Dave Friedman mods to Concorde?

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M Fowler
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Re: Dave Friedman mods to Concorde?

Post by M Fowler »

Ah yes it is 10k on the k60 good catch Dave.
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Colossal
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Re: Dave Friedman mods to Concorde?

Post by Colossal »

Mark, your avatar right now is a fitting tribute to this thread! Wow, that is a great looking head cab. One of these days, I'll treat myself to one like that! 8)
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M Fowler
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Re: Dave Friedman mods to Concorde?

Post by M Fowler »

1. Old notes: One difference between concorde k50 and the k60 is that it uses the 'left-over' triode as a cathode follower...to drive the PI.

2. The third triode is not set up as an asymmetrical clipper. Instead of an unbypassed 10K cathode resistor, it is 3.3K, also unbypassed.

3. The third triode's input is not the 220K/330K voltage divider - it is a simple 330K grid reference....I *think*. The 330K's tail could either be grounded, or it could be series resistance into the grid...but since there must be *some* ground reference I think it must be grounded.

4. The third triode drives a CF (standard configuration, 100K cathode resistor), which in turn drives the PI through the .022uF cap and 220K series resistor. Other than that the differences are in parts selection - there are more Orange Drops in the Concorde, the treble cap is a ceramic disc...there is a big CC resistor in the power supply that was metal oxide in the 60.
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Re: Dave Friedman mods to Concorde?

Post by M Fowler »

Thanks Dave, that Larry Mann (Distortions) does great work. I told Larry take your time and make a beautiful cabinet please, he did.
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Re: Dave Friedman mods to Concorde?

Post by Scumback Speakers »

My Koncorde is a Marshall on steroids (gradual mode) and a TW beast on the "Fast" mode. The tweaks Dave did to mine pushed it to the next level in touch response/gain and tonal nirvana.

Of course, getting the fast/gradual footswitch mod by Allyn was a complete godsend as well.

And I'm sure it didn't hurt that it's got some nice old glass in it, too.
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M Fowler
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Re: Dave Friedman mods to Concorde?

Post by M Fowler »

Jim that sounds like an amp worth having around :)

I tried so many times to get a board set from Dana but no luck so I think I have all the notes I need to try make that foot switch circuit.

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Re: Dave Friedman mods to Concorde?

Post by ampdoc1 »

Jim,

What is the Concorde switch mod,...is that using FETs to switch?

I've used the Concorde a lot, but I dislike having to throw a rear panel switch.

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Re: Dave Friedman mods to Concorde?

Post by M Fowler »

It's a foot switchable fast/gradual mod.
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Colossal
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Re: Dave Friedman mods to Concorde?

Post by Colossal »

Southbay Ampworks wrote:My Koncorde is a Marshall on steroids (gradual mode) and a TW beast on the "Fast" mode. The tweaks Dave did to mine pushed it to the next level in touch response/gain and tonal nirvana.
Jim, thanks for the description, very helpful. The Concorde shares a little in common with a JCM800 in some ways. Of course the the tone stack is plate loaded Trainwreck fashion off the first stage, then the typical Wreck 1k5/22uF stage, then the added warm(er) clipping stage in front of a cathode follower, which then drives the PI. An interesting use of that last triode.
Southbay Ampworks wrote:Of course, getting the fast/gradual footswitch mod by Allyn was a complete godsend as well.
To quote Allyn from the original discussion when the first clones appeared, "The Concorde is played for the most part in Gradual mode. The Fast mode is for lead playing only and adds harmonic content. The VVR brings it down to whisper level but the amp is not made for that. The VVR was to adjust to room size for a gigging musician. That being said, you could whisper over the amp at lowest power. The footswitch makes an almost useless feature usable."
ampdoc1 wrote: What is the Concorde switch mod,...is that using FETs to switch? I've used the Concorde a lot, but I dislike having to throw a rear panel switch.
Mark Huss came up with the high-speed switch and it's based on a mosfet.
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Re: Dave Friedman mods to Concorde?

Post by Colossal »

Can anyone confirm if the original Concordes (K50) used a ceramic treble cap? I have a note that that was the case but I have only seen silver mica caps in the few pictures of clones that have been made so have never been able to confirm that.
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Re: Dave Friedman mods to Concorde?

Post by PCollen »

JamesHealey wrote:Why mod a concorde?
W/R/T the focus of this forum, isn't that kind of like asking why Edmund Hillary climbed Mt. Everest, or why Don Garlits always wanted to go faster ? :wink:
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Re: Dave Friedman mods to Concorde?

