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Old 4th October 2012, 05:02 PM   #1421
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Is that a WE input transformer?
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Old 4th October 2012, 05:56 PM   #1422
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No is a 10uF paper in oil Russian cap.
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Old 4th October 2012, 06:02 PM   #1423
ra7 is offline ra7  United States
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That is wicked, man!
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Old 5th October 2012, 09:22 AM   #1424
protos is offline protos  Greece
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Finally finished one monoblock with mu stage and listened for a few days. I am actually driving both speakers with this using a y connector for the input so the effect is true mono, which is good to get an idea of tonal quality. Power output at auditioning levels must be around 2W total so the amp is comfy with this set up.
Speakers are bastanis prometheus 98db or so with powered sub from 100hz. Line stage is John Broskie Aikido.
Previous pass amps included aleph 5 and aleph x. However those were sidelined in favour of either a 300B/6sn7(ccs stage) SET with good plitron tansformers and all film caps or a 6c33 SET.
After playing around with the bias/current settings to find the ideal mix acoustically I listened more extensively. Initially I was impressed but not particularly blown away. A very SET-like sound in the same playing field as my other valve amps but perhaps a hair less liquidity/immediacy in the mid/highs. However, after trying some output cap combos, initially panasonic 2X4700uf bypass audyncap film 2,2uf, I reasoned that I could get away with better smaller caps as my full range units only go to 100hz (below 100 the sub is driven by the line stage). I tried a set of black gate N 680uf in an anti-parallel set up which was not that great. It was only when I put in a pair of ASC 100uf film in oil caps that the whole musical presentation went up a level quite probably surpassing the valve sound. Electrolytics , even good ones, seem to have a small degree of bloat and smearing. Bypasing helps, only up to a point.
I think this makes a case for "bi-capping" the SITamp. That is to have two outputs : one with large bypassed electrolytics for the bass units and some large film caps for the mids/tweeter.
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Last edited by protos; 5th October 2012 at 09:26 AM.
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Old 5th October 2012, 12:42 PM   #1425
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@tonywong

Awesome. I hereby bestow upon you, the ArcAttack award.

Award

Last edited by Michael Rothacher; 5th October 2012 at 12:54 PM.
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Old 5th October 2012, 12:47 PM   #1426
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@protos

Cool. Interesting. Have you posted the particulars of your mu stage here?
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Old 5th October 2012, 05:39 PM   #1427
protos is offline protos  Greece
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What for? I climbed on the giants shoulders and just borrowed the schematic from this thread. It seemed well tested and liked so thats what I used. I mean the one with the r100 semisouth and the two resistor conection.

I wanted to try a basic version to see if I liked it and then think of any mods. Although I must say I am not that advanced a diyer to confidently design my own mu stage. For valves designing is a bit easier especially if you also have Broskies tubecad software.

I was also surprised how quiet my amp was. With the input shorted there was no noise at all a few inches from the 98db speaker.

I can now say that there is a possibility that I will not have to be spending hundreds of euros/dollars replacing expensive 300B's and various nos valves every couple of years.
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Old 5th October 2012, 09:35 PM   #1428
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Michael,

Inquiring minds want to know-

When will you be putting out another article and on what topic?
I check your site from time to time, but no movement yet.

I wanna know what, "Why would you want to built that..." is!

Have you tried or though about a F5, but with complimentary SITs?
There are a few sets available at diycircuits.com. I don't have the know-how for something like that or if it's even possible. If it were possible, a 10w Class A would be interesting.

Just a though. Please feel free to drill holes in my logic.

Vince
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Old 5th October 2012, 09:43 PM   #1429
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Default F5 with SIT

Quote:
Originally Posted by vdi_nenna View Post
Michael,

Inquiring minds want to know-

When will you be putting out another article and on what topic?
I check your site from time to time, but no movement yet.

I wanna know what, "Why would you want to built that..." is!

Have you tried or though about a F5, but with complimentary SITs?
There are a few sets available at diycircuits.com. I don't have the know-how for something like that or if it's even possible. If it were possible, a 10w Class A would be interesting.

Just a though. Please feel free to drill holes in my logic.

Vince
Yes Michael, I want a F5 with SITs.
Please, Please?

Rush
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Old 5th October 2012, 09:59 PM   #1430
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I really do have some projects in the pipeline. That particular one is a codename for my current project. Of course, that won't be the real title, I was just having a little fun. With a little luck, I'll have some preliminary info ready for BAF, but my lips are sealed for the time being.

I have a few complementary SIT pairs and I have something in mind for them, but I wouldn't want to preempt anyone else's efforts by making any pre-announcements. I will say that it's not an F5 sort of circuit, though.

I had better get back to the lab now. My PCB's arrived today.

Mike
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