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Groups > sci.electronics.design > #452505 > unrolled thread

How do those Spring Reverbs work in guitar amps?

Started byoldschool@tubes.com
First post2017-03-18 19:12 -0500
Last post2017-03-20 16:26 -0400
Articles 2 on this page of 42 — 14 participants

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  How do those Spring Reverbs work in guitar amps? oldschool@tubes.com - 2017-03-18 19:12 -0500
    Re: How do those Spring Reverbs work in guitar amps? rickman <gnuarm@gmail.com> - 2017-03-18 20:47 -0400
      Re: How do those Spring Reverbs work in guitar amps? Phil Allison <pallison49@gmail.com> - 2017-03-18 18:11 -0700
    Re: How do those Spring Reverbs work in guitar amps? Phil Allison <pallison49@gmail.com> - 2017-03-18 18:08 -0700
      Re: How do those Spring Reverbs work in guitar amps? Don Kuenz <g@crcomp.net> - 2017-03-19 05:08 +0000
        Re: How do those Spring Reverbs work in guitar amps? Phil Allison <pallison49@gmail.com> - 2017-03-18 22:38 -0700
          Re: How do those Spring Reverbs work in guitar amps? jurb6006@gmail.com - 2017-03-19 02:46 -0700
            Re: How do those Spring Reverbs work in guitar amps? Phil Allison <pallison49@gmail.com> - 2017-03-19 04:25 -0700
              Re: How do those Spring Reverbs work in guitar amps? jurb6006@gmail.com - 2017-03-19 06:01 -0700
              Re: How do those Spring Reverbs work in guitar amps? jurb6006@gmail.com - 2017-03-19 07:46 -0700
        Re: How do those Spring Reverbs work in guitar amps? "Dave M" <dgminala@mediacombb.net> - 2017-03-19 22:49 -0500
          Re: How do those Spring Reverbs work in guitar amps? Phil Allison <pallison49@gmail.com> - 2017-03-19 22:31 -0700
            Re: How do those Spring Reverbs work in guitar amps? "Michael A. Terrell" <mike.terrell@earthlink.net> - 2017-03-23 19:01 -0400
              Re: How do those Spring Reverbs work in guitar amps? Phil Allison <pallison49@gmail.com> - 2017-03-23 16:24 -0700
                Re: How do those Spring Reverbs work in guitar amps? "dcaster@krl.org" <dcaster@krl.org> - 2017-03-23 16:37 -0700
                  Re: How do those Spring Reverbs work in guitar amps? Phil Allison <pallison49@gmail.com> - 2017-03-23 17:46 -0700
                    Re: How do those Spring Reverbs work in guitar amps? "dcaster@krl.org" <dcaster@krl.org> - 2017-03-23 18:05 -0700
                      Re: How do those Spring Reverbs work in guitar amps? "Michael A. Terrell" <mike.terrell@earthlink.net> - 2017-03-25 03:18 -0400
                Re: How do those Spring Reverbs work in guitar amps? "Michael A. Terrell" <mike.terrell@earthlink.net> - 2017-03-25 03:16 -0400
            Re: How do those Spring Reverbs work in guitar amps? Jasen Betts <jasen@xnet.co.nz> - 2017-03-26 19:36 +0000
          Re: How do those Spring Reverbs work in guitar amps? oldschool@tubes.com - 2017-03-20 14:04 -0500
            Re: How do those Spring Reverbs work in guitar amps? Don Kuenz <g@crcomp.net> - 2017-03-21 17:22 +0000
          Re: How do those Spring Reverbs work in guitar amps? Don Kuenz <g@crcomp.net> - 2017-03-20 19:27 +0000
      Re: How do those Spring Reverbs work in guitar amps? George Herold <gherold@teachspin.com> - 2017-03-20 12:24 -0700
        Re: How do those Spring Reverbs work in guitar amps? Clifford Heath <no.spam@please.net> - 2017-03-21 09:14 +1100
          Re: How do those Spring Reverbs work in guitar amps? George Herold <gherold@teachspin.com> - 2017-03-20 17:04 -0700
            Re: How do those Spring Reverbs work in guitar amps? "dcaster@krl.org" <dcaster@krl.org> - 2017-03-20 20:06 -0700
              Re: How do those Spring Reverbs work in guitar amps? jurb6006@gmail.com - 2017-03-21 00:18 -0700
              Re: How do those Spring Reverbs work in guitar amps? George Herold <gherold@teachspin.com> - 2017-03-21 05:55 -0700
                Re: How do those Spring Reverbs work in guitar amps? "dcaster@krl.org" <dcaster@krl.org> - 2017-03-21 06:46 -0700
        Re: How do those Spring Reverbs work in guitar amps? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-21 03:15 -0400
    Re: How do those Spring Reverbs work in guitar amps? bitrex <bitrex@de.lete.earthlink.net> - 2017-03-19 22:25 -0400
      Re: How do those Spring Reverbs work in guitar amps? Phil Allison <pallison49@gmail.com> - 2017-03-19 19:52 -0700
        Re: How do those Spring Reverbs work in guitar amps? bitrex <bitrex@de.lete.earthlink.net> - 2017-03-19 23:14 -0400
          Re: How do those Spring Reverbs work in guitar amps? bitrex <bitrex@de.lete.earthlink.net> - 2017-03-19 23:14 -0400
          Re: How do those Spring Reverbs work in guitar amps? Phil Allison <pallison49@gmail.com> - 2017-03-19 20:32 -0700
            Re: How do those Spring Reverbs work in guitar amps? bitrex <bitrex@de.lete.earthlink.net> - 2017-03-20 00:01 -0400
              Re: How do those Spring Reverbs work in guitar amps? Phil Allison <pallison49@gmail.com> - 2017-03-19 22:32 -0700
            Re: How do those Spring Reverbs work in guitar amps? jurb6006@gmail.com - 2017-03-20 03:52 -0700
            Re: How do those Spring Reverbs work in guitar amps? bitrex <bitrex@de.lete.earthlink.net> - 2017-03-20 15:18 -0400
              Re: How do those Spring Reverbs work in guitar amps? Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2017-03-20 21:28 +0200
                Re: How do those Spring Reverbs work in guitar amps? bitrex <bitrex@de.lete.earthlink.net> - 2017-03-20 16:26 -0400

