Hi all,
absolute beginner's question for a potential first tube project:
Would the design of a push pull EL34 stereo amp with the following characteristics be worthwile ?
-line input into one half of ECC83 as first stage
-then one half of ECC82 as phase splitter
-then EL34 push pull output tubes
-highest quality non-ultralinear output transformers
-negative feedback from transformer secondary to first stage cathode
-? potentiometer adjustable: AC balance, DC balance, bias/bias balance, NFB (adjustables R/C)
-simple design/short pathways, oriented towards Braun CV11or CSV13 EL84 push pull amp (however with ECC82 and EL34)
Any opinions or recommendations ?
thank you so much,
FrankieS
absolute beginner's question for a potential first tube project:
Would the design of a push pull EL34 stereo amp with the following characteristics be worthwile ?
-line input into one half of ECC83 as first stage
-then one half of ECC82 as phase splitter
-then EL34 push pull output tubes
-highest quality non-ultralinear output transformers
-negative feedback from transformer secondary to first stage cathode
-? potentiometer adjustable: AC balance, DC balance, bias/bias balance, NFB (adjustables R/C)
-simple design/short pathways, oriented towards Braun CV11or CSV13 EL84 push pull amp (however with ECC82 and EL34)
Any opinions or recommendations ?
thank you so much,
FrankieS
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Improve the HT power supply, especially for the screen grids of the EL34's.
What voltage and class of operation are you planning?
What voltage and class of operation are you planning?
Hi Parafeed, thank you. still very, very early ideas. I guess it should become AB operation ?
Have to read a lot (like Morgan Jones). I have the CV11 which sounds nice.
I feel it would be nice to build one, a stronger one then, like EL34 PP.
Would start on a breadboard and with extensive measurements.
And no output transformer compromises.
thank you.
I'd go with LTP. 1/2 12AX7 for voltage amplification, followed bt a DC-coupled LTP using a 6SN7 or similar for the LTP.
PS A good example is the Eico HF-89. Very simple, and sounds great.
PS A good example is the Eico HF-89. Very simple, and sounds great.
Have a look at braun CSV-60 , it has PL500 power tubes but EL34 could be used i think.
The only difference from csv-13 (in my memory) is that csv-60 used a ecf82 as first stage to get a bit more
swing. ( PL500 could be hard to source especially as you want matched tubes )
PL504 are plenty out there, and there are soviet EL500 variants (6P36S) with 6.3V heater.
Your Braun amp uses a split load phase splitter like the early Dynacos. This is OK for guitar amps but not ideal for High Quality reproduction. Really yucky overload behaviour.
I second jcalverez's suggestion you use a LTP phase inverter like the Eico. Only one extra Double Triode for a stereo amp.
This is a move towards the classic Mullard 5-20 and also adopted in the later Dynacos, VTA 'improved' Dynaco kits etc.
There are also articles on 'improving' 5-20 eg Byrith's, but the original is still a good amp. Most of these involve replacing the input EF86 with a triode which fits in with what you've got. Audible improvements with silicon diode power supply, or better still, a SMPS 😲
Not sure why you're against Ultralinear. It gives many advantages with few drawbacks. Have you got existing OPTs that you want to use?
I second jcalverez's suggestion you use a LTP phase inverter like the Eico. Only one extra Double Triode for a stereo amp.
This is a move towards the classic Mullard 5-20 and also adopted in the later Dynacos, VTA 'improved' Dynaco kits etc.
There are also articles on 'improving' 5-20 eg Byrith's, but the original is still a good amp. Most of these involve replacing the input EF86 with a triode which fits in with what you've got. Audible improvements with silicon diode power supply, or better still, a SMPS 😲
Not sure why you're against Ultralinear. It gives many advantages with few drawbacks. Have you got existing OPTs that you want to use?
yes, silicon diode power supply.
no output transformer yet.
considering one of these:
Lundahl, Hashimoto, Hammond ... (or Toroidy ?)
no output transformer yet.
considering one of these:
Lundahl, Hashimoto, Hammond ... (or Toroidy ?)
this is hifi thus no overload expected. In fact concertina is inherently balanced and independent on tube characteristic.
I'm not saying that xP500 is possible. What i am saying is that EL34 is in new production and available as really matched and with warranty, and at the same time not adding money to putins war.
Anyway, we still can source USSR tubes from Ukrainian vendors.
A few thoughts to Frankie's Braun schematics above: Of course you have noticed yet that a ECC83/12AX7A triode prioor to the Concertina suffices with EL84/6BQ5's as finals, but not with PL500's and other more powerful tubes that need more drive umph. The ECF80/6BL8 is apt to do it, as the pentode offers more plate signal swing, and the triode gives a better Concertina. You might also want to have a look to the schematics of German Klein & Hummel/Saba/Telewatt amplifiers V30 with EL36's or EL5000's.
OTOH, I'd also prefer a LTP as phase inverter, preferably with a CCS as the tail.
Best regards!
A few thoughts to Frankie's Braun schematics above: Of course you have noticed yet that a ECC83/12AX7A triode prioor to the Concertina suffices with EL84/6BQ5's as finals, but not with PL500's and other more powerful tubes that need more drive umph. The ECF80/6BL8 is apt to do it, as the pentode offers more plate signal swing, and the triode gives a better Concertina. You might also want to have a look to the schematics of German Klein & Hummel/Saba/Telewatt amplifiers V30 with EL36's or EL5000's.
OTOH, I'd also prefer a LTP as phase inverter, preferably with a CCS as the tail.
Best regards!
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