I found a local fab shop that will engrave my panels for cheap. The top cover will get tube number labels and the back will have input/output etc.
I'm starting to think the plate supply caps I bought are a bit too big. Would these work? UCP2W470MHD Nichicon | Capacitors | DigiKey Is ripple current something I need to take into consideration?
Would this be suitable for wiring? JMS9313-01G: 22 AWG 6 Color Solid Tinned Copper Hook-Up Wire Bundle: Jameco Valuepro
I'm starting to think the plate supply caps I bought are a bit too big. Would these work? UCP2W470MHD Nichicon | Capacitors | DigiKey Is ripple current something I need to take into consideration?
Would this be suitable for wiring? JMS9313-01G: 22 AWG 6 Color Solid Tinned Copper Hook-Up Wire Bundle: Jameco Valuepro
Done...almost
It's all together now...time to move on to testing and tweaking.
First impressions with cheap "AD" film capacitors after 5 hours:
Very good extension with no noticeable LF or HF roll-off...maybe a tad bright but not fatiguing. Coherent soundstage with depth as well as width. Sounds a bit more neutral than musical, and a little lacking in detail (due of course to the film caps, not design). Overall pleasing to listen to but will be improved significantly with better caps.
There's a slight 60hz hum from the unit with the inputs shorted and it's the same on both channels, so I'll need to revisit my grounding...
It's all together now...time to move on to testing and tweaking.
First impressions with cheap "AD" film capacitors after 5 hours:
Very good extension with no noticeable LF or HF roll-off...maybe a tad bright but not fatiguing. Coherent soundstage with depth as well as width. Sounds a bit more neutral than musical, and a little lacking in detail (due of course to the film caps, not design). Overall pleasing to listen to but will be improved significantly with better caps.
There's a slight 60hz hum from the unit with the inputs shorted and it's the same on both channels, so I'll need to revisit my grounding...
Attachments
Quick update:
I determined the hum was due to leaky tubes and not from wiring. This prompted me to upgrade the tubes to 5691/5692 types and lower the value of R21 to double heater current as per specifications...as a result the preamp ran dead quiet. I say ran because after three weeks of daily use the heater winding cooked. That output was rated for 2A and the circuit was 1.8A...maybe it broke down from inrush. It's back online, but on life support via external power supply. I have a 270DX transformer ordered...hopefully the increased capacity will prevent future failure.
Anyway, the failure coincided with a cap upgrade to the 'user-recommended' bunch of Sonicaps and Mundorf silver in oils, sans the russian teflon bypass caps. The .001uf sonicap was discontinued so I used a RelCap RTE. It's burning in as I type and it sounds VERY good so far.
To finish it off I picked up a "coke bottle" 5Y3
I determined the hum was due to leaky tubes and not from wiring. This prompted me to upgrade the tubes to 5691/5692 types and lower the value of R21 to double heater current as per specifications...as a result the preamp ran dead quiet. I say ran because after three weeks of daily use the heater winding cooked. That output was rated for 2A and the circuit was 1.8A...maybe it broke down from inrush. It's back online, but on life support via external power supply. I have a 270DX transformer ordered...hopefully the increased capacity will prevent future failure.
Anyway, the failure coincided with a cap upgrade to the 'user-recommended' bunch of Sonicaps and Mundorf silver in oils, sans the russian teflon bypass caps. The .001uf sonicap was discontinued so I used a RelCap RTE. It's burning in as I type and it sounds VERY good so far.
To finish it off I picked up a "coke bottle" 5Y3
Attachments
Update time. After many nights of listening to the Cornet with the sonicap and mundorf caps (and 5691/5692 tubes) I felt that the preamp sounded overall good but at the same time it sounded "digital" or sterile. After some research and some recommendations by friends in the field I decided to try ClarityCap MR's in the signal path, keeping the teflon bypass caps in the output
The first thing I should point out is the MR's are BIG...I had to do some modifications to get everything to fit inside the chassis. I moved the SC platinums to position C7 replacing a Gen 1. After 4 days of burn-in I gave them a listen.
Claritycap MR first impressions:
I actually said "wow" out loud in an empty room. The clarity caps seem to resolve a level of detail unattained by the previous capacitor compliment. Instruments have more "acoustic space" and I feel that placement depth is much better defined. More listening needed but I really like them so far...
The first thing I should point out is the MR's are BIG...I had to do some modifications to get everything to fit inside the chassis. I moved the SC platinums to position C7 replacing a Gen 1. After 4 days of burn-in I gave them a listen.
Claritycap MR first impressions:
I actually said "wow" out loud in an empty room. The clarity caps seem to resolve a level of detail unattained by the previous capacitor compliment. Instruments have more "acoustic space" and I feel that placement depth is much better defined. More listening needed but I really like them so far...
Attachments
I built this and had the same issues with transformer blowing. With ac to dc rectification, the current rating is different. http://www.hammondmfg.com/pdf/5c007.pdf
Do not use the 270BX with octal tubes.
You need at least a 6.3V 3A secondary current rating.
Hope this helps anyone else out there..
Do not use the 270BX with octal tubes.
You need at least a 6.3V 3A secondary current rating.
Hope this helps anyone else out there..
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