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#452768

FromTauno Voipio <tauno.voipio@notused.fi.invalid>
Date2017-03-20 21:28 +0200
Message-ID<oapab3$o3a$1@dont-email.me>
In reply to#452762
On 20.3.17 21:18, bitrex wrote:
> On 03/19/2017 11:32 PM, Phil Allison wrote:
>> bitrex wrote:
>>
>>> On 03/19/2017 10:52 PM, Phil Allison wrote:
>>>
>>>> The input coil used has a nominal impedance of 8 ohms at 1kHz, much
>>>> lower at 100Hz and much higher at 10kHz.
>>>>
>>>> Drive power requirement is around 10mW, some as other designs, but
>>>> the low impedance means it cannot be driven fully by a single,
>>>> regular op-amp.
>>>
>>> That makes sense. How much average voltage would one expect to see
>>> between terminals 4 and 5 of the tank input prior to the unit distorting
>>> with a guitar signal?
>>>
>>
>>   ** 500mV rms maybe.
>
> Any of them ever use push-pull to drive the transducer? That is to say,
> not push-pull in the way a regular complimentary output amplifier or
> op-amp is, but say a bridged configuration of two op-amps driven
> out-of-phase.
>
> I had wanted to drive an inductive load with a varying impedance over
> frequency with a bridge configuration to put more power into it than
> what the supply could provide single-ended, but couldn't figure out the
> proper sense topology so both amps could provide current drive over the
> whole cycle.


If you look at the schematics, you'll notice that the feedback
is taken from the coil current, rather than voltage. For a bridge
amplifier, you'd need more complicated way of picking up the
feedback signal. Besides, a simple complementary 2n3904/2n3906
would be enough (or a LM386).

-- 

-TV

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#452774

Frombitrex <bitrex@de.lete.earthlink.net>
Date2017-03-20 16:26 -0400
Message-ID<yVWzA.64217$kx.6565@fx33.iad>
In reply to#452768
On 03/20/2017 03:28 PM, Tauno Voipio wrote:
> On 20.3.17 21:18, bitrex wrote:
>> On 03/19/2017 11:32 PM, Phil Allison wrote:
>>> bitrex wrote:
>>>
>>>> On 03/19/2017 10:52 PM, Phil Allison wrote:
>>>>
>>>>> The input coil used has a nominal impedance of 8 ohms at 1kHz, much
>>>>> lower at 100Hz and much higher at 10kHz.
>>>>>
>>>>> Drive power requirement is around 10mW, some as other designs, but
>>>>> the low impedance means it cannot be driven fully by a single,
>>>>> regular op-amp.
>>>>
>>>> That makes sense. How much average voltage would one expect to see
>>>> between terminals 4 and 5 of the tank input prior to the unit
>>>> distorting
>>>> with a guitar signal?
>>>>
>>>
>>>   ** 500mV rms maybe.
>>
>> Any of them ever use push-pull to drive the transducer? That is to say,
>> not push-pull in the way a regular complimentary output amplifier or
>> op-amp is, but say a bridged configuration of two op-amps driven
>> out-of-phase.
>>
>> I had wanted to drive an inductive load with a varying impedance over
>> frequency with a bridge configuration to put more power into it than
>> what the supply could provide single-ended, but couldn't figure out the
>> proper sense topology so both amps could provide current drive over the
>> whole cycle.
>
>
> If you look at the schematics, you'll notice that the feedback
> is taken from the coil current, rather than voltage. For a bridge
> amplifier, you'd need more complicated way of picking up the
> feedback signal. Besides, a simple complementary 2n3904/2n3906
> would be enough (or a LM386).
>

Indeed, the "more complicated way" was what was giving me the trouble. ;-)

In the application I had in mind I'm driving a square wave through an 
actual small step-up transformer, not a reverb tank transducer. I can't 
put feedback from the secondary to the primary, but the output waveform 
looks like trash when using voltage drive, mostly due to the 
aforementioned variation in impedance over frequency

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