Top Hat Club -is it any more than a lightning with 6V6's ?

[chopstuck]

Gee, I tried the pot on the ground leg of the divider without adding the 220k resistor to the PI and it adds quite a mid hump as you increase the gain.
I will try adding the 220K and report back.

I didn't care for the cut control as drawn with the .0047 cap and the 250k pot. I tried the .0022 cap as well but didn't like it either.
Just got too dull past the halfway point. I then put a 47k resistor in series with the cut pot so the range is now 50k-300k and it makes the whole sweep more useful and keeps some high end when on full cut.

I also like the 820R on the PI cathode. - 18watt Marshall territory.
So far I have found some nice tones but a lot of MUD too.

My humbuckers prefer the low gain input. I have to work on that mid-bass hump. Present on my three trial speakers

Any idea how to raise the center freq on the mid control ?

[Gee]

Gee, I tried the pot on the ground leg of the divider without adding the 220k resistor to the PI and it adds quite a mid hump as you increase the gain.
I will try adding the 220K and report back.

I'm not sure why increasing the divider should increase the mids. Update: Perhaps the divider is having an effect on the tone stack that you are hearing.

I searched about quite a bit to find out why the 220k (R10 in the Rocket) is there in quite a few designs. Because it is de-coupled from the PI by the coupling cap, most people say it doesn't act as a grid stopper or create a divider with the PI input impedance. Others say that it does. I will fit one and try it on the basis that it is easier to switch it in and out of the circuit, to try it. My thinking is that if Ken Fisher used it and it is directly in the path of the signal train, then there must have been a reason for it to be there. Otherwise he would have pulled it out.

That divider before the PI is I think one of the main things to tune to your own taste. Matchless uses 220/100 for 31%, Top Hat uses 220/150 for 40% and Vox uses 220/220 for 50% signal attenuation before the PI. The Rocket has no attenuation (assuming that the lone 220k before the PI doesn't reduce the signal). So I think it's a good place for a pot or some switched values.

I didn't care for the cut control as drawn with the .0047 cap and the 250k pot. I tried the .0022 cap as well but didn't like it either.
Just got too dull past the halfway point. I then put a 47k resistor in series with the cut pot so the range is now 50k-300k and it makes the whole sweep more useful and keeps some high end when on full cut.

I checked my amp and I actually have 2n with 250K for my cut control. From memory the cut control cap usually matches the main coupling cap size when 220k grid resistors are used. So if you have 4n7 coupling caps, usually 4n7 is a good size for the cut control cap.

I also like the 820R on the PI cathode. - 18watt Marshall territory.
So far I have found some nice tones but a lot of MUD too.

My humbuckers prefer the low gain input. I have to work on that mid-bass hump. Present on my three trial speakers

Any idea how to raise the center freq on the mid control ?

Increasing the mid pot should do it. Have a look at the TSC Tone Stack program and put the Top Hat values into the Marshall type stack (if you haven't already done so).

I played about with a switched 820r or 1k2 tail resistor and I found that the amp lost some of it's sparkle with the 820R.

[Masco]

I believe all of these designs are slight variations of the Vox AC-30 circuit. The 220k to ground in the divider simulates the mixer resistor from the "Normal" channel in the AC-30/6. It's like playing through the "Brilliant" channel with the Normal channel volume on '0'.

[chopstuck]

Gee, tonite I tried the second 220k resistor in your mod and it seems to decrease the midrange freq. hump. I can see keeping that with the adjustable pre PI boost you drew up.

My amp started to loose it's identity with these mods so I returned to a 1K2 on the PI. I then changed the choke resistor from 1K to 4K to bring down my nodes, (they were all 30v too high ). The amp acts how it's supposed to again.

Do you think I may have dropped the screens too much ? The amp's seems a little down on grunt. My plates are at 377v, screens at 335v. The other nodes are within +/-2v of the hand drawn schematic. Too late tonight. I may try to raise the screens and drop the next nodes with string adjustments. I'm keeping the boost so far...

[Gaz]

I think raising the the dropping resistor to the screens is the less preferred way to lower the other preamp nodes. In fact, I can't think of another amp that does it this way, and I think it's because it causes too much sag, and lowers output power.

You could avoid those problems by simply raising the values of the dropping resistors going to the PI and preamp tubes. I personally think both your plates and screens are way too high for EL84s, but hey, if they're not burning up, more power (pun) to you!

