6aq5 amp

[Berger]

First Stage complete!

Got it wired up as a 5e3 tonight and it worked on the first try.

With my RCA 5y3gt in place its putting out 194 vdc at the first stage of filtering. 160vdc at the second state and 92 vdc at the final stage.

It is definitely not as loud as my 6v6 5e3 which is nice. Still annoyed my wife upstairs, but thats ok

Not the prettiest wiring I've done, but my main goal was getting it fired up as I won't get to mess with it for a week or two.

Now to go through my stash of 6aq5s and see which sound best together.

Thanks for reading.

Aaron

P.S. wow that layout pic is blurry, sorry

[Berger]

Change the 2nd filter resistor from 22K to 10K tonight. I raised the 3 stage voltage from 92vdc to 138vdc. Figured it wouldn't be a bad thing to give the 12ax7s more voltage.

The amp really sounds alive now! definitely a good change.

Next up, making a parallel input with the extra tube, and removing the normal channel and using the bright channel instead. Which the bright cap on a switch.

Thanks for reading.

Aaron

[Phil_S]

You can probably reduce that dropping resistor further. I'd probably try a 1K 1W. The draw across that resistor is less than 0.4W, but I'd go up a notch to be conservative.

I might also be tempted to reduce the 5K dropping resistor to around 2.7K 5W. This will boost your screen voltage closer to plate voltage. I don't think that's a big consideration at the operating points you have. What it will do is pass more voltage downstream for the preamp section.

The 1st preamp tube in a 5E3 usually operates at around 200V on the plates. I suspect you are losing some of the "feel" of the design with lower plate voltage on the preamp tubes. I'd shoot to get V1 closer to 200V. You should get more clean headroom (not that you have a lot with a 5E3) as you raise preamp plate voltage.

You won't experience "not so loud" until you have a 1W amp. What you built (without doing any math) is probably still in the 15W range.

[Berger]

Thanks phil I was wondering how much I could drop those resistors. I figured that since my rectified voltage is so low it wouldn't be a problem.

it seems quieter that my 6v6 5e3. But that may be more perception than anything.

I have a couple ax84 fireflys that I have built as well as a submini tube amp, so ya, this thing is not quiet compared to those.

I tried a bunch of different 6aq5s last night and didn't notice much difference. RCA,DuMont,Ge

Have any of you noticed much of a difference between different brands of 6aq5 tubes?

It was towards of my playing the amp cranked, so my ears may have been a little un happy.

Aaron

[Phil_S]

I'm partial to Sylvania's. That's because I managed to find some that are clearly NOS (without boxes) and they are very robust. I've got a pair running in my variant of a TW Express with Va around 335. I figure, heck, who cares if the tubes blow up -- they were cheap and I've got quite a pile of them.

Otherwise, RCA's are nice, too. I don't think you can go wrong.

[Berger]

I agree Phil, they are all sounding good.

wired up the parallel input on the extra tube last night. Sounds good.

Now just trying to figure out to do with the extra triode I have...may just put a little gain stage in, nothing fancy.

For anyone reading, can I using a switch to have only 1 input and switch between my parallel input and bright channel? or should I just have 2 inputs?

Aaron

[Berger]

And this is how it sits now.

20170223_212544.jpg

1 channel into parallel triode->vol->phase inverter. Apparently during the process I removed the caps for the tone.

My plan is to wire up the tone control, and then may be us the extra 1M pot for a master volume. The 6aq5s didn't really drop the output so it'l a bit loud for what I need.

Not sure what i'll do with the extra socket, I had wired an extra gain stage at one point, but couldn't tame it. maybe I'll try again.

Still a fun amp

[randalp3000]

I've been gigging 6aq5's in two marshall circuits and a tweed dlx for around two years running 325vdc on the plates with no problems.

great tubes.

[Berger]

Yeah they are really nice. I had made a SE 6aq5 that I changed over to a 6Y6. I like the 6Y6 a lot but I will be building another 6aq5 soon.