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50W monoblock "Engineers Amp"
50W monoblock "Engineers Amp"
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Old 21st May 2018, 07:49 PM   #161
anatech is offline anatech  Canada
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50W monoblock "Engineers Amp"
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Old 22nd May 2018, 04:29 AM   #162
kweaver is offline kweaver
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Did any of you guys have trouble with a 60hz hum? I didn't notice it at first but now that I have, it is annoying to say the least.

Actually the more I dig into this, I think it may be a grounding issue. I rewired my rca inputs and grounded the shield on one end. It had no effect. Its just odd that both units are doing the exact same thing. Almost feels like it power related. Definitely more pronounced when running through my preamp than if I plug directly into the amps with my iphone.
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Old 22nd May 2018, 03:35 PM   #163
kstylianos is offline kstylianos  United States
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Just to follow up on my issue with rising bias currents.

Quote:
I also swapped out R13 and R14 for 47k
I did this as well from the direction of Pete and bias levels leveled off nicely. Pretty darn steady now and seem to have settled in.
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Old 25th May 2018, 02:19 AM   #164
kweaver is offline kweaver
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So I am a bit frustrated with this hum issue. I have rewired my inputs exactly the way Pete suggested, using unbalanced guitar cable using the shield as ground. I tried lifting the ground on the on the power supply with no impact. They are totally silent when I plug directly into the amps from my laptop or iphone using a stereo to rca cable but as soon as I connect an actual preamp (and I have tried 3 separate units with different tubes) I pick up a bad hum. I have confirmed that the chassis are properly grounded
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Old 25th May 2018, 03:06 AM   #165
kstylianos is offline kstylianos  United States
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Are IEC and PCB board grounds connected to chassis, preferably as same location? Sounds like something upstream from amp. Is hum induced, using same chain of components, with another amplifier?
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Old 25th May 2018, 04:19 AM   #166
kweaver is offline kweaver
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So embarrassing as this is to admit. You were entirely correct. It seems it was nothing more than a bad cable. Not sorry that rewired the inputs though as that did seem to help quiet things down even more. We are running perfectly quite now.

As for the heat; I removed the bottom panel and installed feet to get the units off the surface. Running much cooler now. I couldn't be happier. These things sound incredible.

BTW I never realized how much noise a phone could create just by proximity to preamp tubes, even when not physically connected.
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Old 15th June 2018, 07:50 PM   #167
pmillett is offline pmillett  United States
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Default New version of PCB without sockets

Hi All -

I now have a version of this board with no tube sockets... just holes so you can chassis mount sockets and wire them up however you want. So you can use whatever tube!

Pete

50W monoblock "Engineers Amp"
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Old 15th June 2018, 09:43 PM   #168
smoking-amp is offline smoking-amp  United States
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Nice!

21/6HJ5, 21LG6A, 21/6EX6, 6CB5A, 26DQ5, 22/17KV6, 33/21JV6, 21HB5A, 22/6KM6, 35LR6, 13/6GB5, EL500, EL36, EL86, 10/6JA5, 21KQ6, 6P36S, 6P44S, 6P42S, 6P45S, 42KN6, 40KG6, 36LW6....

Last edited by smoking-amp; 15th June 2018 at 09:51 PM.
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Old 22nd June 2018, 03:47 PM   #169
cbueche is offline cbueche  Switzerland
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Thanks Pete for again delivering such a beauty ! Eagerly awaiting where George will push this nice one
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Old 24th July 2018, 01:29 AM   #170
nc200 is offline nc200  Portugal
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Afterhaving built the DCPP and being totally satisfied with the quality ofthe amp, i decided to buy the pcb's first version (on the way) forthe 50w monoblocs.

The problem is that currently it is almostimpossible to buy 6hj5 tubes (I thought it would be easier up until startlooking for them). What is the best substitute for 6hj5? and what changes do I have to make?

As I am nota specialist like many of you (this will be the third tube amp that Ibuild), I ask you to have a little patience and try to detail thechanges that I must do as best you can.

Best regards
Caetano
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