My St@ngray GT build and question about 12ax7 volume levels

[daz]

Just finished my chassis build which is a Stangray one channel and maz GT in the other.
Both sound great, the GT side much louder as it doesn't have a tonestack sucking gain like the Stangray side.

I experimented with different 12ax7 on the Gt side and volume and gain difference was incredible. The Shuguang 12ax7B was almost twice as loud and gainy compared to the JJ ECC83S. Does tube gain difference make that much of a change???

[IMG:800:600]http://img.photobucket.com/albums/v179/ ... G_0483.jpg[/img]
[IMG:800:600]http://img.photobucket.com/albums/v179/ ... G_0479.jpg[/img]

[Structo]

Nice looking build!

Yes different tubes can make all the diffference.

[Noval_novice]

That's a cool idea to put both circuits in there. I had been considering building a S-ray with some spare transformers I have, but now I'm considering your approach

[daz]

Thanks for the feedback guys.
Yeah it wasn't too hard to do. Basically built
a s-ray and tied the gt preamp to the other side of the PI.

Need to play around to the volume balance between channels.
With the JJ in the gt side it's balanced but with Chinese it's like "Whoa!" but has that crunchy goodness!!

I gonna try the fischer mod to the ray which is supposed to
broaden the midrange

[Noval_novice]

Make sure to post some sound clips if/when you are able!

[daz]

near completion:
[IMG:799:597]http://img.photobucket.com/albums/v179/ ... e002-1.jpg[/img]

I put an eminence red fang speaker in there which seems to work well.

Having issues with 500mA HT fuse blowing. I was using fast blow but I'll change to slo blo.
The mains fuse also went 2A slo blo, dunno if it was a freak thing or something else going on. I'll need to suss out.
Other than than, it's sounding pretty good - just a few more little tweaks I'd like to do.

[Gaz]

I wouldn't be surprised if Z started building these himself!

[tubeswell]

The mains fuse also went 2A slo blo, dunno if it was a freak thing or something else going on. I'll need to suss out.

Calculating Mains fuse size

multiply volts with amperes (for each winding) and you get VA. Sum up the VA values and you get the whole VA of the secondaries. Divide that by the mains voltage and you get the primary amperage. Take the nearest value and multiply by two.

(For instance

300v x 200ma = 60va
6.3v x 4a = 25.2va
50v x 80ma = 4va
89.2 va altogether

89.2va / 110v = 0.81a

Match to 1A and multiply by two = 2A mains fuse.)

[daz]

Thanks. Diagnosed the new power tubes I got had a short.

[daz]

I wouldn't be surprised if Z started building these himself!

Funnily enough, Z did build one prototype back in '09 but it was channel switching. I only discovered that after I started building it.

[Noval_novice]

Did you resolve the volume discrepancy or is that felt to be inherent to the design of this amp?

[daz]

Did you resolve the volume discrepancy or is that felt to be inherent to the design of this amp?

i had misconceptions of the volume difference because I hooked it up to a speaker that wasn't in a cabinet.
The stang side is plenty loud with lots of headroom, so volume matching with the GT side will depend on how crunchy you want it. Obviously you have to crank the gt side to be louder for more gain, but I put in a master volume to control levels.

I've tried the crossline MV (ala matchless amps) and it's not too bad on the stang side but sounds terrible on the GT side.
I'm going to try the Lemar PPIMV next to compare, then suss out using the VVR.

Once thing I'm also experimenting is increasing the input and output caps values on the PI. I used the stock stang values initially. The stang pre sounds too boomy when upping the PI output caps but the GT pre doesn't mind it.

[daz]

Well I've revoiced the stang tone control as I didn't really like it stock. Knocked back the bottom end and added back some mids.

I also added a lamar PPIMV and must say it's one of the nicest master volumes I've used.

I should be able to do a video clip tonight.

[Gaz]

Thanks for the update, Daz. Can you balance the volumes with just the single master, or is there a good volume jump - I imagine it would.

EDIT: Sorry, didn't see the post where you already talked about this.

[daz]

Thanks for the update, Daz. Can you balance the volumes with just the single master, or is there a good volume jump - I imagine it would.

EDIT: Sorry, didn't see the post where you already talked about this.

No worries!
You can generally balance the levels. Ideally I would like a master just on the gt side, but it would have to be a pre PI arrangement.

OT: Prior to revoicing the tone control, I did try a mod Ken Fischer had done to two stangrays which was a 100k local feedback loop. Personally I thought it sounded muddy (and rendered the tone control useless). It seemed like it was a quick bandaid to rectify the lack of mids.

I'll have my first chance tonight to crank this amp to full volume levels. I'll report back hopefully with a video.