Are there any other EAR 834P modders lately?


I had to beg David Schulte of Upgrade Company to mod my EAR 834P because there are so many detractors. There are also loads of DIY people who have tweaked the circuit in custom ways. The changes I had made include V-cap coupling caps and RFI shileding. Switching from using the 12AX7 tubes to 5751 or 12AT7 tubes if you can handle the lower gain also is highly beneficial. I use Valvo 6201 blue print in the one spot, Brimar and Siemen Halske 12AT7's in the gain stages 2 & 3. 2 is not left and 3 is not right- it sums the tubes for the gain stage left and right. My results are stunning. Because the 12AT7's only have 70% of the gain or the 12AX7, I changed out my Bent Audio step up tranny's for Bob's Devices Cinemag 1131 with a 1:40 or 1:20, ratio which is adjusted at the flip of a toggle switch.
zenbret
Zenbret, You wrote, "Passive preamps and attenuators add resistance to the signal path and boost the voltage." That statement is kind of a mess. Some passive preamps do employ transformers or autoformers as "volume controls". Such devices can change the ratio of voltage to current of an audio signal (i.e., for any increase in V there would be a proportional decrease in current, or vice-versa; it's the law according to Ohm). But there is no free lunch, because they are passive, which by definition means they add no gain. A conventional attenuator, of which there are several types, is purely resistive. It also can add no voltage gain, because such a device is also "passive". A "resistive" attenuator is only able to decrease the amplitude of the signal that passes through it, via presenting a resistance to that signal. The subtracted energy is dissipated as heat.
Zenbret: I was having fun but working hard at the same time. I guess I failed to mention I'm using a BOb's Cinemag 3440 w/ Dyna Karat D3. I'm in the process of listing my system, so it will take a while to complete. In what could only happen to me, last weekend I was using my motor enclosure design and the sound seemed different than ususal which is mainly why I decided to experiment with tubes again. Found out later that night my enclosure had split ( part of it was made from Purpleheart, I'm assumming it hadn't completetly dried. anyway, it changed the character of the sound, thats's when I started another day of re-experimenting. Luckily, I had a replacement (upgrade enclosure already in the works and installed it Tuesday). After tube swapping a good bit this week I'm back close to where I started. Siemens in V1 @ V2, Tele in V3. The enclosure works very well.
Lewm, So you are saying that attenuators made out of resistors only lower the gain by decreasing the amplitude of the wave, but they do not change voltage or current at all?

I mistakenly thought that transformers step up the voltage by adding resistance ( the coil of wire acted like a resistor).

I have used autoformers on OTL amps before to boost the voltage.
Glad you keep me from talking a fool, cause I don't have a full understanding of basic electronics- though I have been reading up.

Slaw- remind me, are you using all 12AX7 tubes?

I actually made one more change- Siemens 12AT7 1982 tube in V3 ( the Syvania 6201 Gold brand was to tight and thin- needed a looser sloppier sound to fatten it up and the Siemens works well)
Found a clarification- thanks for pointing out my flaw Lewm. If a signal in a wire has a high enough gain, then a passive gain limiting preamp using resistors can be used to lower the signal to whatever listening level is desired, with full blast having no resistor in the circuit. These are often considered purer sounding than gain stages if you have enough gain not to need an active gain preamp.

"A resistor is a device that opposes current by reducing the voltage across it. If you look at a series circuit (a bunch of resistors and battery in series) you will see a voltage drop across each resistor, but the same current through each resistor." as one person explained.

V (voltage)= I (current) x R(resistance): is Ohm's law

Capacitors absorb preferentially low wavelengths, inductors absorb high wavelengths, resistors decrease voltage with no affect on frequency overall.

Can someone explain how transformer coils step up the voltage?
Zenbret
A simple transformer consists essentially of two coils of insulated wire. In most transformers, the wires are wound around an iron-containing structure called the core. One coil, called the primary, is connected to a source of alternating current that produces a constantly varying magnetic field around the coil. The varying magnetic field, in turn, produces an alternating current in the other coil. This coil, called the secondary, is connected to a separate electric circuit.

The ratio of the number of turns in the primary coil to the number of turns in the secondary coil—the turns ratio—determines the ratio of the voltages in the two coils. For example, if there is one turn in the primary and ten turns in the secondary coil, the voltage in the secondary coil will be 10 times that in the primary. Such a transformer is called a step-up transformer.

The cartridge is the source of alternating current that the primary winding sees.

If you like equations : Power = V(volts) x I(current)

and VI(primary) = VI (secondary)

The transformer takes the high current low voltage from the cartridge and converts it to higher voltage lower current.

Because of the low current after the transformer, the interconnect from transformer to pre should be kept as short as possible.