Wangs VT-1H All Tube 1 Watt Tiny Amp

Tube or solid-state, this section goes to eleven!

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby mavrim » 07 Mar 2015, 00:37

On my amp, I will be replacing the .022 and .0002 wima caps with vintage mustard caps or vintage polypropelyne (yellow tubular) caps.

The (2) 27 mfd 50V caps shown in circuit are electrolytic. I plan to try poly caps there too!

The wima caps are rated at 630V, but for this circuit it is not necessary to be rated that high. In my own 1/4 and 1/2 watt amps I use 100V green chicklet poly caps with great results. I sometimes find these cheaper green caps to sound better than vintage mallard caps.
mavrim
Breadboard Brother
 
Posts: 75
Joined: 07 Feb 2015, 02:16
Has thanked: 5 times
Have thanks: 23 times

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby Matec » 07 Mar 2015, 02:04

Thank you, mavrim.

R7 is certainly 470k. :hmmm:
If you are measure it, even in the circuit, the value will appear smaller because it is in parallel with the center pin of the volume pot.
With the pot at 100%, the maximum measured resistance is 320K (1M // 470k = 320K).

I believe that R14 should be even 1K, like you said. The 510R value is too low for this polarization. I can not see clearly the color code of this component.

Resistor R17 is even 1.5k, or am I also wrong?

Even if the LED circuit is grounded, as you said, it would be a mistake. For would unbalance the point of the reference heater power, which is given by two resistors 100R. The scheme will be right, but the balance of this circuit, no. :scratch:
..............................................................................................................................................

(I will only repeat this phrase, this time with the correct writing.)

"If you can check the reference numbers of the components, I thank you."
..............................................................................................................................................

Cheers

For this message the author Matec has received thanks:
mavrim (07 Mar 2015, 06:05)
User avatar
Matec
 
Posts: 32
Joined: 28 Feb 2014, 12:04
Has thanked: 4 times
Have thanks: 14 times

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby mavrim » 07 Mar 2015, 05:47

Matec, you are correct! R7 = 470K. Yellow/Violet/Black/Orange (1% metal film resistor). This resistor is tiny, probably an 1/8th watt, hence the difficulty reading value. I was using a jewelers loupe at work which I do not have with me now. Had to use a bright led flashlight to read color code. lol

The 1k value is correct as far as I can tell with my tired eyes. Brown/Black/Black/Brown is what I barely see with naked eye. Will double check with loupe on Monday.

Good night, thank you for your excellent detective work!
mavrim
Breadboard Brother
 
Posts: 75
Joined: 07 Feb 2015, 02:16
Has thanked: 5 times
Have thanks: 23 times

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby mavrim » 07 Mar 2015, 06:04

R17 = 1.5K as noted.

I rechecked the power led. I see the LED anode going to pins 4/5 on one of the tubes. Cathode connects to limiting resistor. Resistor connects to a trace that runs parallel to the edge of the output transformer and connects to ground point on high voltage filter caps. I ohmed this out with a meter earlier today. This ground is isolated from the signal ground.

I usually match my 100 ohm artificial center tap resistors to be sure they will offer the lowest hum. This board reads 100/103 ohms. I will be replacing them with hand matched pair.

Your right about led being unbalanced. I thought the same thing. I will be using a power switch with light or neon panel lamp in my build, so I will not even wire in the led.

I also was going to cut the heater filament traces and run twisted pair wiring raised off the board. Do you think that would lessen the hum compared to non twisted wires with pcb layout? I had noticed a little hum at full volume.
mavrim
Breadboard Brother
 
Posts: 75
Joined: 07 Feb 2015, 02:16
Has thanked: 5 times
Have thanks: 23 times

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby Matec » 07 Mar 2015, 09:21

I do not know if it would be effective to replace the PCB tracks for twisted pair wiring raised.
Maybe it will work, maybe not.
It's all very tight in that box. Perhaps the power transformer itself is causing this noise.

As we doing the circuit checking, I'm changing the schematic. Once we have taken the doubts, I will post the scheme, with the corrections.

