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50W monoblock "Engineers Amp"
50W monoblock "Engineers Amp"
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Old 17th August 2017, 05:51 PM   #111
Tubelab_com is offline Tubelab_com  United States
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Quote:
should not blow even if they are fast (or not?) .....Pete's BOM calls for 2A slow blow
A tube amp, particularly one with solid state rectifiers can be expected to draw a huge turn on current. The tubes are all cold, thus their heater current will be 2 to 4 X the nominal draw for the first few seconds, and the capacitors are all discharged. There is no slow warm up on SS diodes, those hungry caps look like a dead short for the first few milliseconds with the current only limited by the DCR in the power transformer. That's why we use slow blow fuses and inrush current limiters.

Try the correct fuse before going any further.
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Old 18th August 2017, 11:09 PM   #112
hohner2008 is offline hohner2008  Canada
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Fast fuses!!!! Arghhhh. Thank you so much for the advice. I had a bunch of fuses and assumed they are "normal" slow ones. Went today and bought "slow" ones and learned that the new "normal" is "fast".
BTW, I have my bias voltage not fully stable: instead of being 500mV (50mA) i get from 490 to 550mV
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Old 24th October 2017, 04:03 PM   #113
JWags911SC is offline JWags911SC  United States
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I'm building two (2) of Pete's Monoblock versions of the DCPP and am having some difficulty figuring out where to buy the in-chassis heat sink that either mounts to or passes through the top plate of the chassis. Pete's web page describes it but I was wondering if any of you having built the project can tell me your source of this part of the heat sink? I plan on using a couple of Parts-Express.com Shure heat sinks, Part #DC-HS11123 or Part #DC-HS11118 for the exposed part of the enclosure, do you guys know where to source the in-chassis part of the heat sink the MOSFETs are mounted to? Would appreciate any input, thanks!
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Old 25th November 2017, 11:46 PM   #114
mdurian is offline mdurian  United States
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JWags911SC,
Did you figure out how to implement the heat sink? I’m just starting on a couple monoblocks and have the same question.
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Old 28th November 2017, 08:57 PM   #115
JWags911SC is offline JWags911SC  United States
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Default Heatsinks

I found out from Pete that he employed Heat sinks from HeatsinkUSA.com and ordered a couple that I need to anodize. I was advised to use a common L shaped aluminum angle to attach the devices inside the chassis, so I just need to order the aluminum angle, then I plan on drilling through the top plate and secure the top heat sink through the chassis and the aluminum angle. I have a tap and die set already, so this shouldn't be much of a challenge. I hope this helps steer you in the right direction.
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Old 30th November 2017, 03:28 PM   #116
mdurian is offline mdurian  United States
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JWags911SC,
Thanks. That does help. If I'm reading the mechanical drawings correctly, the aluminum angle should be 1" x 2" x 3" with 1/8" walls. Google tells me that is a less common size, though I did find it at onlinemetals.com. Unfortunately, they don't offer that size in anodized stock. Is the anodization important?

mike
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Old 7th December 2017, 08:31 PM   #117
JWags911SC is offline JWags911SC  United States
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I don't believe that the aluminum angle has to be anodized, the only reason I can think you may want it anodized would be to make sure it is electrically insulated from the three components mounted to it. I don't know if this would be to prevent the degradation of the audio signal, or if it pertains to safety. I plan on anodizing mine at the same time I do the heat sinks since I am doing it in house.
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Old 4th February 2018, 04:59 AM   #118
Pegasus123 is offline Pegasus123  United States
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As I was getting ready to purchase this board I realized that unlike the original this mono version does not have plate cap holes. Is there an easy way around this? Also, is there any chance of a new version with minor revisions?
1. Plate cap connection
2. Separate heaters connections for the driver and output tubes (with a jumper if both are the same voltage)
3. Removal of sockets. That way the standoff screws don't need to be so long.

Last question revolves around how the amp actually works. Does the driver contribute to the max wattage that this amp can produce or does it merely provide gain? If it's just gain then I assume that the Aikido preamp I am building would allow me to use much lower transconductance tubes than a 6GU5 (want to try octals).
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Old 15th February 2018, 09:28 AM   #119
jloaf is offline jloaf  United Kingdom
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Right, I have ordered a couple of boards and am going to try to build these beauties. The Mouser list is useful, as they have a UK site and it translates the prices automatically.

My only question (at this stage - I'm sure there will be a few later) is concerning the substitution of parts for UK use.

Is it only the power transformer that needs to be changed, for 240 volt UK supply?
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Old 15th February 2018, 10:17 AM   #120
jamesfeline is online now jamesfeline  United Kingdom
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Hello .. hope you are well

Just one question what are your plans for sourcing the valves ? have you a UK supplier or ebay / or directly from peter's web site
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