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  1. Replies
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    Yes, but not one that I've ever liked much....

    Yes, but not one that I've ever liked much. Triode mode when pushed just doesn't sound to great IMHO. Then consider the voltages, you'll routinely have 1KV across the plates side of the switch, and...
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    My first suspects would be IC41, the DC offset...

    My first suspects would be IC41, the DC offset integrator and the voltage amplifier module. The DCV on IC41 pin 3 should be about the same (a meter will load it slightly) as the output pre-relay i.e....
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    408

    The correct mains fuse is a F1A as indicated on...

    The correct mains fuse is a F1A as indicated on the schematic. Leaving a 2A one in there poses a fire risk.
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    190

    Smells like link building spam to me...

    Smells like link building spam to me...
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    205

    I think it may be you're hitting new poster...

    I think it may be you're hitting new poster restrictions. Try putting on a hosting site such as OneDrive, Google Drive or dropbox and then sharing the link.
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    205

    Try this for the power amp. It's possible the...

    Try this for the power amp. It's possible the transistors in yours have been substituted as the 2N4348 and 2N6262 are similar.

    58631
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    Call me blind as a bat but I can only see a 10V...

    Call me blind as a bat but I can only see a 10V zener. Are you sure it was 15V? Not that I think that is the problem.
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    I think you will struggle to get 6VDC off a 5VAC...

    I think you will struggle to get 6VDC off a 5VAC supply, even using schottky diodes.

    It's not unusual to see discrete twisted pairs for the heater supply, even on a PCB. But that would be counter...
  9. If the position of the tone wheel pickup were...

    If the position of the tone wheel pickup were modulated by another variable speed motor with a crank to move it like a piston, that would also produce a vibrato effect. Then you'd have an all...
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    394

    I'd get measuring. Seriously in order to make...

    I'd get measuring. Seriously in order to make sensible decisions you need data and that means getting a meter or whatever tool it takes to get the info you need.

    With sensible precautions,...
  11. These things do push out a massive signal, maybe...

    These things do push out a massive signal, maybe 10x that of a passive pickup so making it very easy to overdrive the amplifiers. Backing the volume right down will put it into the same range as a...
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    135

    Well that's narrowed it to between the CH3 gain...

    Well that's narrowed it to between the CH3 gain and volume. There's probably one or two 12AX7/ECC83 tubes associated with that section so start pulling them to find out which one(s). Once you know...
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    H&K will not hand out the schematic which makes...

    H&K will not hand out the schematic which makes things hard. I would start by noting what effect the controls have on the problem. So, for example, if the Ch3 gain affects the noise then you've...
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    None of that sounds like shorting out R49. I'm...

    None of that sounds like shorting out R49. I'm not at all clear what you did. Trying to move on.... Is the situation that the pops are gone, it still crackles and otherwise you can hear your guitar...
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    394

    The test was to SHORT OUT R49, not remove it. Not...

    The test was to SHORT OUT R49, not remove it. Not exactly sure what you did as you say both shorted and removed. With it shorted out there's no reason for a loud pop if it didn't do it before. ...
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    414

    Absolutely. The problem was the only spec given...

    Absolutely. The problem was the only spec given was 80pf so you have to work with the cards you're dealt :)
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    394

    You really need to approach this with a divide...

    You really need to approach this with a divide and conquer strategy, which is what nevetslab was trying to get you to do There is no reason why simply disconnecting CON1 on the power amp board will...
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    414

    I think it's just the same. Say you have a 0.5G...

    I think it's just the same. Say you have a 0.5G bias resistor and 10pf capacitance then you have a low pass filter with a pole at 30Hz. I expect suitable high pass filtering say about 50Hz in the...
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    414

    For an 80pf disk, -3db @ 50hz requires a 40meg...

    For an 80pf disk, -3db @ 50hz requires a 40meg ohm input impedance. You previously used 5 meg ( 2 x 10 in AC parallel) which would be 400hz. That might explain part of the sound you got.

    So...
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    Do you have the specs of the disk? What frequency...

    Do you have the specs of the disk? What frequency response requirement is specified? How much gain? What is the signal output voltage of the disk?

    PS: What I'm trying to get to is what is the...
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    The problem is not the cable, it's the source...

    The problem is not the cable, it's the source impedance. Adding more is not going to help in a constructive way as the price you will pay for flattening the frequency response is (a) significant loss...
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    The full range bias current is 7nA. For an...

    The full range bias current is 7nA. For an effective 11Meg source that a 77mV offset that so you'd need the same impedance on the other input.

    The full range offset current is 2nA i.e 11mV....
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    It's best you forget the word 'active' as that is...

    It's best you forget the word 'active' as that is not the property that make the difference. What matters is the impedance of the source be it a guitar pickup, a pedal buffer or a 10,000 watt...
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    Something else to check is the mute FET Q1. It...

    Something else to check is the mute FET Q1. It operates momentarily when switching between vintage and burn.
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    The salient quality issues that spring to mind...

    The salient quality issues that spring to mind are

    Cable capacitance
    Measured as capacitance per unit length. The source impedance forms a low pass filter with the cable capacitance. I'm not...
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    Here is the schematic I have for the 22H. As far...

    Here is the schematic I have for the 22H. As far as I know is correct.

    58460

    It's hard to give good help when you don't know what you dealing with. Once you've gone through it and can provide...
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    The truth is quite the opposite. Taking your cct...

    The truth is quite the opposite. Taking your cct with the master at 2K, the EL84's dissipate a staggering 34W but just 12W with the same drive level with master wide open. The reason being the...
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    Thx. I wanted to check we were on the same page...

    Thx. I wanted to check we were on the same page as I wasn't seeing such large currents. To get those numbers I had to drive the PI with 80Vpp. It's VERY interesting. I've avoided this kind of...
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