70/71 Spec 1987.

Get support and show off your MetroAmp 50 Watt kit builds.

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neikeel
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Re: 70/71 Spec 1987.

Post by neikeel » Mon Apr 15, 2019 8:27 am

axeman wrote:
Mon Apr 15, 2019 1:50 am
Send me the inspection tag so I can initial it.
I have some!
Neil

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Danhalen
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Re: 70/71 Spec 1987.

Post by Danhalen » Thu May 09, 2019 3:05 pm

Wow nice work! Beautiful build!

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Re: 70/71 Spec 1987.

Post by Roe » Fri May 10, 2019 3:06 am

very nice but 2k2 screen resistors is overkill with 460v. 1k should work. and 10k + 8.2k droppers is a little high with 460v on the plates. 8.2+8.2k is more than sufficient. 8.2+6.8k is better perhaps
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Re: 70/71 Spec 1987.

Post by revolver1 » Sun May 19, 2019 4:03 am

Thanks for the response Roe.

Am I right in thinking the 2.2k screen resistors will add a bit of squish at high volume? Will there be any other effect on the sound?

I think your right about the droppers, I'm going to try taking it down to two 8.2k. I thought it was quite aggressive when I tested it, in a really good way there's a lot to like about it but its not exactly what I was shooting for ie, West Coast mod.

I changed the 4700pf bright cap for a 100pf but I suspect it may not be the culprit.

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Re: 70/71 Spec 1987.

Post by revolver1 » Mon Jun 10, 2019 12:17 pm

Having read a bit about screen resistors in regard to a different amp, have I got this right? The 2.2k will lead to faster break up where as the 1k or 1.5k would have slightly more head room?

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Re: 70/71 Spec 1987.

Post by danman » Mon Jun 10, 2019 7:21 pm

Reducing the screen current by using a higher resistor value will cut down on the overall power slightly. I'm not sure that I would say earlier breakup though...the higher value will cause more compression and squish from the power section. I have tried some higher values (above 1k) in my 50 watter and did not care for the change in sound so much.

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Re: 70/71 Spec 1987.

Post by revolver1 » Tue Jun 11, 2019 4:15 am

Thanks for straightening that out for me danman. :toast:

I'm in a really annoying position at the moment....
Its gone a bit quiet on the work front but but I really need to get back into it.

The neighbours have reached breaking point so I need to get to a studio. Can't afford studio with out work.....
There's tweaking to be done, so frustrating when you have the time but not the money and when im back in work ill have the money but not the time...

Always the way.

So I have pulled the 4700pf bright cap for a 100pf and pulled the 10k 2watt preamp dropper resistor so now there are 2x 8.2k 2w in there.

Only slight changes but it may be enough. Like I said before it sounded great as it was but it was more like a really powerful chainsaw type sound which was actually pretty cool and useable in itself, its just not the Band of Gypsies esque tone I was shooting for.

If I can't hit the BOG tone I'll definitely put it back the way it was.

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Re: 70/71 Spec 1987.

Post by danman » Tue Jun 11, 2019 7:07 pm

I know how it can be balancing work and play time as work keeps me pretty busy and not much time for playing :cry:
I built a 50 watter several years ago that I have never been happy with. Tried several mods and circuit changes but always come back to stock in the end.

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Re: 70/71 Spec 1987.

Post by axeman » Wed Jun 26, 2019 1:07 am

My 2 cents in building amps and having an ear for tone, so they say. Your amp should have a women's name because it's sexy. Secant, you are a master builder, very obvious but, you'll never get the band of gypsies tone with a 50 watter.

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Re: 70/71 Spec 1987.

Post by Roe » Wed Jun 26, 2019 6:24 am

revolver1 wrote:
Sun May 19, 2019 4:03 am
Thanks for the response Roe.

Am I right in thinking the 2.2k screen resistors will add a bit of squish at high volume? Will there be any other effect on the sound?
- it reduces power and slows the attack, adding compression as you turn up the amp. It may sound a little softer and smoother, loosing aggression.
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Super 100 amps: 1202-119 & 1202-84
JTM45 RS OT JTM50 JMP50 1959/2203/34/39

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