trinityamps.com

Hello,

I bought a v6 kit several years ago and seeing the new schematic I'm thinking of updating my amp. Just have a few questions about the updates.
-The 200k power tube switch resistors is there to protect from cathode poisoning?
-One thing I noticed right away on my amp was the gain difference from El84 and 6V6. So i used a 3pdt to change the tail resistor simultaneously. No much of a problem since one could use the volume knob to compensate. On the new schematic you have done more. The 200k/270k division and PI changes 470R and 22k. Is this just to compensate for volume difference or do you feel the sound is better/different this way as well? I'm guessing the poweramp still breaks up before the PI? Does it work better with VVR at lower settings perhaps?

I have a VVR kit installed, first I did the whole amp but curiosity made me try scaling the PI and PA only. I can't really say which method I like the best. Maybe a bit more clarity now but sometimes I miss how it was before. A bit darker but still a cool toneful sound.

Nicklas

Ok, I've done some changes. I used the resistors I had at hand so from PI coupling caps I have 150k 270k dividers. 6V6 grid resistor at the top then EL84 at junction and 270k to ground. Tail resistor is the same for both tubes 42k, no switching. PI bias is 700R. The tubes are well balanced, the EL84 has just a bit more drive. Like this so far.

I'm trying out a 10V zener Ruby filter over the 270K to help with buzz at lowest VVR settings. Actually I might not need it know with the voltage divider. I have a 180R cathode resistor on the El84 with 11V on it(B+ 333V). I read what Lindz said about lower zeners so I guess it should be ok. The PI will also be able to swing because of the 150k. Thing is I never run my amp at full power(just when I try clean jazz licks), my neighbours would hate me and my ears would ring even more than they do now if I rocked out at full power. It's a shame that when I played in a band I had a 30W solid state washburn amp at full tilt. We had fun though and were all learing to play and didn't know better to complain about the sound.

let us know how. the ruby filter works. not sure it will. you can pit. a 16or 8 uf filter cap in front of the VRM too.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I'm using this schematic right now, http://rh-tech.org/public/18-Watt/18_Wa ... PI_162.gif

I think I will change my current layout a bit. The first 32uf can cap section is used for ez81 filtering and the second for the screens after the VVR. No filter at VRM output at the moment. This might not be the best layout.
I will move the first section 32uf to after the VRM. Perhaps it will work without a cap before the 1n4007 diodes. Otherwise I'll add a 8-22uf at this point depending on what I find in my stash. I'll keep you updated.

Yes, although it. was not a big concern.

this was done to equalize the drive to the power tubes. they are about the same volume etc. just different tone now.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Ok, thanks for the explanation.

Just to clarify what I said before, I'm still using most of the original sIII v6 trinity schematic. It is just the power supply part of the above schematic I'm using to scale PI+PA only.

got it. we tried and did not like the tone when scaled that way, FWIW!

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Just finished a plexi build, really enjoying the VRM in the recommended position doing the whole amp.

I did add extra filtering right after the rectifier, before the VRM. I just added an extra tagboard over the power ground point... Couple of parallel 22uF 450V caps and 200k worth of bleed resistor...Location to the left of the turretboard in the picture. It should also be better for the MOSFET in the long run to regulate smoother DC. This also cured an unhealthy zipper noise I got when the power knob was turned quickly.

Check out the schematics in the Hall VVR http://soundgaragetales.com/tempo/VVR2.pdf

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Corey

That is good info, on 18watt.com it seemed many liked to scale PI+PA only so I thought it was worth a try. It was more work doing it this way and I wasn't sure if it was for the better. I remember when I first tried it out and probably made this face . Perhaps better clarity at lower setting and half clean sounds, but it seemed there was a change in character of the distortion compared to the whole scaled amp. I will probably change back to whole amp scaling. Or first give PI+PA another chance with different filtering layout.

nzCdog: Yes I remember that sound when turning the pot. Good tip. If I go back I will add a cap here but perhaps not over 22uf, EZ81 says 50uf max and we already have a 32uf. I also added a tag board at that position to accomodate the extra filtering when scaling PA+PI only, a good place for the cap. Your build looks very nice and tidy. The new layout probably helps a bit here as well.

Ah great, thanks for the heads up on the EZ81, Nickebunker... Good to know. I wonder shouldn't it will still be OK in my amp, as my other filters are after the VRM? I appreciate your compliment, this layout was really nice to build... Just about finished the cabs now

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Corey

I don't know how the VRM affects this, I guess it would only be a potential issue when VRM is at max power. This is also depends on the power transformer impedance. You can read about it here: http://www.valvewizard.co.uk/fullwave.html
He talks about adding extra limiting resistors if the PT impedance is too low. However most vintage amps don't use these resistors and the rectifiers seems to last long anyway. I have one old HIFI amp though with a 100uf after a GZ34(max 60uf), to survive this they have added a 47R power resistor in series the rectifier.

/Nicklas

Cool site! Thanks Nicklas, some good reading ahead!

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Corey