Cheers

For this message the author Matec has received thanks:
deadmanamps (23 Mar 2015, 07:51)
User avatar
Matec
 
Posts: 32
Joined: 28 Feb 2014, 12:04
Has thanked: 4 times
Have thanks: 14 times

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby deadmanamps » 12 Mar 2015, 04:28

so do you all feel the build quality is on par for China? or do you feel is a bit better than what normally comes out of there? do you guys feel this worth the money? I know the Zvex is like $350. but I almost feel like this one sounds better! I'm just tired of throwing my money away on cheap Chinese gadgets and hoping this is not one of them.....
deadmanamps
 
Posts: 3
Joined: 03 Mar 2015, 05:53
Has thanked: 2 times
Have thanks: 1 time

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby ppluis0 » 13 Mar 2015, 02:15

mavrim wrote:I usually match my 100 ohm artificial center tap resistors to be sure they will offer the lowest hum. This board reads 100/103 ohms. I will be replacing them with hand matched pair.

Your right about led being unbalanced. I thought the same thing. I will be using a power switch with light or neon panel lamp in my build, so I will not even wire in the led.

I also was going to cut the heater filament traces and run twisted pair wiring raised off the board. Do you think that would lessen the hum compared to non twisted wires with pcb layout? I had noticed a little hum at full volume.


Hi mavrim,

I suggest that you will lift these two 100 ohms resistors from ground and build the following arrangement to supply this virtual center tap

Image

This way you have all heathers "elevated" from ground. This minimizes the parasitic coupling between heater and cathode on each triode. Just search the web typing "elevated heaters" to read several explanations about this matter.

Cheers,
Josè
User avatar
ppluis0
Cap Cooler
 
Posts: 491
Joined: 14 Jul 2010, 19:33
Location: Argentina
Has thanked: 32 times
Have thanks: 56 times

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby cassoulet » 13 Mar 2015, 10:45

Hi all,

Or maybe even use V2a cathode as an already elevated point? How about that?

For this message the author cassoulet has received thanks:
deadmanamps (23 Mar 2015, 07:50)
cassoulet
 
Posts: 16
Joined: 20 Feb 2014, 19:07
Has thanked: 4 times
Have thanks: 5 times

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby pdcorlis » 27 Apr 2015, 00:03

As a new kid on the block may I ask if this little amp is a keeper as she sits? I'm not really interested in modding the amp, only for using it as a little blues practice amp.

Thanks!

Phil.
pdcorlis
 
Posts: 2
Joined: 26 Apr 2015, 02:08
Has thanked: 0 time
Have thanks: 0 time

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby mavrim » 28 Apr 2015, 01:33

It was a good sounding amp. Reminded me of the mahaffay plexi, just louder and with 3 tubes. I ended up selling it because I wanted to finish building my own amp into a gutted Marshall lead 12 head. If your into blues and rock, I think you would be pleased with it. I
mavrim
Breadboard Brother
 
Posts: 75
Joined: 07 Feb 2015, 02:16
Has thanked: 5 times
Have thanks: 23 times

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby pdcorlis » 28 Apr 2015, 02:21

mavrim wrote:It was a good sounding amp. Reminded me of the mahaffay plexi, just louder and with 3 tubes. I ended up selling it because I wanted to finish building my own amp into a gutted Marshall lead 12 head. If your into blues and rock, I think you would be pleased with it. I


Thanks for your help. I think I will pick one up since blues and rock are right up my alley. I especially like simplicity of this tube amps design. Nothing fancy - just tube goodness.
pdcorlis
 
Posts: 2
Joined: 26 Apr 2015, 02:08
Has thanked: 0 time
Have thanks: 0 time

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby HTH » 29 Apr 2015, 13:17

ppluis0 wrote:
mavrim wrote:I usually match my 100 ohm artificial center tap resistors to be sure they will offer the lowest hum. This board reads 100/103 ohms. I will be replacing them with hand matched pair.

Your right about led being unbalanced. I thought the same thing. I will be using a power switch with light or neon panel lamp in my build, so I will not even wire in the led.

I also was going to cut the heater filament traces and run twisted pair wiring raised off the board. Do you think that would lessen the hum compared to non twisted wires with pcb layout? I had noticed a little hum at full volume.


