Vht d-50h tweaks

[daniboy79]

yes, it have LNFB
you can make a switch for that

Agreed ... especially if you go between single coil guitars and Humbucker guitars. I find that the 'tightness' that the LNFB brings to the table can thin out Single coils. Ymmv

[Dansamp1]

Plates and cathodes made a big difference for me, YMMV. I am currently playing around with different cathode caps and you'd be surprised at the difference they make

As Tony states, depending on what you want from the amp, will depend on what resistors and caps you use. Here is a good thread that may help you decide: https://ampgarage.com/forum/viewtopic.php?f=4&t=32580

I prefer Polyester 6PS caps and use them mostly throughout my amps. 183 has polypropylene SBE 715s on the PI couplers and on my 102 I use a Sprague 715 on the mid cap.

In my 183 I used NTE MFs, Roederstein MK3s, Draloric LCAs. For the 124 I used mostly carbon film (MF on cathodes) and 102 I used a mixture of NTE MF, MK3 and Carbon film.

The 183/124/102 layouts are well documented and tried and tested. You may want to start there when deciding how you want to approach this.

Thank you for the link,
It looks like I have quite a bit of homework to do before I fire up the soldering iron .

[groovtubin]

Had one in house, guy wanted more harmonics on OD channel , added another larger value to V2B cathode, did the trick, ymmv..

[Dansamp1]

Had one in house, guy wanted more harmonics on OD channel , added another larger value to V2B cathode, did the trick, ymmv..

may I ask what value cap did you add ?
and by another do you mean , in addition to, or was it substituted ??
Thank you

[SpeedYellow]

Greetings gang, new guy here. I hope this thread continues and that we see some more details about the suggestions. I just got a D-50 mostly out of curiosity and to compare against my C’tone OTS 20 lunchbox ("70s voicing"). My impressions:
1. Overall, in stock form, it falls far short of the OTS20.
2. Lows: It’s bass is tight and clear, quite a bit tighter and more composed than the OTS20.
3. Mids: Very mid-focused, I'd almost say nasally.
4. Highs: Lacking highs, and sounds like a blanket is on top. With my strat on OD channel, it lacks the beloved quack/twang that the OTS20 (and Fender amps) can do. I'm unsure if the problem is poor upper harmonics or just poor high end? Less of an issue with humbuckers but still lacked high end.

I have no idea if the root problem is poor resistor/cap values, poor component quality, or whatever. But would be fun to improve it.

During testing, my chain was Strat or Semi-hollow AS93 -> Amp (D-50 or OTS20) -> Fx loop with Mini-Kleinulator -> Attenuator (JohnH, -14dB) -> 1x12 cab with WGS ET65. I switched many many times back and forth between amps.

Had one in house, guy wanted more harmonics on OD channel , added another larger value to V2B cathode, did the trick, ymmv..

Some details about this would be great! Seems to me this would be a great mod.

[ChopSauce]

Had one in house, guy wanted more harmonics on OD channel , added another larger value to V2B cathode, did the trick, ymmv..

Some details about this would be great! Seems to me this would be a great mod.

I saw V2B bypass cap value of 4u7 on the schematic on first page. Maybe you could try 10uF, but there are several other changes from #183 so I'm not sure I'd go that way...

[Dansamp1]

So,
for those following this thread.
I came across another D-50 on sale at GC.
It was marked down to $719.00 only $40.00 more than the one I purchased used a month ago.
So I returned the used one and purchased the new one, now I have one with a warranty.

The new amp sounds better than the used one.
It seems more open, and a bit brighter ( from what I remember) .
I took a peek inside, and checked the bias. 33-35 ma.
I checked the voltage on the PI it's 444v. -437v.

The 20 meg resistors (LNFB) on the new one are physically smaller than the previous one .
The old resistors looked like they were 2 watt resistors .
everything else looked the same.

I am still considering upgrading this with NOS resistors from Welagen Amps. but maybe now with this new one I am not in such a rush to do it.

Dan.

[Audiodog]

Why bother considering swapping resistors when the circuit has mods that in my opinion should be reverted to more normal Dumble specs. Get rid of that .01 that feeds the OD. The .05 out of V1b is fine for the OD too. Trimming that much bass is a bandaid for other issues. Next, put back 390pf treble cap. Adds the upper mids these amps are known for. Lots of parts too swap too, like the caps and metal oxides.... start with the circuit changes. I don’t trust their ears. I played one and was totally underwhelmed.

