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Car tube amp- looking for advice

Hello,
I am in the process of building a very high end car system. For the top end, I am using B&W Matrix 801 mids and B&W Silver Signature tweeters. I am interested to get opinions on a couple of amp choices. The system will be fully active.

Option #1- PJL boards, SE Ultralinear mono block design. 12au7 pre tube, KT150 power tube. I would use (4) of these, of course. DIY UL SE Mono Block

Option #2- Build my own clone of the Milbert BAM-235ab, which is based off the Berning EA-230. I would buy a pair of these and be done with it, but they are about $4k each. I think I can build for about $500ea? Milbert BaM Mobile Tube Amplifier

Thoughts? TIA, Mike
 
They are completely different animals, option 2 makes a lot more sense - much higher efficiency thus less heat to deal with. Especially if you think you can build it for $500... you must have ninja DIY skills.

Thanks for the reply. I am not too worried about heat, I can do what is necessary to keep the amps cool, regardless of effort needed. The car that this system is going into will strictly be used for audio, not driven daily. Regarding the efficiency of the SE, I believe I will end up with about 49 wpc, vs the Milbert design being about 35 wpc. Either way, I will have plenty of power, despite the relatively low efficiency of the drivers.
I was told by another amp builder that the Milbert could be copied for about $500 in parts, unless he was wrong. I am not an amp builder, but would be looking for advice/assistance from other, even paying someone to build if necessary.
My overall goal is the best possible sound.
 

jazbo8

diyAudio Moderator Emeritus
2011-01-05 8:34 am
In Transient
I was told by another amp builder that the Milbert could be copied for about $500 in parts, unless he was wrong. I am not an amp builder, but would be looking for advice/assistance from other, even paying someone to build if necessary.
My overall goal is the best possible sound.

If it is not a daily driver, then the mechanical shock isolation would be less of a concern. The parts costs is only of minor concern, since the Milbert/Berning design is not conventional, it may require special layout, wiring and chassis construction techniques.
 
What power level are you looking at? That's going to influence your choice of topology and tube selection.

There are plenty of good kits out there (Tubelab, Tubecad, Pete Millet are the first that come to mind) that will give you much better designs than the PJL boards. I have no idea what the Milbert has inside, their webpage is long on marketing speak and short on details. With a good kit, all you would have to do is figure out the power supply. The PJL page has their schematic, at first glance it seems like a solid design (in a follow-the-datasheet kind of way). I don't fancy winding my own transformers, but there are people on here that have built their own high voltage switchmode power supplies, so that's not an impossible task.
 
I ran 1625s in a 1980 Honda for about three years and never had problems. I used a st70 chassis with a different driver so it had 12at7s instead of 7199s. It is worth doing for a daily driver. I ran mine from 100hz up and a mosfet amp for the subwoofers.

If it is not a daily driver, then the mechanical shock isolation would be less of a concern. The parts costs is only of minor concern, since the Milbert/Berning design is not conventional, it may require special layout, wiring and chassis construction techniques.
 
The Milbert design is a screen driven sweep tube amp. My experience with these type of designs has been positive, and they can be quite efficient.

The DIY SE UL design doesn't add up using data posted on their own web site:

What to expect when using recommended tubes and OPT:
EL34 with B+ set to 500v: Plate=455v, G2=441v, Ia=68ma: 12w RMS clean, 16w total.
KT120 with B+ set to 700v: Plate=620v, G2=605v, Ia=170ma: 24w RMS clean, 36w total.
KT150 with B+ set to 700v:

No data is given for the KT150, but the KT120 data shows 105 watts (620V 170mA)being dumped into a tube rated for 60 watts of dissipation. All 105 watts will be dissipated as heat when the amp is idling, which is most of the time. I often run tubes a bit hot, but almost 2 X the raring in an SE amp doesn't make for long life.

Go for the proven design. The Milbert has been around for years.

I put a SE DHT amp in the trunk of my Mustang years ago and microphonics were a big issue......maybe not a problem if you don't want to listen and drive, or you have decent roads.
 
