Hi David,
I will do the modfications to the 725C as to your specifications. I have Victors oscillator to verify.
Cheers,
Mogens
I will do the modfications to the 725C as to your specifications. I have Victors oscillator to verify.
Cheers,
Mogens
The 725C is very similar to the 725. The 725D is a major redesign from case to circuitry. The 725D has differential inputs and one more range on the input.
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Some other difference are a Twin T for the first band eliminate filter (notch filter) and two bridged T BEF following the Twin T. The back plane is completely different and the boards are much more compact so more board can be fitted into the chassis. The bandwidth filters were redesigned and different op amps were used. The analog to digital and digital to analog was redesigned with a newer ADC and DAC. I think much of the differences were to bring the 725D up to date as parts became obsolete. I don't think the older 725/725B/C were designed by the same person as the 725D and it shows. Some of the magic dispersed. The 725D power supply use 78xx and 79xx ICs. Consequently the 725D PS has a lot of high frequency noise. The 725B/C power supply is a discrete design and has a very little high frequency noise.
The 725B/C PS nominal voltages are spot on and never drift.
The 725B/C PS nominal voltages are spot on and never drift.
The concept behind Praxis matches your description with a software controlled i/O and a standard sound card. It's also the best speaker analysis I have used. Obsolete unfortunately.
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Hi Demian. Yes, discontinued. Does it still work running W7?
How does it handle attenuation so one doesn't burn the input?
Regards
How does it handle attenuation so one doesn't burn the input?
Regards
I have it running well in win 10/64. Sample rate changes are a pita. The audpod and probes handle the protection. Stock probes are good for 50V. Change resistors and settings for higher voltages.
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Had an email to QA sales asking about possibility of running qa401 in WINE. They are not confident that it would work.
However they mentioned that boards are done and cases are now being anodized. Getting close.
However they mentioned that boards are done and cases are now being anodized. Getting close.
Does anyone know the price of the QA401 and estimated time availability?
I'm debating whether to get the QA400 now or wait for the QA401.
I'm debating whether to get the QA400 now or wait for the QA401.
For what its worth I have had a chance to test a prototype and it does meet the specs and works as promised. There are still revisions to the PCB and the software before its ready for production. I have a few changes I may push for if Matt is amenable. However there still is work to do so patience is needed.
It showed up in the drop down menu last week ...
QA401 Audio Analyzer
No new info or ordering button but does say shipping to US by end of Feb. Which seems to conflict with Demian's comment just now about possible PCB changes and work to do?
QA401 Audio Analyzer
No new info or ordering button but does say shipping to US by end of Feb. Which seems to conflict with Demian's comment just now about possible PCB changes and work to do?
Davada,
Do you think it would be worth while for someone to design a 725b/c
type power supply for the 725D?
Or
Are there better designs implemented elsewhere that can be a fairly
easy mod to place into the 725D chassis and make it work better?
Cheers,
Sync
I don't see power supply effects in either. The power supply in the the B/C is one of the quietest I've come across. The rail voltages are bang on and won't budge.
I'm a bit suspicious of the PS on the 725D with all the 78xx, 79xx IC regulators but like I said it doesn't seem to matter.
Unless there is obvious problem like a bad cap I would say leave it alone.
This should be in the Shibasoku thread.
I'm a bit suspicious of the PS on the 725D with all the 78xx, 79xx IC regulators but like I said it doesn't seem to matter.
Unless there is obvious problem like a bad cap I would say leave it alone.
This should be in the Shibasoku thread.
What is wrong with it?
Can you produce specification set that Q401 is capable of?
Can it do pre-emphasis RIAA?
Ask QuantAsylum for specs. I can say that in loopback it can get to -110dB THD.
There are some bugs in the software and they are planning to combine the QA400 and the QA401 software. Its too soon to say it will happen.
Personally I prefer a separate RIAA pre-equalizer. The dynamic range requirements are a problem when done in software before a DAC. I don't know what will be included but you can write one since QA has published an API.
There are some bugs in the software and they are planning to combine the QA400 and the QA401 software. Its too soon to say it will happen.
Personally I prefer a separate RIAA pre-equalizer. The dynamic range requirements are a problem when done in software before a DAC. I don't know what will be included but you can write one since QA has published an API.