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Old 22nd August 2009, 03:56 AM   #1
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Default Fonken System Build

Greetings,

I am looking to start designing and building a Fonken system for my office and would like some advice on amplification choices. I want the decisions laid out prior to building and want to maximize the synergy of the system in terms of both sound and aesthetics. The preamplifier will be a Mapletree Audio
Magic 5b that I have already built and use in my living room. The daughter is 2.5 and it needs to go somewhere safer. The beauty of the amp is it lets me use a passive, cathode follower, or srpp circuit at the front end of the system.

I am currently considering the following two amps for this system:

1: Hagtech Cymbal (8W, Class A)
http://www.hagtech.com/cymbal.html
Power 8W into 8 ohms
Input Sensitivity 1.5Vrms (15dB gain)
Input Impedance 47k ohm
Bandwidth (-3dB) 10Hz to 95kHz
Distortion 0.18% @1kHz @1W
SNR 95dB A-weighted
Damping Factor 5
Size 7.25" x 11.65" (PCB)
Weight 14 lbs
Input Voltage 100V, 110V, 120V, 200V, 220V, 240V
Tubes 6H30 x 5, 5AR4 x 1

2. Mapletree Audio Stealth Monoblocks
http://hollowstate.netfirms.com/superstealth.htm

8 W using Class AB ultra-linear push-pull circuit topology.
Tube lineup: 12SJ7, 12SC7, 2 x 6V6GT.
Input level control permits direct connection to line source.
Specifications:
Maximum undistorted power output: 8 W.
Frequency response at 5 W output: 20 Hz20 kHz, -1 dB.
Input resistance: 100 kOhms.
Output impedance: 0.1 Ohms.
Sensitivity: 0.5 V for full output.
Gain: 24 dB.
Output noise: 0.25 mV.
Configurable for 4, 8, and 16 Ohm speakers.
Power consumption: 25 W.


I read that the Fonkens prefer a class A design, but both amplifiers have advantages. The Mapletree has much higher gain and input sensitivity. I am not sure how 8 watts will work with these, a little extra gain may help.

Aesthetically, I am tied to the idea of monoblocks for this design. Any suggestions?
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Old 22nd August 2009, 05:01 AM   #2
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Quote:
Originally Posted by audioferret View Post
I read that the Fonkens prefer a class A design, but both amplifiers have advantages.
It isn't that they prefer Class A, what they prefer is an amp with a highish output impedance.

I historically have been using a pair of RH84 variants (3.8W class A) on them, but of late have been using a modified Grant Fidelity RITA (class AB triode ~15-20W). My favotte is still an El Cheapo variant with Scott iron running triode (3.2 W class A). Chris has a set of Paramours, a set of Wright Mono 7(?) and that lovely Scott.

FirstWatt F2 is also highly rated on these (mine is still parts)

dave
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Old 22nd August 2009, 04:28 PM   #3
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Default Calculating Output Impedence

The Hagtech does not list its output impedence, but does provide dampening factor of 5. Should I assume that speaker impedance divided by the amp's output impedance equals that dampening factor? Thus, the speaker impedance divided by the dampening factor would equal the output impedance?

http://sound.westhost.com/impedanc.htm

Lets assume the Fonken's impedance is basically 8 Ohms. Using that, the Hagtech would have an output impedance of (8/5) = 1.6 Ohm, correct?

If one amp has 1.6 ohm and the other .1, is more better? Or is that not determinative? In other words, as long as am amp is highish, will it likely work? It seems that the Mapletree is thus not a likely contender...

The Hagtech lists a distortion and signal-to-noise figure, while the mapletree does not. Is there a way to calculate that with the information given, or no?

I also take it to assume that if 3.5 watts is plenty, 8 watts is ample?
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Old 22nd August 2009, 04:38 PM   #4
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The hagtech has about the right output impedance. Single number measureddistortion is a totally useless number, a graph of the harmonics that make it up can tell you something. Singnal to noise, in general, lower the better (there are many ways to measure and specify, so often they are not directly comparable)

dave
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Old 22nd August 2009, 09:26 PM   #5
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Default Sounding good...

Cool, this is sounding like the way to go...

Has anyone here tried a Cymbal with a Fonken or other FE127E design?
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Old 23rd August 2009, 04:55 AM   #6
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A concern with the Cymbal would be the cost of retubing...

dave
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Old 23rd August 2009, 04:21 PM   #7
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Default What is $300.00 in the eyes of an Audiophile?

Sovtek 6H30PI: $29.95
Tubes for one Cymbal Amplifier: $150.00
Tubes for two Amplifiers: $300.00
Audio Nirvana: Priceless?

At least it is not the 6H30P-DR ($160.00 each!)
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Old 23rd August 2009, 06:50 PM   #8
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Quote:
Originally Posted by audioferret View Post
What is $300.00 in the eyes of an Audiophile?
About twice the total investment we have in the RH84 mono-bloks that i are the normal amps for my personal Fonkens.

dave
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Old 23rd August 2009, 07:37 PM   #9
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I poked around the Hagtech forum looking for some positive feedback regarding the Cymbal. Doesn't seem to be a whole lot of interest in this amp, considering how long it's been on the market.

Personally, I'd go for the Mapletree 6V6GT mono-blocks. Lots of tube rolling options and potential mods down the road.

Jeff
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Old 23rd August 2009, 11:18 PM   #10
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Default Can you point me in the right direction?

Quote:
Originally Posted by planet10 View Post
About twice the total investment we have in the RH84 mono-bloks that i are the normal amps for my personal Fonkens.
dave
I hope you read the sarcasm in my reply...

Did you use a kit, or did you just figure them out from scratch. I have searched a couple of RH84 threads and am having trouble finding the best place to start studying. Any recommendations? I am currently looking at this thread:
http://www.audiocircle.com/index.php?topic=49263.0

Vinylkid58: Do you think that the Mapletree could work despite its low output impedance?

Last edited by audioferret; 23rd August 2009 at 11:25 PM.
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