Hi mavrim,

I suggest that you will lift these two 100 ohms resistors from ground and build the following arrangement to supply this virtual center tap

[ Image ]

This way you have all heathers "elevated" from ground. This minimizes the parasitic coupling between heater and cathode on each triode. Just search the web typing "elevated heaters" to read several explanations about this matter.

Cheers,
Josè


+1 for elevated ground heaters - I've used this in lots of amps with great results. Really kills the hum. You could add a pot to the design to 'tune' the hum even lower...

Heater-Mod.jpg
You do not have the required permissions to view the files attached to this post.
User avatar
HTH
 
Posts: 49
Joined: 04 Sep 2010, 13:16
Location: Newcastle, UK
Has thanked: 2 times
Have thanks: 1 time

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby mavrim » 29 Apr 2015, 23:45

Thank you!

I was planning to try that on the next build. I sold this wangs amp so I could continue with my Marshall JCM-1 build.
mavrim
Breadboard Brother
 
Posts: 75
Joined: 07 Feb 2015, 02:16
Has thanked: 5 times
Have thanks: 23 times

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby jtn191 » 01 Jun 2015, 06:04

Thinking I'll pull the trigger and buy one! What would you do to get better clean sounds: 1M pot instead of 68k input resistor as input level? reduce the 27uF cap in the first stage or 2200uF cap? Add some kind of bright cap switch around the tone or volume controls?
jtn191
Solder Soldier
 
Posts: 164
Joined: 01 Jan 2011, 11:28
Has thanked: 36 times
Have thanks: 24 times

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby solartony » 06 Apr 2016, 22:36

great work everyone, has anyone drawn or seen a pcb schematic online?
solartony
 
Posts: 2
Joined: 06 Apr 2016, 22:02
Has thanked: 2 times
Have thanks: 0 time

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby solartony » 06 Apr 2016, 22:48

Matec wrote:Hello mavrim.
As I said, I made a schematic of your mini amp. Follow here for you to compare.
It is almost entirely based on his scheme, but also has some of my observations.
There are parts I tried to see the value, and if you see that are wrong, please correct. It's a simple scheme, so there are solutions that may not be the best, but that form the tone of the amp.

Wangs VT 1h PRELIMINAR-01.PNG


If you can check the component reference nómeros and I thank you.

Cheers

Matec


Hi Matec,
great work, is this the final circuit dwg ?
has anyone drawn or seen a pcb schematic online?
best wishes, :applause:
solartony
 
Posts: 2
Joined: 06 Apr 2016, 22:02
Has thanked: 2 times
Have thanks: 0 time

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby Matec » 11 Apr 2016, 17:21

Hello solartony.

Here is the schematic with the latest patches made from the mavrim observations.

Not sure how much will be 100% compatible with the original. But it is consistent. It should work fine.

I do not have the design of the PCB. It would have to be made according to your need.

Cheers.

Image

For this message the author Matec has received thanks: 2
bmxguitarsbmx (31 Dec 2016, 03:12), skywise (14 Jul 2016, 14:33)
User avatar
Matec
 
Posts: 32
Joined: 28 Feb 2014, 12:04
Has thanked: 4 times
Have thanks: 14 times

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby cpu123 » 28 Dec 2016, 20:59

Hello, guys!
Someone tested it?
cpu123
 
Posts: 1
Joined: 26 Dec 2011, 17:39
Has thanked: 0 time
Have thanks: 0 time

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby astrodon » 20 Jan 2017, 18:40

A quick question: How do you remove the circuit board after all the hardware is unscrewed/removed? I think my only problem is the power socket. Do you have to unsolder the 3 power leads or can you disconnect the board from the power socket some other way?

Thanks
astrodon
 
Posts: 2
Joined: 20 Jan 2017, 18:27
Has thanked: 0 time
Have thanks: 0 time

Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby astrodon » 20 Jan 2017, 21:36

Just in case this helps anyone else, the answer is yes, desolder them. According to Wangs, "The VT-1H is handsoldered at those points ...." I desoldered those three points and the board comes out.
astrodon
 
Posts: 2
Joined: 20 Jan 2017, 18:27
Has thanked: 0 time
Have thanks: 0 time

Previous

Return to Amplifiers

Who is online

Users browsing this forum: Bing [Bot] and 8 guests