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PeeCeeBee V4 GB!

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C

cats squirrel

Member
Joined 2011
Hi Shaan

we have briefly mentioned a power supply/supplies. I don't like SMPS as I can't repair them, so they will be linear in my amplifiers. Do I need boutique components, like Schottky diodes, polyprop bypass caps etc.?

I am using two dual power supplies per board, one for just the FETs, and one for the rest, split at the diodes (D1/2). I am adding more capacitance for the FETs, total 22,400uF per rail, just 8,800 for the rest. I do hope this will be enough.

Do you have any idea of output impedance of these amplifiers (V4)?
 
shaan

shaan

Member
Joined 2009
cats squirrel said:
Hi Shaan

we have briefly mentioned a power supply/supplies. I don't like SMPS as I can't repair them, so they will be linear in my amplifiers. Do I need boutique components, like Schottky diodes, polyprop bypass caps etc.?

I am using two dual power supplies per board, one for just the FETs, and one for the rest, split at the diodes (D1/2). I am adding more capacitance for the FETs, total 22,400uF per rail, just 8,800 for the rest. I do hope this will be enough.

Do you have any idea of output impedance of these amplifiers (V4)?
Click to expand...

Hi CS.

If you are talking about the new PSU with speaker protection then No, there will not be a single boutique component on it. You will need a pair of small non-polar electrolytics, however.

Capacitance values seem quite adequate. Take care of grounding.

I have not measured output impedance of V4. Rough guess, it would be close to 20-30milliohm (or less) across the audio band. There has been a case where a member's speakers didn't like the V4 for too low output impedance. A pair of 0.1R 5W resistors at output, and now they do. :)
 
shaan

shaan

Member
Joined 2009
kpsthakur said:
Sorry Shaan, did not understand this part
Click to expand...

Some sensitive light-coned drivers installed in some specific type of enclosures do not like (and usually do not need) aggressive cone control which V4 tries to apply by its very high damping factor. The result of which is usually a dry/clinical sound. The 0.1R resistor placed between amplifier output and speaker defeats the damping factor and the cone gets some freedom and the sonics come to life with warmth.
 
shaan

shaan

Member
Joined 2009
PeeCeeBee V4H First Tests

So, here is a THD sweep of V4H from 500Hz to 10KHz taken at 50VPP output into 10R load (32Watt RMS). +/-35V PSU. Total 100mA output bias. 10mA VAS bias. No Zobel. BC5xxB input + KSE3xx vas + 2SK/J output.

Lower curve - Source THD (-10dB line-in magnitude)
Upper curve - V4H THD (-10dB line-in magnitude)

Comparing the two curves we get

THD1Khz - 0.003%
THD2Khz - 0.003%
THD3Khz - 0.003%
THD4Khz - 0.002%
THD5Khz - 0.002%
THD6Khz - 0.0015%
THD7Khz - 0.0015%
THD8Khz - 0.002%
THD9Khz - 0.0025%
THD10Khz - 0.003%

Note that instead of the gradually rising THD vs frequency of V4 we now have a nearly steady THD which actually gradually decreases somewhat as frequency increases.

Good/Bad? :)

More tuning ahead. So far V4H has shown much better high frequency THD than V4. Let's see how much further it can go without getting more complex, without using a buffer for MOSFETs, without changing the feedback network resistor values and without using high-end components.

So...more coming soon.
 

Attachments

  • v4h 50vpp 10r thd.png
    v4h 50vpp 10r thd.png
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B

brunogiovs

Member
Joined 2014
shaan said:
So, here is a THD sweep of V4H from 500Hz to 10KHz taken at 50VPP output into 10R load (32Watt RMS). +/-35V PSU. Total 100mA output bias. 10mA VAS bias. No Zobel. BC5xxB input + KSE3xx vas + 2SK/J output.

Lower curve - Source THD (-10dB line-in magnitude)
Upper curve - V4H THD (-10dB line-in magnitude)

Comparing the two curves we get

THD1Khz - 0.003%
THD2Khz - 0.003%
THD3Khz - 0.003%
THD4Khz - 0.002%
THD5Khz - 0.002%
THD6Khz - 0.0015%
THD7Khz - 0.0015%
THD8Khz - 0.002%
THD9Khz - 0.0025%
THD10Khz - 0.003%

Note that instead of the gradually rising THD vs frequency of V4 we now have a nearly steady THD which actually gradually decreases somewhat as frequency increases.

Good/Bad? :)

More tuning ahead. So far V4H has shown much better high frequency THD than V4. Let's see how much further it can go without getting more complex, without using a buffer for MOSFETs, without changing the feedback network resistor values and without using high-end components.

So...more coming soon.
Click to expand...

Very interesting.
can you please share the schematic changes?

Thanks
 
D

drgnanam

Member
Joined 2014
shaan said:
Some sensitive light-coned drivers installed in some specific type of enclosures do not like (and usually do not need) aggressive cone control which V4 tries to apply by its very high damping factor. The result of which is usually a dry/clinical sound. The 0.1R resistor placed between amplifier output and speaker defeats the damping factor and the cone gets some freedom and the sonics come to life with warmth.
Click to expand...

Damping factor is much more influenced by speaker cable than amplier and speaker itself , damping factor should be calculated from amplier ,cable and speaker as whole .
 
shaan

shaan

Member
Joined 2009
GB3 Update

arasuk - 2 PCBs - SHIPPED
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Zero Cool - 2 PCBs - shipping invoice sent
 
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