Class A EL84 amp clip and 'live' pic

[Twisteramps]

Re: Class A EL84 amp clip and \'live\' pic

Thanks Bret. That Super Bass sounds killer - how's it sound now?

Pete

Originally posted by slo100:
Pete this is all awesome stuff!

I bought a PTP 1970 Super Bass that had caught fire from a burned out output tube. It needed a lot of work and I decided to do it myself. I found that tinkering in amps is highly addictive. The SB is mostly original so I was not able to do much modding and such.

I want to find a burned out later year JCM/JMP super lead cheap and get a PTP kit as my next project and completely retrofit it from PCB to PTP.

Eventually I'd like to be where you are building from scratch.

Good work!

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[Donnie]

Re: Class A EL84 amp clip and \'live\' pic

Sweet Tone and awsome Playing. Congrats .

[Twisteramps]

Re: Class A EL84 amp clip and \'live\' pic

Originally posted by jeff300:
Wow Pete, that is impressive! Both the amp and the playing. How did you record it?

I'd love to hear a clip of it being overdriven when you get your pedal in.

<font size="2" face="Verdana, Helvetica, sans-serif">Thanks man. SM57 at the cab into a behringer ultragain pro mic preamp into my PC. I can't wait to hear what it sounds like with a pedal either [img]images/icons/smile.gif[/img]

Pete

[Infernal Death]

Re: Class A EL84 amp clip and \'live\' pic

As always very nice work Pete !

Just some questions. Those two big transformers, i guess both of them are power transformers right ? Why 2 ? Is there any advantage of this approach ? In my self-build amp i only have one power transformer which delivers a main voltage of around 260VAC before the rectifier and the 6,3V heater voltage. The 260VAC is then used for both the EL84 power tube and the 2 preamp tubes (of course at a stepped-down voltage).
Matchless Spitfire ? You used the schematic of this amp that's floating around ?
You made the amp cabinet yourself ? Looks very good. I still haven't made a case for my amp, mainly because i suck at wood working [img]graemlins/eyes.gif[/img]

Flo

[Matt Crooks]

Re: Class A EL84 amp clip and \'live\' pic

Pete -

Would you be able to make a low wattage high gain monster? Basically something that was very brutal, but didn't need to be very loud?

Matt

[slo100]

Re: Class A EL84 amp clip and \'live\' pic

Pete check out:

http://www.sandimascharvel.com/70superbass001.jpg

Change the "1" to 2,3,4,5,6 & 7 to see more.

These are "before" pics. I had to replace the socket, all the burned wiring, the screen resistor, and it also needed a pilot lamp and mains cord replacement. Great project for my first real amp repair. I am still tightening up a few things but will post after pics at some point.

It had some extra resistors in the bias feed because someone had installed KT88s. I reversed that all back to EL34 spec.

I also added a depth mod to it because someone had already fiddled with the NFB placement so I felt it was ok to do this one. This is simply a .0047uf cap in there and it really tightened up the low end. Bill at Soldano sent me schematics of all the SLO mods and this is similar to the Soldano depth mod. Amazing...an $.80 mod (when you do it yourself). [img]images/icons/grin.gif[/img]

With a HotPlate and running it at 90VAC it really gets the brown, woody sound those amps are known for. It is not even close to useable without a HotPlate. On 4 it is deafening and barely showing the faintest signs of breakup. I also use a Super Overdrive into the front at times to get super gain...honestly it gets enough without it but it has to be loud and pushing air to really sound good without a boost.

I have two Super Overdrives, one stock and one I modded to (supposedly) 808 specs...guess what? I like the stock one better.

[charvelguy]

Re: Class A EL84 amp clip and \'live\' pic

Originally posted by Infernal Death:
As always very nice work Pete !

Just some questions. Those two big transformers, i guess both of them are power transformers right ? Why 2 ? Is there any advantage of this approach ? In my self-build amp i only have one power transformer which delivers a main voltage of around 260VAC before the rectifier and the 6,3V heater voltage. The 260VAC is then used for both the EL84 power tube and the 2 preamp tubes (of course at a stepped-down voltage).
Matchless Spitfire ? You used the schematic of this amp that's floating around ?
You made the amp cabinet yourself ? Looks very good. I still haven't made a case for my amp, mainly because i suck at wood working [img]graemlins/eyes.gif[/img]

Flo

<font size="2" face="Verdana, Helvetica, sans-serif">If I may---Looks like the power tranny is on the far left as is a rectifier tube, the tranny to the right of that in the middle is the output and to the right of that is the choke in front of the El84's.

That's a cool Super Bass btw.

[Twisteramps]

Re: Class A EL84 amp clip and \'live\' pic

Originally posted by slo100:
With a HotPlate and running it at 90VAC it really gets the brown, woody sound those amps are known for.

<font size="2" face="Verdana, Helvetica, sans-serif">Bret, looks and sounds like an awesome project! The mods I'm doing to the SD-1 are the 'Keeley' mods he has on his website. Basically changing it for more bass, changing the impedence loading on the input, and swapping out the cheap caps for film ones.

