Super Lead Tweaks - Unchained

[emmjaydubya]

Great thread guys, here's the DF spec, posted by Dave himself:

Split cathode V1a 250uF/820,V1b .68/820
All coupling caps are 0.022uF,Bright channel coupling cap is 0.0022uF

470k mixer resistors
500pf [red out of 69 amp] mixer bypass cap
Bypass cap on V2a is .68uF and a 220uf to 470uf
33k/560pF lemco tone stack combo
100k NFB resistor at 4 ohm tap
220k bias splitter resistors
0.1 uF cap on presence control
.022uf output couplers

filtering is
2] 100uf's f&t in series mains
2] 32uf's f&t in series screens
1]100uf lcr phase inverter
1] dual 33 x 33 f&t preamp

Taken from the awesome 'Debate on Eddie's Plexi' thread, on page 42 (fitting that a post by StuntDouble is at the top):

http://forum.metroamp.com/viewtopic.php ... &start=615

[awangotango]

fwiw, the '72 he worked of for me (sounded nasty/sweet) had dual caps on the mixer resistors (keep the stock 560pf lead ch cap and add a 500-560pf to the normal channel) which was a cool mod that's worth a try. It allows you to jack the 'unused' normal channel's volume to squeeze out some extra saturation - as opposed to v2a cap gain which is more distortion than saturation) .......About half of the other values listed were on mine, half different. He just dimes them and then dial's each amp in by ear i'm pretty sure....... feedback of 100/4 is too loose and 'gurgly' imo and was not on mine.........plus if rgalpin is sending the signal to v30's, all bets are off. The missing 'spring' quality might very well be a vintage greenback cab and not in the amp

[rgalpin]

Another clip: no change to the amp here - just some other VH riffs through the same spec...

http://soundclick.com/share.cfm?id=11676508" onclick="window.open(this.href);return false;

FYI - Hang 'em High riff is with the guitar vol at about 7-ish... stays pretty clear.

it's a different game with every amp - every cab - every guitar - every player - yee ha!! My goal is to get this amp sounding cool - I'm going to go through these ideas with my ears on - so I think it's great to know what CAN work and go from there.

[leadguy]

v1b is 2.7k/.68.

I thought that was a later model, more highs and more gain spec.

on v1a i have 1.5k/.68 - how does that compare to the 2.7k/.68?

AND how doe both of those compare to a shared? what is the usual values on a shared setup? dag - i used to know this stuff inside and out...

ok - on the CC placements thanks!

If you stay with the .68 cap, then the lower the resistor value the more gain results and the bass rolloff frequency goes up, meaning it sounds more mids based.

A 820 ohm/.68 combo results in more gain and more emphasis in the mids than a 2.7k/.68 combo.

In the chart below, the 820 ohm/.68 combo starts rolling off the bass around 431Hz whereas the 2.7k/.68 combo starts rolling off the bass around 232Hz meaning that the 2.7k/.68 combo results in more bass frequencies getting through the amp than the 820 ohm/.68 combo.

The cathode resistor/capacitor combos that result in the frequency where the bass starts to roll off is roughly in this chart

[awangotango]

you're getting further away. compare that to clip 1. yes the new clip is tighter, but it's got no character and certainly no more spring........those are 60w speakers and they are each seeing less than 20w each correct? (80w/4) have you tried unwiring two so you can send the remaining 2 some extra volume. May get some extra push/pull (spring) from pushing them harder. the remaining 2 would be like passive radiators. wonder what that would sound like....Probably best to take them out entirely and block off the holes though.......that's alot of work though....keep soldering !

[rgalpin]

those are 60w speakers and they are each seeing less than 20w each correct? (80w/4) have you tried unwiring two so you can send the remaining 2 some extra volume. May get some extra push/pull (spring) from pushing them harder.......

Does the attenuator mess this relationship up? For example, since I would rather not re-wire the cab, I could put 4 tubes in and I'd be sending more push to the ATTENUATOR but would it make any difference to the speakers since the attenuator is soaking it all up? It could be that in an attenuated setup that you change the speakers role and probably limit it rather severely in terms of PHYSICAL speaker action CREATING tone and feel. I imagine that in an attenuated setup the speakers become relatively, if not, totally passive in that respect - depending on how much you attenuate.

If my goal was to create VH tone at all costs I would get rid of the attenuator and start digging into this aspect - but my goal is to have a great sounding rig at just about "yelling at the top of your lungs" volume not at JETS ON THE TARMAC volume. haha!!

So, that comes into play... with my approach.

[rgalpin]

v1b is 2.7k/.68.

I thought that was a later model, more highs and more gain spec.

on v1a i have 1.5k/.68 - how does that compare to the 2.7k/.68?

AND how doe both of those compare to a shared? what is the usual values on a shared setup? dag - i used to know this stuff inside and out...

ok - on the CC placements thanks!

If you stay with the .68 cap, then the lower the resistor value the more gain results and the bass rolloff frequency goes up, meaning it sounds more mids based.

