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Someone actually read my blog?!?!?!
Wow. That installation in the 5e3 was before I had ordered my first board from Dana, so it was the terminal strip method. I like the actual boards from Dana now.
I've always been tempted to build a Tweed Bassman and put VVR3 in it...
you should always use a dedicated heatsink for larger models
Says who The largest heat sink on the amp is the chassis how much more do you think you need? This application has successfully been repeated with excellent results.
you should always use a dedicated heatsink for larger models
Says who The largest heat sink on the amp is the chassis how much more do you think you need? This application has successfully been repeated with excellent results.
That all depends on what the chassis is made of (Steel or aluminum), how thick the chassis is and how many watts the amps is pushing. I suggest an external heatsink, in addition to bolting the mosfet to the chassis, for any amp in the 40-50 watt range.
That all depends on what the chassis is made of (Steel or aluminum), how thick the chassis is and how many watts the amps is pushing. I suggest an external heatsink, in addition to bolting the mosfet to the chassis, for any amp in the 40-50 watt range.
+1
(I put the limit at 30 watts, but I'm from the belt and suspenders school of design)
M Fowler wrote:How many complaints have you had regarding overheating or burnt up mosfets on the VVR Dana?
I don't think there has been that many. At least not noted on the various forums.
Probably incorrect setup is more of an issue than failure due to whether you heat sinked or not.
Recommendations are always good.
Once it is installed and working I have had very few. I have had some amps that were putting out a lot more watts than what they were rated for by the builder that the chassis by itself just wouldn't handle it. I have installed it on a number of Expresses (36 watts) just using the aluminum chassis and it works fine. A JTM 45 style amp with steel chassis will absolutly need an external heatsink IMHO.
I think this is an incredibly interesting subject ... VVR.
Dana sent me the information to read while waiting for the kit. There are a couple of resistor and capacitor adjustments to be made in the preamp along with the VVR installation. I'm sure these changes work well and have been proven out. Might go that way.
But an option to making these changes (the whole amp method) is to apply the VVR to the power tubes alone ... then install a MV. I would think it would have to be post PI since that's where a lot of the tweed sound comes from. Then balance the MV and the VVR. I don't think I'd mind doing this and I think it has an advantage of leaving the pre-amp untouched. Back on the fence ... whole amp vs power amp. Thoughts?
Can anybody point me to a layout showing the addition of a post-PI MV on a 5E3? Just considering all options while the VVR is in the mail.
I had to make the preamp changes as I was getting scratchy DC sounds on my guitar volume as mentioned in the instructions. It wasn't difficult and I preferred the idea of keeping the preamp / power amp automatically in step with the VVR control rather than having to adjust two pots.
Then again I can see that with a PPIMV you may get more control over whether the preamp / PI distorts more in relation to the power amp or not.
I think the main difference with the preamp changes is that the grid leak resistor is moved to be after the grid stopper(s) (my amp had Fender style high / low inputs). This valve wizard link http://www.freewebs.com/valvewizard/resistive.html suggests that you get a little extra signal attenuation this way but I certainly couldn't tell any difference. The extra caps shouldn't have any audible effect in theory - I used the same brand and value as the cap feeding my sole power tube (no phase inverter on my amp) to ensure this.
Last edited by eazilyled on Wed Mar 24, 2010 8:05 am, edited 1 time in total.
Just considering all options while the VVR is in the mail.
You may scale the whole amp and use a larger resistor from pot to ground. Range will be limited - say from 70 - 80V to nominal with a 220K instead of a 100K, the amp won't go down to whisper quiet (only to very quiet), there will be no sonic artifacts and no need for further mods.
If you add a master volume, you may go for a crossline - simple and effective except for max attenuation - or use a bootstrapped MV (cf. enclosed schemo), IMO the best option in a 5E3.
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FYL wrote:You may scale the whole amp and use a larger resistor from pot to ground. Range will be limited - say from 70 - 80V to nominal with a 220K instead of a 100K, the amp won't go down to whisper quiet (only to very quiet), there will be no sonic artifacts and no need for further mods.
I only picked up on this after re-reading Dana's instructions last night. Looks like I could experiment with a 220k for the two resistors ... drop in the VVR (3 wires) and you'd be done. Looks like the amp might only drop from approximately 30w-to-7w ... rather than whisper quiet as you say.
Also interesting ... the 5E3 amp circuit is a bit bassy for my tastes ... sounds like that is very common with all but Teles. The pre-amp caps related to this VVR installation are the same caps that can affect the bass level. So considering killing two birds with one stone. Sara is helping me think through this ... giving me some options.
Also interesting ... the 5E3 amp circuit is a bit bassy for my tastes ... sounds like that is very common with all but Teles.
The 5E3 was designed for late '50s single coils and gentle playing. Today's pups are much hotter and playing style is more agressive.
Fortunately it's quite easy to mod it while keeping it's qualities:
- Lower the value of the coupling caps to reduce boominess and farting. Original: 100n/22n/100n, modified 22n or 47n/10n or 22n/22n or 47n. I use 47n/22n/47n for single coils or P90's, 22n/10n/47n for std humbuckers, 22n/10n/22n for hot humbuckers.
- Add a big grid stopper to the cathodyne in order to avoid blocking disto. I use 220K or 3330K, Merlin advocates up to 1M. CF. the enclosed schemo.
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The largest heat sink on the amp is the chassis how much more do you think you need? This application has successfully been repeated with excellent results.
