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Old 18th March 2009, 03:40 AM   #11
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Originally posted by kevinkr
[wondering how you posted the pictures so the background doesn't show?
gif with a transparent background.

Quote:
I should build me a similar amplifier, (I've got Nord Mende transformers, and Tele 6BQ5s - should be a nice and I am currently contemplating building a pair of Fonkens in the near future.. (I have a very large pair of Onkens in my main system so the Fonken seems like a natural.. )
We've built a couple. My main amps are parafeed mono-blok variation with triode strapped EF86 on the front -- real giant killers (2 grundig consoles were iron donors)

Do you have the little ones or the big ones (i have a pair of each stashed). Nicely built, i expect the little ones will make a great tweeter amp.

Fonken are a really good match for the RH84. If you need the good drivers give me a call....

dave
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Old 18th March 2009, 06:51 PM   #12
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Originally posted by Eli Duttman
Guys,

It should not be especially difficult for keantoken to map the RH84 design onto the "iron" and tubes he already has.

Based on the 6AR5 data sheet Dave (planet10) provided, the B+ rail will be "shorter" than that shown for the 6BQ5/EL84 setup. Would 10M45S CCS loading be a good idea for keeping the gain of the 'T7 section up, at a lower drop in the load? "Check valve" style decoupling between "finals" a voltage amplifiers is another way to hold losses down.

BTW, does anybody know what Akai used the 3rd 6AR5 for? Regulator? Bias erase oscillator? ...
If I go that way, I will probably build a discrete transistor CCS rather than order a new part online.

If I understand the terminology properly, this Akai played reels and cassettes.

Also, I found the motor out of the unit interesting. Would it be possible for me to build a decent record player with the motor? That would be heavy. The motor itself has significant mass and at the other end of the belt is a large aluminum disc that I'm guessing served to dampen the natural vibration of the motor.

Thanks,
- keantoken
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Old 18th March 2009, 07:14 PM   #13
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Originally posted by Eli Duttman
BTW, does anybody know what Akai used the 3rd 6AR5 for? Regulator? Bias erase oscillator?
I've seen a 3rd output tube in quite a few Japanese R-Rs. I suspect to drive some of the erase/record heads or somesuch. I think i have 2 sonys here i haven't dissasebbled yet. I could have a look to see if exactly what can be figured)

dave
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Old 18th March 2009, 11:52 PM   #14
kevinkr is offline kevinkr  United States
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Originally posted by planet10


I've seen a 3rd output tube in quite a few Japanese R-Rs. I suspect to drive some of the erase/record heads or somesuch. I think i have 2 sonys here i haven't dissasebbled yet. I could have a look to see if exactly what can be figured)

dave

Significant bias power is required for the erase head and a substantially lower power level for the record head. Someone recently gave me a Sony SRA3 recording amplifier and the matching deck. (I tend to be a magnet for this stuff.. ) The bias oscillator in this unit is a 12BH7A. As the owner of an Otari MX-55 half track studio recorder and nicely restored half track ReVox G36 this Sony machine is going to a new home this very week-end.. (A Yankee swap at an upcoming audio gathering I going to.)
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