Wangs VT-1H All Tube 1 Watt Tiny Amp

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

Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby mavrim » 17 Feb 2015, 01:16

Has anyone else noticed this new amp recently? I spotted it on ebay about a month ago and now there are sound samples. I just ordered one from a seller on Reverb for $155 with free shipping. I plan to swap out the stock Chinese tubes with (2) Tung-Sol 12AX7 and (1) JJ ECC82 tubes. I will be reverse engineering this pcb and making a schematic. I want to modify this amp!

POWER: 1WATT ALL TUBE
PRE-AMP TUBES: 1.5 (3 stages)12AX7/ECC83
POWER AMP TUBES: 0.5 (1 stage) 12AX7/ECC83 and (1) 12AU7/ECC82
CHANNEL: SINGLE CHANNEL
ADJUST: VOLUME and TONE
OUTPUT: 8Ω/16Ω
WEIGHT: 1.5KG

61delRFY+3L__SL1000_.jpg


61FkHuOrhwL__SL1000_.jpg


I found this internal PCB image. Looks to be 100% tube, unlike the Blackstar HT-1 which has discrete circuitry added to the tube circuitry
71MUgcD+iML__SL1096_.jpg
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Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby Thomas_H » 17 Feb 2015, 03:09

Hi,
I only saw it recently too. Looks a nice amplifier for the price. Need to take a look at that sample.

Interesting way of using both transformers.

My first impression was that it used a SMPS like the nanohead, but apparently the enclosure is big enough for a small OT.

It looks like a smaller 1w JTM marshall or lil night train with a cathodyne PI, 12au7 in PP, and a three gain stage preamp.

You could probably mod it to sound like the vox/marshall amps if the PT and OT could handle it. There is a lot of information at the jtm 1w thread.

I'm interested on the OT's size and primary impedance, if it's in the 18k or 10k range, and how is the tone.

Cheers,

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

Postby bajaman » 17 Feb 2015, 07:51

looks like it uses the 12AU7 as a push pull output stage - I have tried this but it never sounds as good as a push pull pentode output stage in my humble opinion - triodes always sound too mushy to my ears.
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Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby cassoulet » 20 Feb 2015, 15:34

I wonder how this can be switched between 8 and 16 ohm output. Don't see any external switch on the back.
Awaiting your schemo. :thumbsup
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Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby mavrim » 20 Feb 2015, 18:33

On these low wattage amplifiers, there really is no harm with mismatching output impedances. In my 1/4 watt builds, I was using an 8 ohm output transformer that would work for 8/16 ohms. When I use a 4 ohm transformer, I use 4/8 ohm speakers. I tend to see higher speaker impedance used instead of going lower. The blackstar HT-1 output is 4/8/16 ohms from the same output.

My amp should arrive today! Looking forward to testing it out and swapping in Tung-Sol 12AX7's pre-amp tubes and JJ 12AU7 output tube. Then I will reverse engineer the PCB and make a schematic. China always steals American designs and clones them, so now we can do the same to them! :D :applause:
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Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby cassoulet » 20 Feb 2015, 18:49

Great, I guess you'll find out this one design was partly stolen from the brits. :mrgreen: Or maybe it is some sort of Firefly.
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Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby tonyharker » 20 Feb 2015, 20:00

3 tubes is a bit overkill for only 1 watt.
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Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby mavrim » 21 Feb 2015, 02:20

I received the Wangs VT-1H amp today, WOW! Sounded good with stock china tubes, but I swapped JJ and Tung-Sol tubes. I noticed output volume dropped lower with the JJ tube, but I left it in. Stock tubes were not that bad sounding. The output transformer is marked with output impedance, how cool is that! :thumbsup

This is the bottom view of VT-1H PCB
WANGS_VT-1H_PCB_01.JPG


Output transformer for VT-1H. 10K ohm impedance to each plate for push pull operation. 8 ohm output, which works with 8/16 ohm speaker cabinet
WANGS_VT-1H_PCB_02.JPG
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Last edited by mavrim on 21 Feb 2015, 02:37, edited 2 times in total.

