Jazbo
That is another idea as well.You would want a pure sine wave inverter tho to keep noise level down. The down side is you are going to have power that the inverter draws and then your amp or preamp. The thing that would be nice about the little modules is,you can get the 150 watt version for like 22 dollars and the 70 watt version you saw in the video which was 13 dollars.. You take two of those and build an amp,you would not need a power transformer or a choke or big filter caps taking up tons of room.While it won't rival a home system,we are in a car so we don't really care..We just want the elegance of vacuum tube sound which we should be able to achieve.
I don't know...You would need a pure sine wave inverter I would guess but they aren't too bad. If you are going to build the amp,the modules would be cheaper way of doing it because you won't have to buy a power trans and a choke and filters and the power inverter to boot..If you have an amp already,an inverter would be feasible but again,there is ups and downs to both.
If you think about it,I would go with the modules because you can always do the transformer,choke,and inverter option later...Look how cheap the modules are.
Excellent tubes to use..Those are 12v fil 807s and are not to bad to drive with the 7199 or 6u8a tube.
Check out these 150 watt inverters at 450v..I don't know if they are adjustable but the 70 watt ones are and we can also use an extra 70 watt one for the minus 200v supply..We are talking 33usd for 3 including shipping..Here is the 150 watt one tho.
12V to DC450V 150W High Voltage Converter Boost Step Up Power Capacitance Charge | eBay
The power supply options make this easier theese days. I think if I were to build one now, I would go with half cathode bias and use maybe two 9v batteries for negative bias. That worked great before. If you planned to bi-amp with a SS amp on the low end, then you can also choose smaller output transformers. Amp weight could be cut smewhat.
Yes,I like the idea of combination bias and the twin 9v batteries hooked up with pos to ground would be ideal being it draws almost no current.
Hello all, reviving an old post.
I have hooked up with a knowledgeable amp builder, the owner of PJL. I know little about building an amp. He is going to build a Milbert clone and we are going to compare to his SE KT150 design.
I am trying to determine for sure the tubes used in the Milbert.
From what I can tell, here is what I see:
12at7 (2)
6sn7 (2)
6jn6 (4)
?(2)
Here is a pic if it helps. I am also trying to determine the brand they use to try to get as close as possible. I have looked at many pics on line and it looks like they are not consistent, perhaps based on availability? I believe the 6sn7 are only NOS?
Thanks again!
I have hooked up with a knowledgeable amp builder, the owner of PJL. I know little about building an amp. He is going to build a Milbert clone and we are going to compare to his SE KT150 design.
I am trying to determine for sure the tubes used in the Milbert.
From what I can tell, here is what I see:
12at7 (2)
6sn7 (2)
6jn6 (4)
?(2)
Here is a pic if it helps. I am also trying to determine the brand they use to try to get as close as possible. I have looked at many pics on line and it looks like they are not consistent, perhaps based on availability? I believe the 6sn7 are only NOS?
Thanks again!
Attachments
I just found this thread, and I'm fascinated by the idea of 1) building a car tube amp and 2) avoiding blowing a ton of money a commercial one, since they appear to be pretty basic designs.
Since the Milbert is so rare (and expensive) and I can't find schematics, etc., I decided to duplicate a Dynaco ST-70 for now, and see how that goes. I've ordered most of the parts.
Here's what I've planned/ordered so far:
Haven't purchased output transformers yet. I anticipate ~$250 for those.
The total cost, should everything work out, is probably < $400.
I picked the Dynaco since I'm new to tube amps and needed a good starting point. I built a switching DC-DC supply in the past and modified one to +260V out for a preamp but I'd rather avoid the hassle if possible so I'm buying these supplies to try.
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Side note: All the commercial car "tube" amps from back in the day were a joke [except maybe Butler and Milbert], and basically only used preamp stage tubes, and they weren't even running at the optimal (high) voltage, just near 12V.
I owned a Planet Audio HVT754 hybrid tube amp and although it was ok there was not a tonal difference worth mentioning. I could barely tell the difference. So this appeared to have been a marketing/novelty thing rather than real design virtue.
(I used to install car stereo equipment back in the day before I graduated college, and saw a lot of the marketing gimmics over the years. I was fascinated by reading about Earl Zausmer's famous BMW with the Milbert BaM235 amps. Supposedly it sounded superb.)
Since the Milbert is so rare (and expensive) and I can't find schematics, etc., I decided to duplicate a Dynaco ST-70 for now, and see how that goes. I've ordered most of the parts.
Here's what I've planned/ordered so far:
- Negative bias supply: I got an adjustable DC-DC step up supply 0-80V or so and will power from an isolated DC-DC 12V-12V supply, and wire to provide a negative voltage.
