old 1x10" or 12" combo to scavenge for my next project (high sensitivity pre-amp with single ended 500V pentode power amp, likely a 6550).
I sold my Gibson Marauder to my brother so I've only got my Yamaha right now and the action is brutally high on it since the neck is way too stiff and I can't get enough relief to kill low-action rattles.
I have all the parts I need to build a new guitar but that one has been on hold for 4 years. I need to get it done.
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