Full Monkey amps

87.53.108.41

Posted on November 14, 2010 at 03:38:57

Frihed89
Audiophile

Posts: 15703
Location: Copenhagen
Joined: March 21, 2005

In my limited experience, all of the full monkey amps seem to be 2A3 or 45 based. The consensus seems to be that, correctly implemented, this type of DC coupled amp. can be at least as good some of the "best" alternatives, but that the implementation is not as easy or inexpensive as it looks.

Are there other, higher power, DHTs that can benefit from this approach? If so, which ones? If not, why not?

Hide full thread outline!

RE: Full Monkey amps

Palustris

11:36:18 11/14/10

RE: Full Monkey amps

vhrynchuk

08:44:53 11/14/10

7

RE: Full Monkey amps

Palustris

13:23:45 11/14/10

6

...

Show full thread outline!

RE: Full Monkey amps

Palustris

11:36:18 11/14/10

RE: Full Monkey amps

vhrynchuk

08:44:53 11/14/10

7

RE: Full Monkey amps

Palustris

13:23:45 11/14/10

6

RE: Full Monkey amps

danlaudionut

00:35:23 11/15/10

5

6EM7

Frihed89

01:13:50 11/15/10

4

RE: 6EM7

danlaudionut

03:27:48 11/15/10

3

My take (on 6EW7)

gluca

10:26:45 11/15/10

RE: My take (on 6EW7)

danlaudionut

10:39:28 11/15/10

RE: My take (on 6EW7)

gluca

11:34:19 11/15/10

RE: Full Monkey amps

Thorsten

07:41:23 11/14/10

5

For the 211 what driver, what PS voltage?

Frihed89

12:49:11 11/14/10

4

RE: For the 211 what driver, what PS voltage?

Thorsten

18:22:20 11/14/10

RE: For the 211 what driver, what PS voltage?

Frihed89

01:16:45 11/15/10

RE: For the 211 what driver, what PS voltage?

vhrynchuk

16:46:24 11/14/10

RE: For the 211 what driver, what PS voltage?

GTCharlie

22:27:50 11/14/10

RE: Full Monkey amps

David McGown

04:15:35 11/14/10

RE: Full Monkey amps

Paul Joppa

19:23:48 11/14/10

oh!

gluca

12:24:28 11/15/10

RE: Full Monkey amps, posted on November 14, 2010 at 04:15:35

David McGown
Audiophile

Posts: 591
Location: Silver Spring, Maryland
Joined: September 29, 1999

I believe the reason has more to do with power supply than circuit, in my estimation. Using the higher power DHTs means designing power supplies 650VDC or above, which is above the rating most of the commercially available capacitors, outside of motor runs. Also outside the voltage rating of commonly available hook-up wire. You can use of series pairs of lower voltage caps (450V) with voltage dividing resistors in the power supply. Also, drive voltage increases with the higher power low-mu tubes, so it is increasingly difficult to use a single tube driver. (300B is OK with high transconductance triode or triode connected pentodes with a Mu around 45+). Forget about 845s, except at low voltage (211s would work with high voltage supply).

RE: Full Monkey amps, posted on November 14, 2010 at 07:41:23

Thorsten
Manufacturer

Posts: 4209
Location: Somewhere nice on planet dirt
Joined: September 25, 1999

Hi,

A 300B "Monkey" is not a big deal, a 211 and 6S33 one can also be done. I'd not try an 845 one, unless running the 845 at low voltage.

The reason there are few "Monkeys" other than 2A3 or 45 out there is that where only build by a small circle of people, who mostly had very efficient speakers and fancies these lower power tubes more.

In many ways the DRD and "Full Monkey" are the same, actually the DRD could be called a "halve monkey".

The name comes BTW from the old "Monkey on a stick" toy and a "full monkey" simply uses a single resistor chain to which all cathodes are returned, the key is to remove the need for the driver cathode bypass capacitor.

Hence any DC Coupled or DRD circuit can be fully monkeyed up...

With a 211 Monkey Amp you can easily drive any Monkey Coffin, while 2A3 & 45 Monkey's are usually limited to their natural habitat, horn speakers. I heard 45 monkeys on AER/Hedlund horns. Not bad at all.

Ciao T
Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

RE: Full Monkey amps, posted on November 14, 2010 at 08:44:53
vhrynchuk Audiophile Posts: 10 Location: Toronto Joined: December 14, 2009	You can probably use full monkey as a driver for your more powerful tube. Just replace the output transformer with an interstage. (I'm thinking myself to use DRD to drive GM70 or 845).

RE: Full Monkey amps, posted on November 14, 2010 at 11:36:18

Palustris
Audiophile

Posts: 2460
Location: Cape Cod
Joined: September 12, 2008

There is no reason for outrageous power supply voltages with a "monkey" even when using a 300B. Here is my latest version. Note it is not a "full monkey" as the cathode resistor of the driver tube is not within the OP tube cathode resistor chain. The LED bias eliminates the need to do so as there is no cathode capacitor to eliminate. The 6N23P can only just barely drive the 300B to full output so this is not ideal, more of an experiment to try the 6N23P. However, I can easily drive my efficient speakers with a 2A3 amp so I don't need much power.

My next iteration of this amp will be with "stacked" power supplies along the lines of the Komuro 300B. Maybe the is more than meets the eye with this simple circuit, but my own feeling is that the direct coupling and elimination of the grid resistor for the OP tube makes all the difference. I really can't see myself ever going back to cap coupling the driver to the OP tube.

Andreoli stacked supply monkey

For the 211 what driver, what PS voltage?, posted on November 14, 2010 at 12:49:11
Frihed89 Audiophile Posts: 15703 Location: Copenhagen Joined: March 21, 2005	And would it put out 12W+ RMS?