A 820 ohm/.68 combo results in more gain and more emphasis in the mids than a 2.7k/.68 combo.

In the chart below, the 820 ohm/.68 combo starts rolling off the bass around 431Hz whereas the 2.7k/.68 combo starts rolling off the bass around 232Hz meaning that the 2.7k/.68 combo results in more bass frequencies getting through the amp than the 820 ohm/.68 combo.

The cathode resistor/capacitor combos that result in the frequency where the bass starts to roll off is roughly in this chart

cool! I remembered the concept but had it backward. So when you say more mids based it is confusing, at first I'm thinking: more mids = warmer. But I think what you are saying is more mids based COMPARED to a more flat response coming from the 2.7K since the roll off there is so low that it is almost just a "get rid of the bass garbage" filter. Whereas the 820/.68 get's rid of a little bit of the meat underneath, creating more percieved intensity in the mids. Am I right about what I think yer saying? ??

[leadguy]

The 820/.68 combo gets rid of more bass than the 2.7k/.68 combo leaving the sound more based in the mids and the 820/.68 combo results in more gain than the 2.7k/.68 combo.

So a 820/.68 combo will have a more gain in the mids thing happening than a 2.7k/.68 combo.

[rgalpin]

The 820/.68 combo gets rid of more bass than the 2.7k/.68 combo leaving the sound more based in the mids and the 820/.68 combo results in more gain than the 2.7k/.68 combo.

So a 820/.68 combo will have a more gain in the mids thing happening than a 2.7k/.68 combo.

hmmm... squawky kind of mids or lower mids than that? got to try that again.

at one point, didn't we figure out that 1.5K/.68 @ v1 simulated the value you get on a shared cathode with an 820/.68?

[leadguy]

The 820/.68 combo gets rid of more bass than the 2.7k/.68 combo leaving the sound more based in the mids and the 820/.68 combo results in more gain than the 2.7k/.68 combo.

So a 820/.68 combo will have a more gain in the mids thing happening than a 2.7k/.68 combo.

hmmm... squawky kind of mids or lower mids than that? got to try that again.

at one point, didn't we figure out that 1.5K/.68 @ v1 simulated the value you get on a shared cathode with an 820/.68?

To my ears, the 820/.68 has great mid drive when the other gear matches of course.

The 820/.68 does remind me of Ed.

Lots of mids.

Ed's main amp serial number is 12301 and here is a Marshall 1230x circuit schematic http://forum.metroamp.com/viewtopic.php?f=25&t=9680" onclick="window.open(this.href);return false;

Ed's has a 820/.68 on V1 according to Dave Friedman (Ed also had a 820/.68 on V2 but Ed had it changed at some point to a 470uf or something like that in parallel with the .68).

The 1230x circuit which is so close to Ed's, has the 820/.68 combo on V1 and V2 as well.

[vanhalen5150]

If your going to use the attenuator, I say put the 4 tubes in.

[Funky Hunky]

First off. Great sound. A little too tight. Not furry enough in my opinion. Not enough smear to the single notes. Especially the Unchained part. Ed's amp sounds like he went too low on the voltage and it's shitting itself a little. Something missing in the mids too, like a notch.. if you will?

[MrBeasty]

those are 60w speakers and they are each seeing less than 20w each correct? (80w/4) have you tried unwiring two so you can send the remaining 2 some extra volume. May get some extra push/pull (spring) from pushing them harder.......

Does the attenuator mess this relationship up? For example, since I would rather not re-wire the cab, I could put 4 tubes in and I'd be sending more push to the ATTENUATOR but would it make any difference to the speakers since the attenuator is soaking it all up? It could be that in an attenuated setup that you change the speakers role and probably limit it rather severely in terms of PHYSICAL speaker action CREATING tone and feel. I imagine that in an attenuated setup the speakers become relatively, if not, totally passive in that respect - depending on how much you attenuate.

If my goal was to create VH tone at all costs I would get rid of the attenuator and start digging into this aspect - but my goal is to have a great sounding rig at just about "yelling at the top of your lungs" volume not at JETS ON THE TARMAC volume. haha!!

So, that comes into play... with my approach.

You can plug your attenuator (set to full load) in parallel with your cab (as long as they are of the same load value) and loose half your output power and the load would not be affecting the speaker signal directly.

[stef]

100uf's f&t in series mains = 50uf total
32uf's f&t in series screens = 16uf total

[rgalpin]

100uf's f&t in series mains = 50uf total
32uf's f&t in series screens = 16uf total

I KNOW - I thought the same thing.

Does the spec refer to 2 100+100 cans (wired in parallel) in series?

Or does it truly mean 2 100uf caps in series, which you would get by lifting the jumper on each 100+100 can??????????????????

Same for the 32.

Does anyone have a definite answer on this? I know i know - use your ears - but I STILL want to know what the SPEC is so that when we refer to it, we are all referring to the same thing.