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Tuesday, October 31, 2023

Upcoming amps, preamps and DACs with Compactron tubes


A whole bunch of new stuff is in the making in my Compactron line of electronics.

After the introduction of the Compactron Preamplifier and getting orders for a Compactron line stage and Compactron phono stage I decided to launch a full line of electronics with Compactron tubes. The following gear is planned to be finished until end of January 2024:

1. Digital to Analog Converter with Volume Control

This DAC is based on the same concept as my previous DACs just with different output tubes and a more compact approach with simplified power supply so that everything fits into a single chassis. The output will be volume controllable using transformer volume control. This is for people who use digital sources only. It can accept data from a laptop/PC or music server via USB or from a transport via Coax. It can drive a power amp directly through long cables.

2. Preamplifier

A simpler version of the first Compactron Preamplifier. It has a phono section for MC cartridges, a balanced input and two SE inputs. A full function preamplifier but with minimal features, just volume control and source select. Volume control done with transformers. It will have both RCA and XLR outputs and low output impedance.

3. Stereo Power amplifier

A single ended power amp with 5W per channel, two stage design, interstage transformer coupled. Like all Compactron electronics in a single chassis.

4. Digital to Analog Converter

The same as the one above but without volume control. Meant to be used with a preamp. Transformer coupled output. Balanced and single ended outputs.

5. Phono Preamplifier

A entry level phono preamplifier for MC cartridges. Meant to be used with an active preamp.

6. Integrated Amplifier.

Single chassis integrated stereo amp based on the same circuit as the power amp above. 5W per channel.

7+8. Mono power amplifiers.

A pair of mono blocks based on the same principle as the stereo amp above but with 10W per channel.

9. Digital to Analog Converter

A simplifier version of the DAC listed as nr. 4. RC coupled outputs, RCA out only.

10. Line Preamplifier

Line preamplifier similar to the one which I built already. Just without phase switch but 2 balanced inputs and 2 SE inputs.

I plan to demo all these at the Munich High End 2024. Yes I plan to be there again. Each of these units can be customised with different features. Chassis will be made in different colors to showcase the possibilities. Stay tuned for updates as assemblies of these units starts.

Best regards


Wednesday, October 25, 2023

Tube of the Month : The 6AY11


This is the last of a miniseries of 4 consecutive posts about Compactron tubes. This months choice is the 6AY11.

The 6AY11 contains two triodes and two diodes in one bottle. Similar to the 6AG11 which was presented in July. But it has different specs.

The 6AY11 and the 6AG11 share the same pinout but the triodes in the 6AY11 have an even higher amplification factor of 100. This comes with a plate resistance of a bit over 50kOhm. Quite interesting if you are in need of a triode with very high gain and if you do not want to resort to the 12AX7. Both triode systems in the 6AY11 have the same parameters. See the General Electric data sheet for a complete set of technical details. There are so many gems hidden among the Compactron tubes which deserve more attention. This is probably one of them. Time to leave beaten paths and explore some alternatives. As always here the curves from the data sheet:

And curves from a tube sample:

I do not have many 6AY11 in stock, all of mine are Westinghouse branded but probably made by GE.

The tube from different angles:

Some close ups and more angles:

Since I do not have many of these I don't want to open one. The internal construction is anyways similar to that of the 6AG11 which I have shown in detail. But I would like to close this post by entertaining you with pictures of the 6AY11 in operation.

I hope you enjoyed this presentation of yet another Compactron beauty.

Best regards


Wednesday, October 18, 2023

The Compactron Phono Preamplifier - part 2


The variable EQ Compactron Phono Stage is finished.

Some photos of the initial construction steps were shown in part 1. Here the finished unit.

Besides adjustability of input impedance and input capacitance, there are selector switches for different bass turn over frequencies and different amounts of treble roll off to adapt to the recording curves of vintage records labels.

In addition the absolute phase of the output can be switched.

The phono stage is meant to be used with MM cartridges or MC with external step up transformer. However in its highest gain setting it is useable with MC cartridges directly in if they are not loo low in output. That is how I am testing it right now.

Gain is selectable in 4 steps via a switch on the back side. More details about this in the post about the Compactron Preamplifier. The outputs are available as RCA as well as XLR sockets. The outputs are transformer coupled and have very low output impedance.

Knobs can be chosen to taste.

More colors available soon.

My favourite is the all orange front.

