trinityamps.com

I just joined this forum at Stephen's invitation. I am very interested in purchasing a Trinity 18 head with the VVR. I am currently trying to build a 50 watt JCM800 type amp with mods based on KOC's TUT series. I am trying to get a couple of problems worked out with the amp right now, but when those are worked out, I am going to try and incorporate KOC's Power Scaling into it. Based on what I have read on the London Power forum, I will probably scale the power amp and the phase inverter/splitter tube.

I am curious though; it seems like the prototype VVR for the Trinity 18 will scale the voltage back on the entire amp. Why is that more desirable?
Why would you want to scale the preamp?

_________________
My life was never the same after...BLACK SABBATH!

If you ony scale just the power tubes you need to add a new post PI 'master volume' for the amp as well as the power control. This compensates for the abuility of the pre to overdrive the power section. You also need to add several parts to separate and smooth the pre amp supply separately from the power amp. It's a more complicated build that doesnt sound that different from the simpler VRM (Voltage Regulator Module - our name for a simple VVR). It has one advantage and that's it avoids the 'leaky' DC from lowering the pre voltages on V1, V2. As long as that can be solved with the appropriate coupling capacitors, VRM it works very well.

leemo?

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

Hmmm Is the wr power scaling? Is that what you are doing with the mosfets?

Leemo, have you really used the Mosfets from computers.
With jcny coming up (down) next weekend, it would be nice to add this to the sIII. What do you think Coco./ As long as we're finishing the amps. And I now live in a 1/2 double, I could use this, if this is what it's doing.
Thanks
Jac

Thanks for answering the question. On my new 50 watt build, I was told that I should probably Power Scale the power tubes and the PI tube, but I would not need a PPI MV since I have wired in a dual gang MV after the tone stack, B4 the PI tube.

Well, I just put my Marshall 1987x reissue head up for sale on ebay. As soon as it sells I'll be ordering a Trinity 18 head with VRM! I can hardly wait. Now, the big decision will be...purple levant or white? Tough choice.

What colors are most compatable with the VRM control?

_________________
My life was never the same after...BLACK SABBATH!

jac, VRM is B+ power control. you can build one pretty easily but you need to source the parts & build a board.
Worth it.

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

jac,
Yes, very much worth it.
The mosfet from the computer power supply will sometimes work. http://www.18watt.com/modules.php?name=Forums&file=viewtopic&t=18694
I hope the link works. If not , log on to 18watt.com and search the forums for "Layout for VVR mod in Lite2B".
LeeMo

Link worked great Nice layout, I'll have to see what I've got around,
Thanks guys.

Coco,

I have installed the VVR on a few different circuits, Super lite, your Slll and 5e3. All amps work well except your Slll.

I remember you asking over at 18 watt about how you deal with the .1 cap and 1 meg resistor in your Slll that has both Hi and Low inputs going to V1 pin 2.

Did you work that out yet? Did you take the 1 meg off the input jack and if so where did you put it. At this point I just left the 1 meg at the jack and used a .1 off the two 68Ks to pin 2. The amps still on the bench getting new sockets, I'll post the results when I get it together.

AJ

What sort of problems? Leemo got his to work on his v6 and we also did a couple of sIIIs.



If you are getting the 'scratchy pot', try this and let me know how it works out. Leave 1M on the input jacks.

At the V1 terminal strip at the tubes, disconnect the coax cables.
Solder one end of a .01 to .1 uf cap to the terminal strip where the 68K grid resistors are.
Solder a 1M from there to the terminal strip ground lug.
Reconnect the coax to the other end of the capacitor.

This should filter out the DC leaking when the control is at low voltage.

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

Thanks, I didn't use the second 1 meg to ground just a .1 cap where you suggested, I will use the 1 meg next try, I blew the mosfet screwing around trying to get the buzz out.

I had installed this in two other amps with no problems but for some reason I'm having problems with the Slll. The problem I'm having is a light buzzing and hum, (I'm not even concerned with the scratchy pod thing till get this working properly first). I didn't use the 1 meg off grid to ground yet but can't see that giving this buzz problem.

I did change out the 7volt zener in the VVR to 12volts this gave me no voltage loss, B+ is 341 at the rectifier and at the mosfet on hi. VVR works but I have this buzz and strange distortation. If I disconnect the VVR, plays great no buzz, no strange distortion. I'm starting to think it's the Mosfet, I'm using the NTE2973.

What Mosfet's are you using in your amps?

The layout is critical for noise. That's why we made such a small compact board.

Check the installation we did on a TC15 in the VRM thread. Quiet as a mouse.

viewtopic.php?p=10510#10510

and this one in an sIII Plexi first generation VRM but same, quiet

viewtopic.php?t=1175

BTW, your Mosfet should work just fine. We dont use that one.

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

So what exactly does this VRM sound like? What does the pot do?

Well, read this: viewtopic.php?t=1230Be

and this: viewtopic.php?t=1175&highlight=vrm

Basically it allows you to get the cranked distortion sound but at a lower volume. It's simple but it really seems to do the trick - or we wouldnt even bother with it!

Maybe not as good with the clean settings.

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