Wednesday 3 May 2017

LEHLE Sunday Driver

From the Source:

The Lehle Sunday Driver SW is a compact-format high-end preamp for all types of electrical and acoustic instruments - a preamp that enables electric guitars and basses, acoustic guitars, and also other stringed instruments (such as violins, cellos and double basses) to realize all of their musical potential. The switchable version expands the classical Lehle Sunday Driver's features by an On/Off footswitch. 

The Lehle Sunday Driver SW, with its high-quality JFET technology, provides two operating modes. In D (= Driver) mode, the input signal is amplified with zero modification, to eliminate the signal losses that long cable routings and/or effects chains can cause. The signal remains powerful and clear, and retains its dynamics. Mode S (= Sunday) multiplies input impedance by four, bringing out previously inaudible details and, as gain increases, imparting to the guitar a characteristic and unmistakable warmth. There is no distortion at any stage, and the signal always stays clean, even at a maximum gain setting of 15 dB. Thanks to its studio-standard signal-to-noise ratio of better than -100 dB, the Lehle Sunday Driver SW is totally free of background noise. To exploit the dynamics of tube amplifiers to the full, the input voltage is also rectified from the power supply socket, then filtered, stabilized and doubled to 18V. 


In OFF status, the Lehle Sunday Driver SW provides two different modes of operation - in TB (= True Bypass) mode, the input and output are linked with zero losses to one another via a switch with gold-plated contacts. True Bypass mode is the best option for a small set-up with short cable routings and for when a treble-booster or a classical fuzz pedal is looped in after the Lehle Sunday Driver SW. The line-driver function, located at the start of the train or in an effect chain, is the better solution for long cables and for complex effect board configurations. Switch the Lehle Sunday Driver SW to TS (= True Sound) mode, and it is active as a buffer, without amplifying or modifying the signal in any way. In this mode, the Lehle Sunday Driver SW operates as a totally neutral line-driver – equivalent to Mode D with the gain pot turned all the way to the left. The Bypass mode option enables the Lehle Sunday Driver SW to integrate ideally into any set-up, whether as a battery-operated stand-alone unit, or in an existing pedal board. 




Note: I removed the odd power network, which consisted of a diode rectifier and regulator, which should not be needed since it's supposed to run on +9VDC not +9VAC. According to the site, they claim there's a TB/Buffered switch which is not included on the schematic, nor did I see it on the PCB over at FSB when it was reversed engineered.

29 comments:

  1. What switches are being used? Thnx!

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    1. Forgot to put it in the notes. It's a SPDT (on-on) switch.

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    2. So, I'm guessing the boost and the gain are the same thing? Thnx for the clarification.

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    3. yea. they didn't mention the name of the pot in the schematic so was debating what to call it. in any event, i fixed it.

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  2. Are you sure? It feels like a DPDT for me (cause of the 6 legs, not 3). Also there's a note "SW3 empty", but there's a SW3 on the top row as well. Can you take a look? Thanks man!

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    1. You're right, it's a DPDT (on-on) switch. Stupid autocorrect on my iPhone. Didn't realize it changed it to SPDT before I posted it.

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  3. Hi Zach, I think the bridge rectifier -> voltage regulator is to allow any input power supply, AC, or DC between 9 and 20 or so volts, like the Award Session pedals used to accept - presumably there are circumstances in the professional audio industry where >9v power is readily available (though, I'd have thought the obvious >9v supply would be 48v phantom power, which is higher, I think, than the regulator's max input).

    Mind you, a 9v DC input would presumably suffer from 2 diode drops at the bridge, then whatever the dropout voltage of the regulator is too.

    The manual on the LEHLE site mentions, rather alarmingly, that "[the power} connector can also be soldered on to your power-pack mains cable" - I hope there's something lost in translation there!

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  4. Hey Zach,
    What does "switch three empty" mean?
    Thnx! going to attempt this one for acoustic.

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    1. Hey Bro. It's not connected to anything. Usually I leave it blank, but end up getting asked constantly what does it connect to, so I thought putting in the notes that it's empty might prevent any confusion.

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    2. That's what I thought. I was just confused why there would be a switch 3 on the layout and then say switch three empty. Anyways, hopefully I can verify it soon. Thnx!!!

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  5. Hey there,

    to avoid confusion: the schematic you posted is from the SUNDAY DRIVER (neither doesn’t have a TS/TB button nor an on/off footswitch), while the product description is of the SUNDAY DRIVER SW.
    http://lehle.com/EN/Lehle-Sunday-Driver
    http://lehle.com/EN/Lehle-Sunday-Driver-SW

    Cheers
    Joki / Lehle

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  6. This thing is verified! It sounds really good. I don't know if the switch is doing anything. Switch three empty or switch four empty does nothing. I tried putting wire three on switch four and vice versa. Anyways, this is a really nice preamp/boost. This is my first verification! If you figure anything out on the switch let us know thank you all...and Mr. Lehle:)))

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  7. there's a wire going from the board labelled to "sw 3" then the dialog at the bottom says sw 3 empty. should this be "sw 4 empty"? and how do you number switches?

    1 4
    2 5
    3 6

    that correct? is it 3 or 4 that's empty?

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  8. SW4 is empty and SW5 goes to Gain 1 not 2&3.

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  9. Hi,great blog.
    In this layout I think there is missing a 10nf capacitor after the 6.8k input resistor.

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  10. I also think, a 10nF is missing in place. He is between the 6K8/SW2 and the 3M9/120pF/IC2-3.

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  11. I fixed the problem with a cut under the 2,2nF (on K3) and a 10nF as bridge between the 6K8/SW2 and the 3M9/120pF/IC2-3(from K2 to K4).
    Thats all.
    Thanks for this great blog!!

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  12. Hi everyone, I've just finished building one of these, it works well but despite being at the highest level, the output volume is anyway lower than the volume in bypass

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  13. Hello!
    I don't understand if this layout is verified or not.

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  14. I've had another look at this. The "tone switch" is dubious - if it's working it's very, very subtle. The 10nf bridge mentioned a few comments back looks right and I've made that adjustment, though it doesn't seem to do anything. Also in my build the effect boosts the signal a bit even with the gain all the way down. The layout here is definitely missing a few things from the original schematic (the power diodes and 18v thing?) so my guess is that that has unbalanced something somewhere.
    So not verified I would say.

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  15. Hi, I did the board, but, can you explain how SW and Gain work please...

    Fred

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    1. Hi, a another thing. I put 9.1VDC and the voltage to the 8 pin of IC1 is 6.8V? I don't understand why!!!

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  16. The pic needs to be fixed... how on earth can SW3 be empty AND have a wire from the board... confusing as heck

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  17. Switch does nothing, this is the worlds most expensive clean boost.. don't built it

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  18. Caution, there is supposed to be a cut next to the input resistor (6k8)! I guess it gets masked by the capacitor passing over it, at least on my device it's invisible. Omitting this cut will diminish the effect of the "sunday mode", but more importantly it will feed the bias voltage to the input jack.

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