New Amp Project

[jeru]

Kind of excited to hear and play with a 6SL7 driving the preamp stages.
My new amp project is a single 6SL7 driving a single 6V6. Pics are HERE if you're
interested.

Where did you get the schematic from?
Looks interesting.

Uhhh, schematic..?

No schematic, just my layout. It's a 5F2a with a bunch of changes and additions:

- I'm using a 6SL7 tube for the two preamp stages
- The 220K resistor just ahead of the 6V6 grid is a 250K pot that measures low (~232K or so). It's supposed to act as a master volume that when all the way up won't affect the circuit at all - we'll see.
- The 'Pentode/Triode' switch ties the 6V6 screen grid to the plate, effectively eliminating that grid and causing the tube to operate much less efficiently. Some folks call it a 1/2 power switch.
- Negative feedback is switchable on/off
- Preamp gain switch changes the cathode resistance of the two preamp stages from the normal fender-y 1.5k to a much cooler preamp bias
- Output switchable for use with 4/8 ohm speakers and cabs, but leaving the negative feedback connected to both

We'll see how it turns out -- hoping to get it DUNN over this long holiday wknd.

[CoyotesGator]

Looks very cool.

I'm looking forward to its completion.

[jeru]

Amp chassis is done. Thoughts so far -- Sounds good. The bells and whistles are a
mixed bag..

The 1.5k / 2.7k preamp bias switch is great, basically provides two voicings, one deep
and thick, the other more gritty and cutting. Love it.

The NFB defeat has about as much effect as I thought it would -- some taming of the
sound with NFB, a little less refined without. It's not drastic.

The master volume doesn't do what I had hoped it would. Cranking the gain knob and
tamping it down with the master doesn't do that preamp-gain crunch at low volume thing,
but really just throws a blanket over the sound of the amp. As it stands now, If I'm getting
any real crunch going, it's too loud for my apartment. I've read that that a higher resistance
pot in that position may help, but I have to confess to not understanding why.. Need to read
up more on that. Any thoughts or knowledge would be appreciated here..

The Pentode/Tetrode switch is useless. Not only hums fairly loudly with the screen tied
to the 6V6 plate, but I don't really like the sound in that mode anyhow. After bout five minutes
of research on the interwebs, the consensus seems to be that the hum is common when setting
up a SE 6V6 this way.

Anyway, enjoying the trip on this one, and looking forward to hopefully finding some time soon
to make it a proper home.

[NTBluesGuitar]

PICS!!! ...or it didn't happen.

[CoyotesGator]

PICS!!! ...or it didn't happen.

Pics were started in another thread.

https://www.dropbox.com/sh/kq48fse9l...d53j0rxPa?dl=0

[CoyotesGator]

Thanks for for taking the time to post your evaluation on the mods.

How do you like it normal/normal?

Is this going to be the unicorn head/Thiele or large speaker combo or regularly sized speaker combo or the.........

[jeru]

How do you like it normal/normal?

Is this going to be the unicorn head/Thiele or large speaker combo or regularly sized speaker combo or the.........

Normal is great -- it's a really nice amplifier for practice. It's now in a Temporary Home,
although the plan as it stands is to build up a combo cabinet with a 10" Weber.

One thing -- VERY dependent on what speakers it's going through. Through the
homebrew 2x10" that goes with the bassman, it's got some loud-n'-clean.
Hooked up to this single 10" (bass) speaker cab that I've got, it's all crunch-n'-grind.

I never paid much attention to speakers, just figured one is as good as the next.
(Inner dialogue = yeah JR, how's THAT working out for you..?) ...

[CoyotesGator]

Have you thought of making a 12" combo?

There is an almost limitless variety of used 12" speakers to experiment with.

I wish my champ mashup was a 12" instead of the 8" I went with.

[jeru]

Have you thought of making a 12" combo?

There is an almost limitless variety of used 12" speakers to experiment with.

I wish my champ mashup was a 12" instead of the 8" I went with.

I'm having trouble deciding what I want this one to be, and be used for --
that'll dictate the ultimate head/combo/speaker size etc.

I built this to use to play at home, and also to jam with friends (acoustic and some
electric, low volume, some percussion but no drums) roughly once monthly. My
hope was to have this one replace the Vox Pathfinder 15r as the grab n' go for
those jams. (the P15r is SO good for that -- Definitely up there on the list of
best ~$50 spent on used gear..)

Because this thing doesn't really do crunch/grind at properly low volumes, it's not
going to replace the P15 as is for the grab-n'-go. Maybe with a really small/gritty
and/or inefficient speaker..?

So - -I dunno. For the time being, I may just make the little wooden head box
look nice and move on to other things.

There's so much to do -- I've still got those two muzak PAs to mod, and have
all the transformers, parts and a PR-size chassis to clone my '64 bassman
(which I plan on sell once the clone is built), and...

[CoyotesGator]

There is so much to do...

I have this problem, uncureable I'm afraid.