Yarland 34 ciii amp

[arvin]

Just bought one of these amps brand new for 160 GBP off ebay.

What a lovely sound, i am now converted to tubes,goodbye transistors!

[Svein_B]

Yes, this little Yarland (yes it is VERYsmall!), is not at all bad.

Space inside is however a little cramped when you want to start modifying it.

[arvin]

Btw it uses 5670 tubes and sovtek el34 tubes, can anyone recommend superior replacements for these tubes please?

[arvin]

Any advice on modification would be appreciated, ie better capacitors etc.........

BtW where can I get a circuit diagram of this amp?

Thanks

[arnoldc]

5670 = 2C51 = WE396A

Try also Svetlana EL34 (cheap too)

[Svein_B]

Which amp is it you have?
I believe the Yarland FV-34Ciii uses EL84 output tubes.
If it uses EL34 it would probably be a 34A or 34B ?

I can post a diagram I have traced for the 34Ciii with EL84.

Svein.

[arvin]

Yes that would be most appreciated Thanks!!

[Stuart Dean]

Yes you cann't go wrong that the price if you want something to modify and tweak.
With mine I changed the coupling caps but didn't really notice much change.
I then altered the driver valve connections to enable me to use the ECC*** range.More readilly available here in the UK and I've got a shed load of them.
This means cutting the PCB tracks and soldering some links.
I,ve not really come to any firm conclusions as to which ECC is best.
I also slightly lowered the feedback.
If your incoming mains voltage is high you might find heater voltages are a bit high.
I,ve tried various output valves ie. Mullard,TFK and Brimar thinkI can safely say that there is not a lot wrong with the suppied Sovteks.
I also have the Yarland FV 34A which is an SE design using 2 EL34's driven by 5670's.
With this amp I triode connected and removed feeback altogether
As the amp has fixed bias I can treak it within reason for a load of different octal fit valves. I've used 6L6,KT66,EL37,NR77 plus a few other obscure CV marked valves. It has a massive power TX and runs cool all day.
To be quite honest it sounds so good I won't be bothering to make any further changes and all this for £180 delivered.
STU

[Svein_B]

Here is my promised diagram for the EL84 amp:
(there may be errors!)


- The input stage is a classic (old fashioned) paraphase. It requires adjustment for AC balance when changing tubes. It could be fun to try to use the adjustment to tune the harmonic distortion spectrum with an analyser.

- The output stage is pentode mode. The slightly lower than normal common cathode resistor explains the claimed class-A operation.

- The OPT unfortunately lacks UP taps. It will therefore only allow penthode mode, as supplied, with 10W, or rewiring the 100ohm resistors for triode mode which gives around 3W.

- The OPT appears to be fairly decdent. Probably around 1.5 Kg each. Oscilloscope view of square waves look exemplary. HF roll-off start at around 50KHz. My measurements indicate that the primary impedance may be slightly less than the common 8K. The optimum speaker impedance should therefore probably not be much below 8 ohm. (Photo of OPTs]

- The NFB is only around 4dB. Measured output impedance in pentode mode is 5 ohm, and 5 ohm in triode mode. Both with NFB. Triode mode without NFB is 7 ohm.

I have rolled theh tubes with GE 5670 and JJ EL84, and just managed to squeeze in Russian PIO coupling caps. Would probably ditch the circuit board and install new tube sockets for more extensive modifications (re-build).

The sound is decent. Not as sweet and airy as my vintage SE amp, but more bass punch.

Svein.

[baiof versognai]

I also own a FV-34C III....mine has arrived with Shuguang EL84 tubes and not Sovteks....anyway, a very good sounding little amplifier....better than most solid state integrated at the same price....I found it to be very natural sounding...sweet, very detailed...very well integrated in my system with NAD C521BEE and B&W DM601 S3....

for Svein: I'm planning to change the Shuguang EL84 with JJ or TAD.....I'm assuming that no bias settings can be made....can you please describe the procedure to set the AC balance? Do I need to set those two little screws between the tubes? Any particular tools are needed to set that balance? Many thanks.