So,
for those following this thread.
I came across another D-50 on sale at GC.
It was marked down to $719.00 only $40.00 more than the one I purchased used a month ago.
So I returned the used one and purchased the new one, now I have one with a warranty.

The new amp sounds better than the used one.
It seems more open, and a bit brighter ( from what I remember) .
I took a peek inside, and checked the bias. 33-35 ma.
I checked the voltage on the PI it's 444v. -437v.

The 20 meg resistors (LNFB) on the new one are physically smaller than the previous one .
The old resistors looked like they were 2 watt resistors .
everything else looked the same.

I am still considering upgrading this with NOS resistors from Welagen Amps. but maybe now with this new one I am not in such a rush to do it.

Dan.

[krd51@ptd.net]

Question about modding the VHT D-50: I've been using a stock D50 for a couple of months and I've set up (IMHO) a very good
clean sound with my Fraser Strat. My problem is when I switch over to the Over Drive section. The tone becomes very Bass'y
and Boomy. Also the distortion isn't that smooth sounding (rather raspy). I've tried adjusting all the Volume and Gain controls and still can't get
a good Overdrive sound. I would like to mod the amp to get a pleasing overdrive lead sound but would like some idea's as to which
components to change out. I don't want to go in there willy nilly and mess up the clean sound.
thanx,

[ijedouglas]

Question about modding the VHT D-50: I've been using a stock D50 for a couple of months and I've set up (IMHO) a very good
clean sound with my Fraser Strat. My problem is when I switch over to the Over Drive section. The tone becomes very Bass'y
and Boomy. Also the distortion isn't that smooth sounding (rather raspy). I've tried adjusting all the Volume and Gain controls and still can get
a good Overdrive sound. I would like to mod the amp to get a pleasing overdrive lead sound but would like some idea's as to which
components to change out. I don't want to go in there willy nilly and mess up the clean sound.
thanx,

Please provide gut shots of your amp so that we can see what is currently in the amp and what may be tweaked?

[krd51@ptd.net]

User name Neskor posted many internal component pictures and a schematic of the VHT D-50. (page 1 of this string)
It's basically a Dumble 183 ODS with some VHT component changes.

[ijedouglas]

User name Neskor posted many internal component pictures and a schematic of the VHT D-50. (page 1 of this string)
It's basically a Dumble 183 ODS with some VHT component changes.

Perhaps you should then read through the rest of the post to see what tweaks you may want.

[krd51@ptd.net]

I was hoping that someone actually had the same issue and resolved it.
I have read all the posts over and over again and no-one suggestion seems to
nail it.
Short of replacing every component in the amp as some suggest.
But thanx anyway.
KRD

[ijedouglas]

I was hoping that someone actually had the same issue and resolved it.
I have read all the posts over and over again and no-one suggestion seems to
nail it.
Short of replacing every component in the amp as some suggest.
But thanx anyway.
KRD

My original question for detailed gut-shots was to help understand EXACTLY what you have in your amp and to see if there are things that could be changed. Bad lead dress may also be something that is causing your issue along with component choice. Schematics and layouts are also helpful I, and I'm sure a bunch of other forum members are not familiar with the D-50H and so giving us a frame of reference is always helpful.

[JD0x0]

Had one in house, guy wanted more harmonics on OD channel , added another larger value to V2B cathode, did the trick, ymmv..

Some details about this would be great! Seems to me this would be a great mod.

I saw V2B bypass cap value of 4u7 on the schematic on first page. Maybe you could try 10uF, but there are several other changes from #183 so I'm not sure I'd go that way...

I've increased the 1uF on HRM amps to 4.7uF, but IMO going from 4.7u to 10uF will only add bass flub, and wont really add any meaningful harmonics, like originally mentioned. (https://www.ampbooks.com/mobile/amplifi ... capacitor/)
If I wanted more harmonics and clipping, without changing the biasing of the preamp stages, I'd be looking at the voltage dividers between OD stages, for more gain.

If I'm looking for more bass, it'd be more effective to increase the coupling caps in the OD stages than it would to increase the bypass cap if you've already got 4u7 bypass values. A 5nF/250k will shave some lows.