[chopstuck]

No, my build is a Club Deluxe with 6V6's. I'm going off the hand drawn SH schematic.
I will try changing the string back to 1k at the second node and then a 3K to follow, feeding the next two. I should get a little grunt back.

The tone is there now.

[Gee]

Do you think I may have dropped the screens too much ? The amp's seems a little down on grunt. My plates are at 377v, screens at 335v. The other nodes are within +/-2v of the hand drawn schematic. Too late tonight. I may try to raise the screens and drop the next nodes with string adjustments. I'm keeping the boost so far...

Perhaps another way to reduce the voltage would be to introduce a string of high power zeners between the PT and its ground point. Bruce Collins at Mission Amps has suggested this many times as a way to get 5E3 Deluxe B+ down to a 350V sweetspot for 6V6's. I did it on a Deluxe and worked very well.

Changing the 1k for a 4k is too big a deviation from the design I feel.

[bluesfendermanblues]

Why not install VVR power scaling on the output tubes? and a proper dropping string for the PI and Preamp tubes.

Have installed VVR in a 5E3 (clone) works like a charm. However, don't scale the whole amp only the voltages for the Poweramp....6V6 plates (B1) and 6V6 screens (B2).

Allows you to run the 6V6s at any voltage you like.

[Gee]

Why not install VVR power scaling on the output tubes? and a proper dropping string for the PI and Preamp tubes.

In my experience it's better to scale the PA&PI in LTP types of amps.

Using a VVR is always going to be a compromise of some sort, but from my own testing, keeping the pre-amp section at full voltage (with corrected value dropping resistors) and scaling the rest sounds the best.

One disadvantage of that method is that the pre-amp full voltage can vary inversely by about 40v as the PA&Pi are scaled from max to min. Still well worth it though.

[bluesfendermanblues]

In my experience it's better to scale the PA&PI in LTP types of amps.

What is a LTP ?? (long tail phase inverter?)

Doesn't the Suhr Badger use power scaling on the output tubes only?
(I really like the sound of that amp, but so far has not been able to get a schematic of at least some details on that amp.)

One disadvantage of that method is that the pre-amp full voltage can vary inversely by about 40v as the PA&Pi are scaled from max to min. Still well worth it though.

You can add some zeners to the preampsupply to 'clamp down' the voltage to e.g. 300vdc at the beginning of the preamp dropping string

[Gee]

What is a LTP ?? (long tail phase inverter?)

Yes, correct.

[Gaz]

[quote="chopstuck"]No, my build is a Club Deluxe with 6V6's. I'm going off the hand drawn SH schematic.
I will try changing the string back to 1k at the second node and then a 3K to follow, feeding the next two. I should get a little grunt back.

The tone is there now.[/quote

Duh! that's 6V6 is in the title of the thread! Haha.

[rdjones]

What is a LTP ?? (long tail phase inverter?)

Long Tail Pair, derived from the fact that 2 triodes are used.

rd

[chopstuck]

Well the amp sounds killer now.

I have left the 1K choke resistor in place. I then added a 4K resistor before the star point for the 3 parallel strings. This brought the V+ down to +/- 3 vdc of spec. I then had to double my 22k string PI resistor to 44k and all is well.
With the increased PA voltage I also had to increase the Rk to 360R. My old RCA's now draw about 35ma each at idle.

The amp does sound a lot like a Lightning or an AC 30 when clean. The amp had all that sparkle I didn't think I could get from 6V6s but it has a different OD character.
It also stays cleaner longer before a controlled breakup. I think it's a difference in the lower mids that the EL84's don't emphasize.
Their emphasis lies at a higher freq when at breakup. So to answer my own question, I suppose the Club Deluxe is different enough from a lightning. I left in the adjustable PI drive, nice for thickening the tone with clean drivers.
The mid control adds some flexibility too. The amp is sensitive to speaker choice too. Mine likes the Celestion G12k-85 as well as the JBL D-130F. Amp hates the Signature 12s. I will try the greenback 25 next should be fun.

Now I have to get the correct value resistors, instead of the cobbled together values, so the gut shot will look more presentable.

Is this the part of the process people call "voicing" ?

[bluesfendermanblues]

What is a LTP ?? (long tail phase inverter?)

Long Tail Pair, derived from the fact that 2 triodes are used.

rd

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