High-plate Classic

[Charlie Wilson]

Looks great Ian. I live close to Ian and have heard the amp, It sounds great. The only thing you may want to look at is the output transformer secondaries. You are riding right against them with your power tube grid wires. You usually want to keep those away from other signal wires or try to cross at a right angle.
CW

[ijedouglas]

Looks great Ian. I live close to Ian and have heard the amp, It sounds great. The only thing you may want to look at is the output transformer secondaries. You are riding right against them with your power tube grid wires. You usually want to keep those away from other signal wires or try to cross at a right angle.
CW

Thanks CW. I'll try move it but if I remember, that was about as good as I could get it without either the secondaries riding up against the tube or the brown grid riding up against the other PI wires. I've thought about moving the chassis hole for the secondaries which may position them better. I'll crack it open today and take a look.

[ayan]

is that installed like a cut control (Vox style)?

Connected to the input of the OD ratio control.

That's the way I had tried it as well. I think it'd preferable to use a slightly larger resistor at the V2B output, like 180K instead of 150K - in case you haven't done it that way. The HF trim inevitably takes away some of the top end "magic," provided there is some magic going on in the first place. That can be pursued through the careful selection of parts and shielded wire as well. Like many others, I always used the teflon covered shielded cable, which has very low capacitance. In your case,it looks like you used the big guy's recipe to begin with. I'd go back into my amps to replace that, but I don't have it in me to mess with them anymore.

[bepone]

instead to removing all the coax cables to be replaced , it is easy to put 50pF-75pF to the ground on al the nodes where is suspected the cable has too low capacitance (increasing shield capacitance) .

[ayan]

instead to removing all the coax cables to be replaced , it is easy to put 50pF-75pF to the ground on al the nodes where is suspected the cable has too low capacitance (increasing shield capacitance) .

At least in theory, yes. In practice, it doesn't necessarily always seem to be that simple. And this only applies when playing the amps at home, which I really haven't done in years. Live, it doesn't matter and even though the overdrive is bright, it sounds really good when being recorded.

[Smitty]

At least in theory, yes. In practice, it doesn't necessarily always seem to be that simple. And this only applies when playing the amps at home, which I really haven't done in years. Live, it doesn't matter and even though the overdrive is bright, it sounds really good when being recorded.

Realizing that amps sound different at different distances and choosing which distance you want the amp to sound balanced is a struggle reserved for professionals. Thanks, for your perspective, Gil.

For me, listening to an amp from the middle of the room (presumably by a skilled player) and then playing it on stage a few songs later is valuable information. To my ears, top end usually dissipates at about 30 feet. And then there's the mix...

[talbany]

Years ago I used to install the HFT pot in just about all my Non HRM's, (.001,.01, .022) then after finally using most of the same parts as HAD (namely Sprague XF5's) as well as certain select resistors that i liked I've found there was no longer a need for the HFT mod, since then have never looked back.
I also agree that if an amp was a bit bright using it at home in a small room that by the time it hit a decent size stage and in the mix with the rest of the band it was perfect! Let it eat!


This has been my experience with the HFT mod

Nice build Ian.congrats!

Tony

[ijedouglas]

Years ago I used to install the HFT pot in just about all my Non HRM's, (.001,.01, .022) then after finally using most of the same parts as HAD (namely Sprague XF5's) as well as certain select resistors that i liked I've found there was no longer a need for the HFT mod, since then have never looked back.
I also agree that if an amp was a bit bright using it at home in a small room that by the time it hit a decent size stage and in the mix with the rest of the band it was perfect! Let it eat!
This has been my experience with the HFT mod
Nice build Ian.congrats!
Tony

Thanks Tony. The amp is bright but not unpleasant at all. After adding the HFT and setting the trimmer to around 120K it didn't really take much off the top-end but seemed to add something in the mids I liked.

[bepone]

instead to removing all the coax cables to be replaced , it is easy to put 50pF-75pF to the ground on al the nodes where is suspected the cable has too low capacitance (increasing shield capacitance) .

At least in theory, yes. In practice, it doesn't necessarily always seem to be that simple. And this only applies when playing the amps at home, which I really haven't done in years. Live, it doesn't matter and even though the overdrive is bright, it sounds really good when being recorded.

agree that at home and in the stage is different story, this is why room is important.. in hi fi, room is 40% of the sound. playing live always is some missing of highs, crowd acting like a a sponge that absorbs high tones.. but this is now in room acoustic/treatment territory and this is another science. recording of the guitar amp also, top science - where you can get only 20-30% of the real sound recorded with too much effort and spent time. and oftern one i phone is making better and faster job than 10000's usd of microphones and preamps.

i was focusing on the amp only and R-C and C-R filters, where instead of changing the cable to tame the highs, we can increase the coax braid capacitance to shape the top end, where i don't see difference of increasing capacitance externally of hi quality teflon coax braided shield vs using different higher C coax.

[dcribbs1412]

Great looking build
Are those 210k values used in V1, V2 and with OD trimmer?

[ijedouglas]

Great looking build
Are those 210k values used in V1, V2 and with OD trimmer?

Thanks

Yes, they're actually 200K and was as close as I could find.

[ijedouglas]

Looks great Ian. I live close to Ian and have heard the amp, It sounds great. The only thing you may want to look at is the output transformer secondaries. You are riding right against them with your power tube grid wires. You usually want to keep those away from other signal wires or try to cross at a right angle.
CW

I managed to move them away and there was a definite increase in sustain. Great catch! (again )

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