Post by Colossal »

PCollen wrote:
JamesHealey wrote:Why mod a concorde?
W/R/T the focus of this forum, isn't that kind of like asking why Edmund Hillary climbed Mt. Everest, or why Don Garlits always wanted to go faster ? :wink:
A: because you can! :lol: :wink: 8)

Actually, I can see how an amp which is otherwise fantastic might have some trait that when tweaked just makes it that much better and suits an individual's needs and tonal desires just a little more. All part of the fun.

I have a number of ideas of my own but, out of academic curiosity, I would be very interested to know what was modded on Jim's amp to improve touch sensitivity etc. I'm sure it sounds killer.
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M Fowler
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Re: Dave Friedman mods to Concorde?

Post by M Fowler »

I'm not sure what the Friedman mod is but perhaps Allynmey or others will chime in and help us out here :)

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Re: Dave Friedman mods to Concorde?

Post by Jackie Treehorn »

The third triode in the Concorde, will clip asymmetrically, too due to the dc coupled cathode follower. The cool (or frustrating) thing about DC coupling is you can change two things at once. If the third triode was biased colder like a K60 with a 10k bias resistor, then we can estimate that the plate of the triode would be at about 270 volts (I'm using express voltages, here actually) which would put the grid of the cathode follower at 270 volts which would pull the cathode of the cathode follower to something like 271 volts, which greatly exceeds the cathode to heater limit of the tube. By biasing that triode stage hotter, the plate voltage comes down on the triode gain stage and those voltages are more in line. The cathode follower is in a state of grid conduction, so it pulls down the plate voltage of the third triode, causing a colder bias and the clip to be asymetrical, during the positive portion of the signal. I suspect that's why the k60 and k50 sound similar, at least on Komet's website.

I don't think there's any advantage to using the low impedance output to drive the phase inverter, though.

I do remember the thread on TGP with these mods. There were clips to compare. It sounded to me like the mods backed off the signal to the power amp, allowing more gain before losing the tightness, perhaps increasing the 220k in front of the PI. The amp had more of a hair metal sound with the mods.
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Re: Dave Friedman mods to Concorde?

Post by Colossal »

Jackie Treehorn wrote:The third triode in the Concorde, will clip asymmetrically, too due to the dc coupled cathode follower. The cool (or frustrating) thing about DC coupling is you can change two things at once. If the third triode was biased colder like a K60 with a 10k bias resistor, then we can estimate that the plate of the triode would be at about 270 volts (I'm using express voltages, here actually) which would put the grid of the cathode follower at 270 volts which would pull the cathode of the cathode follower to something like 271 volts, which greatly exceeds the cathode to heater limit of the tube. By biasing that triode stage hotter, the plate voltage comes down on the triode gain stage and those voltages are more in line. The cathode follower is in a state of grid conduction, so it pulls down the plate voltage of the third triode, causing a colder bias and the clip to be asymetrical, during the positive portion of the signal. I suspect that's why the k60 and k50 sound similar, at least on Komet's website.
Excellent post as usual Jackie. I suspect they lowered the 3rd stage cathode resistor to 3k3 from 10k with the addition of the cathode follower in the K50 specifically because of the increased gain the CF would add to the 3rd stage. It would be a good idea to DC elevate the follower to bring down the grid-to-cathode voltage.
Jackie Treehorn wrote:I don't think there's any advantage to using the low impedance output to drive the phase inverter, though.
I love what cathode followers can bring to an amp and I'm guessing that there's a bit of added compression with it in the K50 although that could be really enhanced too if desired with some adjustments to the CF. I'm kind of a compression freak though (as long as it's not overdone), just a bit of added warmth and singing sustain.
Jackie Treehorn wrote:I do remember the thread on TGP with these mods. There were clips to compare. It sounded to me like the mods backed off the signal to the power amp, allowing more gain before losing the tightness, perhaps increasing the 220k in front of the PI. The amp had more of a hair metal sound with the mods.
Hmm interesting. So by "hair metal" would that be good or bad? :lol: I can get some really heavy but tight sound out of my modded JCM but I do not care for the buzzy, one-dimensional chain saw tone some of the over-modded JCMs can take on. Lifeless and boring, so that's kind of what I equate with some "hair metal". Pete Thorn's Concorde video demos sound great so I was thinking that the Dave Friedman's mods would certainly not make the amp worse off and Jim's description sounds like it only made the stock amp better.
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