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Old 12th June 2003, 04:50 PM   #1
Joel is offline Joel  United States
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Default A 10W ultralinear amplifier with unique features.

Nuvistor front end, transformer phase inverter, and gas-tube regulation/filtering. It all fits in a 6"x10"x2" chassis too.

Constructive comments are welcome.

Regards,

Joel
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Old 12th June 2003, 05:15 PM   #2
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Default Nice!

Good to see some more of your designs. I like the 6aq5. Only heard them through a Hammond 125ese, though. Very strong!

Pictures coming?

How about your tiny, DHT P-P with trafo inversion? How did that turn out?

Rick
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Old 12th June 2003, 05:19 PM   #3
Joel is offline Joel  United States
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Hi Rick,
The Lundahl transformer just arrived yesterday, so I'll be drilling the chassis this weekend. I have all the parts gathered except the 0B2 tube. I will post picks as soon as it's done.

The 30/31 push-pull is still in the dream stages.

This one I came up with because I wanted a 10 watt tube amp to do a direct comparison with my 10 watt SS amp.
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Old 12th June 2003, 05:34 PM   #4
dhaen is offline dhaen  Europe
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Joel,

JLH 10W?
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Old 12th June 2003, 05:44 PM   #5
Joel is offline Joel  United States
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Yes, it's the JLH, strictly 1969 version. I didn't even add Linsley-Hood's 1970 updates, since he said his units were unmodified. Nice sounding amp.
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Old 12th June 2003, 05:50 PM   #6
dhaen is offline dhaen  Europe
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Joel,

For once (of late) I agree with you. I built it in 69-70 in original form. Later I scaled it to 50W. The heatsink was 2 foot square and needed forced air cooling! Parties could be heard at the end of the street. Police were called on occasions - but that was in my youth.

Back to the sound: Very similar to a reasonable P-P valve amp. beats any mediocre valve amp.

Cheers
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Old 12th June 2003, 06:06 PM   #7
Joel is offline Joel  United States
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Well, we'll see - I have high expectations for this 6AQ5 amp. Whereas with the JLH I had none.
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Old 12th June 2003, 06:21 PM   #8
qwad is offline qwad  Australia
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AAAAH THE 6AQ5, by all accounts a much under rated and neglected tube, with great potential one of joe, [forget his last name ]a frequent poster on audio assylum tubes forum, he reckons it will out perform any of the el-84's for sound quality , and cheap to find even in nos on ebay as it hasn't developed a "cult"following like some other tubes, from what I understand it can even be used to replace the 6bq5 in a circuit as it has many characteristics the same, there was a low power circuit from dynaco I had one time that could use either the 6bq5or 6aq5 without any major mods, good choice for a simple amp I LIKE THE circuit cheers, TC
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Old 12th June 2003, 07:29 PM   #9
EC8010 is offline EC8010  United Kingdom
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A couple of thoughts.

With a shared cathode resistor, your output transformer will almost certainly have an out-of-balance DC - unless you match the valves.

At power-up, when the 6AQ5s are cold, those neon regulators will have to sink a lot of current. Are they up to it?
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Old 12th June 2003, 08:01 PM   #10
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Default Joel's back with a vengance...

Hi Joel,

Great design, interesting tubes and an individual take on topology. That's what we have been missing!

Constructive comments... let me see.... what would I try...

1) Snubbing the 1N4007s does clean up the reverse shutoff switch and might help the sound

2) split the 5.5k resisitor feeding the OB3 for a choke (156C say) cap into resistor might add to the dynamics a bit - but probably wouldn't as this seems to work better with pp.

3) Fixed battery bias???

4)try a 1uF capacitor between the OPT B+ feed and the cathode junction of the 6AQ5s - about all the gas regs would allow?

but I like it as it is. Nice, really nice.

ciao

James
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