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 Hz–20 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?
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 Hz–20 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?
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
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?
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?
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
dave
About twice the total investment we have in the RH84 mono-bloks that i are the normal amps for my personal Fonkens.
dave
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
Personally, I'd go for the Mapletree 6V6GT mono-blocks. Lots of tube rolling options and potential mods down the road.
Jeff
Can you point me in the right direction?
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?
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?
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I'll wager it will sound pretty good, especially with decent OPT's and NOS 6V6GT's. Just don't expect rock concert SPL's with 8 watts.
Jeff
The best RH84 threads on on this form. the new search should give better results than before.
Our RH84s were all based on iron left over from selling (& profiting) on extraction of speakers out of console hifis. The monobloks were built off 2 Grundig consoles. We bought hammond chassi, I/O connections, RS filament trafos, Hammond choke, Solen PS caps (poly), a few specific Rs. All the rest of the bits were out of the junk box/stashes.
dave
So of course, what Dave really means is that the quoted $150 or so is the total invested for new parts listed in this "junk-box" project - all the iron and tubes came from a huge stash of parts. Add a little design advice from Eddie Vaughn (i.e. re power supply configuration and use of triode wired EF86 driver), and this is a pretty nifty little amp that is sonically delightful with the FE127E Fonkens.
Of course, like any DIY electronic project if you want to go gonzo with NOS tubes, boutique parts, laser cut precious metal chassis, or (name your fetish), then what's a few kilobucks to an audiophile? (and you know who you are)
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