Topic: Anyone Built A BoatAnchor Amp Before?

[GAGA@echoloft]

btw, i am suprised no one asked about the gigantic op trans in black. they are from Belgium.
Monolith Magnetics.

[cm]

Finally, another crazy kilovolt man in town 

Now working in China nd moved into a small condo, therefore hobby is at a standstill 
VT-25 goes better with graphite GM70, 300B better with copper plate. 2A3C was the one in between, so that is what I used. I tried 6BX7 GM70 graphite but then it was better for pop music for slam bang, boom boom. Not the refined sound I wanted.

Cooper plate was sweetest at 75mA, 1KV, 7K opt ( chinese opt ). Graphite plate at 120mA, 1400KV, 10K ( audionote ).

Overall, I prefereed copper plate to graphite as I am an old man prefering sweet mellow sound with nice thick midrange. Mr. Boom boom ga ga probably prefer more muscular sounds 

If you want music that goes well with wine to get a mild high, listen for hours, then the best was VT25 - GM70 copper plate. Floats to Nirvana.......

Audionote opt gives a much better and natural, controlled bass response as compared to the chinese opt at 1/4 the price and half the weight.

You need shades and head shields to run this amp. And plenty of muscles. Mine were monoblock and estimated 40 kg per channel. I used a 24V switching power supply ( modified to 21 volts then then went thru a couple of filters ) for the GM0 filaments. My HP 500M scope shows no high frequency noise from the switching power supply. B+ cap was a 51uF Solen mkp cap.

I still have a pair of mullard 813s to play with, and a pair of 805s. Wonder when .........

[garbage]

Now working in China nd moved into a small condo, therefore hobby is at a standstill 

size is relative. your previous place was huge mah.

[cm]

Oops!

Just checked my notes. Graphite plate was ( to my ears ) best at 1200V, 120mA. NOT 1400V

Lot of punch. Dont know if I were over driving the tubes, but the amp sure was hot! Some brothers who came say they could feel the heat from 12 feet away  Yes, I was stingy and did not turn on the aircon. The neigbourhood would have dimmed somewhat if I did.

Anyway, ping me if you are in HK/Shenzhen and I can direct you guys here to shop and where to stay. Bring lots of money and buy lots of baggage if you are coming via jetstar or tiger.

[j45yip]

...i hear you, bro. i think the middle stage in a 3-stage topology act more like a current drive. same experience i had with the 300B SE amp i had way back. the el34 drives the 300B and gave the extra "punch and presence" which was absence in a typical 300B SE topology.

i'm still pondering over what topology i'm using to drive my pair of STC4304CB. most likely be using rod coleman's filament reg. 7.5V 3.25A.

btw, nice output trans from monolith magnetics. wat's the damage to your bank account?

bro, my first exposure to GM70 sound is at CM's place in 2004. He was using 6J5 to 2A3 IT to GM70. Love the sound.
was contemplating a two stage topo.....eg.D3A to GM70. Many mentioned that the D3A has enough gain mu =70 to drive the GM70, which is in fact not difficult to drive. I have wired up experimentally to try out b4 finalising the chassis placements. I referred to Thomas Mayer's expertise. He had mentioned that using the two stage circuit....has enough gain...but the issue is not just gain. These big transmitter tubes require the headroom of the two stage gain in order to sound good. And he has been advocating the VT25 as drivers. Given his track records and experience i take that should be the correct approach. Not that the D3A single stage sound bad, but the DHT drivers have more punch and really makes the amp sound so much bigger. The D3A single stage sounded very sweet and delicate. But when i had this amp in mind, i have intended it for BOOM BOOM BOOM, WHACK WHACK WHACK.... As far as i can remember, CM had posted that the VT25 sound very good in his amp during those days when echoloft forums were still alive. That is how i decided to experiment with the various DHT drivers and the finalised topo.

[ghemml]

@GAGA@echoloft

Yo bro, I have a jig for measuring your amp performance...

[vajrasattvasg]

beautiful!!

DIY seems pretty "far" away for me now.. just had an expensive wedding and a european honeymoon..

[GAGA@echoloft]

Jo, mine is their Summit Series, ie. their 'higher' line, with teflon interwinding dielectric, dual C-cores.
678 Euros a pair. Shipping by EMS is a killer due to the large size and heavy weight of 25kg. 350 Euros.
In total i paid S$1677 after currency conversion.
Of course there are less costly units around. But after communicating and consulting the designer of Monolith, getting reviews by writing to some diyaudio members and looking at how well they document their products and tech specs, i have decided to order from them.

Jo, you may check their pricelist in their website. as well as shipping cost.

To add : checked price of Tango X10 with Larry, they cost a whopping $2.5k now!

[GAGA@echoloft]

@GAGA@echoloft

Yo bro, I have a jig for measuring your amp performance...

tube amps are unlikely to give impressive test results!
But can share what u have ?

[GAGA@echoloft]

beautiful!!

DIY seems pretty "far" away for me now.. just had an expensive wedding and a european honeymoon..

well, u have prioritized correctly bro...
to me hifi will come after family.....work is at the bottom of my list...

[ghemml]

tube amps are unlikely to give impressive test results!
But can share what u have ?

Yeah Tube amp are higher in dsitortion but can measure the freq response performance.

I using this test method below, via voltage probe. RL is the simulated loading of a loudspeaker, for my jig I have 4 ohms and 8ohms. But can add addtinoal 2ohms and 16ohms.



So I made a jig with selectable voltage divider to prevent over voltage at input to soundcard by -30dB, -20dB and -10dB.



So you can have many types of measurements

Freq Response


THD, Odd and Even Order via cross spectrum


Two Sine Wave for Intermodular Distortion(though there are a few class to this)


Spectrum analysis

[ghemml]

This Amplifer measuring tool(DIY) also very interesting... want to try it out also

http://www.audiodesignguide.com/EMUinput/

[U227]

WOW!!! Your amp are beautiful! I love the OPTs.

[j45yip]

...bro, bringing this gorgeous GM70 amp to NoiSING? Would kill to have a listen.

[char siew pau]

Summit Series, ie. their 'higher' line, with teflon interwinding dielectric, dual C-cores.
To add : checked price of Tango X10 with Larry, they cost a whopping $2.5k now!

Bro,

Price of iron aside, to build a "Kondo Ongaku" clone, what would be the better choice-Monolith Summit series type S-7B or ISO Tango X-10SF output trans for the 211 tube?