bevois valley clone from eico hf-12 iron..

mctavish · 18th March 2009, 04:28 AM

so i wire up a clone using the schematic from the mj book i recently received. i used the transformers from an eico hf-12 that was headed for its maker..

everything is great until i connect the feedback with the bypass cap. feedback with just resistance is fine. i have swapped the primary leads on the output trans. already so i know its not that.

i seem to get distortion on peaks when i have the cap across the feedback resistor. im taking feedback off the 8ohm tap which i assume is correct because the schematic in the book shows the o.t. as being 8 ohm. i believe m. j. used an old leak20 for his circuit.

they do seem like different values for feedback than ive seen in most amps, is this circuit just not suitable for this eico iron? what am i doing wrong? --lost in bevois valley

DigitalJunkie · 18th March 2009, 04:37 AM

The cap value is dependent on the particular output transformer used. You will probably have to tinker with the value of the cap to find what works best for that particular OPT. (A scope and sig. gen. are the usual tools used for this)

18th March 2009, 04:28 AM	#1
mctavish diyAudio Member Join Date: Feb 2008 Location: Niederösterreich	bevois valley clone from eico hf-12 iron.. so i wire up a clone using the schematic from the mj book i recently received. i used the transformers from an eico hf-12 that was headed for its maker.. everything is great until i connect the feedback with the bypass cap. feedback with just resistance is fine. i have swapped the primary leads on the output trans. already so i know its not that. i seem to get distortion on peaks when i have the cap across the feedback resistor. im taking feedback off the 8ohm tap which i assume is correct because the schematic in the book shows the o.t. as being 8 ohm. i believe m. j. used an old leak20 for his circuit. they do seem like different values for feedback than ive seen in most amps, is this circuit just not suitable for this eico iron? what am i doing wrong? --lost in bevois valley

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18th March 2009, 04:37 AM	#2
DigitalJunkie diyAudio Member Join Date: Apr 2003 Location: Portland,Oregon Blog Entries: 4	The cap value is dependent on the particular output transformer used. You will probably have to tinker with the value of the cap to find what works best for that particular OPT. (A scope and sig. gen. are the usual tools used for this)