Normal Hum and Noise

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Normal Hum and Noise

Postby kt88pppamp » Fri Aug 22, 2008 5:51 pm

If I purchase a new stereo 70 kit from triode should I expect any audable hum, noise, hiss, etc assuming there are no defects with the parts? Will everything be inaudable even if you place your ear into the speaker? The driver board from blackburn using the 6SN7's is the board I am likely to purchase.
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Postby erichayes » Fri Aug 22, 2008 10:38 pm

No. You could improve the transparency in the low frequencies by increasing the capacitance, but as far as audible hum is concerned (unless you have 100+ dB speakers) it shouldn't be a problem.
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Postby burnedfingers » Sat Aug 23, 2008 6:45 am

If you purchase a new triode kit will it have an add on power supply/bias board?

If purchasing the typical kit with the factory sized power supply cap/can be prepared for some hum even with the "Blackburn" driver board.

The original power supply cap/can is minimal at best and sounds like there is minimal bass response. The power supply needs to be beefed up in order to make these amplifiers come to life. I highly recommend an SDS board or something similar to that.

With respect to the "Blackburn" board...I have one. I installed it in one of my Stereo 70's and it sounds ok. Its nothing special and the "Stock" stereo 70 WILL supply the necessary heater demands of using three 6SN7 tubes for the driver board. It will NOT however supply enough current to run different higher current tubes in the driver board.

If your interested in buying a ready made/stuffed board then send me an email and I will make you a deal on it. If you deciede to go with a different driver board then I can highly recommend the "Mapletree Driver Board" from Lloyd Peppard. If you feel adventurous and want to make the "Mapletree" board I can tell you it is easily done as I made a clone board for one of my other Dynaco amplifiers.
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Postby burnedfingers » Sat Aug 23, 2008 6:52 am

With respect to hum again....

Like any amplifier the Stereo 70's hum capability is directly related to the line stage or preamplifier being used with it.

I am running a 6FQ7/5687 Aikido line stage and it is 100% quiet when used with the modified Dynaco amplifier. with an unmodified Dynaco Stereo 70 there is a slight amount of hum.

I can pull a different line stage off my shelf and hook it up and have a slight amount of hum. So there is something to be said for the equipment being used.

Yes, my speakers are very efficient but then again I can hear hum in some speakers I have that are only 92db 1w 1M.
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Postby kt88pppamp » Sat Aug 23, 2008 12:22 pm

All I am talking about is the amplifier itself. With the triode kit and the upgraded power supply/driver board there should be inaudable hum, hiss, and noise?
Last edited by kt88pppamp on Sat Aug 23, 2008 12:40 pm, edited 1 time in total.
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Postby burnedfingers » Sat Aug 23, 2008 12:30 pm

Quote:

All I am talking about is the amplifier itself. With the triode kit and the upgraded power supply/driver board there should be inaudable hum, hiss, and noise.

Since you will need either a line stage or a preamp of some sort it will also enter into the picture. With the amplifier terminated to the speakers and the inputs to the amplifier shorted there is a chance of a very small amount of noise depending upon the skill of the person that put the amplifier together and the driver board used. In general one should figure a small amount of hum with ANY tube amplifier in my opinion.
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