Flynn Amps - Rory Gallagher HAWK schematic & guts

apollomusicservice · Post by **apollomusicservice** » 02 Sep 2015, 09:34

For all those who like Rory's sound here is Hawk schematic, only for reference or entertainment.

tube-exorcist · Post by **tube-exorcist** » 02 Sep 2015, 12:00

Error in the schema: R9 is after C8.

Funny how people pay big bucks for a solder-jockeys claimed "exact replica" of the Hawk II which isn´t one.

1.) The original unit doesn´t have a gain pot, it has a gain switch.
2.) The maximum gain on the original unit is approx. the same as the minimum gain on the solder-jockeys unit.
3.) The tone control potentiometers are 20k or 50k in the original unit, but not 10k.
4.) R13 in the original unit is 220 Ohm (in some 200 Ohm) instead of the 120 Ohm and R15 is 120 Ohm in the original unit instead of 220 Ohm. This values influence the Q therefore the claimed clone is off. The original unit has a Q of ~4 at 150Hz the solder-jockey unit only ~2. The original unit has a Q of ~2 at 2500 Hz and the solder-jockey unit has ~5,6.
5.) The solder-jockeys unit is obviously voiced at 150 Hz, 800 Hz and 2400 Hz. According to Harry Kolbe himself who built/sold the Hawk II the original unit was voiced at 170 Hz, 550Hz and 2500 Hz.
[quote=Harry Kolbe]
Yea, I am the designer of the S.Hawk Ltd. series. The eq points on the Hawk II Tonal Expander are 170Hz, 550Hz and 2500Hz.These are not the points found on the typical recording and Hi Fi equalizers. More to the point, the Q or shape of the curve is quite different. The Hawk equalizers are the EQs for fretted instrument that implement the eq filters with inductors as opposed to the artificial inductors created by gyrators. hope this answers your question,
Harry Kolbe.
[/quote]
So 150Hz/170Hz and 2340Hz/2500Hz could be of tolerances, but the mid frequency (800 Hz instead of 550Hz) is way off.

Therefore: Never believe the lies a salesman tells you.

apollomusicservice · Post by **apollomusicservice** » 02 Sep 2015, 14:04

Thanks for R9 notes.

phatt · Post by **phatt** » 04 Sep 2015, 12:08

well as I'm into tone circuits,, Thought I'd at least simulate this one as I've never been close enough to even sniff such a unit.

Hum, Unless I'm missing something it seems you would need to re calibrate values if you used 50k pots?
All 3 pots at 5k give more extreme results.

At 25k the mid only imparts a shallow dip,, increase to 50k gives almost no tone control, stays flat.

What ever the correct values maybe it seems to me that some mojo might be found in the addition of C7 (22nF) which rolls off frequencies above 4~5kHz.
Over the years I've come to realize just how important it is to kill off excess hi frequency for electric guitar as it makes any treble boosting brittle and harsh.
In this circuit the treble would likely be smooth because of this and that alone might be part of any magic.

Adding the treble boost Sw gives about 10Db boost at the treble end actual freq depends a lot on the pot values and associated tone parts.

Oh yeah almost forgot,,Even with the corrected values used the mid point is ~700Hz? maybe I messed up but no luck getting it down to 550Hz,,, Yet.

I'll work on later.

Meantime here are several plots,, all taken with Bass & Treb max,, Mid Off.

Just thought I'd post my findings as it may need a lot of tweaking to work well.
Phil.

apollomusicservice · Post by **apollomusicservice** » 04 Sep 2015, 15:02

In this case pots are 10k and R15 is 220 ohm. R4 with C7 makes LPF at 4.8 kHz with -3dB.

tube-exorcist · Post by **tube-exorcist** » 04 Sep 2015, 23:34

phatt wrote:well as I'm into tone circuits,.....

Hum, Unless I'm missing something it seems you would need to re calibrate values if you used 50k pots?
All 3 pots at 5k give more extreme results.

At 25k the mid only imparts a shallow dip,, increase to 50k gives almost no tone control, stays flat.
.....

