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Recent posts
#41
Oscilloscopes, Signal Generators, FFT Analyzers, Multimeters / Re: HP 333A Distortion Analyze...
Last post by nre_admin - Jan 01, 2024, 04:53 PMFFT of residual output of 333A (blue) and Krohn-Hite 6900B distortion analyzer, same input signal. The plot is what's left after the fundamental is filtered out. Note the K-H unit has much lower noise floor. Input signal signal is 1kHz ultra-low distortion sinewave sourced from Stanford Research DS250 Low Distortion Analyzer, split and sent to each unit.
#42
Oscilloscopes, Signal Generators, FFT Analyzers, Multimeters / Re: HP 333A Distortion Analyze...
Last post by nre_admin - Dec 31, 2023, 11:01 AMThe 333A voltmeter is calibrated using a signal sinewave generator capable of micro-volts output. The procedure is to check the voltmeter over a range of frequencies with an input set at 300 micro-volts RMS. The meter, set to 0.0003VRMS peak reading, should not deviate more than +/- a few micro-volts off "3".
The alternative is to assess the distortion residual using an FFT and determine if sufficient attenuation of the fundamental is achieved. I can provide a few screen shots of that.
The alternative is to assess the distortion residual using an FFT and determine if sufficient attenuation of the fundamental is achieved. I can provide a few screen shots of that.
#43
Oscilloscopes, Signal Generators, FFT Analyzers, Multimeters / HP 333A Distortion Analyzer – ...
Last post by M-HZ - Dec 30, 2023, 12:22 AM I have been looking for a HP 333A or a HP 334A Distortion Analyzer that would hopefully be in rather good working condition, but realistically I keep my expectations in check. However, I did come across a 333A that is being offered by an individual within my local vicinity. A price range of $100.00/$150.00 is being negotiated and debating on its acquisition. It's in rather good shape, but a quick check reveals that the 333A is functional, rail voltages are fine, but has not been calibrated for some time. I do not have access at the moment to equipment to produce a high quality (?) 100uV, 400Hz sine wave signal nor any other high level calibration instruments that may be needed? Also, the Frequency Range rotary switch may need a cleaning as would the Meter Range Set level per the owners own tests. There appears to be no physical damage (rotate smoothly) whatsoever nor did I see any form of deterioration/burning components and the like. I gather a high quality cleaner would do the trick? It has been a while since I have flipped on my Tek 2236 and various other pieces of equipment, but would not mind undertaking a reasonable project. I would welcome any suggestions/steps for an attempt to bring this unit up to some form of reasonable performance baring any unknown "pitfalls". I will mainly be utilizing it for measuring THD+N in tube amps/guitar and other forms of experimentation along these lines. Again, much appreciate any form of input.
#44
Vacuum Tube Amplifier Repairs, Restorations and Builds / Re: Scott 222A
Last post by nre_admin - Dec 13, 2023, 05:31 AMQuote from: Capo72 on Dec 11, 2023, 03:46 PMI'm looking forward to hearing this guy! I plan to build a walnut or mahogany case for it so it has WAF.
Excellent!
#45
Vacuum Tube Amplifier Repairs, Restorations and Builds / Re: Scott 222A
Last post by Capo72 - Dec 11, 2023, 03:46 PMI'm looking forward to hearing this guy! I plan to build a walnut or mahogany case for it so it has WAF.
#46
Vacuum Tube Amplifier Repairs, Restorations and Builds / Re: Scott 222A
Last post by nre_admin - Dec 10, 2023, 07:16 AMBandwidth at three different power levels/channel with the HF and LF pots, adjusted to obtain the 1kHz, squarewaves shown above.
#47
Vacuum Tube Amplifier Repairs, Restorations and Builds / Re: Scott 222A
Last post by nre_admin - Dec 09, 2023, 04:47 PM1khz square wave performance.
Typical for a good quality tube amplifier. No evidence of ringing or oscillations.
Typical for a good quality tube amplifier. No evidence of ringing or oscillations.
#48
Vacuum Tube Amplifier Repairs, Restorations and Builds / Re: Scott 222A
Last post by nre_admin - Dec 09, 2023, 04:29 PMI've found that the chassis can be stiffened significantly on these units if the OEM sheet metal screws are replaced with larger (#8) stainless sheet metal HEX head screws. Each screw should be installed into the chassis flanges without the bottom cover in place. Back out the screw and clean up the burrs with a file. Vacuum the unit before attaching the bottom cover.
#49
Vacuum Tube Amplifier Repairs, Restorations and Builds / Re: Scott 222A
Last post by nre_admin - Dec 09, 2023, 04:24 PMSine wave output at 1kHz and 30kHz.
#50
Vacuum Tube Amplifier Repairs, Restorations and Builds / Re: Scott 222A
Last post by nre_admin - Dec 09, 2023, 04:22 PM%THD of each channel with new J&J 6BQ5 outputs, NOS Sylvania 6BL8 inverters. The preamplifier has original Scott 12AX7s (Telefunken). Amperex 5AR4, old.
<1%THD up to about 10VRMS across 8Ohm NI load. Input is cross-correlated MLS at 196k sampling frequency.
<1%THD up to about 10VRMS across 8Ohm NI load. Input is cross-correlated MLS at 196k sampling frequency.