Here a pic of the inside. Some of the wiring still not final in this photo as it just was an initial test run.

All power supplies including the DC heater supply are choke filtered.

Vents directly above and below the tubes.

The feet are stainless steel as well as their counterparts on which they are supposed to sit to avoid damaging the surface below.

Other feet are available on request.

Stay tuned for more new developments in the Compactron series. An entire line of electronics is planned with Compactron tubes and in this chassis style, including DACs and power amps as well as an integrated.

Best regards


Monday, October 2, 2023

Demo Equipment Sale

*** update : most of the items are sold now. All sold items are marked accordingly. I will offer 10% discount on the remaining items if no shipping is required and you arrange a personal pick up ***


I am in the process of changing my entire product line to a new chassis style as could already be seen in the last 10Y line stage and D3a phono stage builds and also the Compactron series of electronics. Since this means a lot of new demo equipment needs to be built, I want to clear out the current stuff. 

Most of the amps and preamps have need used for demo in my workshop and also on audio shows. Some are trade ins from customers who upgraded to higher level units.

All are in good condition but can have the occasional minor scuff mark. Nothing serious. Technically all units are in perfect condition and will be cleaned and thoroughly tested before they leave the house. All will be delivered with fresh tubes and come with full warranty. Some sets do not have matching colours in power supply and signal unit. No changes will be offered. No change of housing, mains voltage or other mods. All are set for 220-230V mains. Your chance to grab one of these at a bargain price. I will ship world wide. Please note that customs fees might be applicable if you live outside the EU. Personal pick up is possible too.

Starting with one of my hot sellers the D3a phono preamplifier with LCR EQ. More info here.

This is the partial silver version. Slight mismatch in tone in the two chassis.

*** SOLD ***

Next the 10Y line preamp, the perfect companion for the D3a phono. This unit has 5 inputs. 2 Direct via RCA only and 3 balanced through input transformers. These have both XLR and RCA jacks. The 3 sets of input transformers are configured for different additional gains over the 6dB base gain of the preamp (0, +6 and +12dB)

*** SOLD ***

Another 10Y line stage. Same inputs configuration as the one above. This one uses now out of production Tribute OPTVCs

*** SOLD ***

A pair of 300B monos. Ideal together with the 10Y line to create an All DHT set up. ER801A driver and ER300B output tubes. ER274B plus 2 6AX4 in the rectification of the PSU.

*** SOLD ***

Digital to Analog Converter. This is the first unit I built an was used in my workshop system and at audio shows. More info here.

*** SOLD ***

Another DAC, this time using silver output transformers.

*** SOLD ***

All silver 46 drive 46 single ended monos. More info here

*** SOLD ***

Something very special, a mono phono stage with adjustable EQ using LCR! Has been used at various audio shows. More info here. Some videos with the unit playing here.

Sale price: 8000,- EUR / set (export without VAT: 6700,-)

6J5 line stage. Single chassis. More info here

Sale price: 4500,- EUR (export without VAT: 3780,-)

D3a Preamplifier with line and phono. More info here. I never actually marketed this approach.

Here your chance to grab this at a bargain

*** SOLD ***

D3a high gain line stage, has a separate power supply (not shown). It is the line section of the D3a Preamplifier. Specialized unit if more gain is needed. has several transformer inputs set for different gains. Email me for more information

Sale price: 8000,- EUR (export without VAT: 6720,-)

6KN6 monos. More info here. I never really marketed these.

*** SOLD ***

Differential D3a phono. A monster of a phone stage. The same as this unit.

*** SOLD ***

Something very special. A fully differential all silver 10Y line stage. my personal unit. 3 inputs all set for different gains. My ultimate statement in terms of line pre-amplification.

*** SOLD ***

And lastly a D3a phono in the new chassis. This was the prototype of this phono in the new style. The metal work is not done by the same supplier who I am using now and is not of the same quality and precision. Before I disassemble the unit maybe someone wants to grab it.

*** SOLD ***

That's all I have to offer. Feel free to email me if you need more information or more detailed photos. I am open for reasonable offers especially if you buy more than one setor if you pick up personally and no shipping crates are needed. Listening before buying is possible at my place. If you live too far away to come for a listen, don't worry. I guarantee full satisfaction. If you do not like what you bought you can send it back within 2 weeks after receipt for a refund of the purchase price, less shipping cost.

Please help me to make room. Everything that does not sell within a month will be disassembled for parts reuse.

Best regards