Very interesting find, I think I must have missed something.....

Now lets have a look, lets take the middle control.
First we use a 5 k potentiometer and turn it fully cw. Now the gain of the stage at the center frequency is determined by the ratio between the feedback resistor (1k5) and the potentiometer (0 Ohm) in series with the reactance of the L and the C and the resistor to ground (220 Ohm).

Now if we use a 50k potentiometer and turn it fully cw the gain of the stage at the center frequency is determined by the ratio between the feedback resistor (1k5) and the potentiometer (0 Ohm) in series with the reactance of the L and the C and the resistor to ground (220 Ohm).

Can you spot the difference ? I can´t.

phatt · Post by **phatt** » 05 Sep 2015, 11:54

apollomusicservice wrote:In this case pots are 10k and R15 is 220 ohm. R4 with C7 makes LPF at 4.8 kHz with -3dB.

I'm only going by the sim which in my hands may not mean much

but at least it gives clues.

Seems over 10k would be of little benefit. 5k pots maybe an improvement but I'd have the test it in the real world to know for sure.
your RC numbers match what the sim displays (at that node) but drops down to 3.5kHz at the output.
Phil.

phatt · Post by **phatt** » 05 Sep 2015, 12:08

tube-exorcist wrote:
phatt wrote:well as I'm into tone circuits,.....

Hum, Unless I'm missing something it seems you would need to re calibrate values if you used 50k pots?
All 3 pots at 5k give more extreme results.

At 25k the mid only imparts a shallow dip,, increase to 50k gives almost no tone control, stays flat.
.....
Very interesting find, I think I must have missed something.....

Now lets have a look, lets take the middle control.
First we use a 5 k potentiometer and turn it fully cw. Now the gain of the stage at the center frequency is determined by the ratio between the feedback resistor (1k5) and the potentiometer (0 Ohm) in series with the reactance of the L and the C and the resistor to ground (220 Ohm).

Now if we use a 50k potentiometer and turn it fully cw the gain of the stage at the center frequency is determined by the ratio between the feedback resistor (1k5) and the potentiometer (0 Ohm) in series with the reactance of the L and the C and the resistor to ground (220 Ohm).

Can you spot the difference ? I can´t.

Yes thanks, I see your point but there are 3 stages which are all interlinked and that would obviously alter the outcome.
If only a single RLC section was in place then your observation would be right but there are 2 more RLC parallel sections involved here so it must alter the outcome?

BTW, When I said I'm into tone circuits that might mislead you into thinking I'm conversant with then all,, I wish

They just fascinate me as they are all subtly different and I've built enough to know what shape the curves will likely sound like if built.

This circuit (using 10k pots) only seems to be able to create a 10Db difference between 2 frequencies and that is unlikely to impress me if i built it.
I already have a tone circuit which delivers over 30Db difference so I'm not about to etch a board just because someone famous used this circuit.
Just sharing my observations.

Phil.

Siberian · Post by **Siberian** » 03 Oct 2018, 12:12

Hello

Mine is too loud even if I lower the volume pot to the minimum.
Any ideias to add a trim inside or change something to control this? Its just too loud can't use it like this

Thank's
JF

ppluis0 · Post by **ppluis0** » 05 Oct 2018, 02:51

Hi JF,

Just increase the value of resistor R7 to 12K (that is the same to put the gain pot to minimum in the actual configuration) and see if this is as you expect.

Cheers,
Jose

malc_p · Post by **malc_p** » 17 Apr 2023, 17:11

Hi - I'm looking at this circuit currently with a view to cobbling one up for testing, and thought I'd make a comment/ask a question:
Regarding 'Q' of the three sections and the statement that Q for the bass control should be 4 or so - I thought 4 would make it sound very peaky?
I checked using the classic formula Q=(1/R)*sqrt(L/C) for a series LCR circuit and the 'correct' values given, I'm getting Q of around 1.5 for bass. I don't think I'm misreading anything but am happy to be corrected...
NB I get around 2 for Mid & Treb
Cheers
Malc