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    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

6SN7 preamp tube alternative with less gain?

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Sorry but both you and the OP are "missing the point". :(

The guitar player can never overdrive his 100W amplifier, simply because it's too loud and neighbours will call the police.
It is NOT a preamp problem but of way too much power available, which he solves by using an "acceptable power" 5W amp.

The OP *already* has a 5W amplifier, again has NOT a preamp problem, if he likes distorted sound he can run his 5W system full blast and not disturb a sleeping baby.

Changing preamp gain by any means, from using the volume control (which I suggested) to adding an attenuator between stages or pulling a cathode cap (same thing but fixed attenuation ;) ) to somehow finding a lower gain tube will NOT address the main problem.

If anything, he might build a similar 1W amplifier, IF 5W is still too much.
 
And of course I read it another way....

You can simply swap in a pair of E-1148 tubes with adapters per 6SN7 and voilá, lower gain.
 

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He's already got a less powerful tube than he indicates. It's a 2A3 SE amp so it's really only putting out about 3.5 watts, not 5 watts, if it's made according to the Sun schematic.
I didn't notice the speakers being used but if you want a meaty sound from 2A3 amps, you definately need the right speakers. Speakers of less than 98dB tend to sound a bit congested at normal levels with 3.5 watt amps IMO.
 
He wants to overdrive the output valves into distortion like an EL34 Guitar amp.
For a "Meaty" sound whatever that means. :eek:

Hahaha I like the OP's style!

Throw in a dinky output transformer and you got yourself a killer geetah amp:D Although you'd really want to probably use a pentode for the output valve with zero feedback, and a speaker with a lumpy response too;)
 
Believe me, there is plenty of power left if I reduce the gain. For normal listening levels I use maybe 5% of the 3.5 watts. The Sun Audio clone amp handles the two horns, that I sculpted on the balcony. Hf rolloff is okay as long as the amp can still produce sound above 440 Hz. The JBL 2225H woofers are handled by my DIY Firstwatt F5.

I am not sure either if lowering gain will improve sound quality. I don't need that much gain, so why have it? Especially if electric guitarists like the sound when the power tubes are more in use. I not after over-drive sound, but neither are some guitarists. Musicians use their gear for clean guitar tone as well you know. Not to confuse anyone again, I am using a hifi tube amp for hifi speakers, and I hope the photo will help against further confusion on this topic. For anyone interested, that is a darn good IPA from Quebec.

Thanks for more suggestions. Not sure about the last suggestion to remove diodes. You are not speaking to a tube amp guru. The Firstwatt solid state amp was easy compared to a tube amp. I have upgraded a few caps in the tube amp, that is all. I may dare to make a few small mods.

About the suggestion to build a 1 watt amp: 1st - I already have an amp, and I just need to reduce the gain on the preamp tubes. 2nd: I have not found a 1 watt 2A3 tube amp design. 3rd: Seems expensive to start over.
 

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Yes you're correct. So don't use too high resistor. With 10K res., the output impedance of driver is about 21K, while the input impedance of power stage is 27k including grid resistor. There is no problem so far with my sim.

I am good to go. Free on Sunday to start modding. I could drill a toggle switch, with or without my resistor of choice, to know instantly if I like the sound or not. If this project is scrapped I can always use the switch for LED lights a la McIntosh. :p Which range of resistors do you think will work best? And how many watts should they handle?
 
Not complicated at all. Just pop in the tubes and the adapters and it's done.

Nothing to adjust or change. Instant lower gain.

I found this adapter, but it does not look like it fits the 6SN7 socket. Which adapters did you use?

I think I found your setup. Looks like a custom job.
 

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