Lavane
Lunatic Member
Ah, at first glance it looked like a relay. Having one acually fit the chassis is nic
I deleted that post. You responded right before I posted. It looked like a relay at first glance. PM coming.
teaching VTA M-125 to sing
no probs 
Legrace
Super Member
I obtained my later revision c/w transformer AB modules from Erhard-Audio and they have performed flawlessly; closing in on two years now. I run my amps typically 10 to 12 hours a session, pretty well day in day out. Pre-autobias amps would red plate at least a couple times a year. Soon came a point I didn't dare leave the room if they were on, especially following one particularly nasty melt down. Not exactly conducive to listening enjoyment. Then I learned about the benefits of auto biasing. Now with almost 2 years issue free operation under the belt the worry around leaving them unattended has totally faded away. In addition to peace of mind I'm saving so much in tubes now. A KT120 imported into Canada tops $100 so the boards have already paid for themselves. Not having to constantly check and readjust bias anymore is just so nice, simply flip the switch and kick back. Plus having those leds to confirm proper bias has been established is also quite comforting.
Service wise Erhard-Audio were excellent. Response time if you have questions or issues is very fast, same day in my case on multiple occasions. Highly recommended.
Service wise Erhard-Audio were excellent. Response time if you have questions or issues is very fast, same day in my case on multiple occasions. Highly recommended.
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lostman0077
New Member
has anybody compared VTA M-120 mono blocks to other high end mono blocks "highs,lows,mid-range" 3D imaging, sound stage. I'm also looking at the primaluna DiaLogue Premium HP, Audio research, I have a Yaqin MS-20L right now will it sound better, and if so in what way. Sorry to asked so many question, but I don't have lots of money to experiment.
Why are people having issues with bias drifting? I haven’t seen this issue unless the tubes are visibly worn or the new Russian tubes.
Pio1980
AK Member
Line voltage variation.
I take that into account when I set bias, trying to keep it at top of recommended range when high.
thats why I bias low. Can’t tell a difference. Also nice to have one of those cheap Amazon variacs with the digital meter on the front so you can keep an eye on the voltage, even if it’s not exactly right when tested with a multimeter (reads high by 5 volts). Now I’m not as knowledgeable as per say most of you guys. But I check bias every few months or when I roll tubes. And leave amps on most of the day.
I did buy some Tung sol vintage tubes that would not hold bias but the getter flash was mostly gone and also had runaway bias with some gold lion kt77 (new sensor). But haven’t had an issue with old stock tubes that don’t look beat up.
Pio1980
AK Member
I've got one of those faded TS 6550 pulls here for display.
Used power tetrodes/pentodes are a crap shoot for grid emission and other faults that may pass a tube tester. Faded flash is a tube that has been ridden hard and long, probably near end of service life if no other faults.
Even free may be too much for such Vintage Tubes.
bias drift is virtually eliminated with auto bias. Pretty much most tube amps can be modified to auto bias. For the VTA ST70/120 or M125, the auto bias pcb's are custom shaped to fit the chassis.
If anyone wants more info on the auto bias modules, 'pm' me.
If anyone wants more info on the auto bias modules, 'pm' me.
KT88Lvr
Active Member
Lots of people documented how much better they liked their VTA amps (ST120 M125, etc) over the Mc's - 240, 275 - you can find many favorable reviews, stories if you search.
As with any amp - you just have to try them out. I get crazy 3D sound - huge headroom - Hendrix - Electric Ladyland - is just amazing with these amps - extremely 3D, deep bass etc.
Lavane
Lunatic Member
I have zero complaints about my M-125's so far. I haven't had any bias issues.
My line voltage is very steady where I live now. A few years back when I was living in the northern Sierra's a stiff wind could knock out the power, or cause lightes to flicker. Power went out pretty regularly. A generator was a must.
I used a power conditioner and GFI outlets. When things were calm the power stayed very steady though. I biased a little low then. But that's what you get living close to the end of the grid.
My line voltage is very steady where I live now. A few years back when I was living in the northern Sierra's a stiff wind could knock out the power, or cause lightes to flicker. Power went out pretty regularly. A generator was a must.
I used a power conditioner and GFI outlets. When things were calm the power stayed very steady though. I biased a little low then. But that's what you get living close to the end of the grid.
Drummerboy2
Well-Known Member
Just ordered the Auto Bias pcb for my VTA-120. I haven't had any issues with "Red Platting" or Bias issues, but just getting older and don't want to be checking often as the tubes are getting older. I get my tubes from Upscale Audio and I use the Gold Lions KT88 which has been very durable. I do want to change to other KT88 tubes and this is were the Auto-Bias pcb comes into play since I haven't used any other KT88 since I built the VTA-120 and put the Gold Lions in. I do use all NEW tubes since NOS are starting to go up in cost.
Drummerboy2
Well-Known Member
Has anyone experienced this humming issue in their VTA-120's? I have only seen this in regards to the VTA-M125. I haven't had this issue but just wondering if I need to get back into my VTA-120 and check for this wiring issue. You know the old saying "If it aint broke, dont fix it it!"
most amps I have sound more open than mc30s that don’t have much sparkle up top.
I think you would like ge 6550 if you haven’t tried them. Very durable tubes and have deep bass as well as clean highs.
I bought a bunch on eBay. You can get singles for 60 ish a piece shipped when they come up for sale rather than buy a quad and save some money. I don’t think the quads people are selling are matched anyways but I don’t need close matched tubes anyways with adjustable bias. Even the ones I have with some wear to the getter flash hold their bias fine in my Lafayette La70 amps and it’s got some brute force.
Drummerboy2
Well-Known Member
I heard quite a bit about the 6550 tubes and how nice they sound. May try these next in my amp. Will there be a loss in power output? I do run my VTA-120 with a GZ37 tube rectifier with no issues.
I have seen posts that the Valve Arts are the 6550 to beat?
6550 is the us version of kt88. Same power (within a gnats ass)
Drummerboy2
Well-Known Member
LOL! Ok, Thank You! I was just looking at them and saw Tung-Sol makes some.