I clonning Milbert BAM230/235 Car Tube Amplifier Supply

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From my posted at Electronics and Tube forum

http://www.diyaudio.com/forums/showthread.php?s=&threadid=76973&highlight=

and

http://www.diyaudio.com/forums/showthread.php?s=&threadid=72262&highlight=

Now I succesfull for fixed my Milbert Car Tube Amplifier by changing PQ35/35 to EI40 choke & step-up ferrite core, I wondered about quality of new core.

I learning its operation and redesigning its PCB (some concept from my master : MR.DAVID LUMANAUW)

I decide for build new Tube CAR Amplifier with 20WATTS Single Ended Class-A : 211 TUBE.

If anybody interested please notice and look this post !!! I shall d o it !!!

Regard
analog guy
 

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Power Supply Section (Broken Core)

Now I changed PQ35/35 to EI40 (not in photo)

The best concept for me is
1.Carbon resistor for tube aplication
2.High FRQ core
3.Teflon insulated wire
4.Low current power amplifier
5.Electrocube Couping Capacitor (I seen in LAMM)
 

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This's Bottom Layer Pcb

I think it's quite complex PCB with output transformer included on PCB.

Could I use EL34 instead of 6JN6 ?

Now I can't drive 5.75" DYNAUDIO 15MA SPEAKER with MILBERT BAM-235, How do I modify this amp for this mission ?

Regard
ANALOG GUY
 

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ANALOG GUY said:
From my posted at Electronics and Tube forum

http://www.diyaudio.com/forums/showthread.php?s=&threadid=76973&highlight=

and

http://www.diyaudio.com/forums/showthread.php?s=&threadid=72262&highlight=

Now I succesfull for fixed my Milbert Car Tube Amplifier by changing PQ35/35 to EI40 choke & step-up ferrite core, I wondered about quality of new core.

I learning its operation and redesigning its PCB (some concept from my master : MR.DAVID LUMANAUW)

I decide for build new Tube CAR Amplifier with 20WATTS Single Ended Class-A : 211 TUBE.

If anybody interested please notice and look this post !!! I shall d o it !!!

Regard
analog guy

Whew, just found this thread, did you ever tried built the 211 tube car amplifier? I am interested in it.

Regards,
 
My experience with 845 tubes is that the filiment is extremelt fragile while hot.

The 211 may be fragile as well.

6JN6 are very hardy, and inexpensive.

If you're building an amp from scratch for a car take a look at tubes that were used in avionics. Loctal base will help keep the tube seated.

John C.

Owner of 3 Milberts.
 
If anyone else is still interested in this subject, post here or PM me.

I just got extremely lucky and got a BAM-235 last week!

It would be great to sort out the design, document it (especially the transformers), and be able to duplicate it. The design is not particularly intricate but the switching power supply details are the critical issue, I think.
 
I'm posting this in case anyone finds this thread and it can be of any use. Here are the differences from a Milbert BAM235 PCB I pulled and inspected vs. the EA 230 schematics that are listed around here. Differences are highlighted in pink.

These are rough drafts and not "cleaned up" yet.

The Milbert PCBs have a slightly different input design (as well as a few values being different) in addition to a ground trace that is also different. Tube heaters are not wired the same as the EA 230, as it's all based off of one 18V supply from the switching power supply. (see images).

Unfortunately the PCB & build quality is nowhere near what you'd expect for what the amps are sold for (I've seen near $2,500 used, I was told by PrecisionMike here $5K new!) and the 6JN6 tubes aren't fixed in place in the sockets - meaning they can become somewhat loose.

I don't have the SMPS layout/schematic; ideally this can be substituted with an alternate source. The SMPS uses 2 custom transformers and provides 4 total output voltages so it's a bit of a challenge. I've been in touch with http://pjlelectronics.com/ as he seems to have a working prototype that can supply the high voltages required.

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.
 
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DC-DC converter...

By the way, is perfectly possible to adapt an existing China 12V-220V converter to amplifier service, like I've made for my car tube amplifier, with 6EM5 in PP-Schade.
Works flawlessy, and with this I don't need to make the transformer. Even the inductor, since I salvaged one from a ~100W Flyback SMPS. Note that the inductor needs to have a GAP to work, since this need to store energy with a non-resonant topology (resonant topologies don't need the output inductor).
 

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http://www.diyaudio.com/forums/tubes-valves/203353-anybody-using-tube-amp-their-car-7.html

In these posts I explain more. If people need some schematics, I draw one (I forget to draw schematic for these :p:D ).

I believe to achieve same results from Milbert PSU sans the effort to make one.

EDIT: note that this modified converter don't offer more than ~275Vdc regulated due to transformer turns ratio. One can use with a voltage doubler and post regulating or pre regulating.
 
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By the way, is perfectly possible to adapt an existing China 12V-220V converter to amplifier service, like I've made for my car tube amplifier, with 6EM5 in PP-Schade.

Thanks for the post...unfortunately it won't work in all cases. Amps like the Berning/Milbert need a negative voltage supply also (-200V) as well as a higher B+ voltage (400V) so you would still need another converter in that case, I think. But that's a good idea for some applications (I've thought about that before in the past).

I think I have the problem solved, I'm working on it right now.

I appreciate the link - I'll check out what you posted.
 
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Travis Clarke,
For curiosity... you have listened this BaM amp?
I've never listened to one, but I'm very satisfied with mine even if it have "only" 14Wrms/ch. It helps to make my car system sounding less "automotive" (for a lack of better word ;) ) and have a great warm sound helping to tame the harshness from head unit, without losing "resolution". Great with high sensitive speakers.

About multi-output SMPS... I worked designing SMPS for a couple of years (2009 and 2010), and I learned that is really far easier to design a single output SMPS, specially push-pull ones, since for it is needed matching not only the trafo but also the coupled choke. But for maintaning the BaM originality is no other choice... I wondering if some maker or DIY designed a resonant supply for automotive use. I never seen one. Hard to design but choke free and low EMI.
 
Travis Clarke,
For curiosity... you have listened this BaM amp?
EMI.

Hi, yes actually I recently became very lucky and bought one off of eBay for a low price, in almost-new condition.

The sound is very good, although the build quality does not match the selling price/hype, and there are some complaints I have after I inspected it and verified the PCB / circuit design. Also, it uses and isolated output SMPS with +18V, -200V, and +400V (w/ +300V derived also) outputs. I have many pictures and I posted my notes earlier in this thread.

Overall, however, it is a great sounding amp but appears that the output transformers could be better.

I built the Berning-based PCBs found in the PJL Electronics link and modified them to duplicate the BaM235 (small changes) and with my transformers, the sound is very good! I had to add an -200V supply, however.

This can be done using an isolated DC-DC 12V supply and a Nixie +200V + step-up supply connected in reverse if you don't have an isolated 12V to +200V DC DC supply.
 
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If anyone is interested, I now have a scanned copy of the Milbert BaM235 owner's manual in .pdf format. I'll see if I can post a link or something for download here soon.

Hi Travis,

I found an old post where you mention that you have a Milbert bam235 manual in pdf form?

I would like to change the tubes in my amplifier, but I do not have my manual and tube bias instructions, and I am hoping that I can impose on you to email a copy of your to me?

I’d greatly appreciate it if you would :)

My email is: peterlufrano@comcast.net

Thank you so much in advance!
 
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