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

Postby mavrim » 21 Feb 2015, 02:34

Push pull operation with 10K ohm impedance of output transformer to each plate (pins 1 & 6)
WANGS_VT-1H_PCB_03.JPG


Top of board has quality components. Hand soldering on bottom of PCB is a bit sloppy. I plan to go over these connections. Looks like they did some cutting to pcb to allow transformer to fit. I may want to use the 110/120 voltage selection switch location for a tone setting switch. I have no need for 220v operation, so I may jumper the pcb for permanent 110v and substitute a sliding switch in this location to select another tone cap or feature? I want to try mullard caps where the wima caps are located. I may put turrets there to make for easy swapping?

Amp sounds very much like the 1/4 watt Mahaffay single ended plexi amp, but with louder push pull operation and an added tube. Check my audio sample under little lanilei 1/4 watt thread on this forum.
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Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby Matec » 21 Feb 2015, 03:09

mavrim

You said you would, and did!

Of course I'm interested in the outcome of their findings.

If I can help just ask.

This tag of OT is a little confusing 10k - 0 -10k. Like you, I interpret this as 10k P-P. Could be more direct.
You're gonna check it, then?

Good luck!

Matec

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

Postby cassoulet » 21 Feb 2015, 12:08

Hi Mavrim,

Thank you for posting these pictures and review. Do you plan to take some voltage measurements here and there? Would be helpful maybe.
Cheers :applause:
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Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby mavrim » 21 Feb 2015, 14:54

Thank you!

I will trace out the entire circuit and make a schematic for it. I will post the schematic when done.

This amp is surprisingly heavy. The power transformer is beefy! During use I noticed that the power transformer was very warm to the touch. All my 1/4 and 1/2 watt builds, the transformer never got warm. I am surprised that this is getting very warm, considering how beefy it is.
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Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby mavrim » 21 Feb 2015, 15:11

I added pin outs with a sharpie just to help with observations.

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

Postby cassoulet » 21 Feb 2015, 16:46

Thanks, makes it even clearer.
I've just downloaded and installed TinyCaD, trying to figure out how to use that prog.
As a beginner, takes me ages to draw a simple schemo. I'll get used to it. Once you have your new amp traced, please post your .dsn file so we can share ideas.

Thanks again. Cheers :thumbsup :applause:
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Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby mavrim » 21 Feb 2015, 19:41

Tiny cad is great! I used that to design the mahaffay/lanilei 1/4 watt schematic. I will share the dsn file when done. I am pretty good with this program.
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Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby cassoulet » 01 Mar 2015, 12:55

Hey mavrim, how is the tracing of this amp going? Any schematic yet? :blackeye :applause:
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Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby deadmanamps » 03 Mar 2015, 06:02

Does that thing even sound good? Is it organic or just fuzzy? those look like Phillips resistors! Are they using American components in China now? The PCB looks thick too...just curious if it was worth getting,
Thanks, not much information on this company at all

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

Postby cassoulet » 03 Mar 2015, 11:00

Why would it sound good or bad just because PCB is more or less thick, or because resistors are chinese and not american? (by the way, Philips is a european company founded in Holland)
Let's wait for the schematic. The circuit design is far more important to the sound quality. :applause:
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Re: Wangs VT-1H All Tube 1 Watt Tiny Amp

Postby smackoj » 03 Mar 2015, 14:04

The cost of components plays a big role in any amp being sold commercially. The PT gets warm because of the current it handles through whatever size wire used to wind the tranny which goes back to the cost of the component, smaller dia. wire means lower production cost. Regarding the quality of the sound, three major factors affect tube amps; output transformer construction, tube quality and the speaker(s) you run it thru. Speaker output impedance will be best if matched for max volume e.g. a 8 ohm out trans. matched to a 8 ohm speaker. Going up to a 16 ohm speaker works fine and puts less strain on the output tube but may not get as loud or focused. Using a less ohm speaker would be tricky if the output is wired for 4 ohms because you are running close to a dead short. However, If the output is set for 8 ohms and you use a 4 ohm speaker, it will not harm the amp but will stress the output tube more and make it's life span shorter. Same would be true if it is wired for 16 ohms and you use a 8 ohm speaker.

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

Postby cassoulet » 03 Mar 2015, 15:34

Your description of impedance mitmatch consequences seems more appropriate for SS than for tube amps. At least, as far as tube stress is concerned. Going towards open circuit is stressful for tube and OT while harmless for SS. The opposite applies when going towards short => stress for SS, less for tube and OT. Not sure about that, though. Please someone correct me if I'm wrong :scratch: :mrgreen:
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