RE: Full Monkey amps, posted on November 14, 2010 at 13:23:45
Palustris Audiophile Posts: 2460 Location: Cape Cod Joined: September 12, 2008	I like it!

RE: For the 211 what driver, what PS voltage?, posted on November 14, 2010 at 16:46:24

vhrynchuk
Audiophile

Posts: 10
Location: Toronto
Joined: December 14, 2009

211 is not the best tube for DRD. The anode voltage for 211 only has to be around 1KV. So for DRD is around 1.3KV. The plate impedance is more than 3KOm which demands an output transformer 15KOm on primary to have a good damping factor. With mu 12 you will need DC on the filaments. All in all for 12 Wats of output power it doesn't worth all efforts. If you need 12 Wats 300BXLS from EML or Kron will sound much better and will cost less despite the price of the tubes.

RE: For the 211 what driver, what PS voltage?, posted on November 14, 2010 at 18:22:20

Thorsten
Manufacturer

Posts: 4209
Location: Somewhere nice on planet dirt
Joined: September 25, 1999

Hi,

> For the 211 what driver, what PS voltage?

You could use E810F or D3a or many others.

The 211 in a slight Class A2 Setup (Audio Note Japan Ongaku Style) needs no more drive than a 300B.

With an E810F driver you would need around 1250V +B and the 211 cathode will be at around 250V.

Power Output? Near 20 Watt I'd guess. The ANJ Ongaku claimed 27W.

I am not suggesting to build such a beast (there is however in my little black book a small design study, with a silver/permalloy TVC, a D3a Driver and full monkey/DRD style circuit with silver/permalloy anode load choke and silver/permalloy parallel feed output transformer plus silver parallel feed cap. Sadly the potential customer got way scared when all was priced out, so it remained a study.

As vhrynchuk points out, any 211 Amp (DC coupled or not) represents a substantial challenge and using one of the Super 300B's (or even just a plain 300B - I mean I get 16W from that alone) can get you as much power at lower voltages and with easier to get transformers etc...

I used the 211 example merely as illustration that there was no real limit to the full monkey design in principle.

Ciao T
Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

RE: Full Monkey amps, posted on November 14, 2010 at 19:23:48
Paul Joppa Industry Professional Posts: 7353 Location: Seattle, WA Joined: April 23, 2001	Like Thorsten, I also have a high-voltage monkey amp in my notes, in which the "customer" lost interest. Mine was a 211 driver, 212 output and should have made some 30 watts. The 2kV+ power supply was a bit of a show-stopper - would have made a nice ozone generator though.

RE: For the 211 what driver, what PS voltage?, posted on November 14, 2010 at 22:27:50
GTCharlie Audiophile Posts: 983 Location: Philippines Joined: December 9, 2004	and take a look at the 211/vt4-c plate curves ...

RE: Full Monkey amps, posted on November 15, 2010 at 00:35:23
danlaudionut Audiophile Posts: 5480 Location: Schenectady Joined: June 6, 2002	I have been playing around with the 6J5/6EM7 in DRD for gain of 100 and an output impedance of 750. Maybe use a Hammond 126B interstage. and Magnquest EXO-010 plate choke. Voltage swing of up to 200V capable. DanL

6EM7, posted on November 15, 2010 at 01:13:50
Frihed89 Audiophile Posts: 15703 Location: Copenhagen Joined: March 21, 2005	Interesting tube: One section is a preamp triode with Ra of 40K, 330 max plate volts, 66X amplification and a 1.5W max dissipation. The other section is a low-mu power triode, 10W max dissipation, Ra of 750 ohms, 330 max plate volts also, and 50mA max current. Are you using both sections (input-driver)?

RE: For the 211 what driver, what PS voltage?, posted on November 15, 2010 at 01:16:45
Frihed89 Audiophile Posts: 15703 Location: Copenhagen Joined: March 21, 2005	Holy smoke! Thanks.

RE: 6EM7, posted on November 15, 2010 at 03:27:48
danlaudionut Audiophile Posts: 5480 Location: Schenectady Joined: June 6, 2002	Frihed The 6EM7 gain section does not lend itself to DRD or Full Monkey as it's Rp is too high. Above is a directly coupled circuit. For FM or DRD use a 6J5 as the gain tube and the 6EM7 power section as the driver. DanL

My take (on 6EW7), posted on November 15, 2010 at 10:26:45

gluca
Audiophile

Posts: 1102
Location: SomeWhere Islands
Joined: February 17, 2005

C1 is actaully smaller ... 4.7uF

RE: My take (on 6EW7), posted on November 15, 2010 at 10:39:28
danlaudionut Audiophile Posts: 5480 Location: Schenectady Joined: June 6, 2002	Gluca Looks good except for one thing. The B+ is way too low. The CCS can only swing about 25V. Make the B+ 350V and replace the CCS with the interstage and all will be well. Slightly higher ouput impedance and slightly less linear but nice. DanL

RE: My take (on 6EW7), posted on November 15, 2010 at 11:34:19
gluca Audiophile Posts: 1102 Location: SomeWhere Islands Joined: February 17, 2005	Actually I am running B+ at 380V and voltage swing is good for my headphones and as line driver. Yes, you need more headroom as driver stage. I must admit I was surprised by this small tube, damn good sounding tube!

oh!, posted on November 15, 2010 at 12:24:28
gluca Audiophile Posts: 1102 Location: SomeWhere Islands Joined: February 17, 2005	that would have been ominous indeed ... I stopped at 1.35kV with my 801A-75TL and I am kind scared. Not building any other high voltage amps any more, now I am relaxing with line driver, DAC, headphones ... AH!

SET Asylum

Full Monkey amps

87.53.108.41