7695...useful audio tube??

bereanbill · 12th May 2009, 08:33 PM

I got my hands on a new pair of 7695s...look like a power pentode. Any potential in a Class A amp ? Or any other ideas ??

Arnulf · 13th May 2009, 09:37 AM

Interesting tube, at least according to the datasheet. You could use that very high heater voltage and rather low anode voltage to your advantage (= no heater transformer/winding required if you hook up heaters in series and add a power resistor or CCS to the chain to drop those extra ~5W).

They also have rather low Zout (1100R). This can be a plus (OTL would be an option if you had more of these) and a downside if you already own output transformers that you want to use with these tubes and they don't allow for suitably (low) transformation ratios.

SY · 13th May 2009, 10:29 AM

Triode connected, you should be able to get 5-7W in push-pull. This would be a good candidate for AB2 or screen-drive, where you could get closer to 10W. The attractive feature is the low load impedance requirement, making the output transformer a much easier proposition.

bereanbill · 13th May 2009, 10:56 AM

Ok...thanks SY...how would I achieve the 50V filaments?

SY · 13th May 2009, 11:05 AM

A transformer might work.

I'd probably series them, add series resistors, and use an isolation transformer.

12th May 2009, 08:33 PM	#1
bereanbill diyAudio Member Join Date: Jan 2009	7695...useful audio tube?? I got my hands on a new pair of 7695s...look like a power pentode. Any potential in a Class A amp ? Or any other ideas ??

13th May 2009, 10:29 AM	#3
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Triode connected, you should be able to get 5-7W in push-pull. This would be a good candidate for AB2 or screen-drive, where you could get closer to 10W. The attractive feature is the low load impedance requirement, making the output transformer a much easier proposition. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

13th May 2009, 11:05 AM	#5
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	A transformer might work. I'd probably series them, add series resistors, and use an isolation transformer. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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13th May 2009, 09:37 AM	#2
Arnulf diyAudio Member Join Date: Feb 2009	Interesting tube, at least according to the datasheet. You could use that very high heater voltage and rather low anode voltage to your advantage (= no heater transformer/winding required if you hook up heaters in series and add a power resistor or CCS to the chain to drop those extra ~5W). They also have rather low Zout (1100R). This can be a plus (OTL would be an option if you had more of these) and a downside if you already own output transformers that you want to use with these tubes and they don't allow for suitably (low) transformation ratios.

13th May 2009, 10:56 AM	#4
bereanbill diyAudio Member Join Date: Jan 2009	Ok...thanks SY...how would I achieve the 50V filaments?

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