I picked up this little amp a few weeks ago and was just wondering if anyone here could offer advice on tubes to improve or change the sound?
Here are the details from the builder in 2010.
I built this little amp about 6 months ago and it's seen about 25 hours of use. You could think of the amp as a JE Labs "Simple 45" except it uses the 1626 output tube (the schematics are virtually identical except for output tubes and naturally different operating points).
The tubes include a 5U4GB rectifier, a pair of 1940's Hytron 1626 power tubes and an RCA JAN Black Plate (graphite coated envelope) 12SL7 driver tube (all tubes were new with the amp and have about 25 hours on them max).
I've really enjoyed this amp in my Den and used it to drive some custom made 94 DB single driver speakers with plenty of volume and dynamics for my listening level. The tube puts out about .75 watts per channel so more efficient speakers will be needed in a larger room. However, I let one of my friends with a pair of Lowther Alerion speakers at around 94 db efficiency listen to it in his larger room and he really liked it. But he already has two of my hand built amps and couldn't really justify buying another one (he has several other tube amps as well) so this one is available to the public at large.
The amp has an overbuilt power supply and is really quiet. I used a seperate filament transformer with center tap to help with hum balance and avoid any coupling noises between windings in the power transformer which I think helped.
Some other details about the amp:
-- NOS USA Made Pyramid Paper in Oil Coupling Capacitors
-- Teflon Jacketed Silver Clad copper for all signal carrying wires.
-- Made in USA new Edcor output transformers
-- Super short signal path, with an attempt to use only the leads on most resistors to minimize the number of solder joints.
-- Lead free Kester 3% silver solder used exclusively
-- Vintage Power transformer that I picked up on Ebay last Summer (spray painted it a hammertone black to match the plinth).
-- A hybrid star ground that uses a short silver clad copper bus bar that is reputed to be quieter than a straight star ground (high currents are kept from commingling with sensative signal circuits).
The amp is point to point wired, although I did build the power supply on a perf-board to conserve space and to better group the power supply grounding node.
Here are the details from the builder in 2010.
I built this little amp about 6 months ago and it's seen about 25 hours of use. You could think of the amp as a JE Labs "Simple 45" except it uses the 1626 output tube (the schematics are virtually identical except for output tubes and naturally different operating points).
The tubes include a 5U4GB rectifier, a pair of 1940's Hytron 1626 power tubes and an RCA JAN Black Plate (graphite coated envelope) 12SL7 driver tube (all tubes were new with the amp and have about 25 hours on them max).
I've really enjoyed this amp in my Den and used it to drive some custom made 94 DB single driver speakers with plenty of volume and dynamics for my listening level. The tube puts out about .75 watts per channel so more efficient speakers will be needed in a larger room. However, I let one of my friends with a pair of Lowther Alerion speakers at around 94 db efficiency listen to it in his larger room and he really liked it. But he already has two of my hand built amps and couldn't really justify buying another one (he has several other tube amps as well) so this one is available to the public at large.
The amp has an overbuilt power supply and is really quiet. I used a seperate filament transformer with center tap to help with hum balance and avoid any coupling noises between windings in the power transformer which I think helped.
Some other details about the amp:
-- NOS USA Made Pyramid Paper in Oil Coupling Capacitors
-- Teflon Jacketed Silver Clad copper for all signal carrying wires.
-- Made in USA new Edcor output transformers
-- Super short signal path, with an attempt to use only the leads on most resistors to minimize the number of solder joints.
-- Lead free Kester 3% silver solder used exclusively
-- Vintage Power transformer that I picked up on Ebay last Summer (spray painted it a hammertone black to match the plinth).
-- A hybrid star ground that uses a short silver clad copper bus bar that is reputed to be quieter than a straight star ground (high currents are kept from commingling with sensative signal circuits).
The amp is point to point wired, although I did build the power supply on a perf-board to conserve space and to better group the power supply grounding node.
Well more than changing the sound I am just wondering if I am getting the best sound it has to offer?
Don't get me wrong it sounds pretty darn good as is but, I was just wondering if others that have this amp discovered any particular tubes that raised its level up a notch or two?
You could play with different 6SL7s, and maybe different rectifiers, though I would NOT change the type (looks like a 5U4). IME 1626s all sound alike, not much to change there.
How overbuild is your power supply? cLCLC with dc-link caps would be ideal.
You could also try different driver tubes like the 8532: https://sites.google.com/view/realworldaudio/audio-gear/pure-darling
You could also try different driver tubes like the 8532: https://sites.google.com/view/realworldaudio/audio-gear/pure-darling
If limited to tube rolling then I'd agree with grovergardiner's post.
If you want to go farther , actually changing tube types, then it's probably best to first document the build you have in an accurate schematic with voltages shown so you can see what the hardware you have can support.
Aside from tube changes ,one thing I would try would be biasing the 6SL7 with an LED or suitable diode instead of the 1K resistor and bypass cap. You could start by just disconnecting the easiest ends to work on and kluge in the LEDs to hear how it sounds. ( The JE schematic shows 1.5V bias with the 1K resistor and an HLMP-6000 series red LED typically runs around 1.6V ) I'd expect an audible change from that. Better or worse? Only you can say.
If you want to go farther , actually changing tube types, then it's probably best to first document the build you have in an accurate schematic with voltages shown so you can see what the hardware you have can support.
Aside from tube changes ,one thing I would try would be biasing the 6SL7 with an LED or suitable diode instead of the 1K resistor and bypass cap. You could start by just disconnecting the easiest ends to work on and kluge in the LEDs to hear how it sounds. ( The JE schematic shows 1.5V bias with the 1K resistor and an HLMP-6000 series red LED typically runs around 1.6V ) I'd expect an audible change from that. Better or worse? Only you can say.
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These sorts of features are all very well and changing tubes is all very well too - but the Elephant in the room is the circuit schematic and how the tubes are biased, how much linearity you want.
All said and done very nice looking amp, well made, well presented, great !!!
Rewire some components, take the Cathode capacitors out, as a starting point try this circuit:
There will be less gain, just drive it from a higher signal amplitude source. Don't put the Volume pot in here, the 100K pot is too high and will introduce noise. You may need to adjust some resistors to get the bias right.
Its not the tube its the circuit.
There will be less gain, just drive it from a higher signal amplitude source. Don't put the Volume pot in here, the 100K pot is too high and will introduce noise. You may need to adjust some resistors to get the bias right.
Its not the tube its the circuit.
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I've moved on from using the 1626 output tubes in my Darling, JE Labs-style to triode connected 6V6 or even better, 6F6Gs in triode, as pictured below.
To my ears this is as close as I could get to the sound of my Simple 45 without using the actual DHT output tube.
Well to be honest I don't want it to sound like my Korneff 45, I just want it to sound as good as I can make without going crazy of breaking the bank!!!
I attended the 1999 nynoise show wherein Jeremy Epstein's 6SN7 driven Darling left a very good impression. When I was about to build my own version, I wanted more gain so the amp could function like an integrated amp. From my tube stash, I chose octal based hi-mu 6F5s which are essentially 6SF5s with a grid cap. Eventually, I thought I could improve the amp by using a more linear audio output tube. Then I remembered a 6V6 PP amp I built in the late 80s using Dyna SCA 35 transformers, which I liked a lot. So I replaced the 1626s with triode connected 6V6s.
The Simple Triode 6V6 amp now drives a pair of Altec 405As in our living room.