Pete

[Twisteramps]

Re: Class A EL84 amp clip and \'live\' pic

Thanks Flo! Charvelguy was right - they are power, output and then choke, respectively. The transformers I'm using are Matchless ones, and are a lot studlier than what usually goes in a 15 watt amp. I've seen 50 watt amps with transformers this size. [img]images/icons/smile.gif[/img]

I used the spitfire schematic as a general guide, but modded it to my taste, and will mod it further. What I've done so far is give it a deeper/bassier tone, and better hum rejection. I'm also playing with lower voltages - I had 350 on the plates, after swapping rectifier tubes I now have 290, which sound better to my ear. Also, even if I did use the exact same schematic, my amp is built on turret board like an old marshall or hiwatt: the original matchless amps were point to point, or each component supported/wired to the next one. I think point to point looks messy as hell and is harder to troubleshoot/repair, personally. But both types of amps will sound a little different due to signal paths and lengths.

So far, this amp sounds dang good and has the best clean of anything I've owned or built. It has a nice chime, and the mids are very 'bouncy' for lack of a better term. A fender clean feels like solid state compared to this thing. Closest amp I've had to this tone was my Budda superdrive for the clean tone, but the overdrives are different. The Budda was much higher gain, this is more of a bluesy amp. I can't wait to see how it takes an overdrive pedal.

I actually had my dad build the cab for me, I have had enough interest in this amp that I may need to learn pretty quickly or chain him to a saw. [img]images/icons/smile.gif[/img]

Pete

Originally posted by Infernal Death:
As always very nice work Pete !

Just some questions. Those two big transformers, i guess both of them are power transformers right ? Why 2 ? Is there any advantage of this approach ? In my self-build amp i only have one power transformer which delivers a main voltage of around 260VAC before the rectifier and the 6,3V heater voltage. The 260VAC is then used for both the EL84 power tube and the 2 preamp tubes (of course at a stepped-down voltage).
Matchless Spitfire ? You used the schematic of this amp that's floating around ?
You made the amp cabinet yourself ? Looks very good. I still haven't made a case for my amp, mainly because i suck at wood working [img]graemlins/eyes.gif[/img]

Flo

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[Shotgun]

Re: Class A EL84 amp clip and \'live\' pic

Nice, Pete. Very very nice.

Keith

[Twisteramps]

Re: Class A EL84 amp clip and \'live\' pic

Yep. Any idea on wattage or volume and how much gain?

Pete

Originally posted by Matt Crooks:
Pete -

Would you be able to make a low wattage high gain monster? Basically something that was very brutal, but didn't need to be very loud?

Matt

<font size="2" face="Verdana, Helvetica, sans-serif">

[Matt Crooks]

Re: Class A EL84 amp clip and \'live\' pic

Gain - Uber/Recto/Pitbull type modern high gain
Volume - Not much

I'd be using this in the studio so there would be no need to be heard over a band in a live situation. So I'd guess 10-15 watts would be more than enough. I'd like to be able to saturate the power tubes, without destroying the walls of the house [img]images/icons/smile.gif[/img]

[Chuckracer]

Re: Class A EL84 amp clip and \'live\' pic

Pete, I can't help but think you're wrong about NOT making high-gain amps. Yes Bogner, VHT, Soldano etc. has that coverd but only in high power form. Low power high gain amps are pretty well non existant.
I think the sales of Hotplates alone would attest to the need for lower power amps.
Give some sculptability on the front panel and you have my interest.

[Twisteramps]

Re: Class A EL84 amp clip and \'live\' pic

I'm actually building a custom rackmounted power amp for a guy here on the JCF, FritzReiser. 2 rack spaces, Class A, with a built in power soak and ability to take just about any common octal tube for the power supply. (ie 6L6, 5881, EL34, KT88, 6550, 6V6, etc). What you could do is take the line out from one of your high gain heads and run it into one of these. This would be a lot more versatile than anything else, in my opinion. You'd get from about 3 - 12 watts or so.

Pete

Originally posted by Matt Crooks:
Gain - Uber/Recto/Pitbull type modern high gain
Volume - Not much

I'd be using this in the studio so there would be no need to be heard over a band in a live situation. So I'd guess 10-15 watts would be more than enough. I'd like to be able to saturate the power tubes, without destroying the walls of the house [img]images/icons/smile.gif[/img]

<font size="2" face="Verdana, Helvetica, sans-serif">

[Twisteramps]

Re: Class A EL84 amp clip and \'live\' pic

I've dabbled in it a bit. To build a two channel or more high-gain beast with turret boards would be a freaking nightmare, as far as oscillations, wire dress and noise are concerned. However, a high quality super-versatile low-wattage power amp is a niche that hasn't been filled, in my opinion. What else is out there? the 20/20 (great power amp, btw) and the marshall 20 watt one. I can't think of anyone else offering a built in power attenuator, abilty to change powertubes at will, and old construction methods that are much more labor intensive but sturdier and considered more toneful by many.

One amp I've tossed around a bit has been a single EL84 powered amp with a hotrodded marshall preamp. It's not ready for primetime just yet, but I'm getting closer all the time. I may build one with the new source for transformers I found... the ones in the latest amp I built really impressed me. Great tone, heavy as hell, and really nice quality.

Pete

Originally posted by Chuckracer:
Pete, I can't help but think you're wrong about NOT making high-gain amps. Yes Bogner, VHT, Soldano etc. has that coverd but only in high power form. Low power high gain amps are pretty well non existant.
I think the sales of Hotplates alone would attest to the need for lower power amps.
Give some sculptability on the front panel and you have my interest.

<font size="2" face="Verdana, Helvetica, sans-serif">