- High-voltage supply: DC-DC step-up supplies, similar to what's been mentioned, from eBay Chinese sellers (I bought 2 so I could try both types).
- Heater voltages:: Either wired in series or using the inexpensive LM2596 adjustable switching supplies from eBay. These are pretty good and $2 or so.
Haven't purchased output transformers yet. I anticipate ~$250 for those.
The total cost, should everything work out, is probably < $400.
I picked the Dynaco since I'm new to tube amps and needed a good starting point. I built a switching DC-DC supply in the past and modified one to +260V out for a preamp but I'd rather avoid the hassle if possible so I'm buying these supplies to try.
-------------------------------------------------------------------------------------------------
Side note: All the commercial car "tube" amps from back in the day were a joke [except maybe Butler and Milbert], and basically only used preamp stage tubes, and they weren't even running at the optimal (high) voltage, just near 12V.
I owned a Planet Audio HVT754 hybrid tube amp and although it was ok there was not a tonal difference worth mentioning. I could barely tell the difference. So this appeared to have been a marketing/novelty thing rather than real design virtue.
(I used to install car stereo equipment back in the day before I graduated college, and saw a lot of the marketing gimmics over the years. I was fascinated by reading about Earl Zausmer's famous BMW with the Milbert BaM235 amps. Supposedly it sounded superb.)
One more thing: you need to anticipate the very likely chance of ground loop noise as the DC-DC supply would not be isolated. It happened to me in the past on a car amp project I built.
I don't know but I assume the Milbert mobile design has input stages for removing this, as do commercial transistor-based amps.
This is a problem I expect to have to deal with, in order to be prepared for "worst case" since it's such a pain. There are inline line-level isolation transformers that some people use but of course the cheap ones have poor frequency response so it would be important to find a better quality one.
I don't know but I assume the Milbert mobile design has input stages for removing this, as do commercial transistor-based amps.
This is a problem I expect to have to deal with, in order to be prepared for "worst case" since it's such a pain. There are inline line-level isolation transformers that some people use but of course the cheap ones have poor frequency response so it would be important to find a better quality one.
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Hello MartyM. Glad to see I am not the only car freak out there. You are correct about Earl's car. I was fortunate enough to hear it many time, several hours of seat time. It was, without question, the most realistic, warm, full, impact sounding system I ever hear; car, home, headphones... Over the years, Earl and I have become good friends. The car I am building is inspired by his car- same yr 5 series, same mid/tweeters and tube amps.
Good luck on your build and keep us posted. Very exciting!
Good luck on your build and keep us posted. Very exciting!
Since there are only about seven people left running their KWM-2 or TR-4 mobile, there are scads of old ham radio DC-DC transceiver supplies left collecting dust, and looking for a purpose.
They can supply B+, screen voltage, and bias; they were made for ICAS, but I bet they could run a twenty watt or so / channel amp on a continuous basis without overheating and croaking. They use a step up transformer ( at least mine do ) so they're isolated.
If it says Collins on it, it would be price prohibitive for this type of project, but other brands should be really inexpensive, since they are effectively useless these days.
Win W5JAG
They can supply B+, screen voltage, and bias; they were made for ICAS, but I bet they could run a twenty watt or so / channel amp on a continuous basis without overheating and croaking. They use a step up transformer ( at least mine do ) so they're isolated.
If it says Collins on it, it would be price prohibitive for this type of project, but other brands should be really inexpensive, since they are effectively useless these days.
Win W5JAG
Wow, that is awesome that you have the same speakers and even the car, plus got to hear his. I of course couldn't, but I did have the magazine issue featuring his car and read elsewhere about other guys who heard it, too and had a extra little info.
I got the Mapleshade Records fidelity music that Earl mentioned somewhere that he had let people try his car also, and the sound is really good and I will use it as reference material from here out (In addition to my Autosound 2000 Test CD).
This is a very worthwhile challenge I think, and going around the problem of super-expensive amps is really motivating to me. Being an engineer now I'm highly motivated to do this. If I'm successful I want to document it well and post it on the internet for others to be able to recreate it fairly easily.
I got the Mapleshade Records fidelity music that Earl mentioned somewhere that he had let people try his car also, and the sound is really good and I will use it as reference material from here out (In addition to my Autosound 2000 Test CD).
This is a very worthwhile challenge I think, and going around the problem of super-expensive amps is really motivating to me. Being an engineer now I'm highly motivated to do this. If I'm successful I want to document it well and post it on the internet for others to be able to recreate it fairly easily.
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