Mike
The biggest is the power supply.My friend Dave at Elpaso tube amps discovered these little 12vdc to 450vdc power modules and they have bigger ones than this but these cost 13 dollars and they are stable and clean..I'm not sure why you need KT150s being that kind of power is usually for bass and a good solid state for bass is usually preferred however,on mids and highs,tubes all the way and I would think 6L6gcs or KT88s would be adequate but maybe not..But look at these modules because you can always run the output tube filaments in series off the 12v battery.
https://www.youtube.com/watch?v=WCv_eKXF2RA
 
OP here, sorry I have not replied back. I honestly didn't think I would get this much feedback, and have not looked lately. Thanks so much for all the info!

Given a choice, I prefer the idea of the Milbert design. I have used the amps before, they run cool-ish, efficient, and sound incredible. Plus they have a proven design since 1988.

From what I know, they are basically a Berning EA-230 with a 12v power supply.

I was able to locate the Berning schematic. Tube amplifiers for high-end audio by The David Berning Company

So hard hard would it be to build a clone and integrate the 12v supply? Approximate cost? I spoke to someone who builds amps and they thought about $500 per amp?

Thanks again for the assistance, it is greatly appreciated!
Mike
 
OP here, sorry I have not replied back. I honestly didn't think I would get this much feedback, and have not looked lately. Thanks so much for all the info!

Given a choice, I prefer the idea of the Milbert design. I have used the amps before, they run cool-ish, efficient, and sound incredible. Plus they have a proven design since 1988.

From what I know, they are basically a Berning EA-230 with a 12v power supply.

I was able to locate the Berning schematic. Tube amplifiers for high-end audio by The David Berning Company

So hard hard would it be to build a clone and integrate the 12v supply? Approximate cost? I spoke to someone who builds amps and they thought about $500 per amp?

Thanks again for the assistance, it is greatly appreciated!
Mike

Hi Mike
I just replied for the first time tonight to your thread but I am very familiar with the EA230 and they run class B and are a very nice amp..That circuit is very nice. What I was thinking was,those modules are perfect for the high voltage B+ SUPPLY and that will solve the power supply issues if you want to use conventional tubes and circuitry. 12vdc in gets you up t0 450vdc out and one module can supply enough current for one channel and it will replace a power transformer and filter and rectifier and regulation all in that little module.I'm going to try a pair of those modules on a sherwood s5000 or Fiisher X202 integrated tube amp..
 
Hi Mike
I just replied for the first time tonight to your thread but I am very familiar with the EA230 and they run class B and are a very nice amp..That circuit is very nice. What I was thinking was,those modules are perfect for the high voltage B+ SUPPLY and that will solve the power supply issues if you want to use conventional tubes and circuitry. 12vdc in gets you up t0 450vdc out and one module can supply enough current for one channel and it will replace a power transformer and filter and rectifier and regulation all in that little module.I'm going to try a pair of those modules on a sherwood s5000 or Fiisher X202 integrated tube amp..

Please report back on your finding, that circuit could be perfect for what I am looking for.

Would it be possible to built the same topography as the EA230 with this new power module, and omit the transformers?

I am looking for about 35 wpc and the best possible sound I can get. I will be using a total of (4) channels (2) stereo amps. The mids will play from about 200hz-4khz, tweeters from 4khz on up. Besides the Berning, are there other PP designs that I should consider? Based on my lack of experience, it would be great if I could find a kit unit, without sacrificing quality. Cost, weight are not much of a concern. Sound, microphonics and heat are considerations.

Thanks again for all the input, this forum is great!
 
Another thought- a few years ago, Milbert came up with a much smaller version of their BAM-235ab amp. The BAM is basically a Berning EA230 with a 12v supply, and it has larger transformers.
I have not seen inside their new amp, but it is a much smaller footprint, the size of 3 reams of paper, and is also based on the Berning EA-230. I wonder if this uses that same new power circuit? The price on the Milbert Liquid is $2k, I am confident I could build it for much less.